This stated, the play of the apparatus may be easily understood. Every ten minutes a regulating clock closes the circuit of the local pile, B2, and establishes a contact at C. The electro-magnet, E4, attracts its armature, and thus acts upon the lever, h, which presses the sheet of paper against the stylet in front that serves to mark the level of the lowest waters, and against the stylet, g, and the wheels, T and Z. In falling back, the lever, h, causes the advance, by one notch, of the ratchet wheel that is mounted at the extremity of the cylinder W, and thus displaces the sheet of paper a distance of 5 mm. The wheel, Z, carries engraved in projection upon its circumference the hours in Roman figures, and moves forward one division every 60 minutes. The motion of this wheel is likewise controlled by the cylinder, W.

It will be seen upon referring to Fig. 7, that there is obtained a very sharp curve marked by points. We have a general view on considering the curve itself, and the height in meters is read directly. The fractions of a meter, as well as the times, are in the margin. Thus, at the point, a, the apparatus gives at 3 o'clock and 20 minutes a height of tide of 4.28 m. above the level of the lowest water.

This apparatus might possibly operate well, and yet not be in accord with the real indications of the float, so it has been judged necessary to add to it the following control.

Every time the float reaches 3 meters above the level of the lowest tide, the circuit of one of the lines that is open at this moment (that of line I, for example) closes at C (Fig. 2), into this new circuit there is interposed a considerable resistance, W, so that the energy of the current is weakened to such a point that it in nowise influences the normal travel of the wheel, r. At the shore station, there is placed in deviation a galvanoscope, K, whose needle is deflected. It suffices, then, to take datum points upon the registering apparatus, upon the wheel, T, and the screw, a, in such a way as to ascertain the moment at which the stylet, g, is going to mark 3 meters. At this moment the circuit of the galvanoscope, K, is closed, and we ascertain whether there is a deviation of the needle.

As the sea generally rises to the height of 3 meters twice a day, it is possible to control the apparatus twice a day, and this is fully sufficient.

It always belongs to practice to judge of an invention. Mr. Von Hefner-Alteneck tells us that two of these apparatus have been set up—one of them a year ago in the port of Kiel, and the other more recently at the Isle of Wangeroog in the North Sea—and that both have behaved excellently since the very first day of their installation. We shall add nothing to this, since it is evidently the best eulogium that can be accorded them.—La Lumiere Electrique.

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DELUNE & CO.'S SYSTEM OF LAYING UNDERGROUND CABLES.

In recent times considerable attention has been paid to the subject of laying telegraph cables underground, and various methods have been devised. In some cases the cables have been covered with an armor of iron, and in others they have been inclosed in cast-iron pipes. For telephonic service they are generally inclosed in leaden tubes. What this external envelope shall be that is to protect the wires from injury is a question of the highest importance, since not only the subject of protection is concerned, but also that of cost. It is therefore interesting to note the efforts that are being made in this line of electric industry.



Messrs. Delune & Co. have recently taken out a patent for an arrangement consisting of pipes made of beton. The annexed cuts, borrowed from L'Electricite, represent this new system. The pipes, which are provided with a longitudinal opening, are placed end to end and coupled with a cement sleeve. The cables are put in place by simply unwinding them as the work proceeds, and thus all that traction is done away with that they are submitted to when cast iron pipes are used. When once the cables are in place the longitudinal opening is stopped up with cement mortar, and in this way a very tight conduit is obtained whose hardness increases with time. The value of the system therefore depends, as in all cement work, on the care with which the manufacturing is done.

Experiments have been made with the system at Toulouse, by the Minister of Post Offices and Telegraphs, and at Lyons, by the General Society of Telephones. Here, as with all similar questions, no opinion can be pronounced until after a prolonged experience. But we cannot help setting forth the advantages that the system offers. These are, in the first place, a saving of about 50 per cent. over iron pipe, and in the second, a better insulation, and consequently a better protection of the currents against all kinds of disturbance, since a non-conducting mass of cement is here substituted for metal.

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ELECTRICITY APPLIED TO HORSE-SHOEING.

"There is nothing new but what has been forgotten," said Marie Antoinette to her milliner, Mdlle. Bertin, and what is true of fashion is also somewhat so of science. Shoeing restive horses by the aid of electricity is not new, experiments thereon having been performed as long ago as 1879 by Mr. Defoy, who operated with a small magneto machine.

But the two photographs reproduced in Figs. 1 and 2 have appeared to us curious enough to be submitted to our readers, as illustrating Mr. Defoy's method of operating with an unruly animal.



The battery used was a small Grenet bichromate of potash pile, which was easy to graduate on account of the depth to which the zinc could be immersed. This pile was connected with the inductor of a small Ruhmkorff coil, whose armature was connected with a snaffle-bit placed in the horse's mouth.



This bit was arranged as follows (Fig. 3): The two conductors, which were uncovered for a length of about three centimeters at their extremity, were placed opposite each other on the two joints of the snaffle, and about five or six centimeters apart. The mouth-pieces of the bit had previously been inclosed in a piece of rubber tubing, in order to insulate the extremities of the conductors and permit the recomposition of the current to take place through the animal's tongue or palate.

Each of the bare ends of the conductors was provided, under a circular brass ligature, with a small damp sponge, which, surrounding the mouth-piece, secured a perfect contact of each end of the circuit with the horse's mouth.



The horse having been led in, defended himself vigorously as long as an endeavor was made to remove his shoes by the ordinary method, but the current had acted scarcely fifteen seconds when it became possible to lift his feet and strike his shoes with the hammer.

The experimenter having taken care during this experiment to place the bobbin quite near the horse's ear, so that he could hear the humming of the interrupter, undertook a second experiment in the following way: Having detached the conductors from the armature, he placed himself in front of the horse (as shown in Fig. 2), and began to imitate the humming sound of the interrupter with his mouth. The animal at once assumed the stupefied position that the action of the current gave him in the first experiment, and allowed his feet to be lifted and shod without his even being held by the snaffle.

The horse was for ever after subdued, and yet his viciousness and his repugnance to shoeing were such that he could only be shod previously by confining his legs with a kicking-strap.

It should be noted that the action of the induction coil, mounted as this was, was very feeble and not very painful; and yet it was very disagreeable in the mouth, and gave in this case a shock with a sensation of light before the eyes, as we have found by experimenting upon ourselves.

From our own most recent experiments, we have ascertained the following facts, which may guide every horse-owner in the application of electricity to an animal that is opposed to being shod: (1) To a horse that defends himself because he is irritable by temperament, and nervous and impressionable (as happens with animals of pure or nearly pure blood), the shock must be administered feebly and gradually before an endeavor is made to take hold of his leg. The horse will then make a jump, and try to roll over. The jump must be followed, while an assistant holds the bridle, and the action of the current must be at once arrested. After this the horse will not endeavor to defend himself, and his leg may be easily handled.

(2) Certain large, heavy, naturally ugly horses kick through sheer viciousness. In this case, while the current is being given it should be gradually increased in intensity, and the horse's foot must be seized during its action. In most cases the passage of a current through such horses (whose mucous membrane is less sensitive) produces only a slightly stupefied and contracted position of the head, accompanied with a slight tremor. The current must be shut off as soon as the horse's foot is well in one's hand, and be at once renewed if he endeavors to defend himself again, as is rarely the case. It is a mare of this nature that is represented in the annexed figures.

We know that this same system has been applied for bringing to an abrupt standstill runaway horses, harnessed to vehicles; but knowing the effect of a sudden stoppage under such circumstances, we believe that the remedy would prove worse than the disease, since the coachman and vehicle, in obedience to the laws of inertia, would continue their motion and pass over the animals, much to their detriment.—Science et Nature.

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ESTEVE'S AUTOMATIC PILE.

Mr. Esteve has recently devised a generator of electricity which he claims to be energetic, constant, and always ready to operate. The apparatus is designed for the production of light and for actuating electric motors, large induction bobbins, etc.

We give a description of it herewith from data communicated by its inventor.

The accompanying cut represents a battery of 6 elements, with a reservoir, R, for the liquid, provided at its lower part with a cock for allowing the liquid to enter the pile. The vessels of the different elements are of rectangular form. At the upper part, and in the wider surfaces of each, there are two tubes. The first tube of the first vessel receives the extremity of a safety-tube, A, whose other extremity enters the upper part of the reservoir, R. This tube is designed for regulating the flow of the liquid into the pile. When the cock, r, is too widely open, the liquid might have a tendency to flow over the edges of the vessel; but this would close the orifice of the tube, A, and, as the air would then no longer enter the reservoir, R, the flow would be stopped automatically. The second tube of the first vessel is connected with a lead tube, 1, one of the extremities of which enters the second vessel. The other tubes are arranged in the same way in the other vessels. The renewal of the liquids is effected by displacement, in flowing upward from one element over into another; and the liquids make their exit from the pile at D, after having served six times. The electrodes of the two first elements are represented as renewed in the cut, in order to show the arrangement of the tubes.



Dimensions.—The zinc, 2, has a superficies of 15x20 centimeters, and is cut out of the ordinary commercial sheet metal. It may be turned upside down when one end has become worn away, thus permitting of its being entirely utilized. The negative electrode is formed of four carbons, which have, each of them, a superficies of 8x21 centimeters. These four carbons are less fragile and are more easily handled than two having the same surface. Their arrangement is shown at the left of the figure. They are fixed to a strip of copper, a, to which is soldered another strip, L, bent at right angles. There are thus two pairs of carbon per element, and these are simply suspended from a piece of wood, as shown in the figure. Upon this wooden holder will be seen the two strips, LL, that are designed to be put in contact with the zinc of the succeeding element by means of pinchers that connect the electrodes with one another. This arrangement permits the pile to be taken apart very quickly.

Charging, Work, and Duration of the Pile.—The inventor has made a large number of experiments with solutions of bichromate of potash of various degrees of saturation, and has found the following to give the best results:

Bichromate of potash. 1 kilogramme. Sulphuric acid 2 liters. Water 8 "

When a larger quantity of the salt is used, crystallization occurs in the pile.

Constants and work Constants and work of an element of a round Bunsen having a zinc of element, 20x30 cm. 16x20 cm.

Volts. 1.9 1.8 Resistance. 0.05 0.24 Work disposable in the external circuit. 1.839 k. 0.344 k.

The work disposable in the external circuit is deduced from the formula:

T = E squared/(4R x 9.81)

It will be seen that an element thus charged gives as much energy as 5.3 large Bunsen elements.

The battery is charged with 10 liters of solution, and is capable of furnishing for 5 hours a current of 7 amperes with a difference of potential of 9 volts at the pile terminals. The work, according to the formula (EI)/g, equals 6.422 kilogram-meters; with a feebler resistance in the external circuit it is capable of producing a current of 19 amperes for an hour and an half. In this case the resistance of the external circuit equals the interior resistance of the pile. Upon immersing the electrodes in new liquid, and with no resistance in the external circuit, the current may reach 100 amperes. On renewing the liquids during the operation of the pile, a current of 7 amperes is kept up if about a liter of saturation per hour be allowed to pass into the battery. For five hours, then, only 5 liters are used instead of the 10 that are necessary when the liquid is not renewed while the pile is in action.—La Nature.

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WOODWARD'S DIFFUSION MOTOR.

The energy produced by the phenomena of diffusion is exhibited in lecture courses by placing a bell glass filled with hydrogen over a porous vessel at whose base is fixed a glass tube that dips into water. The hydrogen, in diffusing, enters the porous vessel, increases the internal pressure, and a number of bubbles escapes from the tube. On withdrawing the bell glass of hydrogen, the latter becomes diffused externally, a lower pressure occurs in the porous vessel, and the level of the water rises.

The arrangement devised by Mr. C.J. Woodward, and recently presented to the Physical Society of London, is an adaptation of this experiment to the production of an oscillating motion by alternations in the internal and external diffusion of the hydrogen.

The apparatus, represented herewith, consists of a scale beam about three feet in length that supports at one end a scale pan and weights, and, at the other, a corked porous vessel that carries a glass tube, c, which dips into a vessel containing either water or methylic alcohol. Three or four gas jets, one of which is shown at E, are arranged around the porous vessel, as close as possible, but in such a way as not to touch it during the oscillation of the beam. These gas jets communicate with a gasometer tilled with hydrogen, the bell of which is so charged as to furnish a jet of sufficient strength. Experience will indicate the best place to give the gas jets, but, in general, it is well to locate them at near the center of the porous vessel when the beam is horizontal.



It is now easy to see how the device operates. When the hydrogen comes in presence of the porous vessel it becomes diffused therein, and the pressure exerted in the interior then produces an ascent. When the bottom of the porous vessel gets above the jets, the internal diffusion ceases and the hydrogen becomes diffused externally, the internal pressure diminishes, and the vessel descends. The vessel then comes opposite the jets of hydrogen and the same motion occurs again, and soon indefinitely. The work produced by this motor, which has purely a scientific interest, is very feeble, and much below that assigned to it by theory. In order to obtain a maximum, it would be necessary to completely surround the porous vessel each time with hydrogen, and afterward remove the jets to facilitate the access of air. All the mechanical arrangements employed for obtaining such a result have failed, because the friction introduced by the maneuvering parts also introduces a resistance greater than the motor can overcome. There is therefore a waste of energy due to the continuous flow of hydrogen; but the apparatus, for all that, constitutes none the less an original and interesting device.—La Nature.

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SOME RELATIONS OF HEAT TO VOLTAIC AND THERMO-ELECTRIC ACTION OF METALS IN ELECTROLYTES.[1]

[Footnote 1: Read before the Royal Society, Nov., 1883.]

By G. GORE, F.R.S., LL.D.

The experiments described in this paper throw considerable light upon the real cause of the voltaic current. The results of them are contained in twenty tables; and by comparing them with each other, and also by means of additional experiments, the following general conclusions and chief facts were obtained.

When metals in liquids are heated, they are more frequently rendered positive than negative in the proportion of about 2.8 to 1.0; and while the proportion in weak solutions was about 2.29 to 1.0, in strong ones it was about 3.27 to 1.0, and this accords with their thermo-electric behavior as metals alone. The thermo-electric order of metals in liquids was, with nearly every solution, whether strong or weak, widely different from the thermo-electric order of the same metals alone. A conclusion previously arrived at was also confirmed, viz., that the liquids in which the hot metal was thermo-electro-positive in the largest proportion of cases were those containing highly electro-positive bases, such as the alkali metals. The thermo-electric effect of gradually heating a metal in a liquid was sometimes different from that of suddenly heating it, and was occasionally attended by a reversal of the current.

Degree of strength of liquid greatly affected the thermo-electric order of metals. Increase of strength usually and considerably increased the potential of metals thermo-electro-negative in liquids, and somewhat increased that of those positive in liquids.

The electric potential of metals, thermo-electro-positive in weak liquids, was usually about 3.87 times, and in strong ones 1.87 times, as great as of those which were negative. The potential of the strongest thermo-electric couple, viz., that of aluminum in weak solution of sodic phosphate, was 0.66 volt for 100 deg. F. difference of temperature, or about 100 times that of a bismuth and antimony couple.

Heating one of the metals, either the positive or negative, of a voltaic couple, usually increased their electric difference, making most metals more positive, and some more negative; while heating the second one also usually neutralized to a large extent the effect of heating the first one. The electrical effect of heating a voltaic couple is nearly wholly composed of the united effects of heating each of the two metals separately, but is not however exactly the same, because while in the former case the metals are dissimilar, and are heated to the same temperature, in the latter they are similar, but heated to different temperatures. Also, when heating a voltaic pair, the heat is applied to two metals, both of which are previously electro-polar by contact with each other as well as by contact with the liquid; but when heating one junction of a metal and liquid couple, the metal has not been previously rendered electro-polar by contact with a different one, and is therefore in a somewhat different state. When a voltaic combination, in which the positive metal is thermo-negative, and the negative one is thermo-positive, is heated, the electric potential of the couple diminishes, notwithstanding that the internal resistance is decreased.

Magnesium in particular, also zinc and cadmium, were greatly depressed in electromotive force in electrolytes by elevation of temperature. Reversals of position of two metals of a voltaic couple in the tension series by rise of temperature were chiefly due to one of the two metals increasing in electromotive force faster than the other, and in many cases to one metal increasing and the other decreasing in electromotive force, but only in a few cases was it a result of simultaneous but unequal diminution of potential of the two metals. With eighteen different voltaic couples, by rise of temperature from 60 deg. to 160 deg. F., the electromotive force in twelve cases was increased, and in six decreased, and the average proportions of increase for the eighteen instances was 0.10 volt for the 100 deg. F. of elevation.

A great difference in chemical composition of the liquid was attended by a considerable change in the order of the volta-tension series, and the differences of such order in two similar liquids, such as solutions of hydric chloride and potassic chloride, were much greater than those produced in either of those liquids by a difference of 100 deg. F. of temperature. Difference of strength of solution, like difference of composition or of temperature, altered the order of such series with nearly every liquid; and the amount of such alteration by an increase of four or five times in the strength of the liquid was rather less than that caused by a difference of 100 deg. F. of temperature. While also a variation of strength of liquid caused only a moderate amount of change of order in the volta-tension series, it produced more than three times that amount of change in the thermo-electric tension series. The usual effect of increasing the strength of the liquid upon the volta-electromotive force was to considerably increase it, but its effect upon the thermo-electro-motive force was to largely decrease it. The degree of potential of a metal and liquid thermo-couple was not always exactly the same at the same temperature during a rise as during a fall of temperature; this is analogous to the variations of melting and solidifying points of bodies under such conditions, and also to that of supersaturation of a liquid by a salt, and is probably due to some hinderance to change of molecular movement.

The rate of ordinary chemical corrosion of each metal varied in every different liquid; in each solution also it differed with every different metal. The most chemically positive metals were usually the most quickly corroded, and the corrosion of each metal was usually the fastest with the most acid solutions. The rate of corrosion at any given temperature was dependent both upon the nature of the metal and upon that of the liquid, and was limited by the most feebly active of the two, usually the electrolyte. The order of rate of corrosion of metals also differed in every different liquid. The more dissimilar the chemical characters of two liquids, the more diverse usually was the order of rapidity of corrosion of a series of metals in them. The order of rate of simple corrosion in any of the liquids examined differed from that of chemico-electric and still more from that of thermo-electric tension. Corrosion is not the cause of thermo-electric action of metals in liquids.

Out of fifty-eight cases of rise of temperature the rate of ordinary corrosion was increased in every instance except one, and that was only a feeble exception—the increase of corrosion from 60 deg. to 160 deg. F. with different metals was extremely variable, and was from 1.5 to 321.6 times. Whether a metal increased or decreased in thermo-electromotive force by being heated, it increased in rapidity of corrosion. The proportions in which the most corroded metal was also the most thermo-electro-positive one was 65.57 per cent. in liquids at 60 deg. F., and 69.12 in the same liquids at 160 deg. F.; and the proportion in which it was the most chemico-electro-positive at 60 F. was 84.44 per cent, and at 160 deg. F. 80.77 per cent. The proportion of cases therefore in which the most chemico-electro-negative metal was the most corroded one increased from 15.56 to 19.23 per cent, by a rise of temperature of 100 deg. F. Comparison of these proportions shows that corrosion usually influenced in a greater degree chemico-electric rather than thermo-electric actions of metals in liquids. Not only was the relative number of cases in which the volta-negative metal was the most corroded increased by rise of temperature, but also the average relative loss by corrosion of the negative to that of the positive one was increased from 3.11 to 6.32.

The explanation most consistent with all the various results and conclusions is a kinetic one: That metals and electrolytes are throughout their masses in a state of molecular vibration. That the molecules of those substances, being frictionless bodies in a frictionless medium, and their motion not being dissipated by conduction or radiation, continue incessantly in motion until some cause arises to prevent them. That each metal (or electrolyte), when unequally heated, has to a certain extent an unlike class of motions in its differently heated parts, and behaves in those parts somewhat like two metals (or electrolytes), and those unlike motions are enabled, through the intermediate conducting portion of the substance, to render those parts electro-polar. That every different metal and electrolyte has a different class of motions, and in consequence of this, they also, by contact alone with each other at the same temperature, become electro-polar. The molecular motion of each different substance also increases at a different rate by rise of temperature.

This theory is equally in agreement with the chemico-electric results. In accordance with it, when in the case of a metal and an electrolyte, the two classes of motions are sufficiently unlike, chemical corrosion of the metal by the liquid takes place, and the voltaic current originated by inherent molecular motion, under the condition of contact, is maintained by the portions of motion lost by the metal and liquid during the act of uniting together. Corrosion therefore is an effect of molecular motion, and is one of the modes by which that motion is converted into and produces electric current.

In accordance with this theory, if we take a thermo-electric pair consisting of a non-corrodible metal and an electrolyte (the two being already electro-polar by mutual contact), and heat one of their points of contact, the molecular motions of the heated end of each substance at the junction are altered; and as thermo-electric energy in such combinations usually increases by rise of temperature, the metal and liquid, each singly, usually becomes more electro polar. In such a case the unequally heated metal behaves to some extent like two metals, and the unequally heated liquid like two liquids, and so the thermo-electric pair is like a feeble chemico-electric one of two metals in two liquids, but without corrosion of either metal. If the metal and liquid are each, when alone, thermo-electro-positive, and if, when in contact, the metal increases in positive condition faster than the liquid by being heated, the latter appears thermo-electro-negative, but if less rapidly than the liquid, the metal appears thermo-electro-negative.

As also the proportion of cases is small in which metals that are positive in the ordinary thermo-electric series of metals only become negative in the metal and liquid ones (viz., only 73 out of 286 in weak solutions, and 48 out of the same number in strong ones), we may conclude that the metals, more frequently than the liquids, have the greatest thermo-electric influence, and also that the relative largeness of the number of instances of thermo-electro-positive metals in the series of metals and liquids, as in the series of metals only, is partly a consequence of the circumstance that rise of temperature usually makes substances—metals in particular—electro-positive. These statements are also consistent with the view that the elementary substances lose a portion of their molecular activity when they unite to form acids or salts, and that electrolytes therefore have usually a less degree of molecular motion than the metals of which they are partly composed.

The current from a thermo-couple of metal and liquid, therefore, may be viewed as the united result of difference of molecular motion, first, of the two junctions, and second, of the two heated (or cooled) substances; and in all cases, both of thermo- and chemico-electric action, the immediate true cause of the current is the original molecular vibrations of the substances, while contact is only a static permitting condition. Also that while in the case of thermo-electric action the sustaining cause is molecular motion, supplied by an external source of heat, in the case of chemico-electric action it is the motion lost by the metal and liquid when chemically uniting together. The direction of the current in thermo-electric cases appears to depend upon which of the two substances composing a junction increases in molecular activity the fastest by rise of temperature, or decreases the most rapidly by cooling.

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AIR REFRIGERATING MACHINE.



Messrs. J. & E. Hall, Dartford, exhibit at the International Health Exhibition, London, in connection with a cold storage room, two sizes of Ellis' patent air refrigerator, the larger one capable of delivering 5,000 cubic feet of cold air per hour, when running at a speed of 150 revolutions per minute; and the smaller one 2,000 cubic feet of cold air per hour, at 225 revolutions per minute. The special features in these machines are the arrangement of parts, by which great compactness is secured, and the adoption of flat slides for the compressor, instead of the ordinary beat valves, which permits of a high rate of revolution without the objectionable noise which is caused by clacks beating on their seats. The engraving shows the general arrangement of the apparatus. Figs. 1 to 4 show details of the compression and expansion valves, which are ordinary flat slides, partly balanced, and held up to their faces by strong springs from behind. The steam, compression, and expansion cylinders are severally bolted to the end of a strong frame, which though attached to the cooler box does not form part of it, the object being to meet the strains between the cylinders and shaft in as direct a manner as possible without allowing them to act on the cooler casting. Each cylinder is double acting, the pistons being coupled to the shaft by three connecting rods, the two outer ones working upon crank pins fixed to overhung disks, and the center one on a crank formed in the shaft. The slide valves for all the cylinders are driven from two weigh shafts, the main valve shaft being actuated by a follow crank, and the expansion and cut off valves from the crosshead pin of the compressor. The machines may be used either in the vertical position as exhibited, or may be fixed horizontally; and it is stated that the construction is such as to admit of speeds of 200 and 300 revolutions per minute respectively for the larger and smaller machines, under which conditions the delivery of cold air may be taken at about 7,000 and 2,600 cubic feet per hour. Messrs. Hall also make this class of refrigerator without the steam cylinder, and arranged to be driven by a belt from a gas engine or any existing motive power.

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A GAS RADIATOR AND HEATER.



There is now being introduced into Germany a gas radiator and heater, the invention of Herr Wobbe. It consists, as will be seen in engraving above, of a series of vertical U-shaped pipes, of wrought iron, 50 millimeters (2 inches) in diameter. The two legs of the U are of unequal length; the longer being about 5 feet, and the shorter 3 feet (exclusive of the bend at the top). Beneath the open end of the shorter leg of each pipe is placed a burner, attached to a horizontal gas-pipe, which turns upon an axis. The object of having this pipe rotate is to bring the burners into an inclined position—shown by the dotted lines in Fig. 2—for lighting them. On turning them back to the vertical position, the heated products of combustion pass up the shorter tube and down the longer, where they enter a common receptacle, from which they pass into the chimney or out of doors. Surrounding the pipes are plates of sheet iron, inclined at the angle shown in Fig. 2. The object of the plates is to prevent the heated air of the room from passing up to the ceiling, and send it out into the room. To prevent any of the pipes acting as chimneys, and bringing the products of combustion back into the room, as well as to avoid any back-pressure, a damper is attached to the outlet receptacle. The heated gas becomes cooled so much (to about 100 deg. Fahr.) that water is condensed and precipitated, and collects in the vessel below the outlet. Each burner has a separate cock, by which it may be kept closed, half-open, or open. To obviate danger of explosion, there is a strip of sheet iron in front of the burners, which prevents their being lighted when in a vertical position; so that, in case any unburned gas gets into the pipes, it cannot be ignited, for the burners can only be lighted when inclined to the front. In starting the stove the burners are lighted, in the inclined position; the chain from the damper pulled up; the burners set vertical; and, as soon as they are all drawing well into the tubes, the damper is closed. If less heat is desired, the cocks are turned half off. It is not permissible to entirely extinguish some of the burners, unless the unused pipes are closed to prevent the products of combustion coming back into the room. The consumption of gas per burner, full open, with a pressure of 8/10, is said to be only 4-3/8 cubic feet per hour.

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CONCRETE WATER PIPES.

Concrete water pipes of small diameter, according to a foreign contemporary, are used in parts of France, notably for water mains for the towns of Coulommiers and Aix-en-Provence. The pipes were formed of concrete in the trench itself. The mould into which the concrete was stamped was sheet iron about two yards in length. The several pipes were not specially joined to each other, the joints being set with mortar. The concrete consisted of three parts of slow setting cement and three parts of river sand, mixed with five parts of limestone debris. The inner diameter of the pipes was nine inches; their thickness, three inches. The average fall is given at one in five hundred; the lowest speed of the current at one foot nine inches per second. To facilitate the cleaning of the pipes, man-holes are constructed every one hundred yards or so, the sides of which are also made of concrete. The trenches are about five feet deep. The work was done by four men, who laid down nearly two hundred feet of pipe in a working day; the cost was about ninety-three cents per running yard. It is claimed as an advantage for the new method that the pipes adhere closely to the inequalities of the trench, and thus lie firmly on the ground. When submitted to great pressure, however, they have not proved effective, and the method, consequently, is only suitable for pipes in which there is no pressure, or only a very trifling one.

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THE SELLERS STANDARD SYSTEM OF SCREW THREADS, NUTS, AND BOLT HEADS.

SCREW THREADS. Diam. Threads Diameter Area of Width of per at root of Bolt at of Screw. inch. Thread. root of Flat. Thread. 1/4 20 .185 13/64 .026 .0062 5/16 18 .240 15/64 .045 .0074 3/8 16 .294 19/64 .067 .0078 7/16 14 .344 11/32 .092 .0089 1/2 13 .400 13/32 .125 .0096 9/16 12 .454 29/64 .161 .0104 5/8 11 .507 33/64 .201 .0113 3/4 10 .620 5/8 .301 .0125 7/8 9 .731 47/64 .419 .0138 1 8 .837 27/32 .550 .0156 1-1/8 7 .940 15/16 .693 .0178 1-1/4 7 1.065 1- 1/16 .890 .0178 1-3/8 6 1.160 1- 5/32 1.056 .0208 1-1/2 6 1.284 1- 9/32 1.294 .0208 1-5/8 5-1/2 1.389 1-25/64 1.515 .0227 1-3/4 5 1.491 1-31/64 1.746 .0250 1-7/8 5 1.616 1-39/64 2.051 .0250 2 4-1/2 1.742 1-23/32 2.301 .0277 2-1/4 4-1/2 1.962 1-31/32 3.023 .0277 2-1/2 4 2.176 2-11/64 3.718 .0312 2-3/4 4 2.426 2-27/64 4.622 .0312 3 3-1/2 2.629 2- 5/8 5.428 .0357 3-1/4 3-1/2 2.879 2- 7/8 6.509 .0357 3-1/2 3-1/4 3.100 3- 3/32 7.547 .0384 3-3/4 3 3.317 3- 5/16 8.614 .0413 4 3 3.567 3- 9/16 9.993 .0413 4-1/4 2-7/8 3.798 3-51/64 11.329 .0435 4-1/2 2-3/4 4.028 4- 1/32 12.742 .0454 4-3/4 2-5/8 4.256 4- 1/4 14.226 .0476 5 2-1/2 4.480 4-31/64 15.763 .0500 5-1/4 2-1/2 4.730 4-47/64 17.570 .0500 5-1/2 2-3/8 4.953 4-61/64 19.267 .0526 5-3/4 2-3/8 5.203 5-13/64 21.261 .0526 6 2-1/4 5.423 5-27/64 23.097 .0555 NUTS. Short Short Long Long Thick- Thick- Diam. Diam. Diam. Diam. ness ness Rough. Finish. Rough. Rough. Rough. Finish. (Hex.) (Hex.) (Hex.) (Square) 1/2 7/16 37/64 7/10 1/4 3/16 19/32 17/32 11/16 10/12 5/16 1/4 11/16 5/8 51/64 63/64 3/8 5/16 25/32 23/33 9/10 1- 7/64 7/16 3/8 7/8 13/16 1 1-15/64 1/2 7/16 31/32 29/32 1- 1/8 1-23/64 9/16 1/2 1-1/16 1 1- 7/32 1- 1/2 5/8 9/16 1-1/4 1-3/16 1- 7/16 1-49/64 3/4 11/16 1-7/16 1-3/8 1-21/32 2- 1/32 7/8 13/16 1- 5/8 1-9/16 1- 7/8 2-19/64 1 15/16 1-13/16 1- 3/4 2- 5/32 2- 9/16 1-1/8 1- 1/16 2 1-15/16 2- 5/16 2-53/64 1-1/4 1- 3/16 2- 3/16 2- 1/8 2-17/32 3- 3/32 1-3/8 1- 5/16 2- 3/8 2- 5/16 2- 3/4 3-23/64 1-1/2 1- 7/16 2- 9/16 2- 1/2 2-31/32 3- 5/8 1-5/8 1- 9/16 2- 3/4 2-11/16 3- 3/16 3-57/64 1-3/4 1-11/16 2-15/16 2- 7/8 3-13/32 4- 5/32 1-7/8 1-13/16 3-1/8 3- 1/16 3- 5/8 4-27/64 2 1-15/16 3-1/2 3- 7/16 4- 1/16 4-61/64 2-1/4 2- 3/16 3-7/8 3-13/16 4- 1/2 5-31/64 2-1/2 2- 7/16 4-1/4 4- 3/16 4-29/32 6 2-3/4 2-11/16 4-5/8 4- 9/16 5- 3/8 6-17/32 3 2-15/16 5 4-15/16 5-13/16 7- 1/16 3-1/4 3- 3/16 5-3/8 5- 5/16 6- 7/32 7-39/64 3-1/2 3- 7/16 5-3/4 5-11/16 6-21/32 8- 1/8 3-3/4 3-11/16 6-1/8 6- 1/16 7- 3/32 8-41/64 4 3-15/16 6-1/2 6- 7/16 7- 9/16 9- 3/16 4-1/4 4- 3/16 6-7/8 6-13/16 7-31/32 9- 3/4 4-1/2 4- 7/16 7-1/4 7- 3/16 8-13/32 10- 1/4 4-3/4 4-11/16 7-5/8 7- 9/16 8-27/32 10-49/64 5 4-15/16 8 7-15/16 9- 9/32 11-23/64 5-1/4 5- 3/16 8-3/8 8- 5/16 9-23/32 11- 7/8 5-1/2 5- 7/16 8-3/4 8-11/16 10- 5/32 12- 3/8 5-3/4 5-11/16 9-1/8 9- 1/16 10-19/32 12-15/16 6 5-15/16 BOLT HEADS. Short Short Long Long Thick- Thick- Diam. Diam. Diam. Diam. ness ness Rough. Finish. Rough. Rough. Rough. Finish. (Hex.) (Hex.) (Hex.) (Square) 1/2 7/16 37/64 7/10 1/4 3/16 19/32 17/32 11/16 10/12 19/64 1/4 11/16 5/8 51/64 63/64 11/32 5/16 25/32 23/32 9/16 1-7/64 25/64 3/8 7/8 13/16 1 1-15/64 7/16 7/16 31/32 29/32 1- 1/8 1-23/64 31/64 1/2 1- 1/16 1 1- 7/32 1- 1/2 17/32 9/16 1- 1/4 1- 3/16 1- 7/16 1-49/64 5/8 11/16 1- 7/16 1- 3/8 1-21/32 2- 1/32 23/32 13/16 1- 5/8 1- 9/16 1- 7/8 2-19/64 13/16 15/16 1-13/16 1- 3/4 2- 5/32 2- 7/16 29/32 1- 1/16 2 1-15/16 2- 5/16 2-53/64 1 1- 3/16 2- 3/16 2- 1/8 2-17/32 3- 3/32 1- 3/32 1- 5/16 2- 3/8 2- 5/16 2- 3/4 3-23/64 1- 3/16 1- 7/16 2- 9/16 2- 1/2 2-31/32 3- 5/8 1- 9/32 1- 9/16 2- 3/4 2-11/16 3- 3/16 3-57/64 1- 3/8 1-11/16 2-15/16 2- 7/8 3-13/32 4- 5/32 1-15/32 1-13/16 3- 1/8 3- 1/16 3- 5/8 4-27/64 1- 9/16 1-15/16 3- 1/2 3- 7/16 4- 1/16 4-61/64 1- 3/4 2- 3/16 3- 7/8 3-13/16 4- 1/2 5-31/64 1-15/16 2- 7/16 4- 1/4 4- 3/16 4-29/32 6 2- 1/8 2-11/16 4- 5/8 4- 9/16 5- 3/8 6-17/32 2- 5/16 2-15/16 5 4-15/16 5-13/16 7- 1/16 2- 1/2 3- 3/16 5- 3/8 5- 5/16 6- 7/32 7-39/64 2-11/16 3- 7/16 5- 3/4 5-11/16 6-21/32 8- 1/8 2- 7/8 3-11/16 6- 1/8 6- 1/16 7- 3/32 8-41/64 3- 1/16 3-15/16 6- 1/2 6- 7/16 7- 9/16 9- 3/16 3- 1/4 4- 3/16 6- 7/8 6-13/16 7-31/32 9- 3/4 3- 7/16 4- 7/16 7- 1/4 7- 3/16 8-13/32 10- 1/4 3- 5/8 4-11/16 7- 5/8 7- 9/16 8-27/32 10-49/64 3-13/16 4-15/16 8 7-15/16 9- 9/32 11-23/64 4 5- 3/16 8- 3/8 8- 5/16 9-23/32 11- 7/8 4- 3/16 5- 7/16 8- 3/4 8-11/16 10- 5/32 12- 3/8 4- 3/8 5-11/16 9- 1/8 9- 1/16 10-19/32 12-15/16 4- 9/16 5-15/16

The dimensions given for diameter at root of threads are also those for diameter of hole in nuts and diameter of lap drills. All bolts and studs 3/4 in. diameter and above, screwed into boilers, have 12 threads per inch, sharp thread, a taper of 1/16 in. per 1 inch; tap drill should be 9/64 in. less than normal diameter of bolts.

The table is based upon the following general formulae for certain dimensions:

Short diam. rough nut or head = 11/2 diam. of bolt + 1/8. " finished nut or head = 11/2 diam. of bolt + 1/16. Thickness rough nut = diameter of bolt. Thickness finished nut = diameter of bolt - 1/16. Thickness rough head = 1/2 short diameter. Thickness finished head = diameter of bolt - 1/16.

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AN ENGLISH RAILWAY FERRY BOAT.



The illustrations above represent a double screw steam ferry boat for transporting railway carriages, vehicles, and passengers, etc., designed and constructed by Messrs. Edwards and Symes, of Cubitt Town, London. The hull is constructed of iron, and is of the following dimensions: Length 60 ft.; beam 16 ft.; over sponsons 25 ft. The vessel was fitted with a propeller, rudder, and steering gear at each end, to enable it to run in either direction without having to turn around. The boat was designed for the purpose of working the train service across the bay of San Juan, in the island of Puerto Rico, and for this purpose a single line of steel rails, of meter gauge, is laid along the center of the deck, and also along the hinged platforms at each end. In the engraving these platforms are shown, one hoisted up, and the other lowered to the level of the deck. When the boat is at one of the landing stages, the platform is lowered to the level of the rails on the pier, and the carriages and trucks are run on to the deck by means of the small hauling engine, which works an endless chain running the whole length of the deck. The trucks, etc., being on board, the platform is raised by means of two compact hand winches worked by worm and worm-wheels in the positions shown; thus these two platforms form the end bulwarks to the boat when crossing the bay. On arriving at the opposite shore the operation is repeated, the other platform is lowered, and the hauling engine runs the trucks, etc., on to the shore. With a load of 25 tons the draught is 4 ft.

The seats shown on the deck are for the convenience of foot passengers, and the whole of the deck is protected from the sun of that tropical climate by a canvas awning. The steering of the vessel is effected from the bridge at the center, which extends from side to side of the vessel, and there are two steering wheels with independent steering gear for each end, with locking gear for the forward rudder when in motion. The man at the wheel communicates with the engineer by means of a speaking tube at the wheel. There is a small deck house for the use of deck stores, on one side of which is the entrance to the engine room. The cross battens, shown between the rails, are for the purpose of horse traffic, when horses are used for hauling the trucks, or for ordinary carts or wagons. The plan below deck shows the arrangement of the bulkheads, with a small windlass at each end for lifting the anchors, and a small hatch at each side for entrance to these compartments. The central compartment contains the machinery, which consists of a pair of compound surface condensing engines, with cylinders 11 in. and 20 in. in diameter; the shafting running the whole length of the vessel, with a propeller at each end. Steam is generated in a steel boiler of locomotive form, so arranged that the funnel passes through the deck at the side of the vessel; and it is designed for a working pressure of 100 lb. per square inch. This boiler also supplies steam for the small hauling engine fixed on the bulkhead. Light to this compartment is obtained by means of large side scuttles along each side of the boat and glass deck lights, and the iron grating at the entrance near the deck house. This boat was constructed in six pieces for shipment, and the whole put together in the builders' yard. The machinery was fixed, and the engine driven by steam from its own boiler, then the whole was marked and taken asunder, and shipped to the West Indies, where it was put together and found to answer the purpose intended.—Engineering.

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[For THE SCIENTIFIC AMERICAN.]



THE PROBLEM OF FLIGHT, AND THE FLYING MACHINE.

As a result of reading the various communications to the SCIENTIFIC AMERICAN and SUPPLEMENT, and Van Nostrand's Engineering Magazine, including descriptions of proposed and tested machines, and the reports of the British Aeronautical Society, the writer of the following concludes:

That, as precedents for the construction of a successful flying machine, the investigation of some species of birds as a base of the principles of all is correct only in connection with the species and habits of the bird; that the general mechanical principles of flight applicable to the operation of the same unit of wing in all species are alone applicable to the flying machine.

That these principles of operation do not demand the principles of construction of the bird.

That as the wing is in its stroke an arc of a screw propeller's operation, and in its angle a screw propeller blade, its animal operation compels its reciprocation instead of rotation.

That the swifter the wing beat, the more efficient its effect per unit of surface, the greater the load carried, and the swifter the flight.

That the screw action being, in full flight, that of a screw propeller whose axis of rotation forms a slight angle with the vertical, the distance of flight per virtual "revolution" of "screw" wing far exceeds the pitch distance of said "screw."

That consequently a bird's flight answers to an iceboat close hauled; the wing force answering to the wind, the wing angle to the sail, the bird's weight to the leeway fulcrum of the ice, and the passage across direction of the wing flop to the fresh moving "inertia" of the wind, both yielding a maximum of force to bird or iceboat.

That the speed of reciprocation of a fly's wing being equivalent to a screw rotation of 9,000 per minute, proves that a screw may be run at this speed without losing efficiency by centrifugal vacuum.

That as the object of wing or screw is to mount upon the inertia of the particles of a mobile fluid, and as the rotation of steamship propellers in water—a fluid of many times the inertia of air—is already in excess of the highest speed heretofore tried in the propellers of moderately successful flying machines, it is plain that the speed employed in water must be many times exceeded in air.

That with a sufficient speed of rotation, the supporting power of the inertia of air must equal that of water.

That as mere speed of rotation of propeller shaft, minus blades, must absorb but a small proportion of power of engine, the addition of blades will not cause more resistance than that actually encountered from inertia of air.

That this must be the measure of load lifted.

That without slip of screw, the actual power expended, will be little in excess of that required to support the machine in water, with a slower rotation of screw.

That in case the same power is expended in water or air, the only difference will lie in the sizes and speed of engines or screws.

That the greater the speed, the less weight of engine, boiler, and screw must be, and the stronger their construction.

That, in consequence, solid metal worked down, instead of bolts and truss work, must be used.

That as the bird wing is a screw in action, and acts directly between the inertias of the load and the air, the position and operation of the screw, to the load, must imitate it.

That, in consequence, machines having wing planes, driven against one inertia of air by screws acting in the line, of flight against another inertia of air, lose fifty per cent. of useful effect, besides exposing to a head wind the cross section of the stationary screw wing planes and the rotating screw discs; and supporting the dead weight of the wing planes, and having all the screw slip in the line of flight, and carrying slow and heavy engines.

That as a result of these conclusions, the supporting and propelling power should be expressed in the rotation of screws combining both functions, the position of whose planes of rotation to a fixed horizontal line of direction determines the progress and speed of machine upon other lines.

That the whole weight carried by the screws should be at all times exactly below the center of gravity of the plane of support, whether it be horizontal or inclined.

That while the permanently positioned weight, such as the engines, frame, holding screws, etc., may be rigidly connected to or around the screw plane of support, the variable positioned weight, such as the passenger and the car, should be connected by a flexible joint to the said plane of support.

Consequently, the car may oscillate without altering its weight position under center of supporting plane, thus avoiding an involuntary alteration of speed or direction of flight.

That to steer a machine so constructed, it is merely necessary to move the point of attachment of car to machine proper, out of the center of plane of support in the desired direction, and thus cause the plane of support or rotation of propellers to incline in that direction.

That the reservoir of power, the boiler, etc., should be placed in the car, and steam carried to engines through joint connecting car with machine.

That at present material exists, and power also, of sufficient lightness and strength to admit of a machine construction capable of a limited successful flight in any fair wind and direction.

That such machine once built, the finding of a power for long flights will be easy, if not already close at hand in electricity.

That the easiest design for such actual machine should be adopted, leaving the adaptation of the principles involved to the making of more perfect machines, to a time after the success of the first.

That such design may be a propeller, and its engine at each end of a steel frame tube, supporting tube horizontally, a car to be supported by a universal joint from center of said tube, and the joint apparatus movable along the tube or a short distance transverse to it, to alter position of center of gravity.

That the machine so built might traverse the water as well as air.

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THE LONGHAIRED POINTER MYLORD.

Pointers are trained to search for game, and to indicate that they have found the same by standing motionless in front of it, and, when it has been shot, to carry the game to the huntsman. Several kinds of pointers are known, such as smooth, longhaired, and bushyhaired pointers. The smoothhaired pointers are better for hunting on high land, whereas the longhaired or bushyhaired dogs are better for low, marshy countries, crossed by numerous streams, etc. Mylord, the dog represented in the annexed cut taken from the Illustrirte Zeitung, is an excellent specimen of the longhaired pointer, and is owned by Mr. G. Borcher, of Braunschweig, Germany.



The longhaired pointer is generally above the medium size, powerful, somewhat longer than the normal dog, the body is narrower and not quite as round as that of the smoothhaired dog, and the muscles of the shoulders and hind legs are not as well developed and not as prominent. The head and neck are erect, the head being specially long, and the tail is almost horizontal to the middle, and then curves upward slightly. The long hair hangs in wavy lines on both sides of his body. The expression of his face is intelligent, bright, and good-natured, and his step is light and almost noiseless.

The pointer is specially valuable, as it can be employed for many different purposes; he is an excellent dog for the woods, for the woodsman and hunter who uses only one dog for different kinds of game. The intelligence of the German pointer is very great, but he does not develop as rapidly as the English dog, which has been raised for generations for one purpose only. The German pointer hunts very slowly, but surely. It is not difficult to train this dog, but he cannot be trained until he has reached a certain age.

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LUNAR HEAT.

By Professor C.A. YOUNG.

One of the most interesting inquiries relating to the moon is that which deals with the heat she sends us, and the probable temperature of her surface. The problem seems to have been first attacked by Tschirnhausen and La Hire, about 1700; and they both found, that even when the moon's rays were concentrated by the most powerful burning-lenses and mirrors they could obtain, its heat was too small to produce the slightest perceptible effect on the most delicate thermometers then known. For more than a hundred years, this was all that could be made out, though the experiment was often repeated.

It was not until 1831 that Melloni, with his newly-invented "thermopile," [1] succeeded in making the lunar heat sensible; and in 1835, taking his apparatus to the top of Vesuvius, he obtained not only perceptible, but measurable, results, getting a deviation of four or five divisions of his galvanometer.

[Footnote 1: Probably most of our readers know that the thermopile consists of a number of little bars of two different metals, connected in pairs, and having the ends joined in a conducting circuit with a galvanometer. If, now, one set of the junctures is heated more than the other set, a current of electricity will be generated, which will affect the galvanometer. The bars are usually made of bismuth and antimony though iron and German silver answer pretty well. They are commonly about half or three-quarters of an inch long, and about half as large as an ordinary match. The "pile" is made of from fifty to a hundred such bars packed closely, but insulated by thin strips of mica, except just at the soldered junctions. With an instrument of this kind and a very delicate galvanometer, Professor Henry found that the heat from a person's face could be perceived at a distance of several hundred feet. There is however, some doubt whether he was not mistaken in respect to this extreme sensitiveness.]

Others repeated the experiment several times between this time and 1856, with more or less success; but, so far as I know, the first quantitative result was that obtained in 1856 by Piazzi Smyth during his Teneriffe expedition. On the top of the mountain, at an elevation of ten thousand feet, he found that the moon's rays affected his thermopile to the same extent as a standard candle ten feet away. Marie Davy has since shown that this corresponds to a heating effect of about 1/1300 of a Centigrade degree.

The subject was resumed in 1868 by Lord Rosse in Ireland; and a long series of observations, running through several years, was made by the aid of his three-foot reflector (not the great six-foot instrument, which is too unwieldy for such work). The results of his work have, until very recently, been accepted as authoritative. It should be mentioned that, at about the same time, observations were also made at Paris by Marie Davy and Martin; but they are generally looked upon merely as corroborative of Rosse's work, which was more elaborate and extensive. Rosse considered that his results show that the heat from the moon is mainly obscure, radiated heat; the reflected heat, according to him, being much less in amount.

A moment's thought will show that the moon's heat must consist of two portions. First, there will be reflected solar heat. The amount and character of this will depend in no way upon the temperature of the moon's surface, but solely upon its reflecting power. And it is to be noted that moon-light is only a part of this reflected radiant energy, differing from the invisible portion of the same merely in having such a wave-length and vibration period as to bring it within the range of perception of the human eye.

The second portion of the heat sent us by the moon is that which she emits on her own account as a warm body—warmed, of course, mainly, if not entirely, by the action of the sun. The amount of this heat will depend upon the temperature of the moon's surface and its radiating power; and the temperature will depend upon a number of things (chiefly heat-absorbing power of the surface, and the nature and density of the lunar atmosphere, as well as the supply of heat received from the sun), being determined by a balance between give and take. So long as more heat is received in a second than is thrown off in the same time, the temperature will rise, and vice versa.

It is to be noted, further, that this second component of the moon's thermal radiance must be mainly what is called "obscure" or dark heat, like that from a stove or teakettle, and characterized by the same want of penetrative power. No one knows why at present; but it is a fact that the heat-radiations from bodies at a low temperature—radiations of which the vibrations are relatively slow, and the wave-length great—have no such power of penetrating transparent media as the higher-pitched vibrations which come from incandescent bodies. A great part, therefore, of this contingent of the lunar heat is probably stopped in the upper air, and never reaches the surface of the earth at all.

Now, the thermopile cannot, of course, discriminate directly between the two portions of the lunar heat; but to some extent it does enable us to do so indirectly, since they vary in quite a different way with the moon's age. The simple reflected heat must follow the same law as moonlight, and come to its maximum at full moon. The radiated heat, on the other hand, will reach its maximum when the average temperature of that part of the moon's surface turned toward the earth is highest; and this must be some time after full moon, for the same sort of reasons that make the hottest part of a summer's day come two or three hours after noon.

The conclusion early reached by Lord Rosse was that nearly all the lunar heat belonged to the second category—dark heat radiated from the moon's warmed surface, the reflected portion being comparatively small—and he estimated that the temperature of the hottest parts of the moon's surface must run as high as 500 deg. F.; well up toward the boiling-point of mercury. Since the lunar day is a whole month long, and there are never any clouds in the lunar sky, it is easy to imagine that along toward two or three o'clock in the lunar afternoon (if I may use the expression), the weather gets pretty hot; for when the sun stands in the lunar sky as it does at Boston at two P.M., it has been shining continuously for more than two hundred hours. On the other hand, the coldest parts of the moon's surface, when the sun has only just risen after a night of three hundred and forty hours, must have a temperature more than a hundred degrees below zero.

Lord Rosse's later observations modified his conclusions, to some extent, showing that he had at first underestimated the percentage of simple reflected heat, but without causing him to make any radical change in his ideas as to the maximum heat of the moon's surface.

For some time, however, there has been a growing skepticism among astronomers, relating not so much to the correctness of his measures as to the computations by which he inferred the high percentage of obscure radiated beat compared with the reflected heat, and so deduced the high temperature of lunar noon.

Professor Langley, who is now engaged in investigating the subject, finds himself compelled to believe that the lunar surface never gets even comfortably warm—because it has no blanket. It receives heat, it is true, from the sun, and probably some twenty-five or thirty per cent. more than the earth, since there are no clouds and no air to absorb a large proportion of the incident rays; but, at the same time, there is nothing to retain the heat, and prevent the radiation into space as soon as the surface begins to warm. We have not yet the data to determine exactly how much the temperature of the lunar rocks would have to be raised above the absolute zero (-273 deg. C. or -459 deg. F.) in order that they might throw off into space as much heat in a second as they would get from the sun in a second. But Professor Langley's observations, made on Mount Whitney at an elevation of fifteen thousand feet, when the barometer stood at seventeen inches (indicating that about fifty-seven per cent. of the air was still above him), showed that rocks exposed to the perpendicular rays of the sun were not heated to any such extent as those at the base of the mountain similarly exposed; and the difference was so great as to make it almost certain that a mass of rock not covered by a reasonably dense atmosphere could never attain a temperature of even 200 deg. or 300 deg. F. under solar radiation, however long continued.

It must, in fact, be considered at present extremely doubtful whether any portion of the moon's surface ever reaches a temperature as high as -100 deg..

The subject, undoubtedly, needs further investigation, and it is now receiving it. Professor Langley is at work upon it with new and specially constructed apparatus, including a "bolometer" so sensitive that, whereas previous experimenters have thought themselves fortunate if they could get deflections of ten or twelve galvanometric divisions to work with, he easily obtains three or four hundred. We have no time or space here to describe Professor Langley's "bolometer;" it must suffice to say that it seems to stand to the thermopile much as that does to the thermometer. There is good reason to believe that its inventor will be able to advance our knowledge of the subject by a long and important step; and it is no breach of confidence to add that so far, although the research is not near completion yet, everything seems to confirm the belief that the radiated heat of the moon, instead of forming the principal part of the heat we get from her, is relatively almost insignificant, and that the lunar surface now never experiences a thaw under any circumstances.

Since the superstition as to the moon's influence upon the wind and weather is so widespread and deep seated, a word on that subject may be in order. In the first place, since the total heat received from the moon, even according to the highest determination (that of Smyth), is not so much as 0.00001 of that received from the sun, and since the only hold the moon has on the earth's weather is through the heat she sends us (I ignore here the utterly insignificant atmospheric tide), it follows necessarily that her influence must be very trifling. In the next place, all carefully collated observations show that it is so, and not only trifling, but generally absolutely insensible.

For example, different investigators have examined the question of nocturnal cloudiness at the time of full moon, there being a prevalent belief that the full moon "eats up" light clouds. On comparing thirty or forty years' observations at each of several stations (Greenwich. Paris, etc.), it is found that there is no ground for the belief. And so in almost every case of imagined lunar meteorological influence. As to the coincidence of weather changes with changes of the moon, it is enough to say that the idea is absolutely inconsistent with that progressive movement of the "weather" across the country from west to east, with which the Signal Service has now made us all so familiar.

Princeton, April 12, 1884.

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APPLE TREE BORERS.

The apple tree borers have destroyed thousands of trees in New England, and are likely to destroy thousands more. There are three kinds of borers which assail the apple tree. The round headed or two striped apple tree borer, Saperda candida, is a native of this country, infesting the native crabs, thorn bushes, and June berry. It was first described by Thomas Say, in 1824, but was probably widely distributed before that. In his "Insects Injurious to Fruit," Prof. Saunders thus describes the borer:

"In its perfect state it is a very handsome beetle, about three-quarters of an inch long, cylindrical in form, of a pale brown color, with two broad, creamy white stripes running the whole length of its body; the face and under surface are hoary white, the antennae and legs gray. The females are larger than the males, and have shorter antennae. The beetle makes its appearance during the months of June and July, usually remaining in concealment during the day, and becoming active at dusk. The eggs are deposited late in June and during July, one in a place, on the bark of the tree, near its base. Within two weeks the young worms are hatched, and at once commence with their sharp mandibles to gnaw their way through the outer bark to the interior. It is generally conceded that the larvae are three years in reaching maturity. The young ones lie for the first year in the sapwood and the inner bark, excavating flat, shallow cavities, about the size of a silver dollar, which are filled with their sawdust-like castings. The holes by which they enter being small are soon filled up, though not until a few grains of castings have fallen from them. Their presence may, however, often be detected in young trees from the bark becoming dark colored, and sometimes dry and dead enough to crack."

On the approach of winter, it descends to the lower part of its burrow, where it remains inactive until spring. The second season it continues its work in the sapwood, and in case two or three are at work in the same tree may completely girdle it, thus destroying it. The third year it penetrates to the heart of the tree, makes an excavation, and awaits its transformation. The fourth spring it comes forth a perfect beetle, and lays its eggs for another generation.

THE FLAT-HEADED BORER.

The flat-headed apple tree borer, Chrysobothris femorata, is also a native of this country. It is a very active insect, delights to bask in the hot sunshine; runs up and down the tree with great rapidity, but flies away when molested. It is about half an inch in length. "It is of a flattish, oblong form, and of a shining, greenish black color, each of its wing cases having three raised lines, the outer two interrupted by two impressed transverse spots of brassy color dividing each wing cover into three nearly equal portions. The under side of the body and legs shine like burnished copper; the feet are shining green." This beetle appears in June and July, and does not confine its work to the base of the tree, but attacks the trunk in any part, and sometimes the larger branches. The eggs are deposited in cracks or crevices of the bark, and soon hatch. The young larva eats its way through the bark and sapwood, where it bores broad and flat channels, sometimes girdling and killing the tree. As it approaches maturity, it bores deeper into the tree, working upward, then eats out to the bark, but not quite through the bark, where it changes into a beetle, and then cuts through the bark and emerges to propagate its kind. This insect is sought out when just beneath the bark, and devoured by woodpeckers and insect enemies.

Another borer, the long-horned borer, Leptostylus aculifer, is widely distributed, but is not a common insect, and does not cause much annoyance to the fruit grower. It appears in August, and deposits its eggs upon the trunks of apple trees. The larvae soon hatch, eat through the bark, and burrow in the outer surface of the wood just under the bark.

PROTECTION AGAINST BORERS.

The practical point is, What remedies can be used to prevent the ravages of the borers? The usual means of fighting the borers is, to seek after them in the burrows, and try to kill them by digging them out, or by reaching them with a wire. This seems to be the most effectual method of dealing with them after they have once entered the tree, but the orchardist should endeavor to prevent the insects from entering the tree. For this purpose, various washes have been recommended for applying to the tree, either for destroying the young larvae before they enter the bark, or for preventing the beetles depositing their eggs. It has been found that trees which have been coated with alkaline washes are avoided by beetles when laying their eggs. Prof. Saunders recommends that soft soap be reduced to the consistency of a thick paint, by the addition of a strong solution of washing soda in water, and be applied to the bark of the tree, especially about the base or collar, and also extended upward to the crotches where the main branches have their origin. It should be applied in the evening of a warm day, so that it may dry and form a coating not easily dissolved by the rain. This affords a protection against all three kinds of borers. It should be applied early in June, before the beetles begin to lay their eggs, and again in July, so as to keep the tree well protected.

Hon. T.S. Gold, of Connecticut, at a meeting of the Massachusetts State Board of Agriculture, in regard to preventing the ravages of the borer, said:

"A wash made of soap, tobacco water, and fresh cow manure mingled to the consistency of cream, and put on early with an old broom, and allowed to trickle down about the roots of the tree, has proved with me a very excellent preventive of the ravages of the borer, and a healthful wash for the trunk of the tree, much to be preferred to the application of lime or whitewash, which I have often seen applied, but which I am inclined to think is not as desirable an application as the potash, or the soda, as this mixture of soft soap and manure."

J.B. Moore, of Concord, Mass., at the same meeting said, in regard to the destruction of the borer:

"I have found, I think, that whale oil soap can be used successfully for the destruction of that insect. It is a very simple thing; it will not hurt the tree if you put it on its full strength. You can take whale oil soap and dilute until it is about as thick as paint, and put a coating of it on the tree where the holes are, and I will bet you will never see a borer on that tree until the new crop comes. I feel certain of it, because I have done it."

For borers, tarred paper 1 or 2 feet wide has been recommended to be wrapped about the base of the trunk of the tree, the lower edge being 1 or 2 inches below the surface of the soil. This prevents the two-striped borer from laying its eggs in the tree, but would not be entirely effectual against the flat-headed borer, which attacks any part of the trunk and the branches. By the general use of these means for the prevention of the ravages of the borers, the damages done by these insects could be brought within very narrow limits, and hundreds of valuable apple trees saved.

H. REYNOLDS, M.D.

Livermore Falls, Me.

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KEFFEL'S GERMINATING APPARATUS.

The apparatus represented in the annexed cut is designed to show the quality of various commercial seeds, and make known any fraudulent adulterations that they may have undergone. It is based upon a direct observation, of the germination of the seeds to be studied.



The apparatus consists of a cylindrical vessel containing water to the height of 0.07 m. Above the water is a germinating disk containing 100 apertures for the insertion of the seeds to be studied, the germinating end of the latter being directed toward the water. After the seeds are in place the disk is filled with damp sand up to the top of its rim, and the apparatus is closed with a cover which carries in its center a thermometer whose bulb nearly reaches the surface of the water.

The apparatus is then set in a place where the temperature is about 18 deg., and where there are no currents of air. An accurate result is reached at the end of about twenty or twenty-four hours. As the germinating disk contains 100 apertures for as many seeds, it is only necessary to count the number of seeds that have germinated in order to get the percentage of fresh and stale ones.

The aqueous vapor that continuously moistens all the seeds, under absolutely identical conditions for each, brings about their germination under good conditions for accuracy and comparison. If it be desired to observe the starting of the leaves, it is only necessary to remove the cover after the seeds have germinated.

This ingenious device is certainly capable of rendering services to brewers, distillers, seedsmen, millers, farmers, and gardeners, and it may prove useful to those who have horses to feed, and to amateur gardeners, since it permits of ascertaining the value and quality of seeds of every nature.—La Nature.

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MILLET.

The season is now at hand when farmers who have light lands, and who may possibly find themselves short of fodder for next winter feeding, should prepare for a crop of millet. This is a plant that rivals corn for enduring a drought, and for rapid growth. There are three popular varieties now before the public, besides others not yet sufficiently tested for full indorsement—the coarse, light colored millet, with a rough head, Hungarian millet, with a smooth, dark brown head, yielding seeds nearly black, and a newer, light colored, round seeded, and later variety, known as the golden millet.

Hungarian millet has been the popular variety with us for many years, although the light seeded, common millet is but slightly different in appearance or value for cultivation. They grow in a short time, eight weeks being amply sufficient for producing a forage crop, though a couple of weeks more would be required for maturing the seed. Millet should not be sown in early spring, when the weather and ground are both cold. It requires the hot weather of June and July to do well; then it will keep ahead of most weeds, while if sown in April the weeds on foul land would smother it.

Millet needs about two months to grow in, but if sowed late in July it will seem to "hurry up," and make a very respectable showing in less time. We have sown it in August, and obtained a paying crop, but do not recommend it for such late seeding, as there are other plants that will give better satisfaction. Golden millet has been cultivated but a few years in this country, and as yet is but little known, but from a few trials we have been quite favorably impressed with it. It is coarser than the other varieties, but cattle appear to be very fond of it nevertheless. It resembles corn in its growth nearly as much as grass, and, compared with the former, it is fine and soft, and it cures readily, like grass, and may be packed away in hay mows with perfect safety. It is about two weeks later than the other millets, and consequently cannot be grown in quite so short a time, although it may produce as much weight to the acre, in a given period, as either of the other more common varieties. A bushel of seed per acre is not too much for either variety of millet.—N.E. Farmer.

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