Chapter 6

In a lecture delivered by me on the 15th of last June in the amphitheater of the Conservatoire des Arts et Metiers, on the application of electricity to the production, transmission, and division of power, I operated for the first time an electric power hammer that I shall here describe. Its essential part is a sectional solenoid that I have likewise made an application of in an electric motor which I presented in July, 1830, to the Societé de Physique. Let us suppose we superpose, one on the other, a hundred flat bobbins of a centimeter in thickness in such a way as to form a single solenoid one meter in height, and that the incoming and outgoing wires of each of them be connected with the contiguous bobbins exactly in the same way as they are in the consecutive sections or a dynamo-electric machine ring. Finally, let us complete the resemblance by causing each junction of the wire of one of the bobbins with the wire of its neighbor to end in a metallic plate set into an insulating piece containing as many plates as there are bobbins, plus one. Over this species of collector, which maybe rectilinear or wound around a cylinder, let us pass two brushes fixed to an insulating piece that may be moved by hand. Now, if we place these two brushes at a distance such that the number of the plates of the collector included between them be, for example, equal to ten, and we give them any degree of displacement whatever, after rendering them interdependent, the current entering through one of these brushes and making its exit through the other will always traverse 10 bobbins. Everything will occur, then, as if we caused the ten-bobbin solenoid to move instead of the brushes. This granted, and the brushes being in any position whatever, let us send a current into the apparatus, and place therein a soft iron cylinder. By virtue of a well known law, such cylinder will remain suspended in the interior of the solenoid, and its longitudinal center will place itself at so much the greater distance from that of the solenoid the more the current increases in intensity. It would even fall entirely if the current had not an intensity above a minimum value dependent upon many elements concerning which we have not now to occupy ourselves. We will suppose the current intense enough to keep the distance of the two centers much below that which would bring about a fall of the cylinder. When such a condition is fulfilled, it is found that if we try to remove the iron cylinder from the equilibrium that it is in, we must apply a pressure that increases with the amount of separation, just exactly as if it were suspended from a spring. It results from this fact that if we displace the brushes a distance equal to the thickness of one plate of the collector, the active solenoid will undergo the same displacement, and its longitudinal center will move away from that of the iron cylinder, and that the attraction exerted upon the latter will increase. It will not be able to assume its first value, and equilibrium cannot be re-established unless the cylinder undergoes a displacement identical with that of the solenoid. Now, as this latter depends upon the motion communicated to the system of brushes, we see that, definitively, the cylinder will faithfully reproduce the motion communicated to the brushes by the hand of the operator. This apparatus, then, constitutes a genuine electric servo-motor in which the current is never interrupted nor modified in quantity or direction, no more indeed than the magnetization developed in the soft iron cylinder. Everything takes place as if the iron cylinder were suspended in a solenoid ten centimeters in length that was caused to rise and fall; with the difference that the weight of the cylinder exerts no action on the hand of the operator.

These explanations being understood, there remain but few things to be said to cause the operation of the hammer to be thoroughly comprehended. The elementary sections constituting the electric cylinder, A B, of the hammer are 80 in number, and form a total length of one meter. Their ingoing and outcoming wires end in a collector of circular form shown at F G. The brushes are replaced by two strips, C E and C D, fixed to the double winch, H C I, which is movable around the fixed center, C. They can make any angle whatever with each other, so that by trial there maybe given the active solenoid the most suitable length. When such angle has been determined, the angle, E C D, is rendered invariable by means of a set screw, and the apparatus is maneuvered by imparting to the double winch, H C I, an alternating circular motion.

The iron cylinder weighs 23 kilogrammes; but, when the current has an intensity of 43 amperes and traverses 15 sections, the stress developed may reach 70 kilogrammes; that is to say, three times the weight of the hammer. So this latter obeys with absolute docility the motions of the operator's hands, as those who were present at the lecture were enabled to see.

I will incidentally add that this power hammer was placed on a circuit derived from one that served likewise to supply three Hefner-Alteneck machines (Siemens D{5} model) and a Gramme machine (Breguet model P.L.). Each of these machines was making 1,500 revolutions per minute and developing 25 kilogrammeters per second, measured by means of a Carpentier brake. All these apparatus were operating with absolute independence, and had for generator the double excitation machine that figured at the Exhibition of Electricity.

In an experiment made since then, I have succeeded in developing in each of these four machines 50 kilogrammeters per second, whatever was the number of those that were running; and I found it possible to add the hammer on a derived circuit without notably affecting the operation of the receivers.

It results from this that with my system of double excitation machine I have been enabled to easily run with absolute independence six machines, each giving a two-third horse-power. The economic performance, e/E, moreover, slightly exceeded 0.50.

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SOLIGNAC'S NEW ELECTRIC LAMP.

When it becomes a question of practical lighting, it is very certain that the best electric lamp will be the one that is most simple and requires the fewest mechanical parts. It is to such simplicity that is due all the success of the Jablochkoff candle and the Reynier-Werdermann lamp. Yet, in the former of these lamps, it is to be regretted that the somewhat great and variable resistance opposed to the current in its passage through two carbons that keep diminishing in length, in measure as they burn, proves a cause of loss of light and of variation in it. And it is also to be regretted that the duration of combustion of the carbons is not longer; and, finally, it is allowable to believe that the power employed in volatilizing the insulator placed between the carbons is prejudicial to the economical use of this system. In order to obviate this latter inconvenience, an endeavor has been made in the Wilde candle to do away with the insulator, but the results obtained have scarcely been encouraging. An endeavor has also been made to render the duration of the carbons greater by employing quite long ones, and causing these to move forward successively through the intermedium of a species of rollers, or of counterpoises, as in the lamps of Mersanne and Werdermann; but then the system becomes more complicated. Finally, in order to keep the resistance of the carbons at a minimum and constant, their contact with the rheophores of the circuit has been established at a short distance from the arc, and this is one of the principal advantages possessed by the Reynier-Werdermann system. At a certain epoch it was thought that the problem might be simply solved by arranging in front of each other two carbons actuated by a spiral spring, as in car lamps, and kept at a proper distance apart for forming the electric arc by two funnel-shaped pieces of calcined magnesia, into which they entered like a wedge in measure as their conical point were away through combustion. This was the system of Mr. De Baillehache, and the trials that were made therewith were very satisfactory. But, unfortunately, the magnesia was not able to resist very long the temperature to which it was submitted. The problem found a better solution in the sun-lamp but has been solved in another manner, and just as simply, by Mr. Solignac, and the results obtained by him have been very satisfactory as regarded from the standpoint of steadiness of the luminous point.

In this system, a general view of which is given in Fig. 1, and the arrangement in Figs. 2 and 3, the carbons, F F, which are horizontal and about fifty centimeters in length, are thrust toward each other by two barrels, K, K, which wind up two chains, E, E, passing around the pulleys, D, D, fitted to the extremities of the carbons. These latter are provided beneath with small glass rods, G, G, whose extremities toward the arc abut at a short distance from the latter against a nickel stop, L (Fig. 3), which supports them, moreover, at M, by means of a tappet whose position is regulated by a screw. The current is transmitted to the carbons by two friction rollers, I, I, which serve at the same time as a guide for them, and which give the electric flux a passage of only one or two centimeters over the front of the carbon to form the arc. Finally, the whole is held by a support, A, and two pieces, CB, CB, which at the same time lead the current to the friction rollers through projections, J. The two systems are made to approach or recede from each other, in order to form the arc, by means of a regulating screw, H.

At present, the lighting of these lamps is effected by means of this screw, H, but Mr. Solignac is now constructing a model in which the lighting will be performed automatically by means of a solenoid that will react upon a carbon lighter, as in several already well known systems.

If the preceding description has been well-understood, it will be seen that the carbons are arrested in their movement toward each other only by the glass rods, G, abutting against L; but, as the stops, L, are not far from the arc, and as the heat to which they are exposed is so much the greater in proportion as the incandescent part of the carbons is nearer them, it results that for a certain elongation of the arc the temperature becomes sufficient to soften the glass of the rods, G, G, so that they bend as shown at O (Fig. 3), and allow the carbons to move onward until the heat has sufficiently diminished to prevent any further softening of the glass. In measure as the wearing away progresses, the preceding effects are reproduced; and, as these are produced in an imperceptible and continuous manner, there is perceived no jumping nor inconstancy in the light of the arc. Under such conditions, then, the regulation of the arc is effected under the very influence of the effect produced; and not under that of an action of a different nature (electro-magnetism), as happens in other regulators. It is certain that this idea is new and original, and the results that we have witnessed from it have been very satisfactory. There is but one regulation to perform, and that at the beginning, but this once done the apparatus operates with certainty, and for a long time. With a Meritens machine of the first model it has been found possible to light five lamps of this kind placed in the same circuit.

According to the inventor, this lamp will give a light of 100 carcels per one horse-power, and with a three horse-power six lamps may be lighted; but we have made no experiments to ascertain the correctness of these figures.

As for the cost of the glass rods, that amounts to one franc per two hundred meters length. They can, then, be considered only as an insignificant expense in the cost of the carbons. We consequently believe that it will be possible to employ this system advantageously in practice.--_Th. du Moncel_.

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MONDOS'S ELECTRIC LAMP.

Since the month of May last, the concert at the Champs Elysées has been lighted by sixteen voltaic arc lamps on a new and very simple system, which gives excellent results in the installation under consideration. The sixteen lamps are on the divisible system, and their regulation is based upon the principle of derivation. They are supplied by a Siemens alternating current machine and arranged in four circuits, on each of which are mounted four lamps in series. The accompanying figures will allow the reader to readily understand the system, which is as simple as it is ingenious, and which has been combined by Mr. Mondos so as to obtain a continuous and independent regulation of each lamp.

In this system the lower carbon is stationary, the luminous point descending in measure as the carbons wear away through combustion. The upper carbon descends by its own weight, and imperceptibly, so as to keep the arc at its normal length.

The mechanism that controls the motions of the upper rod that supports the carbon-holder consists of two bobbins of fine wire, E (Fig. 2), mounted on a derived circuit on the terminals of the lamp; of a lever, L, articulated at O, and supporting a tube, TT', and the whole movable part balanced by a counterpoise, P. This lever, P, carries two soft iron cores, F, which enter the bobbins, E, and become magnetized under the influence of the current that passes through them. The upper part of the tube, T, carries a square upon which is articulated at O' a second lever, L', balanced by a second counterpoise, P', and carrying a flat armature, _p_, opposite the cores, F', that are fixed to the first horizontal lever, L. The carbon-holder rod, CC', slides freely in the tube, TT', and is wedged therein by a small piece, _a m l_, fixed to the lever, L'. For this reason the tube, TT', is provided with a notch opposite the piece _a m l_, and the two arms, _a_ and _m_, of the latter are shaped like a V, as may be seen in part in the plan in Fig. 2. It is now easy to understand how the system operates; when the current is not traversing the circuit, the carbons are separated; but, at the moment the circuit is closed for lighting a series of lamps, it traverses the electro-magnet, which then becomes very powerful, and draws down the cores, F, along with the lever, L, the tube, TT', and the carbon-holder, CC', and brings the carbons in contact. The arc then forms, and the current divides between the arc and the bobbins, E. Its action upon the cores, F, becomes weak, and it can no longer balance the counterpoise, P, which falls back, and raises the system again. The arc thus becomes _primed_. The cores, F, however, preserve a certain amount of magnetization; the armature, _p_, is attracted, and the lever, L', assumes a position of equilibrium such that the piece, _a m l_, wedges the rod, CC', in the tube, TT', and holds it suspended. When, through wear of the carbons, the arc elongates, a greater portion of the current passes into the bobbins, E, the armature, _p_, is attracted with more force, and the lever, L', swings around the point, O'. The rotation of L' separates the piece, _a m l_, from the rod, CC', which, being thus set free, slides by its own weight and shortens the arc. The current then becomes weak in E, the armature, _p_, is not so strongly attracted, the lever, L', pivots slightly around O' under the action of the weight, P', and the brake or wedge enters the notch anew, and stops the descent of the carbon. In practice, the motions that we have just described are exceedingly slight; the carbon moves imperceptibly, and the length of the arc remains invariable.

It will be seen, then, that the lever, L, and the tube, TT', serve exclusively for _lighting_, and the lever, L', exclusively for regulating the distance of the carbons.

This lamp exhibits great elasticity, and can operate, without a change of any part of its mechanism, with currents of very different intensities. It suffices for obtaining a proper working of the apparatus in each case, to regulate the distance from the weight, P', to the point of suspension, O', and the distance from the armature, _p_, to the cores, F. At the Champs Elysées concerts the lamps are operating with alternating currents; but they are capable of operating with continuous ones also, although the slight tremor of the electro-magnetic system, due to the use of alternating currents and as a consequence of rapid changes of magnetization, seems in principle very favorable to systems in which the descent of the carbon is based upon friction instead of a clutch. At the Champs Elysées concerts the lamps burn crayons of 9 to 10 millimeters with a current of 9 to 10 amperes and an effective electro-motive power of 60 volts per lamp. The light is very steady, and the effect produced is most satisfactory. The dispensing with all clock-work movement and regulating springs makes this electric lamp of Mr. Mondos a simple and plain apparatus, capable of numerous applications in the industries, in wide, open spaces, in all cases where foci of medium intensity have to be employed, and where it is desired to arrange several lamps in the same circuit.--_La Nature_.

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[AMERICAN POTTERY AND GLASSWARE REPORTER.]

ALUMINUM--ITS PROPERTIES, COST, AND USES.

Aluminum is a shining, white, sonorous metal, having a shade between silver and platinum. It is a very light metal, being lighter than glass and only about one-fourth as heavy as silver of the same bulk. It is very malleable and ductile, and is remarkable for its resistance to oxidation, being unaffected by moist or dry air, or by hot or cold water. Sulphureted hydrogen gas, which so readily tarnishes silver, forming a black film on the surface, has no action on this metal.

Next to silica, the oxide of aluminum (alumina) forms, in combination, the most abundant constituent of the crust of the earth (hydrated silicate of alumina, clay).

Common alum is sulphate of alumina combined with another sulphate, as potash, soda, etc. It is much used as a mordant in dyeing and calico printing, also in tanning.

Aluminum is of great value in mechanical dentistry, as, in addition to its lightness and strength, it is not affected by the presence of sulphur in the food--as by eggs, for instance.

Dr. Fowler, of Yarmouthport, Mass., obtained patents for its combination with vulcanite as applied to dentistry and other uses. It resists sulphur in the process of vulcanization in a manner which renders it an efficient and economical substitute for platinum or gold.

Aluminum is derived from the oxide alumina, which is the principal constituent of common clay. Lavoissier, a celebrated French chemist, first suggested the existence of the metallic bases of the earths and alkalies, which fact was demonstrated twenty years thereafter by Sir Humphry Davy, by eliminating potassium and sodium from their combinations; and afterward by the discovery of the metallic bases of baryta, strontium, and lime. The earth alumina resisting the action of the voltaic pile and the other agents then used to induce decomposition, twenty years more passed before the chloride was obtained by Oerstadt, by subjecting alumina to the action of potassium in a crucible heated over a spirit lamp. The discovery of aluminum was at last made by Wohler in 1827, who succeeded in 1846 in obtaining minute globules or beads of this metal by heating a mixture of chloride of alumina and sodium. Deville afterward conducted some experiments in obtaining this metal at the expense of Napoleon III., who subscribed £1,500, and was rewarded by the presentation of two bars of aluminum. The process of manufacture was afterward so simplified that in 1857 its price at Paris was about two dollars an ounce. It was at first manufactured from common clay, which contains about one-fourth its weight of aluminum, but in 1855 Rose announced to the scientific world that it could be obtained from a material called "cryolite," found in Greenland in large quantities, imported into Germany under the name of "mineral soda," and used as a washing soda and in the manufacture of soap. It consists of a double fluoride of aluminum, and only requires to be mixed with an excess of sodium and heated, when the mineral aluminum at once separates. Its cost of manufacture is given in this estimate for one pound of metal: 16 lb. of cryolite at 8 cents per pound, $1.28: 2½ lb. metallic sodium at about 26 cents per pound, 70 cents; flux and cost of reduction, $2.02; total, $4.

Aluminum is used largely in the manufacture of cheap jewelry by making a hard, gold-colored alloy with copper, called aluminum bronze, consisting of 90 per cent. of copper and 10 per cent. of aluminum. Like iron, it does not amalgamate directly with mercury, nor is it readily alloyed with lead, but many alloys with other metals, as copper, iron, gold, etc., have been made with it and found to be valuable combinations. One part of it to 100 parts of gold gives a hard, malleable alloy of a greenish gold color, and an alloy of ¾ iron and ¼ aluminum does not oxidize when exposed to a moist atmosphere. It has also been used to form a metallic coating upon other metals, as copper, brass, and German silver, by the electro-galvanic process. Copper has also been deposited, by the same process, upon aluminum plates to facilitate their being rolled very thin; for unless the metal be pure, it requires to be annealed at each passage through the rolls, and it is found that its flexibility is greatly increased by rolling. To avoid the bluish white appearance, like zinc, Dr. Stevenson McAdam recommends immersing the article made from aluminum in a heated solution of potash, which will give a beautiful white frosted appearance, like that of frosted silver.

F.W. Gerhard obtained a patent in 1856, in England, for an improved means of obtaining aluminum metal, and the adaptation thereof to the manufacture of certain useful articles. Powdered fluoride of aluminum is placed alone or in combination with other fluorides in a closed furnace, heated to a red heat, and exposed to the action of hydrogen gas, which is used as a reagent in the place of sodium. A reverberating furnace is used by preference. The fluoride of aluminum is placed in shallow trays or dishes, each dish being surrounded by clean iron filings placed in suitable receptacles; dry hydrogen gas is forced in, and suitable entry and exit pipes and stop-cocks are provided. The hydrogen gas, combining with the fluoride, "forms hydrofluoric acid, which is taken up by the iron and is thereby converted into fluoride of iron." The resulting aluminum "remains in a metallic state in the bottom of the trays containing the fluoride," and may be used for a variety of manufacturing and ornamental purposes.

The most important alloy of aluminum is composed of aluminum 10, copper 90. It possesses a pale gold color, a hardness surpassing that of bronze, and is susceptible of taking a fine polish. This alloy has found a ready market, and, if less costly, would replace red and yellow brass. Its hardness and tenacity render it peculiarly adapted for journals and bearings. Its tensile strength is 100,000 lb., and when drawn into wire, 128,000 lb., and its elasticity is one-half that of wrought iron.