Chapter VII: MISCELLANEOUS.--Turkish Baths for Horses.--With (2)

The paradoxical appearance, then, consists in this, that although the drivers of the three last wheels each have the same number of teeth, yet the central one, H, having a motion of circular translation, remains always parallel to itself, and relatively to it the upper one seems to turn in the same direction as the train-arm, and the lower in the contrary direction. And the appearance is accepted, too, as a reality; being explained, agreeably to the analysis just given, by saying that H has no absolute rotation about its axis, while the other wheels have; that of F being positive and that of K negative.

The Mechanical Paradox, it is clear, may be regarded as composed of three separate trains, each of which is precisely like that of Fig. 16: and that, again, differs from the one of Fig. 15 only in the addition of a third wheel. Now, we submit that the train shown in Fig. 17 is mechanically equivalent to that of Fig. 15; the velocity ratio and the directional relation being the same in both. And if in Fig. 17 we remove the index P, and fix upon its shaft three wheels like E, G, and I of Fig. 18, we shall have a combination mechanically equivalent to Ferguson's Paradox, the three last wheels rotating in vertical planes about horizontal axes. The relative motions of those three wheels will be the same, obviously, as in Fig. 18; and according to the formula their absolute motions are the same, and we are invited to perceive that the central one does not rotate at all about its axis.

But it _does_ rotate, nevertheless; and this unquestioned fact is of itself enough to show that there is something wrong with the formula as applied to trains like those in question. What that something is, we think, has been made clear by what precedes; since it is impossible in any sense to add together motions which are unlike, it will be seen that in order to obtain an intelligible result in cases like these, the equation must be of the form _n'_/(_m'_ - _a_) = _n_/_m_. We shall then have:

n 20 n' 20
For the wheel F, --- = ---- = ----, [therefore] n' = - ---- a;
m 19 -a 19

n n'
For the wheel H, --- = 1 = ----, [therefore] n' = -a;
m -a

n 20 n' 20
For the wheel K, --- = ---- = ----, [therefore] n' = - ---- a,
m 21 -a 21

which corresponds with the actual state of things; all three wheels rotate in the same direction, the central one at the same rate as the train arm, one a little more rapidly and the third a little more slowly.

It is, then, absolutely necessary to make this modification in the general formula, in order to apply it in determining the rotations of any wheel of an epicyclic train whose axis is not parallel to that of the sun-wheels. And in this modified form it applies equally well to the original arrangement of Ferguson's paradox, if we abandon the artificial distinction between "absolute" and "relative" rotations of the planet-wheels, and regard a spur-wheel, like any other, as rotating on its axis when it turns in its bearings; the action of the device shown in Fig. 18 being thus explained by saying that the wheel H turns once backward during each forward revolution of the train-arm, while F turns a little more and K a little less than once, in the same direction. In this way the classification and analysis of these combinations are made more simple and consistent, and the incongruities above pointed out are avoided; since, without regard to the kind of gearing employed or the relative positions of the axes, we have the two equations:

n' - a n
I. -------- = ---, for all complete trains;
m' - a m

n' n
II. -------- = ---, for all incomplete trains.
m' - a m

As another example of the difference in the application of these formulæ, let us take Watt's sun and planet wheels, Fig. 19. This device, as is well known, was employed by the illustrious inventor as a substitute for the crank, which some one had succeeded in patenting. It consists merely of two wheels A and F connected by the link T; A being keyed on the shaft of the engine and F being rigidly secured to the connecting-rod. Suppose the rod to be of infinite length, so as to remain always parallel to itself, and the two wheels to be of equal size.

Then, according to Prof. Willis' analysis, we shall have--

n' - a n -s
-------- = --- = -1, n' = 0, [therefore] -------- = -1, whence
m' - a m m' - a

-a = a - m', or m = 2a.

The other view of the question is, that F turns once backward in its bearings during each forward revolution of T; whence in Eq. 2 we have--

n' n
-------- = --- = -1, n' = -a,
m' - a m

-a
[therefore] -------- -1, which gives -a = a - m', or m' = 2a,
m' - a

as before.

It is next to be remarked, that the errors which arise from applying Eq. I. to incomplete trains may in some cases counterbalance and neutralize each other, so that the final result is correct.

For example, take the combination shown in Fig. 20. This consists of a train-arm T revolving about the vertical axis OO of the fixed wheel A, which is equal in diameter to F, which receives its motion by the intervention of one idle wheel carried by a stud S fixed in the arm. The second train-arm T' is fixed to the shaft of F and turns with it; A' is secured to the arm T, and F' is actuated by A' also through a single idler carried by T'.

We have here a compound train, consisting of two simple planetary trains, A--F and A'--F'; and its action is to be determined by considering them separately. First suppose T' to be removed and find the motion of F; next suppose F to be removed and T fixed, and find the rotation of F'; and finally combine these results, noting that the motion of T' is the same as that of F, and the motion of A' the same as that of T.

Then, according to the analysis of Prof. Willis, we shall have (substituting the symbol _t_ for _a_ in the equation of the second train, in order to avoid confusion):

n n' - a
1. Train A--F. --- = 1 = --------; m' = 0,
m m' - a

n' - a
whence -------- = 1, n' = 0, = rot. of F.
a

n n' - t
2. Train A'--F'. --- = 1 = --------; m' = 0,
m m' - t

n' - t
whence again -------- = 1, t = 0, = rot. of F'.
-t

Of these results, the first is explicable as being the _absolute_ rotation of F, but the second is not; and it will be readily seen that the former would have been equally absurd, had the axis LL been inclined instead of vertical. But in either case we should find the errors neutralized upon combining the two, for according to the theory now under consideration, the wheel A', being fixed to T, turns once upon its axis each time that train arm revolves, and in the same direction; and the revolutions of T' equal the rotations of F, whence finally in train A'--F' we have:

n n' - t
3. --- = 1 = --------; in which t = 0, m' = a,
m m' - t

n' - 0
which gives --------- = 1, or n' = a.
a - 0

This is, unquestionably, correct; and indeed it is quite obvious that the effect upon F' is the same, whether we say that during a revolution of T the wheel A' turns once forward and T' not at all, or adopt the other view and assert that T' turns once backward and A' not at all. But the latter view has the advantage of giving concordant results when the trains are considered separately, and that without regard to the relative positions of the axes or the kind of gearing employed. Analyzing the action upon this hypothesis, we have:

In train A--F:

n n' n'
--- = 1 = --------; m' = 0, [therefore] ---- = 1, or n' = -a;
m m' - a -a

In train A'--F':

n' n' n'
--- = 1 = --------; m' = 0, [therefore] ---- = 1, or n' = -t;
m m' - t -t

In combining, we have in the latter train m' = 0, t = -a, whence

n n' n'
--- = 1 = -------- gives ---- = 1, or n' = a, as before.
m m' - t +a

Now it happens that the only examples given by Prof. Willis of incomplete trains in which the axis of a planet-wheel whose motion is to be determined is not parallel to the central axis of the system, are similar to the one just discussed; the wheel in question being carried by a secondary train-arm which derives its motion from a wheel of the primary train.

The application of his general equation in these cases gives results which agree with observed facts; and it would seem that this circumstance, in connection doubtless with the complexity of these compound trains, led him to the too hasty conclusion that the formula would hold true in all cases; although we are still left to wonder at his overlooking the fact that in these very cases the "absolute" and the "relative" rotations of the last wheel are identical.

In Fig. 21 is shown a combination consisting also of two distinct trains, in which, however, there is but one train-arm T turning freely upon the horizontal shaft OO, to which shaft the wheels A', F, are secured; the train-arm has two studs, upon which turn the idlers B B', and also carries the bearings of the last wheel F'; the first wheel A is annular, and fixed to the frame of the machine. Let it be required to determine the results of one revolution of the crank H, the numbers of teeth being assigned as follows:

A = 60, F = 30, A' = 60, F' = 10.

We shall then have, for the train ABF (Eq. I.),

n 60 n' - a
--- = - ---- = -2 = --------, in which n' = 1, m' = 0,
m 30 m' - a'

1 - a 1
whence -2 = -------, 2a = 1 - a, 3a = 1, a = ---.
-a 3

And for the train A'B'F' (Eq. II.),

n 60 n' 1
--- = ---- = 6 = --------, in which a = ---, m' = 1,
m 10 m' - a' 3

n'
whence 6 = -----------, or n' = 4.
1 - (1/3)

That is, the last wheel F' turns _four_ times about the axis LL during one revolution of the crank H. But according to Profs. Willis and Goodeve, we should have for the second train:

n 60 n' - a 1
--- = ---- = 6 = --------, in which a = ---, m' = 1,
m 10 m' - a' 3

n' - (1/3)
which gives 6 = -----------, n' - (1/3) = 4, n' = 4-1/3,
1 - (1/3)

or _four and one-third_ revolutions of F' for one of H.

This result, no doubt, might be near enough to the truth to serve all practical purposes in the application of this mechanism to its original object, which was that of paring apples, impaled upon the fork K; but it can hardly be regarded as entirely satisfactory in a general way; nor can the analysis which renders such a result possible.

* * * * *

THE PANTANEMONE.

The need of irrigating prairies, inundating vines, drying marshes, and accumulating electricity cheaply has, for some time past, led to a search for some means of utilizing the forces of nature better than has ever hitherto been done. Wind, which figures in the first rank as a force, has thus far, with all the mills known to us, rendered services that are much inferior to those that we have a right to expect from it with improved apparatus; for the work produced, whatever the velocity of the wind, has never been greater than that that could be effected by wind of seven meters per second. But, thanks to the experiments of recent years, we are now obtaining an effective performance double that which we did with apparatus on the old system.

Desirous of making known the efforts that have been made in this direction, we lately described Mr. Dumont's atmospheric turbine. In speaking of this apparatus we stated that aerial motors generally stop or are destroyed in high winds. Recently, Mr. Sanderson has communicated to us the result of some experiments that he has been making for years back by means of an apparatus which he styles a pantanemone.

The engraving that we give of this machine shows merely a cabinet model of it; and it goes without saying that it is simply designed to exhibit the principle upon which its construction is based.

Two plane surfaces in the form of semicircles are mounted at right angles to each other upon a horizontal shaft, and at an angle of 45° with respect to the latter. It results from this that the apparatus will operate (even without being set) whatever be the direction of the wind, except when it blows perpendicularly upon the axle, thus permitting (owing to the impossibility of reducing the surfaces) of three-score days more work per year being obtained than can be with other mills. Three distinct apparatus have been successively constructed. The first of these has been running for nine years in the vicinity of Poissy, where it lifts about 40,000 liters of water to a height of 20 meters every 24 hours, in a wind of a velocity of from 7 to 8 meters per second. The second raises about 150,000 liters of water to the Villejuif reservoir, at a height of 10 meters, every 24 hours, in a wind of from 5 to 6 meters. The third supplies the laboratory of the Montsouris observatory.

The first is not directible, the second may be directed by hand, and the third is directed automatically. These three machines defied the hurricane of the 26th of last January.--_La Nature._

* * * * *

RELVAS'S NEW LIFE-BOAT.

The Spanish and Portuguese papers have recently made known some interesting experiments that have been made by Mr. Carlos Relvas with a new life-boat which parts the waves with great facility and exhibits remarkable stability. This boat, which is shown in front view in one of the corners of our engraving, is T-shaped, and consists of a very thin keel connected with the side-timbers by iron rods. Cushions of cork and canvas are adapted to the upper part, and, when the boat is on the sea, it has the appearance of an ordinary canoe, although, as may be seen, it differs essentially therefrom in the submerged part. When the sea is heavy, says Mr. Relvas, and the high waves are tumbling over each other, they pass over my boat, and are powerless to capsize it. My boat clears waves that others are obliged to recoil before. It has the advantage of being able to move forward, whatever be the fury of the sea, and is capable, besides, of approaching rocks without any danger of its being broken.

A committee was appointed by the Portuguese government to examine this new life-boat, and comparative experiments were made with it and an ordinary life-boat at Porto on a very rough sea. Mr. Relvas's boat was manned by eight rowers all provided with cork girdles, while the government life-boat was manned by twelve rowers and a pilot, all likewise wearing cork girdles. The chief of the maritime department, an engineer of the Portuguese navy and a Portuguese deputy were present at the trial in a pilot boat. The three boats proceeded to the entrance of the bar, where the sea was roughest, and numerous spectators collected upon the shore and wharfs followed their evolutions from afar.

The experiments began at half past three o'clock in the afternoon. The two life-boats shot forward to seek the most furious waves, and were seen from afar to surmount the billows and then suddenly disappear. It was a spectacle as moving as it was curious. It was observed that Mr. Relvas's boat cleft the waves, while the other floated upon their surface like a nut-shell. After an hour's navigation the two boats returned to their starting point.

The official committee that presided over these experiments has again found in this new boat decided advantages, and has pointed out to its inventor a few slight modifications that will render it still more efficient.--_La Nature._

* * * * *

EXPERIMENTS WITH DOUBLE-BARRELED GUNS AND RIFLES.

The series of experiments we are about to describe has recently been made by Mr. Horatio Phillips, a practical gun maker of London. The results will no doubt prove of interest to those concerned in the use or manufacture of firearms.

The reason that the two barrels of a shot gun or rifle will, if put together parallel, throw their charges in diverging lines has never yet been satisfactorily accounted for, although many plausible and ingenious theories have been advanced for the purpose. The natural supposition would be that this divergence resulted from the axes of the barrels not being in the same vertical plane as the center line of the stock. That this is not the true explanation of the fact, the following experiment would tend to prove.

Fig. 1 represents a single barrel fitted with sights and firmly attached to a heavy block of beech. This was placed on an ordinary rifle rest, being fastened thereto by a pin at the corner, A, the block and barrel being free to revolve upon the pin as a center. Several shots were fired both with the pin in position and with it removed, the barrel being carefully pointed at the target each time. No practical difference in the accuracy of fire was discernible under either condition. When the pin was holding the corner of the block, the recoil caused the barrel to move from right to left in a circular path; but when the pin was removed, so that the block was not attached to the rest in any way, the recoil took place in a line with the axis of the bore. It will be observed that the conditions which are present when a double barreled gun is fired in the ordinary way from the shoulder were in some respects much exaggerated in the apparatus, for the pin was a distance of 3 in. laterally from the axis of the barrel, whereas the center of resistance of the stock of a gun against the shoulder would ordinarily be about one-sixth of this distance from the axis of the barrel. This experiment would apparently tend to prove that the recoil does not appreciably affect the path of the projectile, as it would seem that the latter must clear the muzzle before any considerable movement of the barrel takes place.

With a view to obtain a further confirmation of the result of this experiment, it was repeated in a different form by a number of shots being fired from a "cross-eyed" rifle,[1] in which the sights were fixed in the center of the rib. Very accurate shooting was obtained with this arm.

[Footnote 1: A cross-eyed rifle is one made with a crooked stock
for the purpose of shooting from the right shoulder, aim being
taken with the left eye.]

A second theory, often broached, in order to account for the divergence of the charge, is that the barrel which is not being fired, by its _vis inertia_ in some way causes the shot to diverge. In order to test this, Mr. Phillips took a single rifle and secured it near the muzzle to a heavy block of metal, when the accuracy of the shooting was in no way impaired.

So far the experiments were of a negative character, and the next step was made with a view to discover the actual cause of the divergence referred to. A single barrel was now taken, to which a template was fitted, in order to record its exact length. The barrel was then subjected to a heavy internal hydrostatic pressure. Under this treatment it expanded circumferentially and at the same time was reduced in length. This, it was considered, gave a clew to the solution of the problem. A pair of barrels was now taken and a template fitted accurately to the side of the right-hand one. As the template fitted the barrel when the latter was not subject to internal pressure, upon such pressure being applied any alterations that might ensue in the length or contour of the barrel could be duly noted. The right-hand barrel was then subjected to internal hydrostatic pressure. The result is shown in an exaggerated form in Fig. 2. It will be seen that both barrels are bent into an arched form. This would be caused by the barrel under pressure becoming extended circumferentially, and thereby reduced in length, because the metal that is required to supply the increased circumference is taken to some extent from the length, although the substance of metal in the walls of the barrel by its expansion contributes also to the increased diameter. A simple illustration of this effect is supplied by subjecting an India-rubber tube to internal pressure. Supposing the material to be sufficiently elastic and the pressure strong enough, the tube would ultimately assume a spherical form. It is a well known fact that heavy barrels with light charges give less divergence than light barrels with heavy charges.

After the above experiments it was hoped that, if a pair of barrels were put together parallel and soldered only for a space of 3 in. at the breech end, and were then coupled by two encircling rings joined together as in Fig. 4, the left-hand ring only being soldered to the barrel, very accurate shooting would be obtained. For, it was argued, that by these means the barrel under fire would be able to contract without affecting or being affected by the other barrel; that on the right-hand, it will be seen by the illustration, was the one to slide in its ring.

A pair of able 0.500 bore express rifle barrels were accordingly fitted in this way. Fig. 3 shows the arrangement with the rings in position. Upon firing these barrels with ordinary express charges it was found that the lines of fire from each barrel respectively crossed each other, the bullet from the right-hand barrel striking the target 10 in. to the left of the bull's eye, while the left barrel placed its projectile a similar distance in the opposite direction; or, as would be technically said, the barrels crossed 20 in. at 100 yards, the latter distance being the range at which the experiment was made. These last results have been accounted for in the following manner: The two barrels were rigidly joined for a space of 3 in., and for that distance they would behave in a manner similar to that illustrated in Fig. 2, and were they not coupled at the muzzles by the connecting rings they would shoot very wide, the charges taking diverging courses. When the connecting rings are fitted on, the barrel not being fired will remain practically straight, and, as it is coupled to the barrel being fired by the rings, the muzzle of the latter will be restrained from pointing outward.

The result will be as shown in an exaggerated manner by the dotted lines on the right barrel in Fig. 3.

It would appear from these experiments that when very accurate shooting is required at long ranges with double-barreled rifles, they should be mounted in a manner similar to that adopted in the manufacture of the Nordenfelt machine gun, in which weapon the barrels are fitted into a plate at the extreme breech end, the muzzles projecting through holes bored to receive them in a metal plate. No unequal expansion would then take place, and the barrels would be free to become shorter independently of each other. We give the above experiments on the authority of their author, who, we believe, has taken great pains to render them as exhaustive as possible, so far as they go.--_Engineering._

* * * * *

BALL TURNING MACHINE.

The distinguishing feature in the ball turning machine shown opposite is that the tool is stationary, while the work revolves in two directions simultaneously. In the case of an ordinary spherical object, such as brass clack ball, the casting is made from a perfect pattern having two small caps or shanks, in which the centers are also marked to avoid centering by hand. It is fixed in the machine between two centers carried on a face plate or chuck, with which they revolve. One of these centers, when the machine is in motion, receives a continuous rotary motion about its axis from a wormwheel, D. This is driven by a worm, C, carried on a shaft at the back of the chuck, and driven itself by a wormwheel, B, which gears with a screw which rides loosely upon the mandrel, and is kept from rotating by a finger on the headstock. This center, in its rotation, carries with it the ball, which is thus slowly moved round an axis parallel to the face plate, at the same time that it revolves about the axis of the mandrel, the result being that the tool cuts upon the ball a scroll, of which each convolution is approximately a circle, and lies in a plane parallel to the line of centers.

When the chuck is set for one size of ball, which may be done in a few minutes, any quantity of that diameter may be turned without further adjustment. A roughing cut for a 2 in. ball may be done in one minute, and a finishing cut leaving the ball quite bright in the same time. The two paps are cut off within one-sixteenth of an inch and then broken off, and the ball finished in the usual way. On account of the work being geometrically true, the finishing by the ferrule tool is done in one quarter of the time usually required.

The chuck may be applied to an ordinary lathe or may be combined with a special machine tool, as show in our illustration. In the latter case everything is arranged in the most handy way for rapid working, and six brass balls of 2 in. in diameter can be turned and finished in an hour. The machine is specially adapted for turning ball valves for pumps, pulsometers, and the like, and in the larger sizes for turning governor balls and spherical nuts for armor plates, and is manufactured by Messrs. Wilkinson and Lister, of Bradford Road Iron Works, Keighley.--_Engineering._

* * * * *

COOLING APPARATUS FOR INJECTION WATER.

It often happens in towns and where manufactories are crowded together, that the supply of water for condensing purposes is very small, and consequently that it attains an inconveniently high temperature under unfavorable conditions of weather, resulting in the deterioration of the vacuum and a consequent increase in the consumption of fuel. To remedy or to diminish this difficulty, Messrs. Boase and Miller, of London, have brought out the water cooler illustrated above. This consists, says _Engineering_, of a revolving basket of wire gauze surrounding an inner stationary vessel pierced with numerous small holes, through which the heated water discharged by the air pump finds its way into the basket, to be thrown out in the form of fine spray to a distance of 20 ft. at each side. The drops are received in the tank or pond, and in their rapid passage through the air are sufficiently cooled to be again injected into the condenser.

The illustration shows a cooler having a basket three feet in diameter, revolving at 300 revolutions per minute, and discharging into a tank 40 ft. square. It requires 3 to 4 indicated horse-power to drive it, and will cool 300 gallons per minute. The following decrease of temperature has been observed in actual practice: Water entering at 95 deg. fell 20 deg. in temperature; water entering at 100 deg. to 110 deg. fell 25 deg.; and water entering at 110 deg. to 120 deg. fell 30 deg. The machine with which these trials were made was so placed that the top of the basket was four ft. from the surface of the water in the pond. With a greater elevation, as shown in the engraving, better results can be obtained.

The advantages claimed for the cooler are that by its means the temperature of the injection water can be reduced, the cost and size of cooling ponds can be diminished, and condensing engines can be employed where hitherto they have not been possible. The apparatus has been for two years in operation at several large factories, and there is every reason to believe that its use will extend, as it supplies a real want in a very simple and ingenious manner. Messrs. Duncan Brothers, of Dundee and 32 Queen Victoria Street, E.C., are the manufacturers.

* * * * *

CORRUGATED DISK PULLEYS.

This is a pulley recently introduced by Messrs. J. and E. Hall, of Dartford Eng. With the exception of the boss, which is cast, it is composed entirely of steel or sheet iron. In place of the usual arms a continuous web of corrugated sheet metal connects the boss to the rim; this web is attached to the boss by means of Spence's metal. Inside the rim, which is flanged inward, a double hoop iron ring is fixed for strengthening purposes. The advantageous disposition of metal obtained by means of the corrugated web enables the pulley to be made of a given strength with less weight of material, and from this cause and also on account of being accurately balanced these pulleys are well adapted for high speeds.

* * * * *

[KANSAS CITY REVIEW.]

EARLY HISTORY OF THE TELEGRAPH.

Although the electric telegraph is, comparatively speaking, a recent invention, yet methods of communication at a distance, by means of signals, have probably existed in all ages and in all nations. There is reason to believe that among the Greeks a system of telegraphy was in use, as the burning of Troy was certainly known in Greece very soon after it happened, and before any person had returned from Troy. Polybius names the different instruments used by the ancients for communicating information--"pyrsia," because the signals were always made by means of fire lights. At first they communicated information of events in an imperfect manner, but a new method was invented by Cleoxenus, which was much improved by Polybius, as he himself informs us, and which may be described as follows:

Take the letters of the alphabet and arrange them on a board in five columns, each column containing five letters; then the man who signals would hold up with his left hand a number of torches which would represent the number of the column from which the letter is to be taken, and with his right hand a number of torches that will represent the particular letter in that column that is to be taken. It is thus easy to understand how the letters of a short sentence are communicated from station to station as far as required. This is the pyrsia or telegraph of Polybius.

It seems that the Romans had a method of telegraphing in their walled cities, either by a hollow formed in the masonry, or by a tube fixed thereto so as to confine the sound, in order to convey information to any part they liked. This method of communicating is in the present age frequently employed in the well known speaking tubes. It does not appear that the moderns had thought of such a thing as a telegraph until 1661, when the Marquis of Worcester, in his "Century of Inventions," affirmed that he had discovered a method by which a man could hold discourse with his correspondent as far as they could reach, by night as well as by day; he did not, however, describe this invention.

Dr. Hooke delivered a discourse before the Royal Society in 1684, showing how to communicate at great distances. In this discourse he asserts the possibility of conveying intelligence from one place to another at a distance of 120 miles as rapidly as a man can write what he would have sent. He takes to his aid the then recent invention of the telescope, and explains how characters exposed at one station on the top of one hill may be made visible to the next station on the top of the next hill. He invented twenty-four simple characters, each formed of a combination of three deal boards, each character representing a letter by the use of cords; these characters were pushed from behind a screen and exposed, and then withdrawn behind the screen again. It was not, however, until the French revolution that the telegraph was applied to practical purposes; but about the end of 1703 telegraphic communication was established between Paris and the frontiers, and shortly afterward telegraphs were introduced into England.

The history of the invention and introduction of the electric telegraph by Prof. Morse is one of inexhaustible interest, and every incident relating to it is worthy of preservation. The incidents described below will be found of special interest. The article is from the pen of the late Judge Neilson Poe, and was the last paper written by him. He prepared it during his recent illness, the letter embodied in it from Mr. Latrobe being of course obtained at the time of its date. It is as follows:

On the 5th of April, 1843, when the monthly meeting of the directors of the Baltimore & Ohio Railroad Company was about to adjourn, the President, the Hon. Louis McLane, rose with a paper in his hand which he said he had almost overlooked, and which the Secretary would read. It proved to be an application from Prof. Morse for the privilege of laying the wires of his electric telegraph along the line of the railroad between Baltimore and Washington, and was accompanied by a communication from B.H. Latrobe, Esq., Chief Engineer, recommending the project as worthy of encouragement.

On motion of John Spear Nicholas, seconded by the Hon. John P. Kennedy, the following resolution was then considered:

_Resolved_, "That the President be authorized to afford Mr. Morse such facilities as may be requisite to give his invention a proper trial upon the Washington road, provided in his opinion and in that of the engineer it can be done without injury to the road and without embarrassment to the operations of the company, and provided Mr. Morse will concede to the company the use of the telegraph upon the road without expense, and reserving to the company the right of discontinuing the use if, _upon experiment_, it should prove _in any manner injurious_."

"Whatever," said Mr. McLane, "may be our individual opinions as to the feasibility of Mr. Morse's invention, it seems to me that it is our duty to concede to him the privilege he asks, and to lend him all the aid in our power, especially as the resolution carefully protects the company against all present or future injury to its works, and secures us the right of requiring its removal at any time."

[In view of the fact that no railroad can now be run safely without the aid of the telegraph, the cautious care with which the right to remove it if it should become a nuisance was reserved, strikes one at this day as nearly ludicrous.]

A short pause ensued, and the assent of the company was about to be assumed, when one of the older directors, famed for the vigilance with which he watched even the most trivial measure, begged to be heard.

He admitted that the rights and interests of the work were all carefully guarded by the terms of the resolution, and that the company was not called upon to lay out any of its means for the promotion of the scheme. But notwithstanding all this, he did not feel, as a conscientious man, that he could, without further examination, give his vote for the resolution. He knew that this idea of Mr. Morse, however plausible it might appear to theorists and dreamers, and so-called men of science, was regarded by all practical people as destined, like many other similar projects, to certain failure, and must consequently result in loss and possibly ruin to Mr. Morse. For one, he felt conscientiously scrupulous in giving a vote which would aid or tempt a visionary enthusiast to ruin himself.

Fortunately, the views of this cautious, practical man did not prevail. A few words from the mover of the resolution, Mr. Nicholas, who still lives to behold the wonders he helped to create, and from Mr. Kennedy, without whose aid the appropriation would not have passed the House of Representatives, relieved the other directors from all fear of contributing to Mr. Morse's ruin, and the resolution was adopted. Of the President and thirty directors who took part in this transaction, only three, Samuel W. Smith, John Spear Nicholas, and the writer, survive. Under it Morse at once entered upon that test of his invention whose fruits are now enjoyed by the people of all the continents.

It was not, however, until the spring of 1844 that he had his line and its appointments in such a condition as to allow the transmission of messages between the two cities, and it was in May of that year that the incident occurred which has chiefly led to the writing of this paper.

MR. LATROBE'S RECOLLECTIONS.

MY DEAR MR. POE: Agreeably to my promise, this morning I put on paper my recollection of the introduction of the magnetic telegraph between Baltimore and Washington. I was counsel of the Baltimore & Ohio Railroad Co. at the time, and calling on Mr. Louis McLane, the President, on some professional matter, was asked in the course of conversation whether I knew anything about an electric telegraph which the inventor, who had obtained an appropriation from Congress, wanted to lay down on the Washington branch of the road. He said he expected Mr. Morse, the inventor, to call on him, when he would introduce me to him, and would be glad if I took an opportunity to go over the subject with him and afterward let him, Mr. McLane, know what I thought about it. While we were yet speaking, Mr. Morse made his appearance, and when Mr. McLane introduced me he referred to the fact that, as I had been educated at West Point, I might the more readily understand the scientific bearings of Mr. Morse's invention. The President's office being no place for prolonged conversation, it was agreed that Mr. Morse should take tea at my dwelling, when we would go over the whole subject. We met accordingly, and it was late in the night before we parted. Mr. Morse went over the history of his invention from the beginning with an interest and enthusiasm that had survived the wearying toil of an application to Congress, and with the aid of diagrams drawn on the instant made me master of the matter, and wrote for me the telegraphic alphabet which is still in use over the world. Not a small part of what Mr. Morse said on this occasion had reference to the future of his invention, its influence upon communities and individuals, and I remember regarding as the wild speculations of an active imagination what he prophesied in this connection, and which I have lived to see even more than realized. Nor was his conversation confined to his invention. A distinguished artist, an educated gentleman, an observant traveler, it was delightful to hear him talk, and at this late day I recall few more pleasant evenings than the only one I passed in his company.

Of course, my first visit the next morning was to Mr. McLane to make my report. By this time I had become almost as enthusiastic as Mr. Morse himself, and repeated what had passed between us. I soon saw that Mr. McLane was becoming as eager for the construction of the line to Washington as Mr. Morse could desire. He entered warmly into the spirit of the thing, and laughed heartily, if not incredulously, when I told him that although he had been Minister to England, Secretary of State, and Secretary of the Treasury, his name would be forgotten, while that of Morse would never cease to be remembered with gratitude and praise. We then considered the question as to the right of the company to permit the line to be laid in the bed of the road--the plan of construction at that time being to bury in a trench some eight or ten inches deep a half inch leaden tube containing the wrapped wire that was to form the electric circuit. About this there was, in my opinion, no doubt, and it was not long after that the work of construction commenced. I met Mr. Morse from time to time while he lived, and often recurred to the evening's discussion at my house in Baltimore.

The above is the substance of what I have more than once related to other persons. I hope you will persist in your design of putting on paper your own very interesting recollections in this connection, and if what I have contributed of mine is of service to you, I shall be much pleased.

Most truly yours,
JOHN H.B. LATROBE.
March 3, 1881.

* * * * *

THE KRAVOGL ELECTRIC MOTOR.

At the origin of every science, of whatever nature it may be, there is always a fruitless period, of greater or less length, characterized by the warfare of a few superior minds against general apathy. The finest discoveries pass unperceived, so to speak, since they cannot cross the limits of a narrow circle; and it often happens that they fall into oblivion before they have been seriously judged. Meanwhile, a slow progress is imperceptibly made, and, in measure as theoretical principles more clearly disengage themselves, a few industrial applications spring up and have the effect of awakening curiosity. An impulse is thus given, and from this moment a movement in advance goes on increasing at a headlong pace from day to day.

With electricity this period has been of comparatively short duration, since scarcely a century and a half separate us from the first experiments made in this line of research. Now that it has truly taken its place in a rank with the other sciences, we like to go back to the hesitations of the first hour, and trace, step by step, the history of the progress made, so as to assign to each one that portion of the merit that belongs to him in the common work. When we thus cast a retrospective glance we find ourselves in the presence of one strange fact, and that is the simultaneousness of discoveries. That an absolutely original idea, fertile in practical consequences, should rise at a given moment in a fine brain is well; we admire the discovery, and, in spite of us, a little surprise mingles with our admiration. But is it not a truly curious thing that _several_ individuals should have had at nearly the same time that idea that was so astonishing in one? This, however, is a fact that the history of electrical inventions offers more than one example of. No one ignores the fact that the invention of the telephone gave rise to a notorious lawsuit, two inventors having had this ingenious apparatus patented on the same day and at nearly the same hour. This is one example among a thousand. In the history of dynamo-electric machines it is an equally delicate matter to fix upon the one to whom belongs the honor of having first clearly conceived the possibility of engendering continuous currents.

We do not wish to take up this debate nor to go over the history of the question again. Every one knows that the first continuous current electric generator whose form was practical is due to Zenobius Gramme, and dates back to July, 1871, an epoch at which appeared a memoir (entitled "Note upon a magneto-electric machine that produces continuous currents") that was read to the Academy of Sciences by Mr. Jamin. Ten years previous, Pacinotti had had a glimpse of the phenomenon, and of its practical realization, but was unfortunately unable to appreciate the importance of his discovery and the benefit that might be reaped from it. It is of slight consequence whether Gramme knew of this experiment or not, for the glory that attaches to his name could not be diminished for all that. But an interesting fact that we propose to dwell upon now has recently been brought to light in an electrical review published at Vienna.[1] It results from documents whose authenticity cannot be doubted that, as far back as 1867, Mr. L. Pfaundler, a professor at Innsbruck, very clearly announced the reversibility of a magneto-electric motor constructed by Kravogl, a mechanician of the same place, and that he succeeded some time before Gramme in obtaining continuous currents.

[Footnote 1: _Zeitschrift des Electrotechnischen Vereines_ in
_Wien_, July, 1883.]

The Kravogl motor that figured at the Universal Exhibition of 1867 is but little known, and it is now very difficult to obtain drawings of it. What is certain is that this motor is an application of the properties of the solenoid, and, from this standpoint, resembles the Bessolo motor that was patented in 1855. We may figure the apparatus to our mind very well if we suppose that in the Gramme ring a half and almost two-thirds of the core are removed, and the spirals are movable around the said core. If a current be sent into a portion of the spirals only, and in such a way that only half of the core be exposed, the latter will move with respect to the bobbin or the bobbin with respect to the core, according as we suppose the solenoid or the bobbin fixed. In the first case we have a Bessolo motor, and in the second a Kravogl one.

In order to obtain a continuous motion it is only necessary to allow the current to circulate successively in the different portions of the solenoid. It is difficult to keep the core in place, since it is unreachable, being placed in the interior of the bobbin. Kravogl solved this difficulty by constructing a hollow core into which he poured melted lead. This heavy piece, mounted upon rollers, assumed a position of equilibrium that resulted from its weight, from friction, and from magnetic attraction. But for a current of given intensity this position, once reached, did not vary, and so necessitated a simple adjustment of the rubbers. Under such circumstances, with a somewhat large number of sections, the polarity of the core was nearly constant. The spirals as a whole were attached to a soft iron armature that had the effect of closing up the lines of forces and forming a shell, so to speak.

Like Bessolo, Kravogl never thought of making anything but a motor, and did not perceive that his machine was reversible. It results from some correspondence between Dr. A. Von Waltenhofen and Mr. L. Pfaundler at this epoch that the latter clearly saw the possibility of utilizing this motor as a current generator. Under date of November 9, 1867, he wrote, in speaking of the Kravogl motor, which had just been taken to Innsbruck in order to send it to Paris. "I regret that I shall not be able to see it any more, for I should have liked to try to make it act in an opposite direction, that is to say, to produce a current or an electric light by means of mechanical work." A little more than two years later these experiments were carried out on a larger motor constructed by Kravogl in 1869, and Mr. Pfaundler was enabled to write as follows: "Upon running the machine by hand we obtain a current whose energy is that of one Bunsen element." This letter is dated February 11, 1870, that is to say, it is a year anterior to the note of Gramme.

In the presence of the historic interest that attaches to the question, we do not think it will be out of place to reproduce here the considerations that guided Prof. Pfaundler in the researches that led him to convert the Kravogl motor into a dynamo-electric machine. Let us consider two magnetized bars, _db_ and _bd'_, placed end to end and surrounded by a cylindrical armature forming a shell, this armature being likewise supposed to be a permanent magnet and to present poles of contrary direction opposite the poles of the bars. For the sake of greater simplicity this shell is represented by a part only in the figure, _s n n s_. If, into a magnetic field thus formed, we pass a spiral from left to right, the spiral will be traversed by a current whose direction will change according to the way in which the moving is done. It is only necessary to apply Lenz's law to see that a reversal of the currents will occur at the points, _a_ and _c_, the direction of the current being represented by arrows in the figure. If we suppose a continual displacement of the spirals from left to right, we shall collect a continuous current by placing two rubbers at _a_ and _c_. Either the core or the shell may be replaced by a piece of soft iron. In such a case this piece will move with the spiral and keep its poles that are developed by induction fixed in space. From this, in order to reach a dynamo-electric machine it is necessary to try to develop the energy of the magnetic field by the action of the current itself. If we suppose the core to be of soft iron, and make a closer study of the action of the current as regards the polarity that occurs under the influence of the poles, _s_, _n_, _s_, we shall see that from _d_ to _a_ and from _b_ to _c_ the current is contrary, while that from _a_ to _b_ and from _c_ to _d'_ it is favorable to the development of such polarity. In short, with a spiral moving from _d_ to _d'_ the resulting effect is _nil_, a fact, moreover, that is self-evident. Under such circumstances, if we suppose the shell, as well as the core, to be of soft iron, we shall obtain a feeble current due to the presence of remanent magnetism; but this magnetism will not be able to continue increasing under the influence of the current. To solve this difficulty two means present themselves: (1) to cause a, favorable magnetic current and act upon the armature, and (2) to suppress such portions of the current in the spirals as are injurious in effect. The first solution was thought of by Gramme in 1871, and is represented diagramatically in Fig. 2. The second is due to Prof. Pfaundler, and dates back to 1870. The core is cut through the center (Fig. 3), and the portion to the right is suppressed; the current is interrupted between _da_ and _cd'_, and is closed only between _a_ and _c_ (_v_, Fig. 1). It results from this arrangement that, under the action of the current, the polarity due to remanent magnetism does nothing but increase. It suffices then for but little remanent magnetism to prime the machine; the polarity of the shell continues to increase, and the energy of the magnetic field, and consequently of the current, has for a limit only the saturation of the soft iron. If, now, we curve the core, the spirals, and the armature into a circle, we have a Gramme or a Pfaundler machine, according as we consider Fig. 2 or Fig. 3.

This latter apparatus has in this case the form shown in Fig. 4.