STEAM ENGINE ECONOMY.

[4]

An address by Prof. W.H. Corfield, M.D., M.A., delivered before the Sanitary Institute of Great Britain, July 9, 1885.—Building News.

The purpose of this article is to point out an easy method whereby any intelligent engineer can determine the point at which it is most economical to cut off the admission of steam into his cylinder.

In the attack upon such a problem, it is useful to employ all the senses which can be brought to bear upon it; for this purpose, diagrams will be used, in order that the sense of sight may assist the brain in forming its conclusions.

STEAM ENGINE ECONOMY.—BY JOHN LOWE, CHIEF ENGINEER U.S.N.

Fig. XABCX is an ideal indicator card, taken from a cylinder, imagined to be 600 feet long, in which the piston, making one stroke per minute, has therefore a piston speed of 600 feet per minute. Divide this card into any convenient number of ordinates, distantdxfeet from each other, writing upon each the absolute pressure measured upon it from the zero line XX.

By way of example, let the diameter of the cylinder be 29.59 inches, and let the back pressure from all causes be 7 pounds uniformly throughout. It will be represented by the line b1, b2, etc. This quantity subtracted from the pressures p1, p2, etc., leaves the remainder (p-b) upon each ordinate, which remainder represents the net pressures which at that point may be applied to produce external power.

If, now, A is the area of the piston, then the external power (d W) produced between each ordinate is:

To any convenient scale, upon each ordinate, set off the appropriate power as calculated by this equation (1).

A(p-b)dxdW = --------------. (1.)33,000

There will result the curvew, w, w, determining the power which at any point in the diagram is to be regarded as a gain, to be carried to the credit side of the account.

It is evident that, so long as the gains from expansion exceed the losses from expansion, it is profitable to proceed with expansion, but that expansion should cease at that point at which gains and losses just balance each other.

The requisite data are furnished by the experiments conducted some years since by President D.M. Greene, of Troy College, for the Bureau of Steam Engineering, U.S. Navy.

According to these experiments, the heat which is lost per hour by radiation through a metallic plate of ordinary thickness, exposed to dry air upon one side and to the source of heat upon the other, for one degree difference in temperature, is as follows:

Condition. Heat units.Naked...................................... 2.9330672Covered with hair felt, 0.25 inch thick.... 1.0540710" " 0.50 " .... 0.5728647" " 0.75 " .... 0.4124625" " 1.00 " .... 0.3070554" " 1.25 " .... 0.2746387" " 1.50 " .... 0.2507097If now t' = temperature of steam at the ordinate,t = temperature of the surrounding atmosphere,dS = surface of the cylinder included between each ordinate,k = that figure from the table satisfying the conditions,then the power loss (dR) per minute will be:k (t'-t)dSdR = ( -- ) ----------. (2)60 33,000

To the same scale as the power gains, upon each ordinate, set off the appropriate power loss, as calculated by this equation (2).

There will result the curve r, r, r, which determines the power which at any point in the diagram is to be regarded as a loss, to be carried to the debit side of the account. This curve of losses intersects the curve of gains at a point (it is evident) where each equals the other.

Therefore this is the point at which expansion should cease, and this absolute pressure is the economic terminal pressure, which determines the number of expansions profitable under the given conditions.

In the foregoing example are taken k = 0.3070554, t' = 331.169, t = 60, while the back pressure was taken at 7 pounds.

By way of further illustration, first let the back pressure be changed from 7 to 5.

By equation 1 there will result a new curve of gains, W, W, W, a portion only being plotted.

Second, let t' = 331.169 as before.t = 150 instead of 60.k = 0.2507097 instead of 0.3070554.

There will result the second curve of losses, R, R, R, intersecting the second curve of gains at the point F, the new economic point for our new conditions.

These two examples fully illustrate the whole subject, furnishing an easy and, when carefully made, a very exact calculation and result.

The following are a few of the general conclusions to be drawn:

1. That radiation is a tangible and measurable cause, sufficient to account for all losses heretofore ascribed to an intangible, immeasurable, and wholly imaginary cause, viz., "internal evaporation and re-evaporation."

2. In order to prevent the high initial temperatures now used becoming a source of loss, it is necessary to prevent the quantity dS (t'-t) becoming great, by making dS as small as possible. In other words, we must compound our engines. Thus for the first time is pointed out the true reason why compound engines are economical heat engines.

3. The foregoing reasoning being correct, it follows that steam jackets are a delusion.

4. In order to attain economy, we must have high initial temperatures, small high pressure cylinders, low back pressures from whatsoever cause, high piston speeds, short rather than long strokes, to avoid the cooling effects of a long piston rod; but especially must we have scrupulous and perfect protection from radiation, especially about the cylinder heads, now oftentimes left bare.

Lieutenant Fiske began by paying a tribute to the remarkable pioneer efforts of Colonel Samuel Colt, who more than forty years ago blew up several old vessels, including the gunboat Boxer and the Volta, by the use of electricity. Congress voted Colt $17,000 for continuing his experiments, which at that day seemed almost magical; and he then blew up a vessel in motion at a distance of five miles. Lieut. Fiske next referred briefly to the electrical torpedoes employed in the Crimean war and our civil war.

At the present day, an electrical torpedo may be described as consisting of a strong, water-tight vessel of iron or steel, which contains a large amount of some explosive, usually gun-cotton, and a device for detonating this explosive by electricity. The old mechanical mine used in our civil war did not know a friendly ship from a hostile one, and would sink either with absolute impartiality. But the electrical submarine mine, being exploded only when a current of electricity is sent through it from ship or shore, makes no such mistake, and becomes harmless when detached from the battery. The condition of the mine at any time can also be told by sending a very minute current through it, though miles away and buried deep beneath the sea.

When a current of electricity goes through a wire, it heats it; and if the current be made strong enough, and a white hot wire thus comes in contact with powder or fulminate of mercury in a torpedo, an explosion will result. But it is important to know exactly when to explode the torpedo, especially during the night or in a fog; and hence torpedoes are often made automatic by what is called a circuit closer. This is a device which automatically bridges over the distance between two points which were separated, thus allowing the current to pass between them. In submarine torpedoes it is usual to employ a small weight, which, when the torpedo is struck, is thrown by the force of the blow across two contact points, one of which points is in connection with the fuse and the other in connection with the battery, so that the current immediately runs over the bridge thus offered, and through the fuse. In practice, these two contact points are connected by a wire, even when the torpedo is not in the state of being struck; but the wire is of such great resistance that the current is too weak to heat the wire in the fuse. Yet when the weight above mentioned is thrown across the two contact points, the current runs across the bridge, instead of through the resistance wire, and is then strong enough to heat the wire in the fuse and explode the torpedo. The advantage of having a wire of high resistance between the contact points, instead of having no wire between them, is that the current which then passes through the fuse, though too weak to fire it, shows by its very existence to the men on shore that the circuit through the torpedo is all right.

But instead of having the increased current caused by striking the torpedo to fire the torpedo directly, a better way is to have it simply make a signal on shore. Then, when friendly vessels are to pass, the firing battery can be disconnected; and when the friendly ship bumps the torpedo, the working of the signal shows not only that the circuit through the fuse is all right, but also that the circuit closer is all right, so that, had the friendly ship been a hostile ship, she would certainly have been destroyed.

While the management of the torpedo is thus simple, the defense of a harbor becomes a complex problem, on account of the time and expense required to perfect it, and the training of a corps of men to operate the torpedoes.

In order to detect the presence of torpedoes in an enemy's harbor, an instrument has been invented by Capt. McEvoy, called the "torpedo detecter," in which the action is somewhat similar to that of the induction balance, the iron of a torpedo case having the effect of increasing the number of lines of force embraced by one of two opposing coils, so that the current induced in it overpowers that induced in the other, and a distinct sound is heard in a telephone receiver in circuit with them. As yet, this instrument has met with little practical success, but, its principle being correct, we can say with considerable confidence that the reason of its non-success probably is that the coils and current used are both too small.

Lieut. Fiske described the spar torpedo and the various classes of movable torpedoes, including the Lay. His conclusion is that the most successful of the movable torpedoes is the Simms, with which very promising experiments have been conducted under the superintendence of Gen. Abbot.

Recent experiments in England have shown that the Whitehead torpedo, over which control ceases after it is fired, is not so formidable a weapon when fired at a shipunder wayas many supposed, for the simple reason that it can be dodged. But an electrical torpedo, over which control is exercised while it is in motion through the water, cannot be dodged, provided it receives sufficient speed. For effective work against ships capable of steaming fifteen knots per hour, the torpedo should have a speed of twenty knots. There is no theoretical difficulty in the way of producing this, for a speed of eleven knots has already been recorded, though an electric torpedo, to get this speed, would have to be larger than a Whitehead having the same speed. It may be conceived that a torpedo carrying 50 lb. of gun-cotton, capable of going 20 knots per hour, so that it would pass over a distance of 500 yards in about 45 sec., and yet be absolutely under control all the time, so that it can be constantly kept pointed at its target, would be a very unpleasant thing for an enemy to meet.

Military telegraphy is a second use of electricity in warfare. Lieut. Fiske traces its origin to our own civil war. Foreign nations took the hint from us, and during the invasion of France the telegraph played a most important part. In military telegraph trains, miles of wire are carried on reels in specially constructed wagons, which hold also batteries and instruments. Some of the wire is insulated, so that it can rest on the ground, and thus be laid out with great speed, while other wire is bare, and is intended to be put on poles, trees, etc. For mountain service the wires and implements are carried by pack animals. Regularly trained men are employed, and are drilled in quickly running lines, setting up temporary stations, etc. In the recent English operations in Egypt, the advance guard always kept in telegraphic communication with headquarters and with England, and after the battle of Tel-el-Kebir news of the victory was telegraphed to the Queen and her answer received in forty-five minutes.

The telephone is also used with success in warfare, and in fact sometimes assists the telegraph in cases where, by reason of the haste with which a line has been run, the current leaks off. A telephone may then be used to receive the message—and for a transmitter a simple buzzer or automatic circuit breaker, controlled by an ordinary key. In the case of vessels there is much difficulty in using the telegraph and the telephone, as the wire may be fouled and broken when the ship swings by a long chain. In England in the case of a lightship this difficulty has been surmounted, or rather avoided, by making hollow the cable by which the ship rides, and running an insulated wire along the long tube thus formed inside. But the problem is much simplified when temporary communication only is desired between ships at anchor, between a ship and the shore, or even between a ship and a boat which has been sent off on some special service, such as reconnoitering, sounding, etc. In this case portable telephones are used, in which the wire is so placed on a reel in circuit with the telephone that communication is preserved, even while the wire is running off the reel.

The telegraph and telephone are both coming largely into use in artillery experiments, for example, in tracking a vessel as she comes up a channel so that her exact position at each instant may be known, and in determining the spot of fall of a projectile. In getting the time of flight of projectiles electricity is of value; by breaking a wire in circuit with a chronograph, the precise instant of start to within a thousandth of a second being automatically registered. Velocimeters are a familiar application of electricity somewhat analogous. In these, wires are cut by the projectile at different points in its flight, and the breaking of the electric current causes the appearance of marks on a surface moving along at a known speed. The velocity of the projectile in going from one wire to another can then be found.

Electricity is also used for firing great guns, both in ships and forts. In the former, it eliminates the factor of change produced by the rolling of the ship during the movement of the arm to fire the gun. The touch of a button accomplishes the same thing almost instantaneously. Moreover, an absolutely simultaneous broadside can be delivered by electricity. The officer discharges the guns from a fighting tower, whither the wires lead, and the men can at once lie down out of the enemy's machine guns, as soon as their own guns are ready for discharge. The electric motor will certainly be used very generally for handling ordnance on board ships not very heavily plated with armor, since a small wire is a much more convenient mode of conveying energy to a motor of any kind, and is much less liable to injury, than a comparatively large pipe for conveying steam, compressed air, or water under pressure. Besides, the electric motor is the ideal engine for work on shipboard, by reason of its smooth and silent motion, its freedom from dirt and grease, the readiness with which it can be started, stopped, and reversed, and its high efficiency. Indeed, in future we may look to a protected apparatus for all such uses in every fort and every powerful ship.

In photographing the bores of great guns, electric lights are used, and they make known if the gun is accurately rifled and how it is standing the erosion of the powder gases.

In the case of a fort, electricity can be employed in connection with the instruments used for determining at each instant the position of an approaching vessel or army. Whitehead torpedoes are now so arranged that they can be ejected by pressing an electric button.

Electric lights for vessels are now of recognized importance. At first they were objected to on the ground that if the wire carrying the current should be shot away in action, the whole ship would be plunged in darkness; and so it would be in an accident befalling the dynamo that generates the current. The criticism is sensible, but the answer is that different circuits must be arranged for different parts of the ship, and the wires carrying the current must be arranged in duplicate. It is also easy to repair a break in a copper wire if shot away. As to the dynamo and engines, they must be placed below the water line, under a protective deck, and this should be provided for in building the vessel. There should be several dynamos and engines. All the dynamos should, of course, be of the same electromotive force, and feed into the same mains, from which all lamps draw their supply, and which are fed by feeders from the dynamo at different points, so that accident to the mains in one part of the ship will affect that part only. But it is the arc light, used as what is called a search light, that is most valuable in warfare. Lieut. Fiske thinks its first use was by the French in the siege of Paris, to discover the operations of the besiegers. It can be carried by an army in the field, and used for examining unknown ground at night, searching for wounded on the battle field, and so on. On fighting vessels the search light is useful in disclosing the attack of torpedo boats or of hostile ships, in bringing out clearly the target for guns, and in puzzling an enemy by involving him successively in dazzling light and total darkness. Lieut. Fiske suggests that this use would be equally effective in embarrassing troops groping to the attack of a fort at night by sudden alternations of blinding light and paralyzing darkness. There should be four search lights on each side of a ship.

As to the power and beauty of the search light, Lieut. Fiske refers to the magnificent one with which he lighted up Philadelphia last autumn, during the electric exhibition in that city. One night he went to the tower of the Pennsylvania railroad station and watched the light stationed at the Exhibition building on 32d street. The ray of light when turned at right angles to his direction looked like a silver arrow going through the sky; and when turned on him, he could read the fine print of a railroad time table at arm's length. Flashes from his search light were seen at a distance of thirty miles.

In using incandescent lamps for night signaling, the simplest way is to arrange a keyboard with keys marked with certain numbers, indicating the number of lamps arranged in a prominent position, which will burn while that key is being pressed. For example, suppose the number 5348 means "Prepare to receive a torpedo attack." Press keys 5, 3, 4, 8, and the lights of lamps 5, 3, 4, 8, successively blaze out.

Electrical launches have been used to some extent, their storage batteries being first charged ashore or on board the ship to which the launch belongs. They have carried hundreds of people, and have made eight knots an hour. The improvement of storage batteries, steadily going on, will eventually cause the electrical launch to replace the steam launch. One of its advantages is in having no noise from an exhaust and no flame flaring above a smoke pipe to betray its presence. In warfare two sets of storage batteries should be provided for launches, one being recharged while the other is in use.

Mr. Gastine Trouse has recently invented "an electric sight," a filament of fine wire in a glass tube covered with metal on all sides save at the back. The battery is said to be no larger than a man's finger, and to be attached to the barrel near the muzzle by simple rubber bands, so arranged that the act of attaching the battery to the barrel automatically makes connection with the sight; and so arranged also that the liquid of the battery is out of action except when the musket is brought into a horizontal position for firing.

To throw a good light upon the target the same inventor has devised a small electric lamp and projector, which is placed on the barrel near the muzzle by rubber bands, the battery being held at the belt of the marksman, with such connections that the act of pressing the butt of the musket against the shoulder completes the circuit, and causes the bright cylinder of light to fall on the target, thus enabling him to get as good a shot as in the day time.

Search lights and incandescent lights are advantageously used with balloons. In submarine boats electricity will one day be very useful. Submarine diving will play a part in future wars, and the diver's lamp will be electrical.

Progress has been made also in constructing "electrical guns," in which the cartridge contains a fuse which is ignited by pressing an electric button on the gun. A better aim can be had with it, when perfected, than with one fired by a trigger. At present, according to Lieut. Fiske, this invention has not reached the practical stage, and the necessity for a battery to fire a cartridge is decidedly an objection. But the battery is very small, needs little care, and will last a long time. The hard pull of the ordinary trigger causes a movement of the barrel except in the hands of the most highly skilled marksmen, and this hard pull is a necessity, because the hammer or bolt must have considerable mass in order to strike the primer with sufficient force to explode it. Having the mass, it must have considerable inertia; hence it needs a deep notch to hold it firm when jarred at full cock, and this deep notch necessitates a strong pull on the trigger. But with an electric gun the circuit-closing parts are very small and light, and can be put into a recess in the butt of the gun, out of the way of chance blows. Thus a light pressure of the finger is alone needed to fire it, while from the small inertia of the parts a sudden shock will not cause accidental closing of the circuit and firing of the gun.

[5]

From a recent lecture before the Franklin Institute, Philadelphia.

Our readers have already been informed through these columns that, notwithstanding the refusal of the Attorney-General, Mr. Garland, to institute suit for the nullification of the Bell patent, application has again been made by the Globe Telephone Co., of this city, the Washington Telephone Co., of Baltimore, and the Panelectric Co. These applications have been referred to the Interior Department and Patent Office for examination, and upon their report the institution of the suit depends. The evidence which the companies above mentioned have presented includes not only the statement of Prof. Gray and the circumstances connected with his caveat, but brings out fully, for the first time, the claims of Antonio Meucci.

MEUCCI'S CAVEAT, 1871.

The latter evidence is intended to show that Meucci invented the speaking telephone not only before Bell, but that he antedated Reis by several years. In a recent interview with Meucci we obtained a brief history of his life and of his invention, which will, no doubt, interest our readers. Meucci, a native of Italy, was educated in the schools of Florence, devoting his time as a student to mechanical engineering. In 1844 he gave considerable attention to the subject of electricity, and had a contract with the government of the island of Cuba to galvanize materials used in the army. While experimenting with electricity he read the works of Becquerel, Mesmer, and others who treated largely of the virtues of electricity in the cure of disease. Meucci made experiments in this direction, and at one time thought that he heard the sound of a sick person's voice more distinctly than usual, when he had the spatula connected with the wire and battery in his mouth.

FIGS. 1 AND 2.—1849.

The apparatus he used for this purpose is shown in Fig. 1. It consists of an oval disk or spatula of copper attached to a wire which was coiled and supported in an insulating handle of cork. To ascertain that he was able to hear the sound, he covered the device with a funnel of pasteboard, shown in the adjoining figure, and held it to his ear, and thought that he heard the sound more distinctly.

These instruments were constructed in 1849 in Havana, where Meucci was mechanical director of a theater. In May, 1851, he came to this country, and settled in Staten Island, where he has lived ever since. It was not until a year later that he again took up his telephonic studies, and then he tried an arrangement somewhat different from the first. He used a tin tube, Figs. 3 and 4, and covered it with wire, the ends of which were soldered to the tongue of copper. With this instrument, he states, he frequently conversed with his wife from the basement of his house to the third floor, where she was confined as an invalid.

FIGS. 3 AND 4.—1852.

Continuing his experiments, he conceived the idea of using a bobbin of wire with a metallic core, and the first instrument he constructed on this idea is shown in Fig. 5. It consisted of a wooden tube and pasteboard mouth piece, and supported within the tube was a bundle of steel wires, surrounded at their upper end by a bobbin of insulated wire. The diaphragm in this instrument, was an animal membrane, and it was slit in a semicircle so as to make a flap or valve which responded to the air vibrations. This was the first instrument in which he used a bobbin, but the articulation naturally left much to be desired, on account of the use of the animal membrane. Meucci fixes the dates from the fact that Garibaldi lived with him during the years 1851-54, and he remembers explaining the principles of his invention to the Italian patriot.

After constructing the instrument just described, Meucci devised another during 1853-54. This consisted of a wooden block with a hole in the center which was filled with magnetic iron ore, and through the center of which a steel wire passed. The magnetic iron ore was surrounded by a coil of insulated copper wire. But an important improvement was introduced here in the shape of an iron diaphragm. With this apparatus greatly improved effects were obtained.

FIG. 5.—1853.

In 1856 Meucci first tried, he says, a horseshoe magnet, as shown in Fig. 6, but he went a step backward in using an animal membrane. He states that this form did not talk so well as some which he had made before, as might be expected.

During the years 1858-60 Meucci constructed the instrument shown in Fig. 7. He here employed a core of tempered steel magnetized, and surrounded it with a large coil. He used an iron diaphragm, and obtained such good results that he determined to bring his invention before the public. His national pride prompted him to have the invention first brought out in Italy, and he intrusted the matter to a Mr. Bendalari, an Italian merchant, who was about to start for that country. Bendalari, however, neglected the matter, and nothing was heard of it from that quarter. At the same time Meucci described his invention inL'Eco d'Italia, an Italian paper published in this city, and awaited the return of Bendalari.

Meucci, however, kept at his experiments with the object of improving his telephone, and several changes of form were the result. Fig. 8 shows one of these instruments constructed during 1864-65. It consisted of a ring of iron wound spirally with copper wire, and from two opposite sides iron wires attached to the core supported an iron button. This was placed opposite an iron diaphragm, which closed a cavity ending in a mouthpiece. He also constructed the instrument which is shown in Fig. 9, and which, he says, was the best instrument he had ever constructed. The bobbin was a large one, and was placed in a soapbox of boxwood, with magnet core and iron diaphragm. Still seeking greater perfection, Meucci, in 1865, tried the bent horseshoe form, shown in Fig. 10, but found it no improvement; and, although he experimented up to the year 1871, he was not able to obtain any better results than the best of his previous instruments had given.

FIG. 6.—1856.

When Meucci arrived in this country, he had property valued at $20,000, and he entered into the brewing business and into candle making, but he gradually lost his money, until in 1868 he found himself reduced to little or nothing. To add to his misery, he had the misfortune of being on the Staten Island ferryboat Westfield when the latter's boiler exploded with such terrible effect in 1871. He was badly scalded, and for a time his life was despaired of. After he recovered he found that his wife, in their poverty, had sold all his instruments to John Fleming, a dealer in second-hand articles, and from whom parts of the instruments have recently been recovered.

FIG. 7.—1858-60.

With the view of introducing his invention, Meucci now determined to protect it by a patent; and having lost his instrument, he had a drawing made according to his sketches by an artist, Mr. Nestori. This drawing he showed to several friends, and took them to Mr. A. Bertolino, who went with him to a patent attorney, Mr. T.D. Stetson, in this city. Mr. Stetson advised Meucci to apply for a patent, but Meucci, without funds, had to content himself with a caveat. To obtain money for the latter he formed a partnership with A.Z. Grandi, S.G.P. Buguglio, and Ango Tremeschin. The articles of agreement between them, made Dec. 12, 1871, credit Meucci as the inventor of a speaking telegraph, and the parties agree to furnish him with means to procure patents in this and other countries, and to organize companies, etc. The name of the company was "Teletrofono." They gave him $20 with which to procure his caveat, and that was all the money he ever received from this source.

The caveat which Meucci filed contained the drawing made by Nestori, and as shown in the cut, which is a facsimile, represents two persons with telephones connected by wires and batteries in circuit. The caveat, however, does not describe the invention very clearly; it describes the two persons as being insulated, but Meucci claims that he never made any mention of insulating persons, but only of insulating the wires. To explain this seeming incongruity, it must be stated that Meucci communicated with his attorney through an interpreter, as he was not master of the English language; and even at the present time he understands and speaks the language very poorly, so much so that we found it necessary to communicate with him in French during the conversation in which these facts were elicited.

FIG. 8.—1864-65.

In the summer of 1872, after obtaining his caveat, Meucci, accompanied by Mr. Bertolino, went to see Mr. Grant, at that time the Vice President of the New York District Telegraph Company, and he told the latter that he had an invention of sound telegraphs. He explained his inventions and submitted drawings and plans to Mr. Grant, and requested the privilege of making a test on the wires of the company, which test if successful would enable him to raise money. Mr. Grant promised to let him know when he could make the test, but after nearly two years of waiting and disappointment, Mr. Grant said that he had lost the drawings; and although Meucci then made an instrument like the one shown in Fig. 9 for the purpose of a test, Mr. Grant never tried it. Meucci claims that he made no secret of his invention, and as instance cites the fact that in 1873 a diver by the name of William Carroll, having heard of it, came to him and asked him if he could not construct a telephone so that communication could be maintained between a diver and the ship above. Meucci set about to construct a marine telephone, and he showed us the sketch of the instrument in his memorandum book, which dates from that time and contains a number of other inventions and experiments made by him.

FIG. 9.—1864-65.

FIG. 10.—1865.

When Professor Bell exhibited his inventions at the Centennial, Meucci heard of it, but his poverty, he claims, prevented him from making his protestations of priority effective, and it was not until comparatively recently that they have been brought out with any prominence.—The Electrical World.

The late Dr. Mohr7of Bonn, advocated the use of a centrifugal machine as a means of rapidly drying crystals and crystalline precipitates; but although they are admirably adapted for that purpose, centrifugal machines are seldom seen in our chemical laboratories.

The neglect of this valuable addition to our laboratory apparatus is probably owing to the inconvenience involved in driving the machine at a high speed by means of the ordinary hand driving gear, especially when the rotation has to be maintained for a considerable length of time. It occurred to me, therefore, that by attaching the drum or basket of the machine (or the rotating table of Mohr's apparatus) directly to the spindle of an electro-motor, the difficulty of driving might be got over, and at the same time a combination of great efficiency would result, as the electro-motor, like the centrifugal machine, is most efficient when run at a high speed. The apparatus shown in the sketch consists essentially of a perforated basket, A, which is slipped on to a cone attached to the spindle, S, of an electro-motor, and held in position by the nut, D. The casing, B, with its removable cover, C, serves to receive the liquid driven out of the substance being dried. A flat form of the ordinary Siemens H armature, E, revolves between the poles, P, of the electro-magnets, M, which are connected by means of the base plate, I. The brass cross-bar, G, carries the top bearing of the spindle, S, and prevents the magnet poles from being drawn together.

From four to six cells of a bichromate battery or Faure secondary battery furnish sufficient power to run the machine at a high speed. An apparatus with a copper basket four inches in diameter has been found extremely useful in the laboratory for drying such substances as granulated sulphate of copper and sulphate of iron and ammonia, but more especially for drying sugar, which when crystallized in very small crystals cannot be readily separated from the sirupy mother-liquor by any of the usual laboratory appliances. For drying substances which act on copper the basket may be made of platinum or ebonite; in the latter case, owing to the increased size of the perforations, it may be necessary to line the basket with platinum wire gauze or perforated parchment paper.

[6]

Paper read before Section B, British Association, Aberdeen meeting.

[7]

"Lehrb. d. Chem. Analyt. Titrirmethode," 3d ed., 1870, p. 684.

The experiments of M. Marcel Deprez have entered on a decisive phase. The dynamos are completed, and were put in place on the 20th October, when M. Deprez carried out some preliminary tests in the presence of a commission consisting of MM. Collignon, Inspector-General des Ponts et Chaussées; Delebecque, Ingenieur en Chef du Materiel et de la Traction of the Northern Railway of France; Contanini, engineer in the same company; and Sartaux. The generating dynamos made by MM. Breguet, and the receiving dynamos constructed by MM. Mignon and Rouart, were during a preliminary trial placed side by side, one portion of the circuit being very short, and the other twice the distance between La Chapelle and Creil, or seventy miles. In future experiments the two dynamos will be placed in their normal positions at each end of the line. The generating machine is driven by a locomotive engine; the resistance of its field magnets is 5.68 ohms, and of the two armatures 33 ohms. The resistance of the two armatures of the receiving machine is 36.8 ohms, and the resistance of the line is 97 ohms; the generator and receiver field magnets are excited each by a separate machine. Five different trials were made at varying speeds of the driving shaft; the initial work on this shaft was measured by a dynamometer, and the available energy of the shaft of the receiving machine was ascertained by a Prony brake; the other results of the experiments were deduced from the constants of the machines and from galvanometric measurements. For the first trials the different elements were as follows:

1.Generating dynamos:Velocity of shaft 123 revolutions.Electromotive force at terminals, 3370.25 volts." " total 3624.7 "Available work at driving shaft. 43 h. p.Electrical work of generator 37.38 "Difference absorbed 5.62 "2.Line:Work absorbed by the line. 7.59 h. p.3.Receiving dynamos:Velocity of shaft 154 revolutions.Electromotive force at terminals, 2616.25 volts." " total 2336.94 "Electrical work of receiver 24.10 h. p.Available work on shaft 22.10 "Difference absorbed 2 "

The duty obtained would thus be 22.10/43 = 51.3 per cent., if the work absorbed by the exciting machines be not considered. Taking this into account, it would be reduced to 40 per cent.

In subsequent experiments the speed of the generator was increased gradually. In the last trial the following were the elements:

1.Generating dynamos:Speed of shaft 190 revolutions.Electromotive force at terminals 5231.25 volts." " total 5469.75 "Available work on driving shaft, 62 h. p.Electrical work on generator 53.59 "Difference absorbed 8.51 "Work absorbed by armature 2.33 "2.Line:Work absorbed by conductors 7.21 h. p.3.Receiving dynamos:Speed of shaft 248 revolutions.Electromotive force at terminals 4508 volts.Electromotive force total 4242.67 "Electrical work of receiver 41.44 h. p.Work measured on receiver shaft 35.8 "Difference absorbed 5.64 "Duty obtained, not including exciting machine 57 per cent.Duty obtained, including exciting machine 48 "

During the various experiments the current traversing the line varied from 7.59 amperes to 7.21 amperes. No heating of any kind was observed.

M.J. Bertrand, who communicated a paper to the Academy of Sciences on the subject, commented on the relatively low speeds. It corresponds to a linear displacement of the surface armatures, in no case exceeding the speed of a locomotive wheel. The tension reached 5,500 volts., under very satisfactory mechanical conditions, and with a current that in no way endangered the line. This first experiment is certainly encouraging, and it will be followed by others of a more complete and exhaustive character. MM. De Rothschild are now embodying a powerful commission of French and foreign scientists who will follow the subject carefully, and report upon it. It may be safely predicted that one result of this action will be the development of a new series of observations of the highest technical interest and value.—Engineering.

The trick with the locked and corded box, I believe, is an old one, though perhaps not in its present form. In late years it has been revived with improvements, and popularized by those clever illusionists, Messrs. Maskelyne & Cook and Dr. Lynn, at the Egyptian Hall. There are several ways of working the trick or, rather, of arranging the special bit of mechanism wherein the peculiar features of the box consist. The one I am about to describe is, I think, the best of those I am acquainted with, or at liberty to divulge. Indeed, I don't know that any method is better, and this one has the advantage over most others of allowing the performer to get into as well as out of the box, without leaving a trace of his means of ingress. It will be seen the box is paneled, and all the panels look equally firm and fixed. As a matter of fact, one of the panels is movable, though the closest scrutiny would fail to discover this if the box and fittings are carefully made and adjusted. Fig. 1 shows the general appearance of the box, of which the back is the same as the front. In the box I describe, the end marked + has a movable panel. The size of the box should be regulated by the size of the performer; but one measuring 3 feet 6 inches long by 2 feet back to front, and 21 inches high, exclusive of the lid, which may be 3 inches, will be of general use. In making the box it is most important that all sides and panels look alike, and that nothing special in the appearance of the end with the loose panel should attract notice. Fig. 2 shows this end with fittings drawn half of full size, and it will he seen from this that the framing, A, is 3 inches wide by 1¼ inches thick, and the panel, B, ½ inch thick.

FIG. 1.

It will be noticed that the top and bottom rails of the frame are rabbeted to receive the panel, but the sides are grooved, the groove in front rail being double the depth of the one in the back rail.

THE LOCKED AND CORDED BOX TRICK. By DAVID B. ADAMSON.

The dotted line, B, shows the size of the panel; the dotted line, C, shows the depth of groove in the front rail. From this it will be clear that the panel is only held in place at the back and front, and that on sliding it toward the front it will be free out of the groove in the back rail. Three sides of it are thus free, and a little manipulation will allow of its being taken out altogether, leaving plenty of space for the performer to get out, presuming him to have been locked inside the box.

If the panel were to be finished in this way, without further fittings, the secret would soon be discovered; and I now proceed to show how the panel is held in place and firm while under examination.

Determine the size of screws that are to be used in fixing the brass corner clamps. Let us say No. 7 is decided on; and if brass screws are used, then get a piece of brass, Fig. 4, the exact diameter of the screw-head, and a little longer than the thickness of the framing. If iron screws are to be used, then this piece must be iron. Now bore a hole into which this bolt will fit closely, right through the framing at D, Fig. 2. It is most important that the hole should be made close up to the edge of the panel, B, so that when the bolt is in it firmly holds the panel, and prevents it moving from back to front in the grooving. Now get a piece of sheet brass, 1/8 inch thick, and cut it to the shape shown by E, Fig. 2. The width of this piece should not be less than 3/8 inch, and it must be of such length that the end reaches to the middle of the top framing, as shown at L, Fig. 2. This piece of brass is sunk in the top and front framing, as shown by the dotted lines, G, in Figs. 2 and 3, and also in section in the latter.

When the box is open, the lower or short arm of this lever, which is shaped as shown full size, at E, Fig. 8, is kept pressed down on the bolt, D, as shown by the dotted lines, E, E, E, Fig. 2, and E, Fig. 7, by of the spring, J, Fig. 2.

On the box being closed, a pin on the under edge of lid goes into the hole, L, Fig. 3, and presses the end of the lever down in such a way as to raise the claw end of it from D. The thick dotted lines, F, F, F, Fig. 2, show position of lever when box is closed.

It will be noted that the bolt, D, Fig. 4, has a groove cut in it all around, into which the claw fits. This prevents the bolt being pushed backward or forward when the box is open.

The lever must be hung as shown, K, Fig. 2. The exact position of this is immaterial, but it is as well to have the fulcrum as near the end as may be, in order that the claw may be raised sufficiently with only a small movement of the short arm of the lever. Of course, the shorter the arm is, the more accurately the lid and pin must be made to close.

If the pin, pressing short arm down, be too short, the pressure will not be enough to release the claw, and consequently the performer might find himself really unable to get out of the box after it is locked.

The end of the lever should be finished with a wood block, as Fig. 6, larger than the pin on the lid, as represented by L and M, Fig. 3.

The block may be of other material, but should be colored the same as the wood the box is made of, so that, if any one were to look down on it, no suspicion would be aroused, as might be were plain brass used.

FIG 4.

FIG 5.

In Fig. 5, I show an easy way of hanging the lever. It is simply a piece of wire sharpened and notched, so as to form several small barbs, preventing withdrawal. The mode of fixing will be easily understood by reference to B and C, Fig. 5. Some considerable amount of care will have to be bestowed on fitting and adjusting this part of the work, on which the successful performance of the trick consists, and before finally fixing up, it should be ascertained that all the movements work harmoniously. It will be best to cut the groove in which the lever works from below, and, after the lever is fixed, to fill up the space not required by the lever with strips of wood, H, H. If preferred, the space can be shaped out from the back, i.e., the inside of the framing, and then filled where not required, but as this, however neatly done, would show a joint which might be detected by sharp eyes, it is better to cut from below, though more troublesome.

The end containing the movable panel being arranged, make up the rest of the box to it, taking care to make the rebates of the top and bottom frames to correspond with those of the end.

The other panels should not, however, depend on the grooves on two sides only, but at tops and bottoms as well.

FIG. 6.

FIG. 7. & FIG. 8.

FIG. 9.

The rebates are to be cut only to have all the framing inside look alike; and as the panel, B, is made to fit quite close into the rebate, it will not be surmised that it is not fitted in the usual way.

After the box is made and fitted together, the clamping must be done. The only necessity for this is in order that the bolt, D, which we have seen is made on the outside end exactly to match the screws used to fasten the clamps, should not be conspicuous, as it would be were it alone. As it is, it will not be specially observable, being apparently only one of the screws to fasten the clamps.

The clamps may be of thin brass or iron, shaped as shown at Fig. 9. One of the corner holes must be arranged to cover D exactly, and the others regulated to it. Let us suppose that A, Fig. 9, is the one through which the bolt goes; the other corner screw holes must be equally distant from the edges of the clamps. Twelve of these clamps will be needed. After they have been screwed on, put the bolt through, and let the claw of the lever hold it in place. Then mark and cut the bolt flush with the clamp, making a hollow on the end of it to imitate the screws, as D, Fig. 4. The other end of the bolt should either be made flush with the inside of frame and colored to match it, or, better, cut short and faced flush with a piece of wood to match the framing.

If a piece of wood with a knot be chosen for this side of the frame, so much the better. Immediately over the hole, L, a wooden pin should be fixed in the lid, and of such length that it will press the short arm of lever down sufficiently. It should fit the hole pretty closely.

At the other end, a corresponding pin and hole should be made, and, say, two along the front. These will then look as if they were intended merely as fittings to hold the lid in position. The lid at the other end of the box from the movable panel should have a stop of some sort; the ordinary brass joint stop will do as well as any, and should be strong. The reason for placing it at what I may call "the other end" is that, when the box is being examined, it will attract notice, and draw attention from the movable panel end.

We may now finally adjust the loose panel, which must fit tight at top and bottom, and be slightly beveled, as shown on section. Two holes must also be cut through it, at such a distance from each other that a finger and thumb can be put through them, so as to allow of the panel being moved. In the deep grooving in front also put a couple of springs, say pieces of clock springs, as shown, I, I, Fig, 2. These serve to assist the bolt, D, by pushing the panel into position.

Holes to match those in end panel must also be cut in the other panels, and when a lock, preferably a padlock, has been fitted, the box is complete.

I don't know whether it is necessary to say that the lid should be hinged at the back, and of course it will add to the appearance of the box if it be polished or oiled.

Now, for those who may not have seen the locked and corded box trick performed, a few words of caution may not be out of place. Don't forget to have something in a pocket easily got at that will serve to push the bolt out, before going into the box. A piece of stout wire, a small pencil case, or anything of that sort will do. Be careful when getting into the box to lie with your head toward the loose panel end, and face toward the front—as there will be no space to turn round; the right hand will then be uppermost and free to push the bolt out. Having done this, grasp the panel with the finger and thumb by means of the two holes, push it to the front of the box, when the back edge will be clear of the groove. It can now easily be pulled into the box, and the performer can creep out. When out, refix panel and bolt so that everything looks as it was. Any cording that may be over the end of the box will give sufficiently to allow of exit.

I have, I think, made it quite clear that padlock and ropes have nothing to do with the real performance of the trick, but they serve to mystify spectators, who may be allowed to knot the rope and seal the knots in any way they choose.

There must always be a screen or curtain to hide the box from the spectators while the performer is getting in or out.—D.B. Adamson, in Amateur Work.

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