Chapter 8

With this furnace, aluminum can be reduced directly from its ores; and chemical compounds from corundum, cryolite, clay, etc., and silicon, boron, calcium, manganese, magnesium, and other metals are in like manner obtained from their ores and compounds. The reduction of ores according to this process can be practiced, if circumstances require it, without any built furnace.

At present, the Cowles company is engaged mostly in the producing of aluminum bronze and aluminum silver and silicon bronze. The plant, were it run to its full capacity, is capable of turning out eighty pounds of aluminum bronze, containing 10 per cent. of aluminum daily; or, were it to run upon silicon bronze, could turn out one hundred and twenty pounds of that per day, or, we believe, more aluminum bronze daily than can be produced by all other plants in the world combined. This production, however, is but that of the experimental laboratory, and arrangements are making to turn out a ton of bronze daily, and the works have an ultimate capacity of from eight to ten thousand horse power. The energy consumed by the reduction of the ore is almost entirely electrical, only enough carbon being used to unite with the oxygen of the ore to carry it out of the furnace in the form of the carbon monoxide, the aluminum remaining behind. Consequently, the plant necessary to produce aluminum on a large scale involves a large number of the most powerful dynamos. These are to be driven by water-power or natural gas and marine engines of great capacity.

The retail price of standard 10 per cent. aluminum bronze is $1 per pound avoirdupois, which means less than $9 per pound for aluminum, the lowest price at which it has ever been sold, yet the Cowles company has laid a proposition before the Government to furnish this same bronze in large quantities at very much lower prices than this. The Hercules alloy, castings of which will stand over 100,000 pounds to the square inch tensile strain, sells at 75 c. a pound, and is also offered the Government or other large consumers at a heavy discount. The alloys are guaranteed to contain exactly what is advertised; they are standardized into 10 per cent., 7.5 per cent., 5 per cent. and 2.5 per cent. aluminum bronze before shipment.

The current available at the Cowles company's works was, until recently, 330 amperes, driven by an electromotive force of 110 volts and supplied by two Edison dynamos; but the company has now added a large Brush machine that has a current of 560 amperes and 52 volts electromotive force. We shall, on another occasion, give some particulars of experiments in the reduction of refractory ores by the process.--_Eng. and Mining Jour._

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OPTICAL TELEGRAPHY.[1]

[Footnote 1: Continued from page 8094.]

CRYPTOGRAPHY.--PRESERVATION OF TELEGRAMS.

Optical telegraphy, by reason of its very principle, presents both the advantage and inconvenience of leaving no automatic trace of the correspondence that it transmits. The advantage is very evident in cases in which an optical station falls into the hands of the enemy; on the other hand, the inconvenience is shown in cases where a badly transmitted or badly collated telegram allows an ambiguity to stand subject to dispute. Moreover, in case of warfare between civilized nations that have all the resources of science at their disposal, there may be reason to fear lest one of the enemy's optical stations substitute itself for the corresponding station, and take advantage of the situation to throw confusion into the orders transmitted. The remedy for this appears to reside in the use of cryptography and in the exchange, at various intervals, of certain words that have been agreed upon beforehand, and that the enemy is ignorant of.

As for the automatic preservation of telegrams, the problem has not been satisfactorily solved. It has been proposed to connect the key of the manipulator of the optical apparatus with the manipulator of an ordinary Morse apparatus, thus permitting the telegram to be preserved upon a band of paper. It is unnecessary to say that the space occupied by a dispatch thus transmitted would be considerable; but this is not what has stopped innovators. The principal objection resides in the increase in muscular work imposed by this arrangement upon the telegrapher. Obliged to keep his eye fixed intently at the receiving telescope, while at the same time maneuvering the manipulator and spelling aloud the words that he is receiving, the operator should have a very sensitive manipulator at his disposal, and not be submitted to mental or physical overtaxation. So the apparatus that have been devised have not met with much success.

Two French officers, working independently, have hit upon the same idea of receiving the indications transmitted by the vibration of the luminous fascicle directly upon their travel. The method consists in the use of that peculiar property of selenium of becoming a good conductor under the action of a luminous ray, while in darkness it totally prevents the passage of the electric current. Such modification of the physical properties of selenium, moreover, occurs without the perceptible development of any mechanical work. If, then, in the line of travel of the luminous fascicle emitted by the optical apparatus, or in a portion of such fascicle, we interpose a fragment of selenium connected with the two poles of a local pile, it is easy to see that the current from the latter will be opened or closed according as the luminous ray from the apparatus will or will not strike the selenium, and that the length of time during which the current passes will depend upon the length of the luminous attacks. A Morse apparatus interposed in this annexed circuit will therefore give an automatic inscription of the correspondence exchanged. Such is the principle. But, practically, very great difficulties present themselves, these being connected with the rapid weakening of the electric properties of the selenium, and with the necessity of having recourse to infinitely small mechanical actions only. The problem is nevertheless before us, and it is to be hoped that the perseverance of the scientists who are at work upon it will some day succeed in solving it.

Finally, we may call attention to the attempts made to receive the luminous impression upon a band prepared with gelatino-bromide of silver. In practice this band would unwind uniformly at the focus of the receiving telescope, which would be placed in a box, forming a camera obscura. The velocity of this band prepared for photographing the signals would be regulated by clockwork. The experiments that have been made have not given results that are absolutely satisfactory, by reason of the length of the signals received and the mechanical complication of the device.

OPTICAL TELEGRAPHY BY MEANS OF PROJECTORS.

The projectors employed for lighting to a distance the surroundings of a stronghold or of a ship have likewise been applied in optical telegraphy. For this purpose Messrs. Sautter, Lemonnier & Co. have added to their usual projecting apparatus some peculiar arrangements that permit of occultations of the luminous focus at proper intervals. Figs. 21 and 22 show the arrangement of the apparatus, the principle of which is as follows: When the axis of the projector points toward the clouds, and in the direction occupied by a corresponding station, the occultations of the luminous source placed in the focus of the apparatus produce upon the clouds, which act as a screen, an alternate series of flashes and extinctions. It is therefore possible with this arrangement, and by the use of the Morse alphabet, to establish an optical communication at a distance. The use of this projector (the principal inconvenience of which is that it requires a clouded sky) even permits two observers who are hidden from each other by the nature of the ground to easily communicate at a distance of 36 or 48 miles.

USE OF THE PROJECTOR IN OPTICAL TELEGRAPHY.

The apparatus shown in Figs. 21 and 22 permits of signaling in three ways:

1. _Upon the Clouds._--In this case the mirror, A, is removed, and the projector inclined above the horizon in such a way as to illuminate the clouds to as great a distance as possible. A maneuver of the occultator, E, between the lamp and the mirror arrests the luminous rays of the source, or allows them to pass, and thus produces upon the clouds the dots and dashes of the conventional alphabet.

2. _Isolated Communication by Luminous Fascicles._--When it is desired to correspond to a short distance of 2 or 3 miles, and establish a communication between two isolated posts, the mirror, A, is put in place upon its support, B. The luminous fascicle emanating from the source reflected by the mirror is thrown vertically. By revolving the mirror 90° around its horizontal axis the fascicle becomes horizontal, and may thus be thrown in a given direction at unequal intervals and during irregular times, and furnish conventional signs.

3. _Night Communication upon the Entire Horizon._--When we wish to correspond at a short distance, say two miles, and make signals visible from the entire horizon, the mirror, A, is put in place, so that it shall reflect the luminous fascicle vertically. The fascicle, at a distance of about fifty feet, meets a white balloon which it renders visible from every point in the horizon. The maneuver of the occultator brings the balloon out of darkness or plunges it thereinto again, and thus produces the signs necessary for aerial communication.

These ingenious arrangements, which depend upon the state of the atmosphere, do not appear to have been imitated outside of the navy.

CAPT. GAUMET'S OPTICAL TELEGRAPH.

The system of optical communication proposed by Capt. Gaumet, and which he names the _Telelogue_, is based upon the visibility of colored or luminous objects, and upon the possibility of piercing the opaque curtain formed by the atmosphere between the observer's eye and a signal, by utilizing the difference in brightness that exists between such objects and the atmosphere. It is a question, then, of giving such difference in intensity its maximum of brightness. To do this, Capt. Gaumet proposes to employ silvered signals upon a black background. He uses the simple letters of the alphabet, but changes their value. His apparatus has the form of a large album glued at the back to a sloping desk. Each silvered letter, glued to a piece of black cloth, is seen in relief upon the open register. A sort of index along the side, as in commercial blank-books, permits of quickly finding any letter at will. Such is the manipulator of the apparatus.

The receiver consists of a spy-glass affixed to the board that carries the register. For a range of two and a half miles, the complete apparatus, with a 12×16 inch manipulator and telescope, weighs but four and a half pounds. For double this range, with a 20×28 inch manipulator and telescope, the total weight is thirteen pounds. The larger apparatus, according to the inventor, have a range of seven miles.

For night work the manipulator is lighted either by one lamp, or by two lamps with reflector, placed laterally against it.

This apparatus, although well known, and having been publicly experimented with, has not, to our knowledge, been applied practically. From a military standpoint, its short range will evidently not permit it to compete with optical telegraphic apparatus, properly so called. Perhaps it might rather be of service for private communications between localities not very far apart, since it costs but little and is easily operated.

OPTICAL SIGNALING BETWEEN BODIES OF TROOPS.

Optical communications by signals, during day and night, with experienced men, may, in the absence of telephones, telegraphs, and messengers, render important service when the distance involved is greater than two thousand feet.

This mode of correspondence is based upon the use of the Morse alphabet. The signals are divided into night and day ones. The day signals are made with small flags. When these are wanting, sheets of white cardboard may be used. The night signals are made with a lantern provided with a support, which may be fixed to a wall or upon a bayonet.

In day signaling, the dashes of the Morse alphabet are formed by means of two flags (Fig. 23) held simultaneously at arm's length by the signaler. The dots are formed with a single flag held in the right hand (Fig. 24). In this way it is possible, by extremely simple combinations, to establish a correspondence, and produce any conventional signal. By means of relay stations, the signals may be transmitted from one to another to a great distance.

In signaling with the lantern, long and short interruptions of the luminous source are produced by means of a screen.

OPTICAL TELEGRAPHY BY LUMINOUS BALLOONS.

Various interesting experiments have been made with a view to utilizing luminous captive balloons for optical communications. As we have already seen, this maybe effected by using opaque balloons, and throwing upon them at unequal intervals a luminous fascicle by means of a projector. As for using a luminous source placed in the car of a balloon, that cannot be thought of in the present state of aeronautic science; the continual rotation of the balloon around its axis would render the projection and reception of the signals in a given direction impossible.

OPTICAL TELEGRAPHY IN THE MARINE.

For communicating optically from ship to ship during the day, the marine uses flags of different forms and colors, and flames. Between ships and the land there are used what are called semaphore signals, which are made by means of a mast provided with three arms and a disk placed at the upper part. The combinations of signs thus obtained, which are analogous in principle to those of the Chappe telegraph, permit of satisfactorily communicating to a distance.

On board ship, hand signals are used like those employed by the army for communicating between bodies of troops. For night communications the marine employs lights corresponding to the day flags, as well as rockets, and luminous rays projected by means of reflectors and intercepted by screens.

In conclusion, it may be said that optical telegraphy, which has only within a few years emerged from the domain of theory to enter that of practice, has taken a remarkable stride in the military art and in science. It is due to its processes that Col. Perrier has in recent years been enabled to carry out certain geodesic work that would have formerly been regarded as impracticable, notably the prolongation of the arc of the meridian between France and Spain. Very recently, an optical communication established between Mauritius and Reunion islands, to a distance of 129 miles, with 24 inch apparatus, proved that, in certain cases, the costly laying of a submarine cable may be replaced by the direct emission of a luminous ray.

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A NEW STYLE OF SUBMARINE TELEGRAPH.

Mr. F. Von Faund-Szyll has devised an original system of submarine telegraph, which is based upon the well known property that selenium exhibits of modifying its resistance under the influence of luminous rays, and which he styles the _Selen-Differenzialrecorder_.

Contrary to what is found in the other systems hitherto employed, the Faund-Szyll system utilizes the cable current merely for starting the receiving apparatus, which are operated by means of strong local batteries. The result is that the mechanical work that devolves upon the line current, which is, as well known, very weak, is exceedingly reduced.

The system consists of two essential parts: (1) The receiver, properly so called. (2) The relay as well as the registering apparatus or _differenzialrecorder_. The receiver consists of a closed box, K, in the interior of which there is a very intense source of light whose rays escape by passing through apertures, _a a'_, in the front part (Fig. 1).

As a source of light, there may be conveniently employed an incandescent lamp, _g_, capable of giving an intense light, and arranged (as shown in Fig. 2) behind the side that contains the slits, _a a'_.

The starting apparatus consists of a small galvanometric helix, _r_, analogous to Thomson's siphon recorder, which is suspended from a cocoon fiber and capable of moving in an extremely powerful magnetic field, N S. This helix carries, as may be seen in Figs. 1, 3 and 4, a prolongation, _v_, at its lower end whose form is that of a prism, and which is arranged in front of the partition of the box, K, in such a way that it exactly covers the two slits, a and _a_ when the bobbin is at rest, and in this case prevents the luminous rays of the lamp, _g_, from escaping from the box. But, as soon as the current sent through the cable reaches the spirals of the bobbin, through the conductors, _y y'_, the sum of the elementary electrodynamic actions that arise causes the helix to revolve to the right or left, according to the polarity of the current, while at the same time the helix slightly approaches one or the other of the poles of the magnet. The prolongation, _v_, of the helix, being firmly united with the latter, follows it in its motion, and has the effect of permitting the luminous rays to escape through one or the other of the slits, _a a'_, so that the freeing of the luminous fascicle, if such an expression is allowable, is effected.

In order to prevent oscillations, which could not fail to occur after each emission of a current (so that the helix, instead of returning to a position of equilibrium and stopping there, would go beyond it and alternately uncover the slits, _a a'_), the apparatus is provided with a liquid deadener. To this end, the prolongation, _v_, carries a piece, _o_, which dips into a cup containing a mixture of glycerine and water.

We shall now describe the _differenzialrecorder_. Opposite the two slits, _a_ and _a'_, there are two powerful converging lenses, _l_ and _l'_, whose foci coincide with two sorts of selenium plate rheostat, _z_ and _z'_. The result of this arrangement is that as soon as one of the slits, as a consequence of the displacement of the helix, _r_, allows a luminous fascicle to escape, this latter falls upon the corresponding lens, which concentrates it and sends it to the selenium plates just mentioned. Under the influence of the luminous rays, the resistance that the selenium offers to the passage of an electric current instantly changes. At M and M' are placed two horseshoe magnets whose poles are provided with pieces of soft iron that serve as cores to exceedingly fine wire bobbins, _d_. These polarized pieces are arranged in the shape of a St. Andrew's cross, and in such a way that the poles of the same name occupy the two extremities of the same arm of the cross, an arrangement very clearly shown in Fig. 2.

Between the poles of the magnets, M and M', there is a permanent magnet, A, movable around a vertical axis, _i_. Four spiral springs, _f_, whose tension may be regulated, permit of centering this latter piece in such a way that when the current is traversing the spirals of the polar bobbins it is equally distant from the four poles, _n_, _s_, _s'_, and _n'_. Under such circumstances it is evident that a difference in the power of attraction of these four poles, however feeble it be, will result in moving the magnet, A, in one direction or the other around its axis. The energy and extent of such motion may, moreover, be magnified by properly acting upon the four regulating springs.

The bobbins of the magnet, M, are mounted in series with the selenium plates, _z_, the local battery, B, and a resistance box, W. Those of the magnet, M', are in series with _z'_, B', and W'. The local batteries, B and B', are composed of quite a large number of elements. The current from the battery, B, traverses the selenium plates and the bobbins of the magnet, M, and returns to B through the rheostat, W; and the same occurs with the current from B'. The two currents, then, are absolutely independent of one another.

From this description it is very easy to see how the system works. Let us suppose, in fact, that the current which is traversing the spirals of the helix, _r_, has a direction such that the helix in its movement approaches the pole, S; then the prolongation, _v_, will uncover the slit, _a_, which, along with _a'_, had up to this moment been closed, and a luminous fascicle escaping through _a_ will strike the lens, _l'_, and from thence converge upon the selenium plates, _z'_. This is all the duty that the line current has to perform.

The luminous rays, in falling upon the selenium plates, _z'_, modify the resistance that these offered to the passage of the current produced by the battery, B'. As this resistance diminishes, the intensity of the current in the circuit supplied by the battery, B', increases, the attractive action of the polar pieces of the magnet, M', diminishes, the equilibrium is destroyed, and the piece, A, revolves around the axis, _i_. If the polarity of the line current were different, the same succession of phenomena would occur, save that the direction of A's rotation would be contrary. As for the rheostats, W W', their object is to correct variations in the selenium's resistance and to balance the resistances of the two corresponding circuits. The magnet, A, will be combined with a registering apparatus so as to directly or indirectly actuate the printing lever. The entire first part of this apparatus, which is very sensitive, may be easily protected from all external influence by placing it in a box, and, if need be, in a room distant from the one in which the employes work.

The _differenzialrecorder_ alone has to be in the work room.

As may be seen, the system is not wanting in originality. Experience alone will permit of pronouncing upon the question as to whether it is as practical as ingenious.--_La Lumiere Electrique._

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A NEW CIRCUIT CUTTER.

Messrs. Thomson & Bottomley have recently invented a peculiar circuit cutter based upon the use of a metal whose melting point is exceedingly low. Recourse is had to this process for breaking the current within as short a time as possible. In this new device the ends of the conductors are soldered together with the metal in question at one or several points of the circuit. The metal employed is silver or copper of very great conductivity, seeing that the increase of temperature in a conductor, due to a sudden increase of the current, is inversely proportional to the product of the electric resistance by the specific heat of the conductor; that these metals are best adapted for giving constant and definite results; and that the contacts are better than with lead or the other metals of low melting point which are frequently employed in circuit cutters.