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The cement mixture or slurry, instead of being burnt in lumps, is passed between rollers or any suitable mill, when, it readily falls into coarse dry powder, which powder is thence conveyed by an elevator and fed into the revolving furnace by means of a hopper and pipe, which, being set at an angle with the horizon, as it turns gradually conveys the cement material in a tortuous path toward the lower and hotter end, where it is discharged properly calcined. The material having been fed into the upper end of the cylinder falls through the flame to the lower side of it; the cylinder being in motion lifts it on its advancing side, where it rests against one of its projecting fins or ledges until it has reached such an angle that it shoots off in a shower through the flame and falls once more on the lower side. This again causes it to travel in a similar path, and every rotation of the cylinder produces a like effect, so that by the time it arrives at the lower and hotter end it has pursued a roughly helical path, during which it has been constantly lifted and shot through the flame, occupying about half an hour in its transit.
To some who have been accustomed to the more tedious process of kiln burning, the time thus occupied may appear insufficient to effect the combinations necessary to produce the required result; but it will be seen that the conditions here attained are, in fact, those best suited to carry out effectively the chemical changes necessary for the production of cement. The raw material being in powder offers every facility for the speedy liberation of water and carbonic acid, the operation being greatly hastened by the velocity of the furnace gases through which the particles pass. That such is practically the case is shown by the following analysis of cement so burnt in the revolving furnace or cylinder:
Per cent. Carbonic acid, anhydrous 0.4 Sulphuric acid, anhydrous 0.26 Silica soluble 24.68 Silica insoluble 0.6 Alumina and oxide of iron 10.56 Lime 61.48 Magnesia, water, and alkalies 2.02 ——— 100
Again, fineness of the particles results in their being speedily heated to a uniform temperature, so that they do not serve as nuclei for the condensation of the moisture existing in the furnace gas. The calcined material, on reaching the lower end of the furnace, is discharged on to the floor or on to a suitable "conveyer," and removed to a convenient locality for cooling and subsequent grinding or finishing. It, however, is not in the condition of hard, heavy clinkers, such as are produced in the ordinary cement kiln, which require special machinery for breaking up into smaller pieces before being admitted between the millstones for the final process of grinding; nor does it consist of an overburnt exterior and an underburnt core or center portion; but it issues from the cylindrical furnace in a condition resembling in appearance coarse gunpowder, with occasional agglutinations of small friable particles readily reduced to fine powder in an ordinary mill, requiring but small power to work, and producing but little wear and tear upon the millstones. The operation is continuous. The revolver or furnace, once started, works on night and day, receiving the adjusted quantity of powdered material at the upper or feed end, and delivering its equivalent in properly burnt cement at the opposite end, thus effecting a great saving of time, and preventing the enormous waste of heat and serious injury to the brickwork, etc., incidental to the cooling down, withdrawing the charge, and reloading the ordinary kiln.
Cement, when taken from the furnace, weighed 110 lb. per bushel. Cement, when ground, leaving 10 percent. on sieve with 2,500 holes to the inch, weighed 121 lb. per bushel, and when cold 118 lb. per bushel. When made into briquettes, the tensile breaking strain upon the square inch:
At 4 days was 410 lb. per square inch. At 6 days " 610 " " " " At 14 days " 810 " " " " At 49 days " 900 " " " " At 76 days " 1,040 " " " "
A cylindrical furnace, such as the author has described, is capable of turning out at least 20 tons of good cement per day of twenty-four hours, with a consumption of about 3 tons of slack coal. It will be readily understood that these furnaces can be worked more economically in pairs than singly, as they can be so arranged that one producer may furnish a sufficient quantity of gas for the supply of two cylinders, and the same labor will suffice; but in order to provide for possible contingencies the author advises that a spare gas producer and an extra furnace should be in readiness, so that by a simple arrangement of valves, etc., two cylinders may always be in operation, while from any cause one may be undergoing temporary repairs, and by this means any diminution in the output may be avoided.
The author considers it unnecessary here to discuss either the advantages or the economy of fuel effected by the employment of gas producers for such a purpose. These have been abundantly proved in steel and glass making industries, where a saving of from 50 to 70 per cent. of the fuel formerly employed has been made. Their cost is small, they occupy little room, they can be placed at any reasonable distance from the place where the gas is to be burnt; any laborer can shovel the slack into them, and they do not require constant skilled supervision. It is claimed by the author of this paper that the following are among the many advantages derivable from the adoption of this method of manufacturing Portland cement, as compared with the old system:
(1) Economy of space—the furnaces, with their appurtenances, requiring only about one-fourth the space of what would be occupied by the ordinary kilns for producing the same quantity of finished cement.
(2) Continuous working, and consequent economy of fuel lost by cooling and subsequent reheating of the kiln walls.
(3) Economy of repairs, which are of a simple and comparatively inexpensive character, and of much less frequent occurrence, as the continuous heat avoids the racking occasioned by the alternate heating and cooling.
(4) Economy in first cost.
(5) Economy in grinding, a friable granular substance being produced instead of a hard clinker, whereby crushers are quite abolished, and the wear and tear of millstones greatly reduced.
(6) Economy of labor, the conveyance to and removal from, the revolving furnace being conducted automatically by mechanical elevators and conveyers.
(7) Improved quality of the cement, from non-mixture with fuel, ash, or other impurities, and no overburning or underburning of the material.
(8) Thorough control, from the facility of increasing or diminishing the flow of crushed slurry and of regulating the heat in the furnace as desirable.
(9) Absence of smoke and deleterious gases.
It is well known that in some localities the materials from which Portland cement is made are of such a powdery character that they have to be combined or moulded into balls or bricks previous to calcination in the ordinary way, thus entailing expense which would be entirely obviated by the adoption of the patent revolving furnace, as has been proved by the author in producing excellent cement with a mixture of slag sand from the blast furnaces of the Cleveland iron district, with a proper proportion of chalk or limestone, which, in consequence of the friable nature of the compound, he was unable to burn in the ordinary cement kiln, but which, when burnt in the revolving furnace, gave the most satisfactory results. The cement so made possessed extraordinary strength and hardness, and it has been a matter of surprise that iron masters and others have not adopted such a means of converting a waste material—which at the present time entails upon its producers constant heavy outlay for its removal—into a remunerative branch of industry by the expenditure of a comparatively small amount of capital. The demand for Portland cement has increased and is still increasing at a rapid ratio. It is being manufactured upon a gigantic scale.
Great interests are involved; large sums of money are being expended in the erection and maintenance of expensive plant for its production; and the author submits that the development of any method which will improve the quality and at the same time reduce the cost of manufacture of this valuable material will tend to increase the prosperity of one of our great national industries, and stimulate commercial enterprise. Works are in progress for manufacturing cement by this improved process, and the author trusts the time is not far distant when the unsightly structures which now disfigure the banks of some of our rivers will be abolished—the present cement kilns, like the windmills once such a common feature of our country, being regarded as curiosities of the past, and cement manufacturers cease to be complained of as causing nuisances to their neighbors.
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MIX AND GENEST'S MICROPHONE TELEPHONE.
We illustrate in the annexed engraving the microphone-telephone constructed by Messrs. Mix & Genest, of Berlin, which, after extended trials, has been adopted in preference to others by the imperial postal department of Germany. There are now more than 5,000 of these instruments in use, and we need scarcely mention that the invention has been patented in many countries.
In some microphones a rattling noise is frequently occasioned, which borne along with the sound of the human voice causes an audible disturbance in the telephone. The chief cause of these disturbances may be ascribed to the fact that the carbon rollers in their journals, rest loose in the flutings of the beam, which is fastened to the sound plate. Owing to the shocks given to the entire apparatus, and independent of the oscillations of the sound plate, they are set in motion and roll to and fro in their bearings.
In microphones in which the sound plates are arranged vertically (as shown in Fig. 2), these disturbances assume such a character that there is no possibility of understanding the speaker, for in this case the horizontally directed oscillations of the sound plate, m, cause themselves a backward and forward motion on the part of the carbon rollers without increasing or decreasing at the same time the lying-on pressure of the roller journals, and by doing so bring the places of contact one on the other, and thus occasion a conducting resistance of greater or less force. This circumstance serves as an explanation of the reason why the sound plates in Ader's microphones are not arranged vertically, although this way of arranging them offers many advantages over a horizontal or slightly inclined arrangement of the sound plates. Speaking is more convenient in the vertical arrangement, and moreover the plates can be fitted on to instruments better in this way.
All the drawbacks just enumerated and found in Ader's microphones are avoided in the apparatus made by Messrs. Mix & Genest. A sort of braking contrivance operates on the carbon rollers in such a way as to prevent their journals from lying on the lower points in the flutings of the beams. Thus, for instance, if in a microphone with a horizontal sound plate, as illustrated in Fig. 3, the carbon rollers are pressed upward by outward force, it is evident that only a very trifling rolling and disturbing motion can occur, and only small pieces of carbon can be knocked off, which would act injuriously as a secondary contact. The same may be said of the journals of microphones with vertical sound plates, as represented in Fig. 2, when the carbon rollers are pressed in the direction of the arrow, p, that is to say, against the sound plate. In this case the journals, a, are fixed in the flutings of the beams, b, in a direction given them by the power and gravity operating on them, which is clearly represented in the accompanying design, Fig. 2.
In all such cases the regulating contrivance applied to brake the carbon rollers in their motion has the result that only the oscillations transmitted from the sound plate on to the contacts come in operation, whereas disturbing mechanical shocks resulting from any outward influences occasion very insignificant vibrations, which are not perceptible in the telephone. The separate contacts thus form a firm system with the sound plate, so that the former are influenced in their motions and effects solely and alone by the shocks and oscillations which operate direct on these sound plates. The roller motion of the carbon is thus removed, and the distinctness of the words spoken is greatly augmented.
The above Figs. 1 and 2 show the microphone in side view and in cross section.
A metal ring, R (see Fig. 1), is fastened by means of the four screws, _r_{1}_ _r_{2}_ _r_{3}_ _r_{4}_, on a wooden mouthpiece. In a recess of the above ring is the diaphragm, M, which is provided on its outer edge with an India rubber band and is held in position by the two clamps, _a_ and _a_{1}_. The diaphragm is cut out of finely fibered firwood and is well lacquered to preserve it against dampness. On it there are two carbon beams, _b_, and in the perforations of the latter are the journals of the carbon rollers, _k_. The alterations in contact take place in the touching points. The cross piece, _f_, that runs straight across the carbon rollers serves as a braking contrivance, which is regulated as may be necessary by the large projecting screws.
Fig. 3 shows the apparatus in cross section. T is the mouth piece, R the metal ring, M the diaphragm, f the breaking cross piece. On the latter is a metal block fastened by means of two screws. On this metal block is a soft elastic strip (d) of felt or similar material. The letters s and s indicate the regulating screws for the braking contrivance.
The excellent qualities of other microphones, in particular their extreme sensibility for the very least impressions, are undeniable; but it is just this sensibility that is the cause of the complaints made by the public. In practical use this overgreat sensibility proves to be a fault.
In the apparatus constructed by Messrs. Mix and Genest the well-known deficiencies of other systems are avoided. The effect of the sound and the distinctness of the human voice are clearer and far more intelligible. One simple regulation of the microphone suffices for the installation, for there is no danger of its getting out of order. Owing to its peculiar construction, this new microphone is very firm and solid, and for this very reason offers another advantage, namely, the possibility of transmitting sound over very long distances. In the competitive trials instituted by order of the imperial postal department, apparatus of various systems and constructions were subjected to tests, and the apparatus we are speaking of showed the favorable results just mentioned. This microphone has overcome in particular the difficulties connected with the using of combined lines above and below ground, and with the aid of it the excellent telephonic communication is carried on in Berlin, in which city the telephone net is most extensive and complicated. At the same time this microphone transmits the sound over long distances (up to 200 kilom. even) in the most satisfactory manner. Another peculiar advantage of this construction is that it exercises a very small inductive effect on cables and free lines, and consequently the simultaneous speaking on parallel lines causes but little disturbance.
After repeated trials made by the German imperial postal department with the microphones constructed by Messrs. Mix and Genest, these apparatus have been introduced in the place of the telephones and Bell-Blake microphones hitherto used in the telephone service. At present we understand there are about 8,000 of these apparatus in use.
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ELECTROLYSIS AND REFINING OF SUGAR.
Mr. G. Fahrig, of Eccles, Lancashire, has invented a new process of refining sugar through electrolysis. The brown sugar is decolorized by means of ozone produced by electric currents of high tension from a dynamo. The electrodes consist of metal grills covered with platinum or some other inoxidizable metal, and are placed in a vat with the intervention of perforated earthenware plates. After being ground and dried in hot air, the crude sugar is placed between the plate and the grills, and the discharges passing between the electrodes produce ozone, which separates the sugar from the coloring matter. To purify the sugar still further, Mr. Fahrig dries it and places it in another vat, with carbon or platinum conducting plates separated by a porous partition. The sugar is placed on one side of this partition, and water circulates on the other side.
The current from a dynamo of feeble tension is sent through the vat between the plates. The water carries along the impurities separated by the current, and the sugar is further whitened and refined.
The accompanying figure shows a series of four vats arranged one above another, in order to permit the water to circulate. Here i and h represent the plates connected with the poles of the dynamo through the conductors, f and g; m represents the porous partition; L, the spaces filled with sugar; and l, the compartments in which the water circulates.—La Lumiere Electrique.
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[THE ELECTRICIAN.]
A CURRENT METER.
We give a description of a meter we made in June, 1883. You will find a cross section of the meter and also a printed dial we had made at the time. We called it an ampere register, but no doubt we would give it a better name to-day. The meter consisted of a glass tube, c, both ends of which were fitted into two bent pieces of piping, D and F, as shown. Through these bent tubes, D and F, passed the wires, a and b, which were connected to the binding posts, A and B. The part of the wire where it passed into the tubes was well insulated. At the ends, a' and b', was connected the coil, R, which consisted simply of a few turns of copper wire whose diameter was less than the leading wires, a and b. To the tube, D, was attached a square tube, E, which had a little opening at the top so as to permit a small undershot wheel, I, to revolve freely. This undershot wheel was well pivoted and constructed very light. To the axis of this wheel was connected another system of wheels with indicators, as shown, J. Now the tubes, E and F, were connected to a reservoir, G. This reservoir consisted of a square tank, in the inside of which were soldered in an alternating manner square sheets of copper as shown in the drawing, g g' g'' g''' ... These sheets acted as diffusers. These plates or sheets presented a very large surface. On the outside of the tank, G, were also diffusers, h h' ... arranged all round and presenting an appearance as if two books were open so as to form a square with their covers, the leaves being the diffusers. The diffusers on the outside were at right angles to those inside.
The action of the meter was thus: When a current passes through the coil, R, it heats the liquid at the place, thus causing a circulation, the warm liquid ascending while the cold liquid descends as shown by the arrows. This circulation causes the undershot wheel to revolve, and its revolutions are registered by the clockwork. The stronger the current, the more the heat, and thus the more rapid the circulation. The warm liquid once in the tank, which is of a reasonable size, will impart its heat to all the diffusers. The surface of the glass tube, etc., is very small in comparison to the surface of the tank. It will be seen that the function of this apparatus is independent of the outward temperature, for the motion of the liquid is due only to that heat which is generated by the current. When the current does not pass, it is evident that the liquid, at whatever temperature it may be, does not circulate, as all parts are of the same temperature; but the moment the current passes, a difference is produced, which causes a circulation in proportion to the current. We may mention that we tried various liquids, and give preference to pure olive oil. It will also be seen that this meter is good for alternating currents. In conclusion, we may remark that the tests we made gave satisfaction, and we wanted to publish them, but that Mr. Jehl was called away to fit up the Edison exhibit in the Vienna exhibition for the Societe Electrique Edison of Paris. After the exhibition we began our work upon our disk machine, and had almost forgotten our meter. The whole apparatus is mounted on a base, K.
JEHL AND RUPP. Bruenn, Sept. 26, 1887.
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STORAGE BATTERIES FOR ELECTRIC LOCOMOTION.[1]
[Footnote 1: From a paper read before the National Electric Light Association, New York, August, 1887.]
By A. RECKENZAUN.
The idea of employing secondary batteries for propelling vehicles is almost contemporaneous with the discovery of this method of storing energy. To Mr. Plante, more than to any other investigator, much of our knowledge in this branch of electrical science is due. He was the first to take advantage of the action of secondary currents in voltaic batteries. Plante is a scientist of the first grade, and he is a wonderfully exact experimenter. He examined the whole question of polarization of electrodes, using all kinds of metal as electrodes and many different liquids as electrolytes, and during his endless researches he found that the greatest useful effect was produced when dilute sulphuric acid was electrolyzed between electrodes of metallic lead.
A set of Plante's original cells was exhibited for the first time in March, 1860, before the Paris Academy of Sciences. Scientists admired and praised it, but the general public knew nothing of this great discovery thus brought to notice. Indeed, at that period little commercial value could be attached to such apparatus, since the accumulator had to be charged by means of primary batteries, and it was then well known that electrical energy, when produced by chemical means in voltaic cells, was far too expensive for any purpose outside the physical laboratory or the telegraph office.
It was twenty years after this exhibition at the Academy of Sciences in Paris that public attention was drawn to the importance of storage batteries, and that Mr. Faure conceived the idea of constructing plates consisting of lead and oxides of lead. At that time the advantages accruing through a system of electrical storage could be fully appreciated, since electrical energy was already being produced by mechanical means through the medium of dynamo-electric machines.
It was the dynamo machine which created the demand for the storage battery, and the latter was introduced anew to the public at large and to the capitalist with great pomp and enthusiasm. One of Faure's accumulators was sent to Sir William Thomson, and this eminent scientist in the course of experiments ascertained that a single cell, weighing 165 lb., can store two million foot-pounds of energy, or one horse power for one hour, and that the loss of energy in charging did not exceed 15 per cent. These results appeared highly encouraging. There we had a method of storing that could give out the greater part of the energy put in. The immense development which the electric transmission of energy was even at that early day expected to undergo pointed to the fact that a convenient method of receiving large quantities of transmitted energy, and of holding it in readiness until wanted, must be of the highest importance. Numerous applications of the Faure battery were at once suggested, and the public jumped to the conclusion that a thing for which so many uses could be instantly found must necessarily be a profitable investment, and plenty of money was provided forthwith, not with the idea of commencing careful experiments and developing the then crude invention, which would have been the correct thing, but for manufacturing tons of accumulators in their first and immature form.
I need not describe the disappointments which followed the first unfulfilled hopes, nor repeat the criticism that was heaped upon the heads of the early promoters. Those early hopes were untimely and unreasonable. A thousand difficulties had to be overcome—scientific difficulties and manufacturing difficulties. This invention, like most others, had to go through steady historical developments and evolution, and follow the recognized laws of nature, which are against abnormal and instantaneous maturity. The period of maturity has also been retarded by injudicious treatment, but the ultimate success was inevitable. Great advances have been made within the last few years, and I propose now to offer a few facts and figures relating to the present state of the subject with reference to the application of storage batteries to locomotive purposes. It is not within the province of this paper to discuss all the different inventions of secondary batteries nor to offer any suggestions with regard to priority, therefore I will confine myself to general statements. I am aware of the good work that was done in the United States by Kirchhoff twenty-six years ago, and of the more recent work of Mr. Brush, of Cleveland, Mr. Julien and others, but I am more particularly acquainted with the recent achievements of the Electrical Accumulator Company, who own the rights of the Electrical Power Storage Company, of London. I have used the batteries of the latter company for propelling electric boats and electric street cars. The first of the boats was the Electricity, which was launched in September, 1882, and which attained a speed of seven miles an hour for six consecutive hours. Since then a dozen electric boats of various sizes have been fitted up and worked successfully by means of storage batteries and motors of my design. The most important of these were the launch Volta and another similar craft, which is used by the Italian government for torpedo work in the harbor of Spezia. On the measured mile trial trips the Italian launch gave an average speed of 8.43 miles an hour with and against the tide. The hull of this vessel was built by Messrs. Yarrow & Co., and the motors were manufactured by Messrs. Stephens, Smith & Co., of London. The Volta, which was entirely fitted by the latter firm, is 37 feet long and 7 feet beam. She draws 2'6" of water when carrying 40 persons, for whom there is ample sitting accommodation. There are 64 cells in this boat. These are placed as ballast under the floor, and actuate a pair of motors and a screw coupled direct to the armature shaft running at 700 revolutions a minute. We crossed the English Channel with this boat in September of last year, leaving Dover at 10:40 in the morning, arriving at Calais at 2:30 P.M.; stayed about an hour in the French harbor for luncheon and floated into Dover docks the same evening, at 6:30, with full speed. The actual distance traversed without entirely discharging the cells was 54 miles. The current remained constant at 28 amperes until 5 P.M., and it only dropped to 25 amperes at the completion of the double voyage between England and France. Several electric launches are now being constructed in London, and one in New York by the Electrical Accumulator Company.
M. Trouve exhibited a small boat and a tricycle, both worked by Plante accumulators, at Paris, in 1881.
The first locomotive actuated by storage batteries was used at a bleaching works in France in 1882. During the same year I designed an electric street car for the storage company, and this was tried on the lines of the West Metropolitan Tramways in March, 1883. It had accommodation for 46 passengers. This car had many defects, and I reconstructed it entirely, and ran it afterward in its improved form on the South London Tramways, and also on a private track at Millwall, where it is now in good condition, and I have a similar car in Berlin. M. Phillippart exhibited a car in Paris and M. Julien made successful experiments in Brussels, Antwerp, and Hamburg. Mr. Elieson is running storage battery locomotives in London. Mr. Julien has also been experimenting with a car in New York, and I believe one is in course of construction for a line in the city of Boston. Messrs. W. Wharton, Jr. & Co. have a storage battery car running at Philadelphia on Spruce and Pine streets, and this energetic firm is now fitting up another car with two trucks, each carrying an independent motor, similar to my European cars.
I have mentioned all these facts in order to show that there is a considerable amount of activity displayed in the matter of storage batteries for street cars, and that continued and substantial progress is being made in each successive case. The prejudices against the application of secondary batteries are being rapidly dispelled, and there are indications everywhere that this method of propulsion will soon take a recognized place among the great transit facilities in the United States. I feel convinced that this country will also in this respect be far ahead of Europe before another year has passed over our heads.
There are several popular and I may say serious objections to the employment of storage batteries for propelling street cars. These objections I will now enumerate, and endeavor to show how far they are true, and in what measure they interfere with the economical side of the question.
First objection: The loss of energy, which amounts in practice to 20 and sometimes 30 per cent. Now, every method of storing or transmitting energy involves some waste, but in saying this we need not condemn the system, for after all the term efficiency is only a relative one. For instance, a 10 horse power steam engine consumes three times as much fuel per horse power hour as a 1,000 horse power engine does, yet this small engine must be, and is regarded as, one of the most economical labor-saving appliances known to us. Considered as a heat engine, the efficiency of the most economical steam motor is but ten per cent.—90 per cent of the available units of heat contained in coal being lost during its transformation into mechanical energy. Thus, if we find that the storage battery does not return more than 70 per cent, of the work expended in charging it, we ought not to condemn it on that account until we have ascertained whether this low efficiency renders the system unfit for any or all commercial purposes. It is needless to go into figures in order to show that, when compared with animal power, this objection drops into insignificance.
The second, more formidable, objection relates to the weight of storage batteries—and this involves two disadvantages, viz., waste of power in propelling the accumulator along with the car, and increased pressure upon the street rails, which are only fitted to carry a maximum of 5 tons distributed over 4 points, so that each wheel of an ordinary car produces a pressure of 11/4 tons upon a point of the rail immediately under it.
The last mentioned objection is easily overcome by distributing the weight of the car with its electrical apparatus over 8 wheels or 2 small trucks, whereby the pressure per unit of section on the rails is reduced to a minimum. With regard to the weight of the storage batteries, relatively to the amount of energy the same are capable of holding and transmitting, I beg to offer a few practical figures. Theoretically, the energy manifested in the separation of one pound of lead from its oxide is equivalent to 360,000 foot pounds, but these chemical equivalents, though interesting in themselves, gives us no tangible idea of the actual capacity of a battery.
Repeated experiments have shown me that the capacity of a secondary battery cell varies with the rate at which it is charged and discharged. For instance, a cell such as we use on street cars gave a useful capacity of 137.3 ampere hours when discharged at the average rate of 45.76 amperes, and this same cell yielded 156.38 ampere hours when worked at the rate of 22.34 amperes. At the commencement of the discharge the E.M.F of the battery was 2.1 volts, and this was allowed to drop to 1.87 volts when the experiment was concluded. The entire active material contained in the plates of one cell weighed 11.5 lb., therefore the energy given off per pound of active substance at the above high rate of discharge was 62.225 foot pounds, and when discharging at the lower rate of 22.34 amperes the available useful energy was 72.313 foot pounds, or nearly 2.2 electrical horse power per pound of active matter. But this active substance has to be supported, and the strength or weight of the support has to be made sufficiently great to give the plate a definite strength and durability. The support of the plates inclusive of the terminals above referred to weighs more than the active material, which consists of peroxide of lead and spongy lead; so that the plates of one cell weigh actually 26.5 pounds. Add to this the weight of the receptacle and acid, and you get a total of about 41 pounds per cell when in working order. Seventy of these cells will propel an ordinary street car for four hours and a half, while consuming the stored energy at the rate of 30 amperes, or over 5.6 electrical horse power. The whole set of seventy cells weighs 2,870 lb., which is barely one-fifth of the entire weight of the car when it carries forty adult passengers. Therefore the energy wasted in propelling the accumulator along with a ear does not amount to more than 20 per cent. of the total power, and this we can easily afford to lose so long as animal power is our only competitor. From numerous and exhaustive tests with accumulators on cars in this country and abroad, I have come to the conclusion that the motive power for hauling a full-sized street car for fifteen hours a day does not exceed $1.75, and this includes fuel, water, oil, attendance, and repairs to engine, boiler, and dynamo. We have thus an immense margin left between the cost of electric traction and horse traction, and the last objection, that relating to the depreciation of the battery plates, can be most liberally met, and yet leave ample profits over the old method of propulsion by means of animals.
The advantages of storage battery street cars for city traffic are self-evident, so that I need not trouble you with further details in this respect, but I would beg those who take an interest in the progress of the electric locomotive to give this subject all the consideration it deserves, and I would assure them that the system which I have advocated in this brief but very incomplete sketch is worthy of an extended trial, and ready for the purposes set forth. There is no reason why those connected with electric lighting interests in the various cities and towns should not give the matter their special attention, as they are the best informed on electrical engineering and already have a local control of the supply of current needed for charging.
In the car which we use in Philadelphia there are actually 80 cells, because there are considerable gradients to go over. Each cell weighs 40 pounds and the average horse power of each battery is six. Sometimes we only use two horse power and sometimes, going up grades of 5 per cent., we use as much as 12 horse power, but the average rate is 6 electrical horse power. With reference to the weight of passengers on the cars, we have never carried more than 50 passengers on that car, because it is impossible to put more than 50 men into it. There are seats for 24, and the rest have to stand on the platforms or in the aisle.
The changing of the batteries takes three minutes with proper appliances. One set of cells is drawn out by means of a small winch and a freshly charged set is put in. It takes the same time to charge the battery as it does to discharge it in the working of the cars, so one reserve set would be sufficient to keep the car continually moving.
The loss of energy from standing about is probably nothing. If a battery were to stand charged for three months in a dry case, the loss of energy might be in three months 10 per cent. I purposely had a set of cells standing for two years charged and never used them. After two years there was still a small amount of energy left. So as regards the loss of energy in a battery standing idle, it is practically nothing, because no one would think of charging a battery and letting it stand for three months or a year.
I have had them stand three or four months and I could hardly appreciate the loss going on, provided always that the cells are standing on a dry floor. If the exterior of the box be moist, or if it stands on a moist floor, there will naturally be a surface leakage going on: but where there is no surface leakage the mere local action between the oxides and metallic lead will not discharge the battery for a very considerable time.
I have made experiments in London with a loaded car pulled by two horses. I put a dynamometer between the attachment of the horse and the car, so as to ascertain exactly the amount of pull, measured in pounds multiplied by the distance traversed in a minute. You will be surprised to know that two horses, when doing their easiest work, drawing a loaded car on a perfectly level road, exert from two to three horse power. I have mentioned a car in Philadelphia where we use between two and twelve horse power. A horse is capable of exerting eight horse power for a few minutes, and when a car is being driven up grades, such as I see in Boston, for instance, pulling a load of passengers up these grades, the horses must be exerting from 12 to 16 horse power, mechanical horse power. That is the reason that street car horses cannot run more than three or four hours out of the twenty-four. If they were to run longer, they would be dead in a few weeks. If they run two hours a day, they will last three or four years.
The life of the cells must be expressed upon the principle of ampere hours or the amount of energy given off by them. Street car service requires that the cells work their hardest for fifteen or sixteen hours a day. The life of the cells has to be divided; first, into the life of the box which contains the plates. This box, if appropriately constructed of the best materials, will last many years, because there is no actual wear on it. The life of the negative plates will be very considerable, because no chemical action is going on in the negative plate. The negative plate consists almost entirely of spongy lead, and the hydrogen is mechanically occluded in that spongy lead. Therefore the depreciation of the battery is almost entirely due to the oxidation of the positive plates. If we were to make a lead battery of plates 1/4 inch thick, it would last many years; but for street car work that would be far too heavy. Therefore we make the positive plates a little more than one-eighth of an inch thick. I find that the plates get sufficiently brittle to almost fall to pieces after the car has run fifteen hours a day for six months. The plates then have to be renewed. But this renewal does not mean the throwing away of the plates. The weight is the same as before, because no consumption of material takes place. We take out peroxide of lead instead of red lead. That peroxide, if converted, produces 70 per cent. of metallic lead, so that there is a loss of 30 per cent. in value. Then comes the question of the manufacture of these positive plates, which, I believe, at the present day are rather expensive. But I believe the time will come when battery plates will be manufactured like shoe nails, and the process of renewing the positive plates will be a very cheap one.
I ascertained in Europe that the motive power costs 2 cents per car mile; that is, the steam power and attendance for charging the batteries. We have to allow twice as much for the depreciation of a battery at the present high rate at which we have to pay for the battery—$12 for each cell. But I believe that as soon as the storage battery industry is sufficiently extended, the total cost for propelling these cars will not be more than six cents a mile, or about one half the cost of the cheapest horse traction.
I have made some very careful observations on the cable tramway in Philadelphia, which is quite an extensive system. I have never been able to ascertain the exact amount of waste in pulling the cable itself; but I have it on the authority of certain technical papers that there is a waste of about eighty per cent. I do not intend to depreciate cable or any other tramways, but there is a difficulty about introducing cable tramways. It is necessary to dig up the streets and interfere with the roadways. I have been told that the cable arrangements in Philadelphia cost $100,000 a mile, and that the cable road in San Francisco cost more than that. One of the directors of the cable company in Philadelphia told me that if he had seen the battery system before the introduction of the cable, he would probably have made up his mind in favor of the former. The wear and tear in the case of the storage system is also considerable. There is a waste of energy in the dynamo; secondly, in the accumulator charged by that dynamo; thirdly, in the motor which is driven by the accumulator; and fourthly, in the gearing that reduces the speed of the motor to the speed required by the car axles. It would be difficult to make a motor run at the rate of eighty revolutions per minute, which is the number of revolutions of the street car axle when running at the rate of ten miles an hour. Take all these wastes, and you find in practice that you do not utilize more than 40 per cent. of the energy given by the steam engine. But this is quite sufficient to make this system much cheaper than horse traction.
It is well known that we can discharge the storage battery ad libitum at the rate of 2 amperes or 200 amperes. I can get out of a storage battery almost any horse power I like for a short space of time. I have not the least objection to the direct system. But when you come to run twenty or thirty or fifty cars on one line, you will require very large conductors or dangerously high electromotive force. The overhead system is applicable to its own particular purposes. Where there are only five or ten, or even twenty, cars running on one line, and that line runs through a suburb or a part of a city where there are not many houses, that system is to be preferred. The objection to the overhead system is not so much the want of beauty, but the want of practicability. You have to put your posts very high indeed, so as to let great wagon loads of hay and all sorts of things pass underneath. Most of the trouble comes in winter, and when it is snowing hard a great many difficulties arise. As regards the loss, suppose that the resistance of the overhead lines is one ohm. To draw one car it will take an average of 20 amperes, and the only loss will be 20 multiplied by 20, that is, 400 watts through line resistance. But if there are ten cars on that line, you get 40,000 watts loss of energy, unless you increase the conductor in proportion to the number of cars. If you do that, you get an enormous conductor, and have a sort of elevated railroad instead of a telegraph wire, as most people imagine an overhead conductor to be.
The current required to run a street car is about thirty amperes, and an electromotive force of about 180 volts. If cars are run in connection with an incandescent light station, we can arrange our apparatus so that we can use an E.M.F. say of 110 volts, and then we can put in a smaller number of cells with a larger capacity that will give a corresponding horse power. We can charge such larger cells with 50 or 60 amperes instead of thirty.
In regard to arc lighting machinery, the arc lighting dynamo should not be used to charge the accumulators. They can be used, but they require such constant attention as to make them impracticable. We can only use shunt-wound dynamos conveniently for that purpose.
In regard to using two motors on a car, there are several advantages in it. I use two motors on all my cars in Europe, and always have done so from the beginning. One of the advantages is that in case of an accident to one motor the other will bring the car home; secondly, with two motors we can vary the speed without changing the E.M.F. of the battery. If I want very much power, I put two motors in parallel, getting four times the power that I do with one machine, and an intermediate power of two motors.
There is another advantage of having two motors, and that is that we can use two driving axles instead of one, and we can go up grades with almost double the facility that way, because the adhesion would be double. These are the main advantages arising from the use of two or more motors.
Mr. Mailloux asked if I would give my experience in regard to the mechanical transmission between the motor and the car axle. I have used almost everything that was known at the time, but in order to give you a full and detailed account of the various modes of transmission which I have used I should have to give you figures to bear out certain experiments. I should only be able to do that in a lecture of at least five hours' duration, so I hope that you will kindly excuse me on that point.
With regard to the durability of plates, I have taken into consideration fifteen hours a day. In regard to the application of electrical brakes, I will say that that was one of the first ideas that entered my head when I began to use electric motors, and other people had that idea long before me. I have used an electric brake, using the motor itself as a brake—that is, as the car runs down a grade by momentum, it generates a current, but this current cannot be used for recharging a battery. It is utter nonsense to talk about that unless we have a steady grade four or five miles long. The advantages are very small indeed, and the complications which would be introduced by employing automatic cut-outs, governors, and so on, would counterbalance anything that might be gained. As regards going up an incline, of course stopping and starting again has to be done often, and anybody who at any time works cars by electricity, whether they have storage batteries or not, has to allow for sufficient motive power to overcome all the difficulties that any line might present.
One of the great mistakes which some of the pioneers in this direction made was that they did not put sufficient power upon the cars. You always ought to put on the cars power capable of exerting perhaps 20 to 40 per cent. more than is necessary in the ordinary street service, so that in case of the road being snowed up, or in the case of any other accident which is liable to occur, you ought to have plenty of power to get out of the scrape.
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BRISTOL CATHEDRAL.
An Augustinian monastery, founded by Robert Fitzhardinge in 1142, had its church, of Norman architecture, to which additions were made in the early English period. When Edmund Knowle was abbot, from 1306 to 1332, the Norman choir was replaced by that which now exists. His successor, Abbot Snow, built the chapels on the south side of the choir. Abbot Newland, between 1481 and 1515, enriched the transepts with a groined roof and with ornamental work of the decorated Gothic style, and erected the central tower. Abbot Elliott, who followed Newland, removed the Norman nave and aisles, intending to rebuild them; but this was prevented by his death in 1526 and by the dissolution of the monastery a few years afterward; he completed, however, the vaulting of the south transept. The church remained with a nave, and otherwise incomplete, until the modern restorations; after which, in 1877, it was reopened with a special service. Messrs. Pope & Bindon, of Bristol, were the architects employed. The exterior, of which we give an illustration, viewed from St. Augustine's Green, or Upper College Green, is not very imposing; from the Lower Green there is a good view of the central tower and the transept. The height of the tower is but 127 ft. It is of perpendicular Gothic architecture, but the piers supporting it are Norman. The interior presents many features of interest. The clustered triple shafts of the piers in the choir, with their capitals of graceful foliage, the lofty pointed arches between them, and the groined vaulting, have much beauty. The chancel is decorated with tracery of a peculiar pattern.
The Abbey of St. Augustine at Bristol was surrendered to King Henry VIII. in 1538, and became, in 1542, the cathedral of the new Episcopal see then created. The first Bishop of Bristol, Paul Bush, was deprived of his see by Queen Mary, being a married clergyman and refusing to part with his wife. Bishop Fletcher, in Queen Elizabeth's time, afterward Bishop of Worcester and of London, was twice married, at which this queen likewise expressed her displeasure. He was father of Fletcher, the dramatic poet; and he is said to have been one of the first English smokers of tobacco. Among noted Bishops of Bristol were Bishop Lake, afterward of Chichester, and Bishop Trelawny (Sir Jonathan Trelawny, Bart., of Cornwall), two of the "seven bishops"; imprisoned for disobeying an illegal order of James II. "And shall Trelawny die? Then twenty thousand Cornishmen will know the reason why." But the most eminent was Bishop Joseph Butler, the author of "The Analogy of Natural and Revealed Religion" and of the "Sermons on Human Nature." He was born at Wantage, in Berkshire, and was educated as a Nonconformist. He was Bishop of Bristol from 1738 to 1750, when he was translated to Durham. In 1836, the see of Bristol was joined with that of Gloucester; and the Right Rev. Drs. J.H. Monk, O. Baring, W. Thomson (now Archbishop of York), and C.J. Ellicott have been Bishops of Gloucester and Bristol.—Illustrated London News.
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WAVES.
In the first days of August, two startling announcements reached us from the United States. They were as follows:
(1.) "The commander of the Cunarder Umbria reports that at 3 o'clock on July 27, about 1,500 miles from Sandy Hook, the vessel was struck by a tidal wave 50 ft. high, which swept the decks, carried away a portion of the bridge and the forward hatch, and flooded the cabins and steerage."
(2.) "The captain of the Wilson line steamer Martello reports that at half-past 8 on the evening of July 25, when in lat. 49 deg. 3' N., long. 31 deg. W., an enormous wave struck the vessel, completely submerging the decks."
In view of these reports, and inasmuch as questions were asked on the subject in Parliament, though it is quite possible that, as regards the "tidal" character of the waves, there may be something of newspaper gobemoucherie in the announcements, we offer a few remarks on waves in general, which may be useful to some of our readers.
Tidal phenomena present themselves under two aspects: as alternate elevations and depressions of the sea and as recurrent inflows and outflows of streams. Careful writers, however, use the word tide in strict reference to the changes of elevation in the water, while they distinguish the recurrent streams as tidal currents. Hence, also, rise and fall appertain to the tide, while flood and ebb refer to the tidal current.
The cause of the tides is the combined action of the sun and moon. The relative effects of these two bodies on the oceanic waters are directly as their mass and inversely as the square of their distance; but the moon, though small in comparison with the sun, is so much nearer to the earth that she exerts the greater influence in the production of the great tide wave. Thus the mean force of the moon, as compared with that of the sun, is as 21/4 to 1.
The attractive force of the moon is most strongly felt by those parts of the ocean over which she is vertical, and they are, consequently, drawn toward her. In the same manner, the influence of the luminary being less powerfully exerted on the waters furthest from her than on the earth itself, they must remain behind. By these means, at the two opposite sides of the earth, in the direction of the straight line between the centers of the earth and moon, the waters are simultaneously raised above their mean level; and the moon, in her progressive westerly motion, as she comes to each meridian in succession, causes two uprisings of the water—two high tides—the one when she passes the meridian above, the other when she crosses it below; and this is done, not by drawing after her the water first raised, but by raising continually that under her at the time; this is the tide wave. In a similar manner (from causes already referred to) the sun produces two tides of much smaller dimensions, and the joint effect of the action of the two luminaries is this, that instead of four separate tides resulting from their separate influence, the sun merely alters the form of the wave raised by the moon; or, in other words, the greater of the two waves (which is due to the moon) is modified in its height by the smaller (sun's) wave. When the summit of the two happens to coincide, the summit of the combined wave will be at the highest. When the hollow of the smaller wave coincides with the summit of the larger, the summit of the combined wave will be at the lowest.
It is necessary to have a clear and distinct conception of the difference between the motion of a wave and that of a current. In the current there is a transfer of water; in the wave the transfer is no more than would be brought about by a particle of water impinging on another where that particle has a motion perpendicular to the surface, and a rising and falling results. The onward movement of the wave itself is always perceptible enough. That the water is not moving with the same velocity is also evident from watching the progress of any light body floating on its surface. This fact may be practically illustrated in the case of a ship at sea, sailing before the wind in the same direction as the waves are moving. When the crest of a wave is near the stern, drop a piece of wood on it. Almost instantly the wave will be seen shooting ahead of the vessel, while the wood is scarcely removed from the position where it fell on the water. The wave has moved onward, preserving its identity as a wave, the water of which it is formed being constantly changed; and thus the motion of the wave is one thing, that of the water in which the waves are formed is quite another thing.
Again, waves are formed by a force acting horizontally; but in the case of the tide wave, that force acts uniformly from the surface to the lowest depths of the ocean, and the breadth of the wave is that curved surface which, commencing at low water, passes over the summit of the tide down to the next low water—this is a wave of the first order. In waves of the second order, the force raising them acts only on the surface, and there the effect is greatest (as in the wind waves)—where one assists in giving to the water oscillating motion which maintains the next, and gradually puts the whole surface in commotion; but at a short distance down that effect entirely disappears.
If the earth presented a uniform globe, with a belt of sea of great and uniform depth encircling it round the equator, the tide wave would be perfectly regular and uniform. Its velocity, where the water was deep and free to follow the two luminaries, would be 1,000 miles an hour, and the height of tide inconsiderable. But even the Atlantic is not broad enough for the formation of a powerful tide wave. The continents, the variation in the direction of the coast line, the different depths of the ocean, the narrowness of channels, all interfere to modify it. At first it is affected with only a slight current motion toward the west—a motion which only acquires strength when the wave is heaped up, as it were, by obstacles to its progress, as happens to it over the shallow parts of the sea, on the coasts, in gulfs, and in the mouths of rivers. Thus the first wave advancing meets in its course with resistance on the two sides of a narrow channel, it is forced to rise by the pressure of the following waves, whose motion is not at all retarded, or certainly less so than that of the first wave. Thus an actual current of water is produced in straits and narrow channels; and it is always important to distinguish between the tide wave, as bringing high water, and the tidal stream—between the rise and fall of the tide and the flow and ebb.
In the open ocean, and at a distance from the land, the tide wave is imperceptible, and the rise and fall of the water is small. Among the islands of the Pacific four to six feet is the usual spring rise. But the range is considerably affected by local causes, as by the shoaling of the water and the narrowing of the channel, or by the channel opening to the free entrance of the tide wave. In such cases the range of tide is 40 to 50 feet or more, and the tidal stream is one of great velocity. It may under such circumstances even present the peculiar phenomenon called the bore—a wave that comes rolling in with the first of flood, and, with a foaming crest, rushes onward, threatening destruction to shipping, and sweeping away all impediments lying in its course.
It is certain that in the open ocean the great tide wave could not be recognized as a wave, since it is merely a temporary alteration of the sea level.
Waves which have their origin in the action of the wind striking the surface of the water commence as a series of small and slow undulations or wavelets—a mere ripple. As the strength, and consequently the pressure, of the wind increases, waves are formed; and a numerical relation exists between the length of a wave, its velocity of progress, and the depth of the water in which it travels.
The height of a wave is measured from trough to crest; and though waves as seen from the deck of a small vessel appear to be "enormous" and "overwhelming," their height, in an ordinary gale, in deep water, does not exceed 15 to 20 feet. In a very heavy gale of some days' continuance they will, of course, be much higher.
Scoresby has observed them 30 ft. high in the North Atlantic; and Ross measured waves of 22 ft. in the South Atlantic. Wilkes records 32 ft. in the Pacific. But the highest waves have been reported off the Cape of Good Hope and Cape Horn, where they have been observed, on rare occasions, from 30 to 40 ft high; and 36 ft. has been given as the admeasurement in the Bay of Biscay, under very exceptional circumstances. In the voyage round the world the Venus and Bonite record a maximum of 27 ft., while the Novara found the maximum to be 35 ft. But waves of 12 to 14 ft. in shallow seas are often more trying than those of larger dimensions in deeper water. It is generally assumed that a distance from crest to crest of 150 to 350 ft. in the storm wave gives a velocity (in the change of form) of from 17 to 28 miles per hour. But what is required in the computation of the velocity is the period of passage between two crests. Thus a distance of 500 to 600 ft. between two crests, and a period of 10 to 11 seconds, indicates a velocity of 34 miles per hour.
The following table, by Sir G.B. Airy (late Astronomer Royal), shows the velocities with which waves of given lengths travel in water of certain depth:
Depth of Length of the Wave in Feet.[1] the Water in Feet. 10 100 1,000 10,000 100,000 1,000,000 10,000,000 - - - - Corresponding Velocity of Wave per Hour in Nautical Miles. 1 3.2 3.4 3.4 3.4 3.4 3.4 3.4 10 4.3 10.1 10.7 10.8 10.8 10.8 10.8 100 4.3 13.5 32.0 34.0 34.0 34.0 34.0 1,000 4.3 13.5 42.9 101.8 107.5 107.5 107.5 10,000 4.3 13.5 42.9 135.7 320.3 340.0 340.3 100,000 4.3 13.5 42.9 135.7 429.3 1013.0 1075.3 - - - -
[Footnote 1: As an example, this table shows that waves 1,000 feet in length travel 43 nautical miles per hour in water 1,000 feet deep. The length is measured from crest to crest.]
From these numbers it appears that—
1. When the length of the wave is not greater than the depth of the water, the velocity of the wave depends (sensibly) only on its length, and is proportional to the square root of its length.
2. When the length of the wave is not less than a thousand times the depth of the water, the velocity of the wave depends (sensibly) only on the depth, and is proportional to the square root of the depth.
It is, in fact, the same as the velocity which a free body would acquire by falling from rest under the action of gravity through a height equal to half the depth of the water.
Rollers are of the nature of a violent ground swell, and possibly the worst of them may be due to the propagation of an earthquake wave. They come with little notice, and rarely last long. All the small islands in the Mid-Atlantic experience them, and they are frequent on the African coast in the calm season. They are also not unknown in the other oceans. In discussing the meteorology of the equatorial district of the Atlantic, extending from lat. 20 deg. to 10 deg. S, Captain Toynbee observes that "swells of the sea are not always caused by the prevailing wind of the neighborhood. For instance, during the northern winter and spring months, northwesterly swells abound. They are sometimes long and heavy, and extend to the most southern limit of the district. Again, during the southern winter and spring months, southerly and southwesterly swells abound, extending at times to the most northern limit of the district. They are frequently very heavy and long."
The great forced sea waves, due to earthquakes, and generally to subterranean and volcanic action, have been known to attain the enormous height of 60 feet or more, and sweep to destruction whole towns situated on the shores where they have broken—as for example Lisbon and places on the west coast of America and in the island of Java. Though so destructive when they come in toward the land, and begin to feel the shelving sea bottom, it is not probable that, in the open ocean, this wave would do more than appear as a long rolling swell. It has, however, been observed that "a wave with a gentle front has probably been produced by gentle rise or fall of a part of the sea bottom, while a wave with a steep front has probably been due to a somewhat sudden elevation or depression. Waves of complicated surface form again would indicate violent oscillations of the bottom."
The altitude and volume of the great sea wave resulting from an earthquake depend upon the suddenness and extent of the originating disturbance and upon the depth of water at its origin. Its velocity of translation at the surface of the sea varies with the depth of the sea at any given point, and its form and dimensions depend upon this also, as well as upon the sort of sea room it has to move in. In deep ocean water, one of these waves may be so long and low as to pass under a ship without being observed, but, as it approaches a sloping shore, its advancing slope becomes steeper, and when the depth of water becomes less than the altitude of the wave, it topples over, and comes ashore as an enormous and overwhelming breaker.
Lastly, there is the storm wave—the result of the cyclone or hurricane—and, perhaps, the greatest terror to seamen, for it almost always appears in the character of a heavy cross sea, the period of which is irregular and uncertain. The disturbance within the area of the cyclone is not confined to the air, but extends also to the ocean, producing first a rolling swell, which eventually culminates in a tremendous pyramidal sea and a series of storm waves, the undulations of which are propagated to an extraordinary distance, behind, before, and on each side of the storm field.
Enough has now been said to show that whatever the character of the waves encountered by the Umbria and Martello in July last, they were in no sense "tidal," but, if approximating to the dimensions stated, they were either due to storm or earthquake, or, possibly, to a combination of both the last agents.
For those of our readers who may be interested in wave observations, we conclude by introducing Prof. Stokes' summary of the method of observing the phenomenon:
"For a Ship at Sea.
"(1.) The apparent periodic time,[2] observed as if the ship were at rest.
"(2.) The true direction from which the waves come, also the ship's true course and speed per hour.
"(3.) A measure or estimate of the height of the waves.
"(4.) The depth of the sea if it is known, but, at any rate, the position of the ship as near as possible, either by cross bearings of land or any other method, so that the depth may be got from charts or other sources.
"For a Ship at Anchor.
"(1.) The periodic time.
"(2.) The true direction from which the waves come.
"(3.) A measure or estimate of the height of the waves.
"(4.) The depth of water where she is anchored."
[Footnote 2: The period of a wave is the interval of time which elapses between the transits of two successive wave crests past a stationary floating body, the wave crest being the highest line along the ridge.]
It is the opinion of scientists that when the period of oscillation of the ship and the period of the wave are nearly the same, the turning over of the ship is an approximate consequence, and thus the wave to such a ship would appear more formidable than to another ship with a different period of oscillation.—Nautical Magazine.
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PRACTICAL EDUCATION.
It is now recognized that one of the elements in which the public school systems of the United States are most lacking is in the practical branches in teaching trades and industry. There is too much book learning, too little practical education. Throughout the continent of Europe there are trade and industrial schools which have accomplished much in turning out skilled workmen for the various branches of industry. Here we have one. Our deficiency in this matter was recognized by the late commissioner of education, and attention called to it in several of his reports, and a number of the State superintendents of education have also urged the establishment of manual or training schools as a part of the State systems. We have such an institution here in the Tulane Manual School. In Philadelphia, Cleveland, and Chicago, the system has been adopted on a large scale, and made part of the high school course. Another city which has inaugurated the manual training school as a part of its public schools is Toledo, O. A rich citizen of that town, who recently died, left a large sum for the establishment of a university of arts and trades. Instead of founding a separate university, however, the money was applied to the establishment of manual schools in connection with the public schools, for both boys and girls.
The course of girls' work given will afford some idea of what it is proposed to do. This begins with the senior grammar school grade and continues three years in high school. It includes free hand, mechanical, and architectural drawing, light carpentry, wood carving, designing for wood carving, wood turning, clay moulding, decorative designing, etc. But more practical than these things are the lessons in cooking, sewing, and household management. The course in domestic economy "is arranged with special reference to giving young women such a liberal and practical education as will inspire them with a belief in the dignity and nobleness of an earnest womanhood, and incite them to a faithful performance of the every day duties of life. It is based upon the assumption that a pleasant home is an essential element of broad culture, and one of the surest safeguards of morality and virtue." The report of the school also remarks that "the design of this course is to furnish thorough instruction in applied housekeeping, and the sciences related thereto, and students will receive practical drill in all branches of housework; in the purchase and care of family supplies, and in general household management; but will not be expected to perform more labor than is actually necessary for the desired instruction."
A special branch which will be well received is that which proposes to teach the girls how to cook. The curriculum is one that every housekeeper ought to go through.
Boiling—Practical illustrations of boiling and steaming, and treatment of vegetables, meats, fish, and cereals, soup making, etc.
Broiling—Lessons and practice in meat, chicken, fish, oysters, etc.
Bread Making—Chemical and mechanical action of materials used. Manipulations in bread making in its various departments. Yeasts and their substitutes.
Baking—Heat in its action on different materials in the process of baking. Practical experiments in baking bread, pastry, puddings, cakes, meat, fish, etc.
Frying—Chemical and mechanical principles involved and illustrated in the frying of vegetables, meats, fish, oysters, etc.
Mixing—The art of making combinations, as in soups, salads, puddings, pies, cakes, sauces, dressings, flavorings, condiments, etc.
In "marketing, economy," etc., the course comprises general teaching on the following subjects:
"The selection and purchase of household supplies. General instructions in systematizing and economizing the household work and expenses. The anatomy of animals used as food, and how to choose the several parts. Lessons on the qualities of water and steam; the construction of stoves and ranges; the properties of different fuels."
Again, there is a dressmaking and millinery department, where the girls are taught how to cut and make dresses and other garments, and the economical and tasteful use of materials.
So much for the girls. The courses in the boys' schools are somewhat similar, turning, however, on the more practical instruction in trades and industries, in carpentering, wood and iron work, etc.
The Toledo experiment has been tried there but one year, and has given general satisfaction. The board of school directors has interested the public in its efforts, and advisory committees of ladies and gentlemen have been appointed to assist in managing these schools.
It is to be hoped that other and larger cities will imitate Toledo in the matter. Those philanthropists who are giving money so liberally for the establishment of institutions of higher learning might do much good in providing for manual training schools of this kind that will assure the country good housewives and skilled mechanics in the future.—Trustees' T. Jour.
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A GIGANTIC LOAD OF LUMBER.
When it was announced in the Lumberman that the barge Wahnapitae had carried a cargo of 2,181,000 feet of lumber, letters were received asking if it was not a typographical error. It was thought by many that no boat could carry such a load. For the purpose of showing the barge on paper, a photograph was obtained of her when loaded at Duluth, which is herewith reproduced. The freight rate obtained to Tonawanda was $3.75 a thousand, which footed up to a total of $8,178.75 The owners of the boat, however, were not satisfied with such a record, and proceeded to break it by loading at Duluth 2,409,800 feet of lumber, which also went to Tonawanda, and which is put down as the biggest cargo of lumber on record. At the latter place the cargo was unloaded on Saturday afternoon and Monday forenoon—one working day. It will be readily understood that the money-making capacity of the barge is of the Jumbo order also.
The barge is owned by the Saginaw Lumber and Salt Company and the Emery Lumber Company, and cost $30,000. She is 275 feet long and 51 feet beam. The lumber on her was piled 22 feet high and she drew 11 feet of water. Had she been 10 inches wider, she could not have passed through the Soo canal. The boat was built on the Saginaw river a year ago last winter, and was designed for carrying logs from the Georgian bay to the Saginaw river and Tawas mills. The Canadian government, however, increased the export duty on logs, and the barge was put into the lumber-carrying trade—N.W. Lumberman.
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THE NEWBERY-VAUTIN CHLORINATION PROCESS.
The process of extracting gold from ores by absorption of the precious metal in chlorine gas, from which it is reduced to a metallic state, is not a very new discovery. It was first introduced by Plattner many years ago, and at that time promised to revolutionize the processes for gold extraction. By degrees it was found that only a very clever chemist could work this process with practically perfect results, for many reasons. Lime and magnesia might be contained in the quartz, and would be attacked by the chlorine. These consume the reagents without producing any results, earthy particles would settle and surround the small gold and prevent chlorination, then lead and zinc or other metals in combination with the gold would also be absorbed by the chlorine; or, again, from some locally chemical peculiarity in the water or the ore, gold held in solution by the water might be again precipitated in the tailings before filtration was complete, and thus be lost. Henderson, Clark, De Lacy, Mears, and Deacon, all introduced improvements, or what were claimed to be improvements, on Plattner, but these chiefly failed because they did not cover every particular variety of case which gold extraction presented. Therefore, where delicate chemical operations were necessary for success, practice generally failed from want of knowledge on the part of the operator, and many times extensive plants have been pronounced useless from this cause alone. Hence it is not to be wondered that processes requiring such care and uncommon knowledge are not greatly in favor.
Mr. Claude Vautin, a gentleman possessed of much practical experience of gold mining and extraction in Queensland, together with Mr. J. Cosmo Newbery, analytical chemist to the government of Victoria, have developed a process which they claim to combine all the advantages of the foregoing methods, and by the addition of certain improvements in the machinery and mode of treatment to overcome the difficulties which have hitherto prevented the general adoption of the chlorination process.
By reference to the illustrations of the plant below, the system by which the ore is treated can be readily understood. The materials for treatment—crushed and roasted ore, or tailings, as the case may be—are put into the hopper above the revolving barrel, or chlorinator. This latter is made of iron, lined with wood and lead, and sufficiently strong to bear a pressure of 100 lb. to the square inch, its capacity being about 30 cwt of ore. The charge falls from the hopper into the chlorinator. Water and chlorine-producing chemicals are added—generally sulphuric acid and chloride of lime—the manhole cover is replaced and screwed down so as to be gas tight. On the opposite side of the barrel there is a valve connected with an air pump, through which air to about the pressure of four atmospheres is pumped in, to liquefy the chlorine gas that is generated, after which the valve is screwed down. The barrel is then set revolving at about ten revolutions a minute, the power being transmitted by a friction wheel. According to the nature of the ore, or the size of the grains of gold, this movement is continued from one to four hours, during which time the gold, from combination with the chlorine gas, has formed a soluble gold chloride, which has all been taken up by the water in the barrel. The chlorinator is then stopped, and the gas and compressed air allowed to escape from the valve through a rubber hose into a vat of lime water. This is to prevent the inhalation of any chlorine gas by the workmen. The manhole cover is now removed and the barrel again set revolving, by which means the contents are thrown automatically into the filter below. This filter is an iron vat lined with lead. It has a false bottom, to which is connected a pipe from a vacuum pump working intermittently. As soon as all the ore has fallen from the chlorinator into the filter, the pump is set going, a partial vacuum is produced in the chamber below the false bottom in the filter, and very rapid filtration results. By this means all the gold chlorides contained in the wet ore may be washed out, a continual stream being passed through it while filtration is going on. The solution running from the filter is continually tested, and when found free from gold, the stream of water is stopped, as is also the vacuum pump. The filter is then tipped up into a truck below, and the tailings run out to the waste heap. The process of washing and filtration occupies about an hour, during which time another charge may be in process of treatment in the chlorinator above. The discharge from the filter and the washings are run into a vat, and from this they are allowed to pass slowly through a tap into a charcoal filter. During the passage of the liquid through the charcoal filter, the chloride of gold is decomposed and the gold is deposited on the charcoal, which, when fully charged, is burnt, the ashes are fused with borax in a crucible, and the gold is obtained.
We have specified above the objections to the old processes of chlorination, so it may be fairly asked in what way the Newbery-Vautin process avoids the various chemical actions which have hitherto proved so difficult to contend with.
For any system of chlorination yet introduced it is necessary to free the ore from sulphides. This is done by roasting according to any of the well-known systems in vogue. It is a matter which requires great care and considerable skill. The heat must be applied and increased slowly and steadily. If, through any neglect on the part of the roaster, the ore is allowed to fuse, in most cases it is best to throw the charge away, as waste. This roasting applies equally to the Vautin process as to any others. So on this head there is no alteration. One of the most important advantages is not a chemical one, but is the rapidity with which the charge can be treated. In the older styles of treatment the time varied from thirty six to ninety hours. Now this is accomplished in from three to six hours with a practically perfect result. The older processes required a careful damping of the ore, which, to get good results, must leave the ore neither too wet nor too dry. Now "damping" is entirely done away with, and in its place water is poured into the barrel. Pressure to the extent of four atmospheres causes chlorine gas to leave its vaporous form. Thus the pressure applied not only enables a strong solution of chlorine to be formed with the water in the barrel, but forces this into contact with the gold through every crevice in the ore. Chlorine gas also takes up any silver which may exist in association with the gold. In the older processes this is deposited as a film of chloride of silver around the fine gold grains, and from its insolubility in water prevents the absorption of the gold. The rotary motion of the barrel in the Newbery-Vautin method counteracts this by continually rubbing the particles together; this frees the particles from any accumulations, so that they always present fresh surfaces for the action of the solvent. Again, the short time the ore is in contact with the chlorine does not allow of the formation of hydrochloric acid, which has a tendency to precipitate the gold from its soluble form in the water before being withdrawn from the chlorinator.
Hitherto, when the ore was very fine or contained slimes, the difficulty of filtration was increased, sometimes in extreme cases to such an extent that chlorination became impracticable. By the introduction of the vacuum pump this is greatly facilitated; then by making the action intermittent a jigging motion is given to the material in the filter which prevents any clogging except in cases of extreme fineness.
The advantage of using charcoal as a decomposing agent for chloride of gold was pointed out by Mr. Newbery some twenty years ago; four or five years since the idea was patented in the United States, but as this was given gratis to the world years before, the patent did not hold good. The form of precipitation generally adopted was to add sulphate of iron to the liquid drawn from the filter. This not only threw down the gold it contained, but also the lime and magnesia. Then very great care was necessary, and a tedious process had to be gone through to divide the gold from these. Now, by filtration through charcoal everything that is soluble in hydrochloric acid passes away with the water; for instance, lime and magnesia, which before gave such great trouble. In passing through the charcoal, the chloride of gold is decomposed and all fine gold particles are taken up by the charcoal, so that it is coated by what appears to be a purple film.
Should copper be associated with the gold, the water, after running through the charcoal filter, is passed over scrap iron, upon which the copper is precipitated by a natural chemical action. If silver is contained in the ore, it is found among the tailings in the filter, in a chloride which is insoluble in water. Should the quantity prove sufficiently large, it may be leached out in the usual way by hyposulphites.
One of the great advantages common to all systems of chlorination is that ores may be crushed dry and treated, so that the loss from float gold may be avoided. Of this loss, which is most serious, we shall have something to say on another occasion. An advantage in amalgamation with chlorine gas instead of amalgamation with quicksilver in the wet way, is that the ore need not be crushed so finely. Roasting takes the place of fine crushing, as the ore from the roasting furnace is either found somewhat spongy in texture or the grains of silica in which fine gold may be incased are split or flawed by the fire. For quicksilver amalgamation very fine crushing is necessary to bring all gold particles in contact with it. Quicksilver being so thick in substance, it will not find its way readily in and out of a microscopically fine spongy body or through very fine flaws in grains of silica, whereas chlorine gas or a solution of liquefied chlorine does this, and absorbs the gold far more readily.
There are cases when gold is contained in ores in what is known as a perfectly "free" form—that is, there is an absence of all sulphides, arsenides, etc.—when it is not practicable to extract it either with the ordinary forms of quicksilver amalgamation of or any process of chlorination, without first roasting. This is because the finer gold is locked up inside fine grains of silica and hydrated oxide of iron. No ordinary crushing will bring this fine enough, but when roasting is resorted to by drawing it rapidly through a furnace heated to a cherry red, these grains are split up so that chlorine gas is enabled to penetrate to the gold.
It may be said that an equally clever chemist will be required to work this improved process as compared with those that have, one by one, fallen into disuse, mainly from want of knowledge among the operators. To a certain extent this is so. The natural chemical actions are not so delicate, but an ignorant operator would spoil this process, as he does nearly every other. When a reef is discovered, practice shows that its strongest characteristics are consistently carried throughout it wherever it bears gold. Before Messrs. Newbery and Vautin leave a purchaser to deal himself with their process, they get large samples of his ore to their works and there experiment continually until a practically perfect result is obtained; then any one with a moderate amount of knowledge can work with the formula supplied. It has been their experience that the ore from any two mines rarely presents the same characteristics. Experiments are begun by treating very coarse crushings. These, if not satisfactory, are gradually reduced until the desired result is obtained.
To treat the whole body of ore from a mine, dry crushing is strongly recommended. To accomplish this in the most efficient manner, a stone breaker which will reduce to about 1/4 in. cubes is necessary. For subsequent crushing Kroms rolls have, up to the present time, proved most satisfactory. They will crush with considerable evenness to a thirty mesh, which is generally sufficient. The crushings are then roasted in the ordinary way in a reverberatory furnace and the whole of the roastings are passed through the machine we have just described. By this it is claimed that over 90 per cent. of the gold can be extracted at very much the same cost as the processes now in general use in gold producing countries, which on the average barely return 50 per cent. If so, the gentlemen who have brought forward these improvements deserve all the success their process promises.—Engineering.
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APPARATUS FOR EXERCISING THE MUSCLES.
The apparatus herewith illustrated consists of a wooden base, which may be bolted to the floor, and which supports two wooden uprights, to which is affixed the apparatus designed to exercise the legs. The apparatus for exercising the arms is mounted upon a second frame that slides up and down the wooden supports. It is fixed in position at any height by means of two screws.
The apparatus for exercising the legs, as well as the one for the arms, consists essentially of a fly wheel mounted upon an axle extending to the second upright and bent into the form of a crank in the center. The fly wheel is provided with a winch whose arm is capable of elongation in order to accommodate it to the reach of the sound limb.
The apparatus for the legs is arranged in a contrary direction, that is to say, the wheel is on the opposite side of the frame, and upon the fixed uprights. It is really a velocipede, one of the pedals of which is movable upon the winch, and is capable of running from the axle to the extremity, as in the upper apparatus. This pedal has the form of a shoe, and is provided with two straps to keep the foot in place and cause it to follow the pedal in its rotary motion. A movable seat, capable of rising and descending and moving backward and forward, according to the leg that needs treatment, is fixed back of the apparatus.
The operation is as follows: Suppose that the atrophied arm is the left one. The invalid, facing the apparatus, grasps the movable handle on the crank with his left hand, and revolves the winch with his right. The left hand being thus carried along, the arm is submitted to a motion that obliges it to elongate and contract alternately, and the result is an extension of the muscles which strengthens them.
The apparatus, which is as simple as it is ingenious, can, it is true, be applied only when one of the two limbs, arm or leg, is diseased, the other being always necessary to set the apparatus in motion; but, even reduced to such conditions, it is destined to render numerous services in cases of paralysis, atrophy, contusions, etc.—Moniteur des Inventions Industrielles.
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THE BULL OPTOMETER.
Dr. Javal has just presented to the Academy of Medicine a very ingenious and practical optometer devised by George J. Bull, a young American doctor, after a number of researches made at the laboratory of ophthalmology at the Sorbonne. Among other applications that can be made of it, there is one that is quite original and that will insure it some success in the world. It permits, in fact, of approximately deducing the age of a person from certain data that it furnishes as to his or her sight. As well known, the organs become weak with age, their functions are accomplished with less regularity and precision, and, according to the expression of the poet,
"En marchant a la mort, on meurt a chaque pas,"
the senses become blunted, the hearing becomes dull, the eyes lose their luster, vivacity, and strength, and vision becomes in general shorter, less piercing, and less powerful.
The various parts of the eye, but more particularly the crystalline lens, undergo modifications in form and structure. Accommodation is effected with more and more difficulty, and, toward the age of sixty, it can hardly be effected at all.
These changes occur in emmetropics as well as in hypermetropics and myopics.
As will be seen, then, there is a relation between the age of a person and the amplitude of the accommodation of his eyes. If we cannot express a law, we can at least, through statistics, find out, approximately, the age of a person if we know the extent of the accommodation of his eyes.
A Dutch oculist, Donders, has got up a table in which, opposite the amplitudes, the corresponding ages are found. Now, the Javal-Bull optometer permits of a quick determination of the value of the amplitude of accommodation in dioptries. (A dioptrie is the power of a lens whose focal distance is one meter.)
The first idea of this apparatus is due to the illustrious physicist Thomas Young, who flourished about a century ago. The Young apparatus is now a scarcely known scientific curiosity that Messrs. Javal and Bull have resuscitated and transformed and completed.
It consists of a light wooden rule about 24 inches long by 11/4 inch wide that can easily be held in the hand by means of a handle fixed at right angles with the flat part (Fig. 1). At one extremity there is a square thin piece of metal of the width of the rule, and at right angles with the latter, but on the side opposite the handle. This piece of metal contains a circular aperture a few hundredths of an inch in diameter (Fig. 3). Toward this aperture there may be moved either a converging lens of five dioptries or a diverging lens of the same diameter, but of six dioptries.
On holding the apparatus by the handle and putting the eye to the aperture, provided or not with a lens, we see a series of dominoes extending along the rule, from the double ace, which occupies the extremity most distant from the eye, to the double six, which is very near the eye (Fig. 2). The numbers from two to twelve, simply, are indicated, but this original means of representing them has been chosen in order to call attention to them better.
Figures are characters without physiognomy, if we may so express ourselves, while the spots on the dominoes take particular arrangements according to the number represented, and differentiate themselves more clearly from each other than figures do. They are at the same time more easily read than figures or regularly spaced dots. Now, it is very important to fix the attention upon the numbers, since they are arranged at distances expressed in dioptries and indicated by the number of the spots. On looking through the aperture, we see in the first place one of the dominoes more distinctly than the rest. Then, on endeavoring to see those that are nearer or farther off, we succeed in accommodating the eye and in seeing the numbers that express the extreme terms of the accommodation, and consequently the amplitude.
Let us now take some examples: If we wish to express in dioptries the myopia of a person, we put the apparatus in his hand, and ask him to place his eye very near the aperture and note the number of spots on the most distant domino that he sees distinctly. This is the number sought. If the observation be made through the upper lens, it will be necessary to subtract five from the number obtained; if, on the contrary, the other lens is used, it will be necessary to add six.
If it is a question of a presbyope, let him look with his spectacles, and note the nearest domino seen distinctly. This will be the number of dioptries expressing the nearest point at which he can read. This number permits us to know whether it is necessary to add or subtract dioptries in order to allow him to read nearer by or farther off. If, for example, he sees the deuce and the ace distinctly, say 3 dioptries or 0.33 meter, and we want to allow him to read at 0.25 meter, corresponding to four dioptries, it will be necessary to increase the power of his spectacles by one dioptrie.
Upon the whole, Dr. Bull's optometer permits of measuring the amplitude of accommodation, and, consequently, of obtaining the approximate age of people, of knowing the extreme distances of the accommodation, and of quickly finding the number of the glass necessary for each one. It reveals the defects in the accommodation, and serves for the quick determination of refraction. So, in saying that this little instrument is very ingenious and very practical, Dr. Javal has used no exaggeration.—La Nature. |
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