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Scientific American Supplement No. 458
NEW YORK, OCTOBER 11, 1884
Scientific American Supplement. Vol. XVIII, No. 458.
Scientific American established 1845
Scientific American Supplement, $5 a year.
Scientific American and Supplement, $7 a year.
TABLE OF CONTENTS.
I. CHEMISTRY AND METALLURGY.—Chemical Nature of Starch Grains.
The Amalgamation of Silver Ores.—Description of the Francke tina, or vat process for amalgamation of silver ores.—By E.P. RATHBONE.—6 figures.
Interesting Facts about Platinum.—Draw stones used for drawing wire of precious metals.
II. ENGINEERING, MINING, ETC.—Modern Locomotive Practice.—Paper read before the Civil and Mechanical Engineers' Society.—By H. MICHELL WHITLEY—10 figures.
New Screw Steam Collier, Frostburg.—1 figure.
Destruction of the Tardes Viaduct by Wind.—With engraving.
Joy's Reversing and Expansion Valve Gear.—1 figure.
The Steam Bell for Locomotives.—2 figures.
Diamond Mining in Brazil.—With engravings showing the dam on the Ribeirao Inferno at Portao de Ferro, and the arrangement of the machinery.
III. ELECTRICITY, ETC.—The Frankfort and Offenbach Electric Railway.—With 3 engravings.
Possibilities of the Telephone.—Its use by vessels at sea.
Pyrometers.—The inventions of Siemens and others.
IV. ARCHAEOLOGY.—The Cay Monument at Uxmal.—Discovered by Dr. Le Plongeon on June 1, 1881.—With engraving.
V. ASTRONOMY.—The Temperature of the Solar Surface Corresponding with the Temperature Transmitted to the Sun Motor.—By J. ERICSSON.—With 2 engravings of the sun motor.
VI. HORTICULTURE.—Halesia Hispida, a Hardy Shrub.—With engraving.
Windflowers or Anemone.—With engraving.
VII. MEDICINE, HYGIENE. ETC.—What we Really Know about Asiatic Cholera.—By J.C. PETERS, M.D.
Dr. Koch on the Cholera.
Malaria.—The natural production of malaria and the means of making malarial countries healthier.—By C.T. CRUDELI, of Rome.
Story of Lieut. Greely's Recovery.—Treatment by Surgeon Green.
VIII. MISCELLANEOUS.—Bayle's New Lamp Chimney.—With engraving.
Lieut. Greely before the British Association.
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THE FRANKFORT AND OFFENBACH ELECTRIC RAILWAY.
The electric railway recently set in operation between Frankfort and Offenbach furnishes an occasion for studying the question of such roads anew and from a practical standpoint. For elevated railways Messrs. Siemens and Halske a long time ago chose rails as current conductors. The electric railway from Berlin to Lichterfelde and the one at Vienna are in reality only elevated roads established upon the surface.
Although it is possible to insulate the rails in a satisfactory manner in the case of an elevated road, the conditions of insulation are not very favorable where the railway is to be constructed on a level with the surface. In this case it becomes necessary to dispense with the simple and cheap arrangement of rails as conductors, and to set up, instead, a number of poles to support the electric conductors. It is from these latter that certain devices of peculiar construction take up the current. The simplest arrangement to be adopted under these circumstances would evidently be to stretch a wire upon which a traveler would slide—this last named piece being connected with the locomotive by means of a flexible cord. This general idea, moreover, has been put in practice by several constructors.
In the Messrs. Siemens Bros.' electric railway that figured at Paris in 1881 the arrangement adopted for taking up the current consisted of two split tubes from which were suspended two small contact carriages that communicated with the electric car through the intermedium of flexible cables. This is the mode of construction that Messrs. Siemens and Halske have adopted in the railway from Frankfort to Offenbach. While the Paris road was of an entirely temporary character, that of Frankfort has been built according to extremely well studied plans, and after much light having been thrown upon the question of electric traction by three years of new experiments.
Fig. 1 shows the electric car at the moment of its start from Frankfort, Fig. 2 shows the arrangement of a turnout, and Fig. 3 gives a general plan of the electric works.
The two grooved tubes are suspended from insulators fixed upon external cast iron supports. As for the conductors, which have their resting points upon ordinary insulators mounted at the top of the same supports, these are cables composed of copper and steel. They serve both for leading the current and carrying the tubes. The same arrangement was used by Messrs. Siemens and Halske at Vienna in 1883.
The motors, which are of 240 H.P., consist of two coupled steam engines of the Collmann system. The one shaft in common runs with a velocity of 60 revolutions per minute. Its motion is transmitted by means of ten hempen cables, 3.5 cm. in diameter. The flywheel, which is 4 m. in diameter, serves at the same time as a driving pulley. As the pulley mounted upon the transmitting shaft is only one meter in diameter, it follows that the shafting has a velocity of 240 revolutions per minute. The steam generators are of the Ten Brink type, and are seven in number. The normal pressure in them is four atmospheres. There are at present four dynamo-electric machines, but sufficient room was provided for four more. The shafts of the dynamos have a velocity of 600 revolutions per minute. The pulleys are 60 cm. in diameter, and the width of the driving belts is 18 cm. The dynamos are mounted upon rails so as to permit the tension of the belting to be regulated when necessity requires it. This arrangement, which possesses great advantages, had already been adopted in many other installations.
The electric machines are 2 meters in height. The diameter of the rings is about 45 cm. and their length is 70 cm. The electric tension of the dynamos measures 600 volts.
The duty varies between 80 and 50 per cent., according to the arrangement of the cars. The total length of the road is 6,655 meters. Usually, there are four cars en route, and two dynamos serve to create the current. When the cars are coupled in pairs, three dynamos are used—one of the machines being always held in reserve. All the dynamos are grouped for quantity.
The company at present owns six closed and five open cars. In the former there is room for twenty-two persons. The weight of these cars varies between 3,500 and 4,000 kilos.—La Lumiere Electrique.
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By the addition of ten parts of collodion to fifteen of creasote (says the Revue de Therap.) a sort of jelly is obtained which is more convenient to apply to decayed teeth than is creasote in its liquid form.
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POSSIBILITIES OF THE TELEPHONE.
The meeting of the American Association was one of unusual interest and importance to the members of Section B. This is to be attributed not only to the unusually large attendance of American physicists, but also to the presence of a number of distinguished members of the British Association, who have contributed to the success of the meetings not only by presenting papers, but by entering freely into the discussions. In particular the section was fortunate in having the presence of Sir William Thomson, to whom more than to any one else we owe the successful operation of the great ocean cables, and who stands with Helmholtz first among living physicists. Whenever he entered any of the discussions, all were benefited by the clearness and suggestiveness of his remarks.
Professor A. Graham Bell, the inventor of the telephone, read a paper giving a possible method of communication between ships at sea. The simple experiment that illustrates the method which he proposed is as follows: Take a basin of water, introduce into it, at two widely separated points, the two terminals of a battery circuit which contains an interrupter, making and breaking the circuit very rapidly. Now at two other points touch the water with the terminals of a circuit containing a telephone. A sound will be heard, except when the two telephone terminals touch the water at points where the potential is the same. In this way the equipotential lines can easily be picked out. Now to apply this to the case of a ship at sea: Suppose one ship to be provided with a dynamo machine generating a powerful current, and let one terminal enter the water at the prow of the ship, and the other to be carefully insulated, except at its end, and be trailed behind the ship, making connection with the sea at a considerable distance from the vessel; and suppose the current be rapidly made and broken by an interrupter; then the observer on a second vessel provided with similar terminal conductors to the first, but having a telephone instead of a dynamo, will be able to detect the presence of the other vessel even at a considerable distance; and by suitable modifications the direction of the other vessel may be found. This conception Professor Bell has actually tried on the Potomac River with two small boats, and found that at a mile and a quarter, the furthest distance experimented upon, the sound due to the action of the interrupter in one boat was distinctly audible in the other. The experiment did not succeed quite so well in salt water. Professor Trowbridge then mentioned a method which he had suggested some years ago for telegraphing across the ocean without a cable, the method having been suggested more for its interest than with any idea of its ever being put in practice. A conductor is supposed to be laid from Labrador to Patagonia, ending in the ocean at those points, and passing through New York, where a dynamo machine is supposed to be included in the circuit. In Europe a line is to extend from the north of Scotland to the south of Spain, making connections with the ocean at those points, and in this circuit is to be included a telephone. Then any change in the strength of the current in the American line would produce a corresponding change in current in the European line; and thus signals could be transmitted. Mr. Preece, of the English postal telegraph, then gave an account of how such a system had actually been put into practice in telegraphing between the Isle of Wight and Southampton during a suspension in the action of the regular cable communication. The instruments used were a telephone in one circuit, and in the other about twenty-five Leclanche cells and an interrupter. The sound could then be heard distinctly; and so communication was kept up until the cable was again in working order. Of the two lines used in this case, one extended from the sea at the end of the island near Hurst Castle, through the length of the island, and entered the sea again at Rye; while the line on the mainland ran from Hurst Castle, where it was connected with the sea, through Southampton to Portsmouth, where it again entered the sea. The distance between the two terminals at Hurst Castle was about one mile, while that between the terminals at Portsmouth and Rye amounted to six miles.—Science.
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PYROMETERS.
The accurate measurement of very high temperatures is a matter of great importance, especially with regard to metallurgical operations; but it is also one of great difficulty. Until recent years the only methods suggested were to measure the expansion of a given fluid or gas, as in the air pyrometer; or to measure the contraction of a cone of hard, burnt clay, as in the Wedgwood pyrometer. Neither of these systems was at all reliable or satisfactory. Lately, however, other principles have been introduced with considerable success, and the matter is of so much interest, not only to the practical manufacturer but also to the physicist, that a sketch of the chief systems now in use will probably be acceptable. He will thus be enabled to select the instrument best suited for the particular purpose he may have in view.
The first real improvement in this direction, as in so many others, is due to the genius of Sir William Siemens. His first attempt was a calorimetric pyrometer, in which a mass of copper at the temperature required to be known is thrown into the water of a calorimeter, and the heat it has absorbed thus determined. This method, however, is not very reliable, and was superseded by his well-known electric pyrometer. This rests on the principle that the electric resistance of metal conductors increases with the temperature. In the case of platinum, the metal chosen for the purpose, this increase up to 1,500 deg.C. is very nearly in the exact proportion of the rise of temperature. The principle is applied in the following manner: A cylinder of fireclay slides in a metal tube, and has two platinum wires one one-hundredth of an inch in diameter wound round it in separate grooves. Their ends are connected at the top to two conductors, which pass down inside the tube and end in a fireclay plug at the bottom. The other ends of the wires are connected with a small platinum coil, which is kept at a constant resistance. A third conductor starting from the top of the tube passes down through it, and comes out at the face of the metal plug. The tube is inserted in the medium whose temperature is to be found, and the electric resistance of the coil is measured by a differential voltameter. From this it is easy to deduce the temperature to which the platinum has been raised. This pyrometer is probably the most widely used at the present time.
Tremeschini's pyrometer is based on a different principle, viz., on the expansion of a thin plate of platinum, which is heated by a mass of metal previously raised to the temperature of the medium. The exact arrangements are difficult to describe without the aid of drawings, but the result is to measure the difference of temperature between the medium to be tested and the atmosphere at the position of the instrument. The whole apparatus is simple, compact, and easy to manage, and its indications appear to be correct at least up to 800 deg.C.
The Trampler pyrometer is based upon the difference in the coefficients of dilatation for iron and graphite, that of the latter being about two-thirds that of the former. There is an iron tube containing a stick of hard graphite. This is placed in the medium to be examined, and both lengthen under the heat, but the iron the most of the two. At the top of the stick of graphite is a metal cap carrying a knife-edge, on which rests a bent lever pressed down upon it by a light spring. A fine chain attached to the long arm of this lever is wound upon a small pulley; a larger pulley on the same axis has wound upon it a second chain, which actuates a third pulley on the axis of the indicating needle. In this way the relative dilatation of the graphite is sufficiently magnified to be easily visible.
A somewhat similar instrument is the Gauntlett pyrometer, which is largely used in the north of England. Here the instrument is partly of iron, partly of fireclay, and the difference in the expansion of the two materials is caused to act by a system of springs upon a needle revolving upon a dial.
The Ducomet pyrometer is on a very different principle, and only applicable to rough determinations. It consists of a series of rings made of alloys which have slightly different melting-points. These are strung upon a rod, which is pushed into the medium to be measured, and are pressed together by a spiral spring. As soon as any one of the rings begins to soften under the heat, it is squeezed together by the pressure, and, as it melts, it is completely squeezed out and disappears. The rod is then made to rise by the thickness of the melted ring, and a simple apparatus shows at any moment the number of rings which have melted, and therefore the temperature which has been attained. This instrument cannot be used to follow variations of temperature, but indicates clearly the moment when a particular temperature is attained. It is of course entirely dependent on the accuracy with which the melting-points of the various alloys have been fixed.
Yet another principle is involved in the instrument called the thalpotasimeter, which may be used either with ether, water, or mercury. It is based on the principle that the pressure of any saturated vapor corresponds to its temperature. The instrument consists of a tube of metal partly filled with liquid, which is exposed to the medium which is to be measured. A metallic pressure gauge is connected with the tube, and indicates the pressure existing within it at any moment. By graduating the face of the gauge when the instrument is at known temperatures, the temperature can be read off directly from the position of the needle. From 100 deg. to 220 deg.F. ether is the liquid used, from thence to 680 deg. it is water, and above the latter temperature mercury is employed.
Another class of pyrometers having great promise in the future is based on what may be called the "water-current" principle. Here the temperature is determined by noting the amount of heat communicated to a known current of water circulating in the medium to be observed. The idea, which was due to M. De Saintignon, has been carried out in its most improved form by M. Boulier. Here the pyrometer itself consists of a set of tubes one inside the other, and all inclosed for safety in a large tube of fireclay. The central tube or pipe brings in the water from a tank above, where it is maintained at a constant level. The water descends to the bottom of the instrument, and opens into the end of another small tube called the explorer (explorateur). This tube projects from the fireclay casing into the medium to be examined, and can be pushed in or out as required. After circulating through this tube the water rises again in the annular space between the central pipe and the second pipe. The similar space between the second pipe and the third pipe is always filled by another and much larger current of water, which keeps the interior cool. The result is that no loss of heat is possible in the instrument, and the water in the central tube merely takes up just so much heat as is conducted into it through the metal of the explorer. This heat it brings back through a short India-rubber pipe to a casing containing a thermometer. This thermometer is immersed in the returning current of water, and records its temperature. It is graduated by immersing the instrument in known and constant temperatures, and thus the graduations on the thermometer give at once the temperature, not of the current of water, but of the medium from which it has received its heat. In order to render the instrument perfectly reliable, all that is necessary is that the current of water should be always perfectly uniform, and this is easily attained by fixing the size of the outlet once for all, and also the level of water in the tank. So arranged, the pyrometer works with great regularity, indicating the least variations of temperature, requiring no sort of attention, and never suffering injury under the most intense heat; in fact the tube, when withdrawn from the furnace, is found to be merely warm. If there is any risk of the instrument getting broken from fall of materials or other causes, it may be fitted with an ingenious self-acting apparatus shutting off the supply. For this purpose the water which has passed the thermometer is made to fall into a funnel hung on the longer arm of a balanced lever. With an ordinary flow the water stands at a certain height in the funnel, and, while this is so, the lever remains balanced; but if from any accident the flow is diminished, the level of the water in the funnel descends, the other arm of the lever falls, and in doing so releases two springs, one of which in flying up rings a bell, and the other by detaching a counterweight closes a cock and stops the supply of water altogether.
It will be seen that these instruments are not adapted for shifting about from place to place in order to observe different temperatures, but rather for following the variations of temperature at one and the same place. For many purposes this is of great importance. They have been used with great success in porcelain furnaces, both at the famous manufactories at Sevres and at another porcelain works in Limoges. From both these establishments very favorable reports as to their working have been received.—W.R. Browne, in Nature.
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[NATURE.]
THE TEMPERATURE OF THE SOLAR SURFACE.
I have, during the summer solstice of 1884, carried out an experimental investigation for the purpose of demonstrating the temperature of the solar surface corresponding with the temperature transmitted to the sun motor. Referring to the illustrations previously published, it will be seen that the cylindrical heater of the sun motor, constructed solely for the purpose of generating steam or expanding air, is not well adapted for an exact determination of the amount of surface exposed to the action of the reflected solar rays. It will be perceived on inspection that only part of the bottom of the cylindrical heater of the motor is acted upon by the reflected rays, and that their density diminishes gradually toward the sides of the vessel; also that owing to the imperfections of the surface of the reflecting plates the exact course of the terminal rays cannot be defined. Consequently, the most important point in the investigation, namely, the area acted upon by the reflected radiant heat, cannot be accurately determined. I have accordingly constructed an instrument of large dimensions, a polygonal reflector (see Fig. 1), composed of a series of inclined mirrors, and provided with a central heater of conical form, acted upon by the reflected radiation in such a manner that each point of its surface receives an equal amount of radiant heat in a given time. The said reflector is contained within two regular polygonal planes twelve inches apart, each having ninety-six sides, the perimeter of the upper plane corresponding with a circle of eight feet diameter, that of the lower plane being six feet. The corresponding sides of these planes are connected by flat taper mirrors composed of thin glass silvered on the outside. When the reflector faces the sun at right angles, each mirror intercepts a pencil of rays of 32.61 square inches section, hence the entire reflecting surface receives the radiant heat of an annular sunbeam of 32.61 x 96 = 3,130 square inches section. It should be observed that the area thus stated is 0.011 less than the total foreshortened superficies of the ninety-six mirrors if sufficiently wide to come in perfect contact at the vertices. Fig. 2 represents a transverse section of the instrument as it appears when facing the sun; the direct and reflected rays being indicated by dotted lines. The reflector and conical heater are sustained by a flat hub and eight radial spokes bent upward toward the ends at an angle of 45 deg.. The hub and spokes are supported by a vertical pivot, by means of which the operator is enabled to follow the diurnal motion of the sun, while a horizontal axle, secured to the upper end of the pivot, and held by appropriate bearings under the hub, enables him to regulate the inclination to correspond with the altitude of the luminary. The heater is composed of rolled plate iron 0.017 inch thick, and provided with bead and bottom formed of non-conducting materials. By means of a screw-plug passing through the bottom and entering the face of the hub the heater may be applied and removed in the course of five minutes, an important fact, as will be seen hereafter. It is scarcely necessary to state that the proportion of the ends of the conical heater should correspond with the perimeters of the reflector, hence the diameter of the upper end, at the intersection of the polygonal plane, should be to that of the lower end as 8 to 6, in order that every part may be acted upon by reflected rays of equal density. This condition being fulfilled, the temperature communicated will be perfectly uniform. A short tube passes through the upper head of the heater, through which a thermometer is inserted for measuring the internal temperature. The stem being somewhat less than the bore of the tube, a small opening is formed by which the necessary equilibrium of pressure will be established with the external atmosphere. It should be mentioned that the indications of the thermometer during the experiment have been remarkably prompt, the bulb being subjected to the joint influence of radiation and convection.
The foregoing particulars, it will be found, furnish all necessary data for determining with absolute precision the diffusion of rays acting on the central vessel of the solar pyrometer. But the determination of temperature which uninterrupted solar radiation is capable of transmitting to the polygonal reflector calls for a correct knowledge of atmospheric absorption. Besides, an accurate estimate of the loss of radiant heat attending the reflection of the rays by the mirrors is indispensable. Let us consider these points separately.
Atmospheric Absorption.—The principal object of conducting the investigation during the summer solstice has been the facilities afforded for determining atmospheric absorption, the sun's zenith distance at noon being only 17 deg. 12' at New York. The retardation of the sun's rays in passing through a clear atmosphere obviously depends on the depth penetrated; hence—neglecting the curvature of the atmospheric limit—the retardation will be as the secants of the zenith distances. Accordingly, an observation of the temperature produced by solar radiation at a zenith distance whose secant is twice that of the secant of 17 deg. 12', viz., 61 deg. 28', determines the minimum atmospheric absorption at New York. The result of observations conducted during a series of years shows that the maximum solar intensity at 17 deg. 12' reaches 66.2 deg. F., while at a zenith distance of 61 deg. 28' it is 52.5 deg. F.; hence, minimum atmospheric absorption at New York, during the summer solstice,
13.7 is 66.2 deg.-52.5 deg. = 13.7 deg. F., or ——— = 0.207 of the sun's 66.2
radiant energy where the rays enter the terrestrial atmosphere.
In order to determine the loss of energy attending the reflection of the rays by the diagonal mirrors, I have constructed a special apparatus, which, by means of a parallactic mechanism, faces the sun at right angles during observations. It consists principally of two small mirrors, manufactured of the same materials as the reflector, placed diagonally at right angles to each other; a thermometer being applied between the two, whose stem points toward the sun. The direct solar rays entering through perforations of an appropriate shade, and reflected by the inclined mirrors, act simultaneously on opposite sides of the bulb. The mean result of repeated trials, all differing but slightly, show that the energy of the direct solar rays acting on the polygonal reflector is reduced 0.235 before reaching the heater.
In accordance with the previous article, the investigation has been based on the assumption that the temperatures produced by radiant heat at given distances from its source are inversely as the diffusion of the rays at those distances. In other words, the temperature produced by solar radiation is as the density of the rays.
It will be remembered that Sir Isaac Newton, in estimating the temperature to which the comet of 1680 was subjected when nearest to the sun, based his calculations on the result of his practical observations that the maximum temperature produced by solar radiation was one-third of that of boiling water. Modern research shows that the observer of 1680 underrated solar intensity only 5 deg. for the latitude of London. The distance of the comet from the center of the sun being to the distance of the earth from the same as 6 to 1,000, the author of the "Principia" asserted that the density of the rays was as 1,000 squared to 6 squared = 28,000 to 1; hence the comet was subjected to a temperature of 28,000 x 180 deg./3 = 1,680,000 deg., an intensity exactly "2,000 times greater than that of red-hot iron" at a temperature of 840 deg.. The distance of the comet from the solar surface being equal to one-third of the sun's radius, it will be seen that, in accordance with the Newtonian doctrine, the temperature to which it was subjected indicated a solar intensity of
4 squared x 1,680,000 ——————— = 2,986,000 deg. F. 3
The writer has established the correctness of the assumption that "the temperature is as the density of the rays," by showing practically that the diminution of solar temperature (for corresponding zenith distances) when the earth is in aphelion corresponds with the increased diffusion of the rays consequent on increased distance from the sun. This practical demonstration, however, has been questioned on the insufficient ground that "the eccentricity of the earth's orbit is too small and the temperature produced by solar radiation too low" to furnish a safe basis for computations of solar temperature.
In order to meet the objection that the diffusion of the rays in aphelion do not differ sufficiently, the solar pyrometer has been so arranged that the density, i. e., the diffusion of the reflected rays, can be changed from a ratio of 1 in 5,040 to that of 1 in 10,241. This has been effected by employing heaters respectively 10 inches and 20 inches in diameter. With reference to the "low" solar temperature pointed out, it will be perceived that the adopted expedient of increasing the density of the rays without raising the temperature by converging radiation, removes the objection urged.
Agreeably to the dimensions already specified, the area of the 10-inch heater acted upon by the reflected solar rays is 331.65 square inches, the area of the 20-inch heater being 673.9 square inches. The section of the annular sunbeam whose direct rays act upon the polygonal reflector is 3,130 square inches, as before stated.
Regarding the diffusion of the solar rays during the investigation, the following demonstration will be readily understood. The area of a sphere whose radius is equal to the earth's distance from the sun in aphelion being to the sun's area as 218.1 squared to 1, while the reflecter of the solar pyrometer intercepts a sunbeam of 3,130 square inches section, it follows that the reflector will receive the radiant heat developed by 3,130 / 218.1 squared = 0.0658 square inch of the solar surface. Hence, as the 10-inch heater presents an area of 331.65 square inches, we establish the fact that the reflected solar rays, acting on the same, are diffused in the ratio of 331.65 to 0.0658, or 331.65 / 0.0658 = 5,040 to 1; the diffusion of the rays acting on the 20-inch heater being as 673.9 to 0.0658, or 673.9 / 0.0658 = 10,241 to 1.
The atmospheric conditions having proved unfavorable during the investigation, maximum solar temperature was not recorded. Accordingly, the heaters of the solar pyrometer did not reach maximum temperature, the highest indication by the thermometer of the small heater being 336.5 deg., that of the large one being 200.5 deg. above the surrounding air. No compensation will, however, be introduced on account of deficient solar heat, the intention being to base the computation of solar temperature solely on the result of observations conducted at New York during the summer solstice of 1884. It will be noticed that the temperature of the large heater is proportionally higher than that of the small heater, a fact showing that the latter, owing to its higher temperature, loses more heat by radiation and convection than the former. Besides, the rate of cooling of heated bodies increases more rapidly than the augmentation of temperature.
The loss occasioned by the imperfect reflection of the mirrors, as before stated, is 0.235 of the energy transmitted by the direct solar rays acting on the polygonal reflector, hence the temperature which the solar rays are capable of imparting to the large heater will be 200.5 deg. x 1.235 = 247.617 deg.; but the energy of the solar rays acting on the reflector is reduced 0.207 by atmospheric absorption, consequently the ultimate temperature which the sun's radiant energy is capable of imparting to the heater is 1.207 x 247.617 deg. = 298.87 deg. F. It is hardly necessary to observe that this temperature (developed by solar radiation diffused fully ten-thousandfold) must be regarded as an actual temperature, since a perfectly transparent atmosphere, and a reflector capable of transmitting the whole energy of the sun's rays to the heater, would produce the same.
The result of the experimental investigation carried out during the summer solstice of 1884 may be thus briefly stated. The diffusion of the solar rays acting on the 20 inch heater being in the ratio of 1 to 10,241, the temperature of the solar surface cannot be less than 298.87 deg. x 10,241 = 3,060,727 deg. F. This underrated computation must be accepted unless it can be shown that the temperature produced by radiant heat is not inversely as the diffusion of the rays. Physicists who question the existence of such high solar temperature should bear in mind that in consequence of the great attraction of the solar mass, hydrogen on the sun's surface raised to a temperature of 4,000 deg. C. will be nearly twice as heavy as hydrogen on the surface of the earth at ordinary atmospheric temperatures; and that, owing to the immense depth of the solar atmosphere, its density would be so enormous at the stated low temperature that the observed rapid movements within the solar envelope could not possibly take place. It scarcely needs demonstration to prove that extreme tenuity can alone account for the extraordinary velocities recorded by observers of solar phenomena. But extreme tenuity is incompatible with low temperature and the pressure produced by an atmospheric column probably exceeding 50,000 miles in height subjected to the sun's powerful attraction, diminished only one-fourth at the stated elevation. These facts warrant the conclusion that the high temperature established by our investigation is requisite to prevent undue density of the solar atmosphere.
It is not intended at present to discuss the necessity of tenuity with reference to the functions of the sun as a radiator; yet it will be proper to observe that on merely dynamical grounds the enormous density of the solar envelope which would result from low temperature presents an unanswerable objection to the assumption of Pouillet, Vicaire, Sainte-Claire Deville, and other eminent savants, that the temperature of the solar surface does not reach 3,000 deg. C.
J. ERICSSON.
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CHEMICAL NATURE OF STARCH GRAINS.
Dr. Brukner has contributed to the Proceedings of the Vienna Academy of Sciences a paper on the "Chemical Nature of the Different Varieties of Starch," especially in reference to the question whether the granulose of Nageli, the soluble starch of Jessen, the amylodextrin of W. Nageli, and the amidulin of Nasse are the same or different substances. A single experiment will serve to show that under certain conditions a soluble substance maybe obtained from starch grains.
If dried starch grains are rubbed between two glass plates, the grains will be seen under the microscope to be fissured, and if then wetted and filtered, the filtrate will be a perfectly clear liquid showing a strong starch reaction with iodine. Since no solution is obtained from uninjured grains, even after soaking for weeks in water, Brukner concludes that the outer layers of the starch grains form a membrane protecting the interior soluble layers from the action of the water.
The soluble filtrate from starch paste also contains a substance identical with granulose. Between the two kinds of starch, the granular and that contained in paste, there is no chemical but only a physical difference, depending on the condition of aggregation of their micellae.
W. Nageli maintains that granulose, or soluble starch, differs from amylodextrin in the former being precipitated by tannic acid and acetate of lead, while the latter is not. Brukner fails to confirm this difference, obtaining a voluminous precipitate with tannic acid and acetate of lead in the case of both substances. Another difference maintained by Nageli, that freshly precipitated starch is insoluble, amylodextrin soluble in water, is also contested; the author finding that granulose is soluble to a considerable extent in water, not only immediately after precipitation, but when it has remained for twenty-four hours under absolute alcohol. Other differences pointed out by W. Nageli, Brukner also maintains to be non-existent, and he regards amidulin and amylodextrin as identical. Brucke gave the name erythrogranulose to a substance nearly related to granulose, but with a stronger affinity for iodine, and receiving from it not a blue but a red color. Brukner regards the red color as resulting from a mixture of erythrodextrin, and the greater solubility of this substance in water.
If a mixture of filtered potato starch paste and erythrodextrin is dried in a watch glass covered with a thin pellicle of collodion, and a drop of iodine solution placed on the latter, it penetrates very slowly through the pellicle, the dextrin becoming first tinctured with red, and the granulose afterward with blue. If, on the other hand, no erythrodextrin is used, the diffusion of the iodine causes at once simply a blue coloring.
With regard to the iodine reaction of starch, Brukner contests Sachsse's view as to the loss of color of iodide of starch at a high temperature. He shows that the iodide may resist heat, and that the loss of color depends on the greater attraction of water for iodine as compared with starch, and the greater solubility of iodine in water at high temperatures.
The different kinds of starch do not take the same tint with the same quantity of (solid) iodine. That from the potato arum gives a blue, and that from wheat and rice a violet tint; while the filtrate from starch paste, from whatever source, always gives a blue color.
* * * * *
THE AMALGAMATION OF SILVER ORES.
DESCRIPTION OF THE FRANCKE "TINA" OR VAT PROCESS FOR THE AMALGAMATION OF SILVER ORES.
[Footnote: Paper read before the Institution of Mechanical Engineers at the Cardiff meeting.—Engineering.]
By Mr. EDGAR P. RATHBONE, of London.
In the year 1882, while on a visit to some of the great silver mines in Bolivia, an opportunity was afforded the writer of inspecting a new and successful process for the treatment of silver ores, the invention of Herr Francke, a German gentleman long resident in Bolivia, whose acquaintance the writer had also the pleasure of making. After many years of tedious working devoted to experiments bearing on the metallurgical treatment of rich but refractory silver ores, the inventor has successfully introduced the process of which it is proposed in this paper to give a description, and which has, by its satisfactory working, entirely eclipsed all other plans hitherto tried in Bolivia, Peru, and Chili. The Francke "tina" process is based on the same metallurgical principles as the system described by Alonzo Barba in 1640, and also on those introduced into the States in more recent times under the name of the Washoe process.[1]
[Footnote 1: Transactions of the American Institute of Mining Engineers, vol. ii., p. 159.]
It was only after a long and careful study of these two processes, and by making close observations and experiments on other plans, which had up to that time been tried with more or less success in Bolivia, Peru, and Chili—such as the Mexican amalgamation process, technically known as the "patio" process; the improved Freiberg barrel amalgamation process; as used at Copiapo; and the "Kronke" process—that Herr Francke eventually succeeded in devising his new process, and by its means treating economically the rich but refractory silver ores, such as those found at the celebrated Huanchaca and Guadalupe mines in Potosi, Bolivia. In this description of the process the writer will endeavor to enter into every possible detail having a practical bearing on the final results; and with this view he commences with the actual separation of the ores at the mines.
Ore Dressing, etc.—This consists simply in the separation of the ore by hand at the mines into different qualities, by women and boys with small hammers, the process being that known as "cobbing" in Cornwall. The object of this separation is twofold: first to separate the rich parts from the poor as they come together in the same lump of ore, otherwise rich pieces might go undetected; and, secondly, to reduce the whole body of ore coming from the mine to such convenient size as permits of its being fed directly into the stamps battery. The reason for this separation not being effected by those mechanical appliances so common in most ore dressing establishments, such as stone breakers or crushing rolls, is simply because the ores are so rich in silver, and frequently of such a brittle nature, that any undue pulverization would certainly result in a great loss of silver, as a large amount would be carried away in the form of fine dust. So much attention is indeed required in this department that it is found requisite to institute strict superintendence in the sorting or cobbing sheds, in order to prevent as far as practicable any improper diminution of the ores. According to the above method, the ores coming from the mine are classified into the four following divisions:
1. Very rich ore, averaging about six per cent. of silver, or containing say 2,000 ounces of silver to the ton (of 2,000 lb.).
2. Rich ore, averaging about one per cent. of silver, or say from 300 to 400 ounces of silver to the ton.
3. Ordinary ore, averaging about 1/2 per cent. of silver, or say from 150 oz. to 200 oz. of silver to the ton.
4. Gangue, or waste rock, thrown on the dump heaps.
The first of these qualities—the very rich ore—is so valuable as to render advantageous its direct export in the raw state to the coast for shipment to Europe. The cost of fuel in Bolivia forms so considerable a charge in smelting operations, that the cost of freight to Europe on very rich silver ores works out at a relatively insignificant figure, when compared with the cost of smelting operations in that country. This rich ore is consequently selected very carefully, and packed up in tough rawhide bags, so as to make small compact parcels some 18 in. to 2 ft. long, and 8 in. to 12 in. thick, each containing about 1 cwt. Two of such bags form a mule load, slung across the animal's back.
The second and third qualities of ore are taken direct to the smelting works; and where these are situated at some distance from the mines, as at Huanchaca and Guadalupe, the transport is effected by means of strong but lightly built iron carts, specially constructed to meet the heavy wear and tear consequent upon the rough mountain roads. These two classes of ores are either treated separately, or mixed together in such proportion as is found by experience to be most suitable for the smelting process.
On its arrival at the reduction works the ore is taken direct to the stamp mill. At the Huanchaca works there are sixty-five heads of stamps, each head weighing about 500 lb., with five heads in each battery, and crushing about 50 cwt. per head per twenty-four hours. The ore is stamped dry, without water, requiring no coffers; this is a decided advantage as regards first cost, owing to the great weight of the coffers, from 2 to 3 tons—a very heavy item when the cost of transport from Europe at about 50l. per ton is considered. As fast as the ore is stamped, it is shoveled out by hand, and thrown upon inclined sieves of forty holes per lineal inch; the stuff which will not pass through the mesh is returned to the stamps.
Dry stamping may be said to be almost a necessity in dealing with these rich silver ores, as with the employment of water there is a great loss of silver, owing to the finer particles being carried away in suspension, and thus getting mixed with the slimes, from which it is exceedingly difficult to recover them, especially in those remote regions where the cost of maintaining large ore-dressing establishments is very heavy. Dry stamping, however, presents many serious drawbacks, some of which could probably be eliminated if they received proper attention. For instance, the very fine dust, which rises in a dense cloud during the operation of stamping, not only settles down on all parts of the machinery, interfering with its proper working, so that some part of the battery is nearly always stopped for repairs, but is also the cause of serious inconvenience to the workmen. At the Huanchaca mines, owing to the presence of galena or sulphide of lead in the ores, this fine dust is of such an injurious character as not unfrequently to cause the death of the workmen; as a precautionary measure they are accustomed to stuff cotton wool into their nostrils. This, however, is only a partial preventive; and the men find the best method of overcoming the evil effect is to return to their homes at intervals of a few weeks, their places being taken by others for the same periods. In dry stamping there is also a considerable loss of silver in the fine particles of rich ore which are carried away as dust and irrevocably lost. To prevent this loss, the writer proposed while at Huanchaca that a chamber should be constructed, into which all the fine dust might be exhausted or blown by a powerful fan or ventilator.
Roasting.—From the stamps the stamped ore is taken in small ore cars to the roasting furnaces, which are double bedded in design, one hearth being built immediately above the other. This type of furnace has proved, after various trials, to be that best suited for the treatment of the Bolivian silver ores, and is stated to have been found the most economical as regards consumption of fuel, and to give the least trouble in labor.
At the Huanchaca mines these furnaces cost about 100l. each, and are capable of roasting from 2 to 21/2 tons of ore in twenty-four hours, the quantity and cost of the fuel consumed being as follows:
Bolivian dollars at 3s. 1d. Tola (a kind of shrub), 3 cwt., at 60 cents. 1.80 Yareta (a resinous moss), 4 cwt., at 80 cents. 3.20 Torba (turf), 10 cwt., at 40 cents. 4.00 —— Bolivian dollars. 9.00, say 28s.
One man can attend to two furnaces, and earns 3s. per shift of twelve hours.
Probably no revolving mechanical furnace is suited to the roasting of these ores, as the operation requires to be carefully and intelligently watched, for it is essential to the success of the Francke process that the ores should not be completely or "dead" roasted, inasmuch as certain salts, prejudicial to the ultimate proper working of the process, are liable to be formed if the roasting be too protracted. These salts are mainly due to the presence of antimony, zinc, lead, and arsenic, all of which are unfavorable to amalgamation.
The ores are roasted with 8 per cent. of salt, or 400 lb. of salt for the charge of 21/2 tons of ore; the salt costs 70 cents, or 2s. 2d. per 100 lb. So roasted the ores are only partially chlorinized, and their complete chlorination is effected subsequently, during the process of amalgamation; the chlorides are thus formed progressively as required, and, in fact, it would almost appear that the success of the process virtually consists in obviating the formation of injurious salts. All the sulphide ores in Bolivia contain sufficient copper to form the quantity of cuprous chloride requisite for the first stages of roasting, in order to render the silver contained in the ore thoroughly amenable to subsequent amalgamation.
Amalgamating.—From the furnaces the roasted ore is taken in ore cars to large hoppers or bins situated immediately behind the grinding and amalgamating vats, locally known as "tinas," into which the ore is run from the bin through a chute fitted with a regulating slide. The tinas or amalgamating vats constitute the prominent feature of the Francke process; they are large wooden vats, shown in Figs. 1 and 2, page 173, from 6 ft. to 10 ft. in diameter and 5 ft. deep, capacious enough to treat about 21/2 tons of ore at a time. Each vat is very strongly constructed, being bound with thick iron hoops. At the bottom it is fitted with copper plates about 3 in. thick, A in Fig. 1; and at intervals round the sides of the vat are fixed copper plates, as shown in Figs. 3 and 4, with ribs on their inner faces, slightly inclined to the horizontal, for promoting a more thorough mixing. It is considered essential to the success of the process that the bottom plates should present a clear rubbing surface of at least 10 square feet.
Within the vat, and working on the top of the copper plates, there is a heavy copper stirrer or muller, B, Figs. 1 and 2, caused to revolve by the shafting, C, at the rate of 45 revolutions per minute. At Huanchaca this stirrer has been made with four projecting radial arms, D D, Figs. 1 and 2; but at Guadalupe it is composed of one single bell-shaped piece, Figs. 3 and 4, without any arms, but with slabs like arms fixed on its underside; and this latter is claimed to be the most effective. The stirrer can be lifted or depressed in the vat at will by means of a worm and screw at the top of the driving shaft, Fig. 3.
The bevel gearing is revolved by shafting connected with pulley wheels and belting, the wheels being 3 ft. and 11/2 ft. in diameter, and 6 in. broad. The driving engine is placed at one end of the building. Each vat requires from 21/2 to 3 horse-power, or in other words, an expenditure of 1 horse-power per ton of ore treated.
At the bottom of the vat, and in front of it, a large wooden stop-cock is fitted, through which the liquid amalgam is drawn off at the end of the process into another shallow-bottomed and smaller vat, Figs. 1 and 2. Directly above this last vat there is a water hose, supplied with a flexible spout, through which a strong stream of water is directed upon the amalgam as it issues from the grinding vat, in order to wash off all impurities.
The following is the mode of working usually employed. The grinding vat or tina is first charged to about one-fifth of its depth with water and from 6 cwt. to 7 cwt. of common salt. The amount of salt required in the process depends naturally on the character of the ore to be treated, as ascertained by actual experiment, and averages from 150 lb. to 300 lb. per ton of ore. Into this brine a jet of steam is then directed, and the stirrer is set to work for about half an hour, until the liquid is in a thoroughly boiling condition, in which state it must be kept until the end of the process.
As soon as the liquid reaches boiling point, the stamped and roasted ore is run into the vat, and at the end of another half-hour about 1 cwt. of mercury is added, further quantities being added as required at different stages of the process. The stirring is kept up continuously for eight to twelve hours, according to the character and richness of the ores. At the end of this time the amalgam is run out through the stop-cock at bottom of the vat, is washed, and is put into hydraulic presses, by means of which the mercury is squeezed out, leaving behind a thick, pulpy mass, composed mainly of silver, and locally termed a "pina," from its resembling in shape the cone of a pine tree. These pinas are then carefully weighed and put into a subliming furnace, Figs. 5 and 6, in order to drive off the rest of the mercury, the silver being subsequently run into bars. About four ounces of mercury are lost for every pound of silver made.
The actual quantities of mercury to be added in the grinding vat, and the times of its addition, are based entirely on practical experience of the process. With ore assaying 150 oz. to 175 oz. of silver to the ton, 75 lb. of mercury are put in at the commencement, another 75 lb. at intervals during the middle of the process, and finally another lot of 75 lb. shortly before the termination. When treating "pacos," or earthy chlorides of silver, assaying only 20 oz. to 30 oz. of silver to the ton, 36 lb. of mercury is added to 21/2 tons of ore at three different stages of the process as just described.
The rationale of the process therefore appears to be that the chlorination of the ores is only partially effected during the roasting, so as to prevent the formation of injurious salts, and is completed in the vats, in which the chloride of copper is formed progressively as required, by the gradual grinding away of the copper by friction between the bottom copper plates and the stirrer; and this chloride subsequently becoming incorporated with the boiling brine is considered to quicken the action of the mercury upon the silver.
Subliming.—The subliming furnace, shown in Figs. 5 and 6, is a plain cylindrical chamber, A, about 4 ft. diameter inside and 41/2 ft. high, lined with firebrick, in the center of which is fixed the upright cast-iron cylinder or retort, C, of 1 ft. diameter, closed at top and open at bottom. The furnace top is closed by a cast-iron lid, which is lifted off for charging the fuel. Round the top of the furnace is a tier of radial outlet holes for the fuel smoke to escape through; and round the bottom is a corresponding tier of inlet air-holes, through which the fuel is continually rabbled with poles by hand. The fuel used is llama dung, costing 80 cents, or 2s. 6d., per 250 lb.; it makes a very excellent fuel for smelting purposes, smouldering and maintaining steadily the low heat required for subliming the mercury from the amalgam. Beneath the furnace is a vault containing a wrought-iron water-tank, B, into which the open mouth of the retort, C, projects downward and is submerged below the water. For charging the retort, the water-tank is placed on a trolly; and standing upright on a stool inside the tank is placed the pina, or conical mass of silver amalgam, which is held together by being built up on a core-bar fitted with a series of horizontal disks. The trolly is then run into the vault, and the water-tank containing the pina is lifted by screw-jacks, so as to raise the pina into the retort, in which position the tank is then supported by a cross-beam. The sublimed mercury is condensed and collected in the water; and on the completion of the process the tank is lowered, and the spongy or porous cone of silver is withdrawn from the retort. The subliming furnaces are ranged in a row, and communicate by lines of rails with the weigh-house.
* * * * *
INTERESTING FACTS ABOUT PLATINUM.
After an excellent day of weakfishing on Barnegat Bay and an exceptionable supper of the good, old fashioned, country tavern kind, a social party of anglers sat about on Uncle Jo Parker's broad porch at Forked River, smoking and enjoying the cool, fragrant breath of the cedar swamp, when somehow the chat drifted to the subject of assaying and refining the precious metals. That was just where one of the party, Mr. D.W. Baker, of Newark, was at home, and in the course of an impromptu lecture he told the party more about the topic under discussion, and especially the platinum branch of it, than they ever knew before.
"Our firm," he said, "practically does all the platinum business of this country, and the demand for the material is so great that we never can get more than we want of it. The principal portion, or, in fact, nearly all of it, comes from the famous mines of the Demidoff family, who have the monopoly of the production in Russia. It is all refined and made into sheets of various thicknesses, and into wire of certain commercial sizes, before it comes to us; but we have frequently to cut, roll, and redraw it to new forms and sizes to meet the demands upon us. At one time it was coined in Russia, but it is no longer applied to that use. We have obtained some very good crude platinum ore from South America and have refined it successfully, but the supply from that source is, as yet, very small. I am not aware that it has been found anywhere else than in Colombia, on that continent, but the explorations thus far made into the mineral resources of South America have been very meager, and it is by no means improbable that platinum may yet be discovered there in quantities rivaling the supply of Russia.
"A popular error respecting platinum is that its intrinsic value is the same as that of gold. At one time it did approximate to gold in value, but never quite reached it, and is now worth only $8 to $12 an ounce, according to the work expended upon it in getting it into required forms and the amount of alloy it contains. The alloy used for it is iridium, which hardens it, and the more iridium it contains the more difficult it is to work, and consequently the more expensive. When pure, platinum is as soft as silver, but by the addition of iridium it becomes the hardest of metals. The great difficulty in manipulating platinum is its excessive resistance to heat. A temperature that will make steel run like water and melt down fireclay has absolutely no effect upon it. You may put a piece of platinum wire no thicker than human hair into a blast furnace where ingots of steel are melting down all around it, and the bit of wire will come out as absolutely unchanged as if it had been in an ice box all the time.
"No means has been discovered for accurately determining the melting temperature of platinum, but it must be enormous. And yet, if you put a bit of lead into the crucible with the platinum, both metals will melt down together at the low temperature that fuses the lead, and if you try to melt lead in a platinum crucible, you will find that as soon as the lead melts the platinum with which it comes into contact also melts and your crucible is destroyed.
"A distinguishing characteristic of platinum is its extreme ductility. A wire can be made from it finer than from any other metal. I have a sample in my pocket, the gauge of which is only one two-thousandth of an inch, and it is practicable to make it thinner. It has even been affirmed that platinum wire has been made so fine as to be invisible to the naked eye, but that I do not state as of my own knowledge. This wire my son made."
Mr. Baker exhibited the sample spoken of. It looked like a tress of silky hair, and had it not been shown upon a piece of black paper could hardly have been seen. He went on:
"The draw plates, by means of which these fine wires are made, are sapphires and rubies. You may fancy for yourselves how extremely delicate must be the work of making holes of such exceeding smallness to accurate gauge, too, in those very hard stones. I get all my draw plates from an old Swiss lady in New York, who makes them herself to order. But, delicate as is the work of boring the holes, there is something still more delicate in the processes that produce such fine wire as this. That something is the filing of a long point on the wire to enable the poking of the end of it through the draw plate so that it can be caught by the nippers. Imagine yourself filing a long, tapering point on the end of a wire only one eighteen-hundredths of an inch in diameter, in order to get it through a draw plate that will bring it down to one two-thousandths. My son does that without using a magnifying glass. I cannot say positively what uses this very thin wire is put to, but something in surgery, I believe, either for fastening together portions of bone or for operations. A newly invented instrument has been described to me, which, if it does what has been affirmed, is one of the greatest and most wonderful discoveries of modern science. A very thin platinum wire loop, brought to incandescence by the current from a battery—which, though of great power, is so small that it hangs from the lapel of the operator's coat—is used instead of a knife for excisions and certain amputations. It sears as it cuts, prevents the loss of blood, and is absolutely painless, which is the most astonishing thing about it.
"Our greatest consumers of platinum are the electricians, particularly the incandescent light companies. I supply the platinum wire for both the Edison and the Maxim companies, and the quantity they require so constantly increases that the demand threatens to exceed the supply of the metal. Sheets of platinum are bought by chemists, who have them converted into crucibles and other forms."
The reporter's curiosity was awakened by Mr. Baker's mention of the old lady who made those very fine draw plates, and on his return to the city he hunted her up. Mrs. Francis A. Jeannot, the lady in question, was found in neat apartments in a handsome flat in West Fifty-first street. Age has silvered her hair, but her eyes are still bright, and her movements indicate elasticity and strength. She is a native of Neufchatel, Switzerland, and speaks English with a little difficulty, but whenever the reporter's English was a little hard for her a very pretty girl with brilliant eyes and crinkly jet-black hair, who subsequently proved to be a daughter of Mrs. Jeannot, came to the rescue. With the girl's occasional aid, the old lady's story was as follows:
"I have been in this business for thirty years. I learned it when I was a girl in Switzerland. Very few in this country know anything correctly about it. Numbers of people endeavor to find it out, and they experiment to learn it, especially to do it by machinery, but without success. But, ah, me! It is no longer a business that is anything worth. Thirty years ago many stone draw plates were wanted, for then there was a great deal done in filigree gold jewelry. Then the plates were worth from $2.50 up to as high as $15, according to the magnitude of the stones and the size of the holes I bored in them. Now, however, all that good time is past. Nobody wants filigree gold jewelry any more, and there is so little demand for fine wire of the precious metals that few draw plates are desired. The prices now are no more than from $1.25 up to say $8, but it is very rare that one is required the cost of which is more than $4. And of that a very large part must go to the lapidary to pay for the stone and for his work in cutting it to an even round disk. Then, what I get for the long and hard work of boring the stone by hand is very little. 'By hand?' Oh, yes. That must always be the only good way. The work of the machine is not perfect. It never produces such good plates as are made by the hand and eye of the trained artisan. 'How are they bored?' Ah, sir, you must excuse me that I do not tell you that. It is simple, but there is just a little of it that is a secret, and that little makes a vast difference between producing work which is good and that which is not. It has cost me no little to learn it, and while it is worth very little just now, perhaps fashion may change, and plates may be wanted to make gold wire again to an extent that may be profitable. I do not wish to tell everybody that which will deprive me of the little advantage my knowledge gives me. 'The stones?' Oh, we of course do not use finely colored ones. They are too valuable. But those that we employ must be genuine sapphires and rubies, sound and without flaws. Here are some. You see they look like only irregular lumps of muddy-tinted broken glass. Here is a finished one."
The old lady exhibited a piece of solid brass about an inch long, three-quarters of an inch in width, and one-sixteenth in thickness. In its center was a small disk of stone with a hole through it, a hole that was very smooth, wide on one side and hardly perceptible on the other. The stone was sunk deep into the brass and bedded firmly in it. She went on:
"You will find, if you try, that you can with difficulty push through that hole a hair from your beard. But, small as it is, it must be perfectly smooth, and of an accurate gauge. I do not any longer myself set the stones in the brass, as I am not so strong as I once was. My son does that for me. But neither he nor my daughter, nor anybody else in this country, I believe, can bore the holes so well as I can even yet. 'How long does a draw plate last?' Ah! Practically forever. Except by clumsy handling or accident, it does not need to be replaced, at least in one lifetime. And there is another reason why I sell so few now. Those who require them are supplied. 'Watch jewels?' Yes, I used to make them, but do so no longer. They can be imported from Europe at the price of $1 a dozen, and at such a figure one could not earn bread in making them here."—Manuf. Gazette.
* * * * *
BAYLE'S LAMP CHIMNEY.
The different types of lamps used in domestic lighting present several imperfections, and daily experience shows too often how difficult it is, even with the most careful and best studied models, to have a perfect combustion of the usual liquids—oil, kerosene, etc.
Mr. P. Bayle has endeavored to remedy this state of things by experiments upon the chimney, inasmuch as he could not think of modifying the arrangements of the lamps of commerce "without injury to man" interests, and encountering material difficulties.
The chimney is not only an apparatus designed to carry off the smoke and gases due to combustion, for its principal role is to break the equilibrium of the atmospheric air, which is the great reservoir of oxygen, and to suck into the flame, through the difference of densities, this indispensable agent to combustion. The lamps which we now use are provided with cylindrical chimneys either with or without a shoulder at the base. The shouldered chimney would be sufficient to suck in the quantity of air necessary for a good combustion if we could at will increase its dimensions in the direction of the diameter or height. But, on account of the fragile nature of the material of which it consists, as also because of the arrangement of the lighting apparatus, we are forced lo give the chimney limited dimensions. The result is an insufficient draught, and consequently an imperfect combustion. It became a question, then, of finding a chimney which, with small dimensions, should have great suctional power. Mr. Bayle has taken advantage of the properties of convergent-divergent ajutages, and of the discovery of Mr. Romilly that a current of gas directed into the axis and toward the small base of a truncated cone, at a definite distance therefrom, has the property of drawing along with it a quantity of air nearly double that which this same current could carry along if it were directed toward a cylinder. In getting up his new chimney, Mr. Bayle has utilized these principles as follows: Round-burner lamps have, as well known, two currents of air—an internal current which traverses the small tube that carries the wick, and an external one which passes under the chimney-holder externally to the wick. In giving the upper part of the chimney, properly so called, the form of a truncated cone whose smaller base is turned toward the internal current of air, that is to say, in directing this current toward the contracted part of the upper cone, at the point where the depression is greatest, a strong suction is brought about, which has the effect of carrying along the air between the wick and glass, and giving it its own velocity. The draught of the two currents having been effected through the conical form of the upper part of the chimney, it remained to regulate the entrance of the external current into the flame. If this current should enter the latter at too sharp an angle, it would carry it toward the mouth of the chimney before the chemical combustion of the carbon and oxygen was finished; and if, on the contrary, it should traverse it at too obtuse an angle, it would depress and contract it. Experience has shown that in the majority of cases the most favorable angle at which the external current of air can be led into the flame varies between 35 deg. and 45 deg.. We say in the majority of cases, for there are exceptions; this depends upon the combustive materials and upon the conditions under which they enter the flame. The annexed figure shows the form adopted by the inventor for oil and kerosene lamps. As may be seen, the chimney consists of two cones, A and B, connected end to end by their small bases. The upper one, A, or divergent cone, is constructed according to a variable angle, but one which, in order to produce its maximum effect, ought not to differ much from 5 deg.. This cone rests upon the convergent one, B, whose angle, as we have said, varies between 35 deg. and 45 deg.. To the large base of this cone there is soldered a cylindrical part, c, designed for fixing the chimney to the holder. The height given the divergent cone is likewise variable, but a very beautiful light is obtained, when it is equal to six times the diameter of the contracted part. When the lamp is designed to be used in a still atmosphere, free from abrupt currents of air, the height may be reduced to four times the diameter of the base, without the light being thereby rendered any the less bright. As for the height to be given the convergent cone, B, that is determined by the opening of the angle according to which it has been constructed. Finally, as a general thing, the diameter of the small base should be equal to half the large base of the convergent cone, B.
The new chimney should be placed upon the holder in such a way that the upper part of the wick tube, D, is a few millimeters beneath the base of the convergent cone. The height to be given the wick varies according to the lamp used. It is regulated so as to obtain a steady and regular combustion. In oil lamps it must project about 11/2 centimeters. If two lamps of the same size be observed, one of which is fitted with the new chimney and the other with the old style, we shall be struck with the difference that exists in the color of the flame as well as in its intensity. While in the case of the cylindrical glass the flame is red and dull, in that of the circuit it is white and very bright. This, however, is not surprising when we reflect upon the theoretical conditions upon which the construction of the new chimney is based—the strong influx of air having the result of causing a more active combustion of the liquid, and consequently of raising to white heat the particles of carbon disseminated through the flame. As it was of interest to ascertain what the increase of illuminating power was in a given lamp provided with the new chimney, Mr. Felix le Blanc undertook some photometric experiments. The trials were made with a Gagneau lamp provided with a chimney of the ordinary shape, and then with one of Mr. Bayle's. The measurements were made after each had been burned half an hour. The light of the standard Carcel lamp being 1, there was obtained with the Gagneau lamp with the ordinary chimney 1.113 carcels, and with the Bayle chimney 1.404 carcels. Thus 1.113:1.404 represents the ratio of the same lamp with the ordinary chimney and with that of Bayle. Whence it follows that the light of the lamp with the old chimney being 1, that with the new one is 1.26, say an increase of about 25 per cent. There is nothing absolute about this figure, however. On kerosene lamps the new chimney, compared with the contracted Prussian one, gives an increase of 40 per cent. in illuminating power, and the oil is burned without odor or smoke.
As it was of interest to see whether this increase in intensity was not due to a greater consumption of oil, a determination was made of the quantity of the latter consumed per hour. The Gagneau lamp, with the old chimney, burned 62.25 grammes per hour, and with the Bayle 63 grammes in the same length of time.
It may be concluded, then, that the increase in light is due to the special form given the chimney. This new burner is applicable to gas lamps as well as to oil and petroleum ones.
The effects obtained by the new chimney may be summed up as follows: increase in illuminating power, as a natural result of a better combustion; suppression of smoke; and a more active combustion, which dries the carbon of the wick and thus facilitates the ascent of the oil. The velocity of the current of air likewise facilitates the action of capillarity by carrying the oil to the top of the wick. Moreover, the great influx of air under the flame continually cools the base of the chimney as well as the wick tube, and the result is that the excess of oil falls limpid and unaltered into the reservoir, and produces none of those gummy deposits that soil the external movements and clog up the conduits through which the oil ascends. Finally, the influx of air produced by this chimney permits of burning, without smoke and without charring the wick, those oils of poor quality that are unfortunately too often met with in commerce.—La Nature.
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MODERN LOCOMOTIVE PRACTICE.
[Footnote: Paper read before the Civil and Mechanical Engineers' Society, April 2, 1884.]
By H. MICHELL WHITLEY, Assoc. M.I.C.E., F.G.S.
A little more than half a century ago, but yet at a period not so far distant as to be beyond the remembrance of many still living, a clear-headed North-countryman, on the banks of the Tyne, was working out, in spite of all opposition, the great problem of adapting the steam engine to railway locomotion. Buoyed up by an almost prophetic confidence in his ultimate triumph over all obstacles, he continued to labor to complete an invention which promised the grandest benefits to mankind. What was thought of Stephenson and his schemes may be judged by the following extracts from the Quarterly Review of 1825, in which the introduction of locomotive traction is condemned in the most pointed manner:
"As to those persons who speculate on making railways general throughout the kingdom, and superseding every other mode of conveyance by land and water, we deem them and their visionary schemes unworthy of notice.... The gross exaggeration of the locomotive steam engine may delude for a time, but must end in the mortification of all concerned.... It is certainly some consolation to those who are to be whirled, at the rate of 18 or 20 miles per hour, by means of a high-pressure engine, to be told that they are in no danger of being sea-sick while on shore, that they are not to be scalded to death or drowned by the bursting of a boiler, and that they need not mind being shot by the shattered fragments, or dashed in pieces by the flying off or breaking of a wheel. But with all these assurances, we would as soon expect the people of Woolwich to suffer themselves to be fired off upon one of Congreve's ricochet rockets, as trust themselves to the mercy of such a machine going at such a rate."
These words, strange and ludicrous as they seem to us, but tersely expressed the general opinion of the day; but fortunately the clear head and the undaunted will persevered, until success was at last attained, and the magnificent railway system of the present, which has revolutionized the world, is the issue. And the results are almost overwhelming in their magnitude. Here, in Great Britain alone, 654,000,000 people travel annually. There are 14,000 locomotives, and the rolling stock would form a train nearly 2,000 miles long; while the number of miles traveled in a year by trains is more than 10,000 times round the world; and the passengers would form a procession 100 abreast, a yard apart, and 3,700 miles long.
These stupendous results have been attained gradually; if we go back to 1848, we find that on the London and Birmingham Railway the number of trains in and out of Euston was forty-four per day. The average weight of the engines was 18 tons, and the gross loads were, for passenger trains 76 tons, and for goods 160. Now, the weight of an express engine and tender is about 65 tons, and gross loads of 250 to 300 tons for an express, and 500 tons for a coal train are not uncommon, while not only have the trains materially increased in weight, owing to the carriage of third-class passengers by all (except a few special) trains, and also to the lowering of fares and consequent more frequent traveling, but the speed, and therefore the duty of the engines, is greatly enhanced. A "Bradshaw's Guide" of thirty-five years ago is now a rare book, but it is very interesting to glance over its pages, and in doing so it will be found that the fastest speed in all cases but one falls far short of that which obtains at present. The following table will show what the alteration has been:
1849. 1884. Speed miles Speed miles per hour. per hour. - - -+ Great Western London to Didcot. 56 " " to Swindon. 53 North-Western Euston to Wolverton. 37 " Northampton to Willesden. 511/2 South-Western Waterloo to Farnborough. 39 " Yeovil to Exeter. 46 Brighton London Bridge to Reigate. 36 " Victoria to Eastbourne. 45 Midland Derby to Masborough. 43 " London to Kettering. 47 North-Eastern York to Darlington. 38 " " 50 Great Eastern London to Broxbourne. 29 " Lincoln to Spalding. 49 Great Northern King's Cross to Grantham. 51 Cheshire Lines Manchester to Liverpool. 51 -+ - -
With this problem then before them, increased weight, increased speed, and increased duty, the locomotive superintendents of our various railways have designed numerous types of engines, of which the author proposes to give a brief account, confining himself entirely to English practice, as foreign practice in addition would open too wide a field for a single paper.
Commencing then with passenger engines for fast traffic, and taking first in order the Great Western Railway, we find that it holds a unique position, as its fast broad gauge trains are worked by the same type of engine as that designed by Sir Daniel Grooch in 1848, although, of course, the bulk of the stock has been rebuilt, almost on the same lines, and rendered substantially new engines. They are single engines of 7 ft. gauge with inside cylinders 18 in. diameter, and 24 in. stroke; the driving-wheels are 8 ft. in diameter, and there are two pairs of leading wheels, and one of trailing, all of 4 ft. 6 in. diameter. The total wheel base is 18 ft. 6 in.; the boiler is 4 ft. 6 in. diameter, and 11 ft. 3 in. long. The grate area is 21 square feet, and the heating surface is, in the fire-box, 153 square feet; tubes, 1,800 square feet; total, 1,953 square feet. The weight in full working order is, on the four leading wheels, 15 ton 18 cwt.; driving wheels, 16 tons; trailing wheels, 9 tons 10 cwt.; total, 41 tons 8 cwt. The tender, which is low-sided and very graceful in appearance, weighs 15 tons 10 cwt., and will hold 2,700 gallons of water.
The boiler pressure is 140 lb. on the square inch, and the tractive power per pound of steam pressure in the cylinders is 81 lb. These engines take the fast trains to the West of England; the Flying Dutchman averages 170 tons gross load, and runs at a mean time-table speed of 53 miles per hour, which allowing for starting, stopping, and slowing down to 25 miles per hour through Didcot gives a speed of nearly 60 miles an hour.
The average consumption of coal per mile, of thirteen of these engines, with the express trains between London and Bristol, during the half-year averaged 24.67 lb. per mile, the lowest being 23.22 lb., and the highest 26.17 lb., the average load being about eight coaches, or 243 tons. We have already seen that in 1849 the Great Western express ran at a higher rate than at present, being an exception to the general rule; and the fastest journey on record was performed at this time by one of these engines, when on May 14, 1848, the Great Britain took this Bristol express, consisting of four coaches and a van, to Didcot, fifty-three miles, in forty-seven minutes, or at the average speed of sixty-eight miles an hour. The maximum running speed was seventy-five miles an hour, and the indicated horse-power 1,000. A class of engines corresponding to this type in their general dimensions, but with 7 ft. coupled wheels, was introduced on the line, but it was not found successful. Through the courtesy of Mr. Dean, I am enabled to give a table showing the running speeds and loads of the principal express trains, broad and narrow gauge, to the West and North of England, run on the Great Western Railway.
Great Western Railway.—Average Speed and Weight of Express Trains.
- Speed to first stopping station. Weight of train. - - - - - Average Train. speed Engine Carriages miles per and and vans, Station Distance hour. tender. empty. Total - - - - - miles tons. tons. BROAD GAUGE TO WEST OF ENGLAND: 9.0 Paddington to Reading 36 47 67 149 216 Plymouth 11.45 do. Swindon 771/4 53 67 104 171 NARROW GAUGE TO THE NORTH 10.0 Paddington to Reading 36 39.2 60 190 250 Birkenhead 4.45 do. Oxford 631/2 48.8 60 129 189 - - - - -
The narrow gauge trains are worked by two classes of engines. The first is a single engine with inside cylinders 18 in. diameter, 24 in. stroke. The driving wheels are 7 ft. diameter, and the leading and trailing wheels 4 ft. The frames are double, giving outside bearings to the leading and trailing axles, and outside and inside bearings to the driving axle; this arrangement gives a very steady running engine, and insures, as far as can possibly be done, safety in case of the fracture of a crank axle. The frames are 15 inches deep, of BB Staffordshire iron. The wheel base is, leading to driving wheels, 8 ft. 6 in; driving to trailing wheels, 9 ft.; total, 17 ft. 6 in. The boiler is of Lowmoor iron, 10 ft. 6 in. long and 4 ft. 2 in. outside diameter. The grate area is 17 square feet, and the heating surface is, tubes, 1,1451/2 square feet; fire-box 133 square feet; total, 1,2781/2 square feet. The boiler pressure is 140 lb. on the square inch, and the tractive power per lb. of mean pressure in cylinders, 92 lb. The weight in full working order is, engine, leading wheel, 10 tons; ditto driving wheels, 14 tons; ditto trailing wheels, 9 tons 10 cwt.; tender, with 40 cwt. coal and 2,600 gals. water, 26 tons 10 cwt.; total, 60 tons. These engines are extremely simple, but well proportioned, and are a very handsome type, and their average consumption of coal, working trains averaging ten coaches, is about 24.87 lb. per mile. The standard coupled passenger express engine on the narrow gauge has inside cylinders 17 in. diameter and 24 in. stroke; the coupled wheels are 6 ft. 6 in. diameter, and the leading wheels 4 ft.; the wheel base is 16 ft. 9 in. The frames are double, giving outside bearings to the leading axle, and inside bearings to the coupled wheels. The boiler is 11 ft. long by 4 ft. 2 in. diameter; the grate area is 16.25 square feet; and the heating surface is, tubes, 1,216.5 square feet; fire-box, 97.0 square feet; total, 1,313.5 square feet. The boiler pressure is 140 lb., and the tractive power per lb. of steam pressure in the cylinders, 88 lb. The weight in full working order is on the leading wheels, 10 tons 5 cwt.; driving wheels, 11 tons; trailing wheels, 9 tons 15 cwt.; total, 31 tons.
Turning now to the London and North-Western Railway, we find that between 1862 and 1865 the express trains were worked with a handsome type of engines, known as the "Lady of the Lake" class. They have outside cylinders 16 in. diameter and 24 in. stroke, with single driving wheels of 7 ft. 6 in. diameter, and leading and trailing wheels 3 ft. 6 in. diameter, with a total wheel base of 15 ft. 5 in. The frames are single, with inside bearings to all the wheels. The boiler is 11 ft. long and 4 ft. diameter, and the heating surface is in the tubes, 1,013 feet; fire-box, 85 ft.; total, 1,098 feet. The tractive power per lb. of steam pressure in the cylinders is 68 lb. The weight in full working order is on the leading wheels, 9 tons 8 cwt.; driving wheels, 11 tons 10 cwt.; trailing wheels, 6 tons 2 cwt.; total, 27 tons. The tender weighs 171/2 tons in working order. These engines burn about 27 lb. of coal per mile with trains of the gross weight of 117 tons, which is not at all an economical duty. About 1872, the weight of the heavier express trains on the North-Western had so increased, that a new standard type for this service was designed, and is now the standard passenger engine; it has inside cylinders 17 in. diameter and 24 in. stroke; the driving and trailing wheels are coupled, and are 6 ft. 6 in. diameter, and the leading wheels 3 ft. 6 in. The frames of steel are single, with inside bearings to all the wheels, and the boiler, of steel, is 9 ft. 10 in. long and 4 ft. 2 in. diameter. The steel used has a tensile strength of 32 to 34 tons per square inch, all the rivets are put in by hydraulic pressure, and the magnetic oxide on the surface of the plates where they overlap is washed off by a little weak sal-ammoniac and water. In testing, steam is first got up to 30 lb. on the square inch, the boiler is then allowed to cool, it is then proved to 200 lb. with hydraulic pressure, and afterward to 160 lb. with steam. The fire-box is of copper, fitted with a fire brick arch for coal burning, and the grate area is 15 square feet. The heating surface is, in the tubes, 1,013 square feet; fire-box, 89 square feet; total, 1,102 square feet. The wheel base is 15 ft. 8 in., and the tractive power 88 lb. for each lb. of steam pressure in the cylinders. These engines, working the fast passenger trains at a speed of about 45 miles per hour, burn about 35 lb. of coal per mile, when taking trains weighing about 230 tons gross. A variation from this type has been adopted on the Northern and Welsh sections, known as the "Precursor" class. These engines have 5 ft. 6 in. coupled wheels, and weigh 31 tons 8 cwt. in working order, but in other respects are very similar to the standard engines just described; with the Scotch express, averaging in total weight 187 tons, between Crewe and Carlisle, over heavy gradients, they burn 33 lb. of coal per mile. These engines, although much more powerful than the standard type, are not nearly of so handsome an appearance, the drivers seeming much too small for the boiler under which they are placed. But by far the boldest innovation on existing practice is the new class of compound locomotives now being introduced by Mr. Webb. It is a six wheel engine, with leading wheels 4 ft. diameter, and two pairs of drivers, 6 ft. 6 in. diameter. The trailing drivers are driven by a pair of outside cylinders, 18 in. diameter and 24 in. stroke; and the leading drivers by a single low-pressure cylinder—which takes the exhaust steam from the high-pressure cylinders—of 26 in. diameter and 24 in. stroke, placed under the center of the smoke-box. The boiler is the same as that in the standard type of engine, but the wheel base is 17 ft. 7 in., and in order to allow it to traverse curves easily, the front axle is fitted with a radial axle-box, which is in one casting from journal to journal, and fitted at each end with brass steps for the bearings; the box is radial, struck from the center of the rigid wheel base, and the horn plates are curved to suit the box, the lateral motion being controlled by strong springs. Another peculiarity of this engine is that, instead of the ordinary link motion, it is fitted with Joy's valve gear, which is now being more and more adopted. This gear—which is of a most ingenious decription—dispenses altogether with eccentrics, and so allows the inside bearings to be much increased, those on these engines being 131/2 in. long; and it is also claimed for it that it is simpler and less costly, weighs less, and is more correct in its action than the ordinary link motion; the friction is less, the working parts are simplified, it takes less oil, and is well under the driver's eye. It also allows larger cylinders to be got in between the frames of inside cylinder engines, as, the slide valves may be placed on the top or bottom of the cylinders. This latter advantage is a great one, as, with the ordinary link motion, large cylinders are exceedingly difficult to design so as to get the requisite clear exhaust. The action of the gear is as follows: A rod, a, is fixed by a pin at b, on which it is free to turn, and is attached to a rod, c, at d, the other end of which link is fastened to the connecting rod at e. At the point, f, in this rod another lever, g, is connected to it, the upper end of which is coupled to the valve rod, h, at i, and just below this point a second connection is made to a block at j, sliding in a short curved piece, k. The inclination of the block, k, governs the travel of the valve. The total weight of the engine in working order is: On the leading wheels, 10 tons 8 cwt.; front drivers, 14 tons 4 cwt.; rear drivers, 13 tons 10 cwt.; total, 37.75 tons. The tender weighs 25 tons in full working order. The boiler pressure is 150 lb., and the usual point of cut-off in the high pressure cylinders, when running at speed, is half-stroke, while the pressure of steam admitted to the large cylinder is never to exceed 75 lb. per square inch. The average consumption of coal between London and Crewe is 26.6 lb. per train mile, or about 8 lb. per mile less than the standard coupled engine. In an experiment made in October, 1883, one of these engines took the Scotch express from Euston to Carlisle at an average speed, between stations, of 44 miles an hour, the engine, tender, and train weighing 230 tons, with a consumption of 291/2 lb. of coal per mile, and an evaporation of 8.5 lb. of water per pound of fuel.
Mr. Webb's object, in designing this engine was to secure in the first place a greater economy of fuel, and secondly, to do away with coupling rods, while at the same time obtaining greater adhesion, with the freedom of a single engine. The cost is much more than an ordinary locomotive, but the saving in fuel is said to be 20 per cent. over the other engines of the North Western Rail way. These engines run very sweetly, and are said to steam freely, although with only half the usual number of blasts; but from the small size of the high pressure cylinders, they are liable to slip when starting heavy trains, as the low pressure cylinders are not then effective, while the consumption of coal does not seem to show the saving that would have been expected, when compared with ordinary engines doing similar duty on other lines; for instance, the Great Northern single engine takes trains of the same weight with the same consumption of coal and at a somewhat higher speed. But it must, of course, be borne in mind in making such a comparison, that the fuel used may not be of the same quality.
Mr. Stirling, of the Great Northern, has adopted an entirely different type of engine to those last described. Holding strongly that single engines are more economical not only in running, but in repairs, and that cylinder power is generally inadequate to the adhesion, he has designed his magnificent well-known class of express engines. They have single driving wheels 8 ft. in diameter, with a four-wheel bogie in front and a pair of trailing wheels, 4 ft. diameter, behind. The frames are single, and inside of one solid piece; the cylinders are outside 18 in. diameter and 28 in. stroke; and the valve gear is of the usual shifting link description. The boiler is of Yorkshire plates, 11 ft. 5 in. long and 4 ft. diameter, and the steam pressure is 140 lb.; while the tractive power per lb. of steam in the cylinders is 94 lb. The fire-box is of copper, and the roof is stayed to the outer shell by wrought iron radiating stays screwed into both; a sloping mid-feather is placed in the fire-box.
The tubes, 217 in number, are of brass, 1-9/16 in. diameter; and the heating surface is in the tubes, 1,043 square feet; fire-box, 122 square feet; total, 1,165 square feet. The fire-grate area is 17.6 square feet. The wheel base from the center of the bogie pin to the trailing axle is 19 ft. 5 in., and the weight in working order is, on the bogie wheels, 15 tons; driving wheels, 15 tons; trailing wheels, 8 tons; total, 38 tons. The tender weighs 27 tons. These engines are remarkable for their efficiency; the traffic of the Great Northern Railway is exceedingly heavy, and the trains run at a high rate, the average speed of the Flying Scotchman being fifty miles an hour, and no train in the kingdom keeps better time. "Those who remember this express at York in the icy winter of 1879-80, when the few travelers who did not remain thawing themselves at the waiting-room fires used to stamp up and down a sawdusted platform, under a darkened roof, while day after day the train came gliding in from Grantham with couplings like wool, icicles pendent from the carriage eaves, and an air of punctual unconcern; or those who have known some of our other equally sterling trains—these will hardly mind if friendship does let them drift into exaggeration when speaking of expresses." The author well remembers how, when living some years ago at Newcastle-on-Tyne, it was often his custom to stroll on the platform of the Central Station to watch the arrival of the Flying Scotchman, and as the hands of the station clock marked seven minutes past four he would turn around, and in nine cases out of ten the express was gliding into the station, punctual to the minute after its run of 272 miles. Such results speak for themselves, and for the power of the engines employed, and one of the best runs on record was that of the special train, drawn by one of these locomotives, which in 1880 took the Lord Mayor of London, to Scarborough. The train consisted of six Great Northern coaches, and ran the 188 miles to York in 217 minutes, including a stop of ten minutes at Grantham, or at the average rate of 541/2 miles an hour. The speed from Grantham to York, 821/2 miles, with three slowing downs at Retford, Doncaster, and Selby, averaged 57 miles an hour, and the 59 miles from Claypole, near Newark, to Selby, were run in 601/2 minutes, and for 221/2 consecutive miles the speed was 64 miles an hour. In ordinary working these engines convey trains of sixteen to twenty-six coaches from King's-Cross with ease, and often twenty-eight are taken and time kept. Considering that the Great Northern main line rises almost continuously to Potter's Bar, 13 miles, with gradients varying from 1 in 105 to 1 in 200, this is a very high duty, while, with regard to speed, they have run with sixteen coaches for 15 miles at the rate of 75 miles an hour. Their consumption of coal with trains averaging sixteen ten ton carriages is 27 lb. per mile, or 8 lb. per mile less than the standard coupled engine of the North-Western with similar loads. Mr. Stirling's view, that the larger the wheel the better the adhesion, seems borne out of these facts; thus to take twenty-eight coaches, or a gross load of 345 tons, up 1 in 200 at a speed of 35 miles an hour, would require an adhesive force of 8,970 lb., or 600 lb. per ton—more than a quarter the weight on the driving wheels. These engines are magnificent samples of the most powerful express engines of the present day. |
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