IMPROVED RECIPROCATING GAS EXHAUSTER.IMPROVED RECIPROCATING GAS EXHAUSTER.
The principal advantages to be gained by the use of this exhauster are stated by M. Meizel to be the following: Considerably less motive force is necessary than is the case with other exhausters, which require steam engines and all the auxiliary mechanism for the transmission of power. By its quiet and regular action, it prevents oscillation and unsteadiness in the flow of gas in the hydraulic main, as well as in the pipes leading therefrom—a defect which has been found to exist with other exhausters. The bells, being of large area, serve the purpose of a condenser; and as, owing to its density, the tar falls to the bottom of the lower vessels, which are filled with water, contact between the gas and tar is avoided. Although the appliance is of substantial construction, its action is so sensitive that it readily adapts itself to the requirements of production. It may be placed in the open air; and therefore its establishment is attended with less outlay than is the case with other exhausters, which have to be placed under cover, and provided with driving machinery and, of course, a supply of steam.
The total superficial area of the exhauster above described, including the governor, is 150 square feet; and its capacity per 24 hours is 230,000 cubic feet. It works silently, with an almost entire absence of friction; and consequently there are few parts which require lubrication. Exhausters of this type (which, M. Meizel says, could be made available for ventilation purposes, in case of necessity) may be constructed of all sizes, from 500 cubic feet per hour upward.
When, at an elevated point in a meadow, there exists a spring or vein of water that cannot be utilized at a distance, either because the supply is not sufficient, or because of the permeability of the soil, it becomes very advantageous to accumulate the water in a reservoir, which may be emptied from time to time through an aperture large enough to allow the water to flow in abundance over all parts of the field.
GIRAL'S AUTOMATIC SIPHON.GIRAL'S AUTOMATIC SIPHON.
The storing up of the water permits of irrigating a much greater area of land, and has the advantage of allowing the watering to be effected intermittingly, this being better than if it were done continuously. But this mode of irrigating requires assiduous attention. It is necessary, in fact, when the reservoir is full, to go and raise the plug, wait till the water has flowed out, and then put in the plug again as accurately as possible—a thing that it is not always easy to do. The work is a continuous piece of drudgery, and takes just as much the longer to do in proportion as the reservoir is more distant from one's dwelling. In order to do away with this inconvenience, Mr. Giral, of Langogne (Lozere), has invented a sort of movable siphon that primes itself automatically, however small be the spring that feeds the reservoir in which it is placed. The apparatus (see figure) consists of an elbowed pipe, C A B D E, of galvanized iron, whose extremity, C, communicates with the outlet, R, where it is fixed by means of a piece of rubber of peculiar form that allows the other extremity, B D E, to revolve around the axis, K, while at the same time keeping the outlet pipe hermetically closed. This rubber, whose lower extremity is bent back like the bell of a trumpet, forms a washer against which there is applied a galvanized iron ring that is fixed to the mouth of the outlet pipe by means of six small screws. This ring is provided with two studs which engage with two flexible thimbles, K and L, that are affixed to the siphon by four rivets. These studs and thimbles, as well as the screws, are likewise galvanized. Between the branches, A B D E, of the pipe there is soldered a sheet of galvanized iron, which forms isolatedly a receptacle or air-chamber, F, that contains at its upper part a small aperture,b, that remains always open, and, at its lower part, a copper screw-plug,d, and a galvanized hook, H.
In the interior of this chamber there is arranged a small leaden siphon,a b c, whose longer leg,a, passes through the bottom, where it is soldered, and whose shorter one,c, ends in close proximity to the bottom. Finally, a galvanized iron chain, G H, fixed at G to the bottom of the reservoir, and provided with a weight, P, of galvanized iron, is hooked at H to the siphon and allows it to rise more or less, according as it is given a greater or less length.
From what precedes, it will be seen that the outlet is entirely closed, so that, in order that the water may escape, it must pass into the pipe in the direction, E D B A C.
This granted, let us see how the apparatus works: In measure as the water rises in the reservoir, the siphon gradually loses weight, and its extremity, B D H, is finally lifted by the thrust, so that the entire affair revolves upon the studs, K, until the chain becomes taut. The apparatus then ceases to rise; but the water, ever continuing to rise, finally reaches the apex,b, of the smaller siphon, and, through it, enters the air chamber and fills it. The equilibrium being thus broken, the siphon descends to the bottom, becomes primed, and empties the reservoir. When the level of the water, in descending, is at the height of the small siphon,a b c, this latter, which is also primed, empties the chamber, F, in turn, so that, at the moment the large siphon loses its priming, the entire apparatus is in the same state that it was at first.
In short, when the water enters the reservoir, the siphon, movable upon its base, rises to the height at which it is desired that the flow shall take place. Being arrested at this point by the chain, it becomes primed, and sinks, and the water escapes. When the water is exhausted, the siphon rises anew in order to again sink; and this goes on as long as the period of irrigation lasts.
This apparatus, which is simple in its operation, and not very costly, is being employed with success for irrigating several meadows in the upper basin of the Allier.—Le Genie Civil.
Lead oxide melted or incompletely vitrified is still in common use in the manufacture of inferior earthenware, and sometimes leads to serious results. To detect lead in a glaze, M. Herbelin moistens a slip of white linen or cotton, free from starch, with nitric acid at 10 per cent. and rubs it for ten to fifteen seconds on the side of the utensil under examination, and then deposits a drop of a solution of potassium iodide, at 5 per cent. on the part which has been in contact. A lead glaze simply fused gives a very highly colored yellow spot of potassium iodide; a lead glaze incompletely vitrified gives spots the more decided, the less perfect the vitrification; and a glaze of good quality gives no sensible color at all.—M. Herbelin.
The application of electricity to metallurgical processes has hitherto been confined to the reduction of metals from solutions, and few attempts have been made to effect dry reductions by means of an electric current. Sir W. Siemens attempted to utilize the intense heat of an electric arc for this purpose, but accomplished little beyond fusing several pounds of steel. A short time since, Eugene H. Cowles and Alfred H. Cowles of Cleveland conceived the idea of obtaining a continuous high temperature on an extended scale by introducing into the path of an electric current some material that would afford the requisite resistance, thereby producing a corresponding increase in the temperature. After numerous experiments that need not be described in detail, coarsely pulverized carbon was selected as the best means for maintaining a variable resistance and at the same time as the most available substance for the reduction of oxides. When this material, mixed with the oxide to be reduced, was made a part of the electric circuit in a fire clay retort, and submitted to the action of a current from a powerful dynamo machine, not only was the oxide reduced, but the temperature increased to such an extent that the whole interior of the retort fused completely. In other experiments lumps of lime, sand, and corundum were fused, with indications of a reduction of the corresponding metal; on cooling, the lime formed large, well-defined crystals, the corundum beautiful red, green, and blue hexagonal crystals.
Following up these results with the assistance of Charles F. Mabery, professor of chemistry in the Case School of Applied Science, who became interested at this stage of the experiments, it was soon found that the intense heat thus produced could be utilized for the reduction of oxides in large quantities, and experiments were next tried on a large scale with a current from two dynamos driven by an equivalent of fifty horse power. For the protection of the walls of the furnace, which were made of fire brick, a mixture of the ore and coarsely pulverized gas carbon was made a central core, and it was surrounded on the sides and bottom by fine charcoal, the current following the lesser resistance of the central core from carbon electrodes which were inserted at the ends of the furnace in contact with the core. In order to protect the machines from the variable resistance within the furnace, a resistance box consisting of a coil of German silver wire placed in a large tank of water was introduced into the main circuit, and a Brush ammeter was also attached by means of a shunt circuit, to indicate the quantity of current that was being absorbed in the furnace. The latter was charged by first filling it with charcoal, making a trough in the center, and filling this central space with the ore mixture, which was covered with a layer of coarse charcoal. The furnace was closed at the top with fire brick slabs containing two or three holes for the escape of the gaseous products of the reduction, and the entire furnace made air-tight by luting with fire clay. Within a few minutes after starting the dynamo, a stream of carbonic oxide issued through the openings, burning usually with a flame eighteen inches in height. The time required for complete reduction was ordinarily about an hour.
The furnace at present in use is charged in substantially the same manner, and the current is supplied by a Brush machine of variable electromotive force driven by an equivalent of forty horse power. A Brush machine capable of utilizing 125 horse power, or two and one-half times as large as any hitherto constructed by the Brush Electric Company, is being made for the Cowles Electric Smelting and Aluminum Company, and this machine will soon be in operation. Experiments already made so that aluminum, silicon, boron, manganese, magnesium, sodium and potassium can be reduced from their oxides with ease. In fact, there is no oxide that can withstand temperatures attainable in this electrical furnace. Charcoal is changed to graphite. Does this indicate fusion or solution of carbon? As to what can be accomplished by converting enormous electrical energy into heat within a limited space, it can only be said that it opens the way into an extensive field for both pure and applied chemistry. It is not difficult to conceive of temperatures limited only by the capability of carbon to resist fusion. The results to be obtained with the large Brush machine above mentioned will be of some importance in this direction.
Since the cost of the motive power is the chief expense in accomplishing reductions by this method, its commercial success is closely connected with the cheapest form of power to be obtained. Realizing the importance of this point, the Cowles Electric Smelting and Aluminum Company has purchased an extensive and reliable water power, and works are soon to be erected for the utilization of 1,200 horse power. An important feature in the use of these furnaces, from a commercial standpoint, is the slight technical skill required in their manipulation. The four furnaces in operation in the experimental laboratory at Cleveland are in charge of two young men twenty years of age, who, six months ago, knew absolutely nothing of electricity. The products at present manufactured are the various grades of aluminum bronze made from a rich furnace product that is obtained by adding copper to the charge of ore, silicon bronze prepared in the same manner, and aluminum silver, an alloy of aluminum with several other metals. A boron bronze may be prepared by the reduction of boracic acid in contact with copper.
As commercial results may be mentioned the production in the experimental laboratory, which averages fifty pounds of 10 per cent. aluminum bronze daily, and it can be supplied to the trade in large quantities at prices based on $5 per pound for the aluminum contained, the lowest market quotation of this metal being at present $15 per pound. Silicon bronze can be furnished at prices far below those of the French manufacturers.
The alloys which the metals obtained by the methods above described form with copper have been made the subject of careful study. An alloy containing 10 per cent. of aluminum and 90 per cent. of copper forms the so-called aluminum bronze with a fine golden color, which it retains for a long time. The tensile strength of this alloy is usually given as 100,000 pounds to the square inch; but castings of our ten per cent. bronze have stood a strain of 109,000 pounds. It is a very hard, tough alloy, with a capacity to withstand wear far in excess of any other alloy in use. All grades of aluminum bronze make fine castings, taking very exact impressions, and there is no loss in remelting, as in the case of alloys containing zinc. The 5 per cent. aluminum alloy is a close approximation in color to 18 carat gold, and does not tarnish readily. Its tensile strength in the form of castings is equivalent to a strain of 68,000 pounds to the square inch. An alloy containing 2 or 3 per cent. aluminum is stronger than brass, possesses greater permanency of color, and would make an excellent substitute for that metal. When the percentage of aluminum reaches 13, an exceedingly hard, brittle alloy of a reddish color is obtained, and higher percentages increase the brittleness, and the color becomes grayish-black. Above 25 per cent. the strength again increases.
The effect of silicon in small proportions upon copper is to greatly increase its tensile strength. When more than 5 per cent. is present, the product is exceedingly brittle and grayish-black in color. It is probable that silicon acts to a certain extent as a fluxing material upon the oxides present in the copper, thereby making the metal more homogeneous. On account of its superior strength and high conductivity for electrical currents, silicon bronze is the best material known for telegraph and telephone wire.
The element boron seems to have almost as marked an effect upon copper as carbon does upon iron. A small percentage in copper increases its strength to 50,000 or 60,000 pounds per square inch without diminishing to any large extent its conductivity.
Aluminum increases very considerably the strength of all metals with which it is alloyed. An alloy of copper and nickel containing a small percentage of aluminum, called Hercules metal, withstood a strain of 105,000 pounds, and broke without elongation. Another grade of this metal broke under a strain of 111,000 pounds, with an elongation equivalent to 33 per cent. It must be remembered that these tests were all made upon castings of the alloys. The strength of common brass is doubled by the addition of 2 or 3 per cent. of aluminum. Alloys of aluminum and iron are obtained without difficulty; one product was analyzed, containing 40 per cent. of aluminum. In the furnace iron does not seem to be absorbed readily by the reduced aluminum when copper is present; but in one experiment a mixture composed of old files, 60 per cent.; nickel, 5 per cent.; and of 10 per cent. aluminum bronze 35 per cent., was melted together, and it gave a malleable product that stood a strain of 69,000 pounds.
When the reduction of aluminic oxide by carbon is conducted without the addition of copper, a brittle product is obtained that behaves in many respects like pig iron as it comes from the blast furnace. The same product is formed in considerable quantities, even when copper is present, and frequently the copper alloy is found embedded in it. Graphite is always found associated with it, even when charcoal is the reducing material, and analysis invariably shows a very high percentage of metallic aluminum. This extremely interesting substance is at present under examination.
[1]
Read at the recent meeting of the American Association, Ann Arbor, Mich.
Read at the recent meeting of the American Association, Ann Arbor, Mich.
The use of electricity in the reduction of metals from their ores is extending so rapidly, and the methods of its generation and application have been so greatly improved within a few years, that the possibility of its becoming the chief agent in the metallurgy of the future may now be admitted, even in cases where the present cost of treatment is too high to be commercially advantageous.
The refining of copper and the separation of copper, gold, and silver by electrolysis have thus far attracted the greatest amount of attention, but a commercial success has also been achieved in the dry reduction by electricity of some of the more valuable metals by the Cowles Electric Smelting and Aluminum Company, of Cleveland, Ohio. Both this method of manufacture and the qualities of the products are so interesting and important that it is with pleasure we call attention to them as steps toward that large and cheap production of aluminum that the abundance of its ores and the importance of its physical properties have for several years made the unattained goal of many skillful metallurgists.
The Messrs. Cowles have succeeded in greatly reducing the market value of aluminum and its alloys, and thereby vastly extending its uses, and they are now by far the largest producers in the world of these important products. As described in their patents, the Cowles process consists essentially in the use for metallurgical purposes of a body of granular material of high resistance or low conductivity interposed within the circuit in such a manner as to form a continuous and unbroken part of the same, which granular body, by reason of its resistance, is made incandescent, and generates all the heat required. The ore or light material to be reduced—as, for example, the hydrated oxide of aluminum, alum, chloride of sodium, oxide of calcium, or sulphate of strontium—is usually mixed with the body of granular resistance material, and is thus brought directly in contact with the heat at the points of generation, at the same time the heat is distributed through the mass of granular material, being generated by the resistance of all the granules, and is not localized at one point or along a single line. The material best adapted for this purpose is electric light carbon, as it possesses the necessary amount of electrical resistance, and is capable of enduring any known degree of heat when protected from oxygen without disintegrating or fusing; but crystalline silicon or other equivalent of carbon can be employed for the same purpose. This is pulverized or granulated, the degree of granulation depending upon the size of the furnace. Coarse granulated carbon works better than finely pulverized carbon, and gives more even results. The electrical energy is more evenly distributed, and the current can not so readily form a path of highest temperature, and consequently of least resistance through the mass along which the entire current or the bulk of the current can pass. The operation must necessarily be conducted within an air-tight chamber or in a non-oxidizing atmosphere, as otherwise the carbon will be consumed and act as fuel. The carbon acts as a deoxidizing agent for the ore or metalliferous material treated, and to this extent it is consumed, but otherwise than from this cause, it remains unimpaired.
Fig. I. of the accompanying drawings is a vertical longitudinal section through a retort designed for the reduction of zinc ore, according to this process, and Fig. II. is a front elevation of the same. Fig. III. is a perspective view of a furnace adapted to withstand a very high temperature, and Figs. IV. and V. are respectively longitudinal and transverse sections of the same.
THE COWLES ELECTRIC SMELTING PROCESS.THE COWLES ELECTRIC SMELTING PROCESS.
This retort consists of a cylinder, A, made of silica or other non-conducting material, suitably embedded in a body, B, of powdered charcoal, mineral wool, or of some other material which is not a good conductor of heat. The rear end of the retort-cylinder is closed by means of a carbon plate, C, which plate forms the positive electrode, and with this plate the positive wire of the electric circuit is connected. The outer end of the retort is closed by means of an inverted graphite crucible, D, to which the negative wire of the electric circuit is attached. The graphite crucible serves as a plug for closing the end of the retort. It also forms a condensing chamber for the zinc fumes, and it also constitutes the negative electrode. The term "electrode" is used in this case as designating the terminals of the circuit proper, or that portion of it which acts simply as an electrical conductor, and not with the intention of indicating the ends of a line between which there is no circuit connection. The circuit between the "electrodes," so called, is continuous, being established by means of and through the body of broken carbon contained in the retort, A. There is no deposit made on either plate of the decomposed constituents of the material reduced. The mouth of the crucible is closed with a luting of clay, or otherwise, and the opening,d, made in the upper side of the crucible, near its extremity, comes entirely within the retort, and forms a passage for the zinc fumes from the retort chamber into the condensing chamber. The pipe, E, serves as a vent for the condensing chamber. The zinc ore is mixed with pulverized or granular carbon, and the retort charged nearly full through the front end with the mixture, the plug, D, being removed for this purpose.
A small space is left at the top, as shown. After the plug has been inserted and the joint properly luted, the electric circuit is closed and the current allowed to pass through the retort, traversing its entire length through the body of mixed ore and carbon. The carbon constituents of the mass become incandescent, generating a very high degree of heat, and being in direct contact with the ore, the latter is rapidly and effectually reduced and distilled. The heat evolved reduces the ore and distills the zinc, and the zinc fumes are condensed in the condensing chamber, precisely as in the present method of zinc making, with this important exception that, aside from the reaction produced by heating carbon in the presence of zinc oxide, the electric current, in passing through the zinc oxide, has a decomposing and disintegrating action upon it, not unlike the effect produced by an electric current in a solution. This action accelerates the reduction, and promotes economy in the process.
Another form of furnace is illustrated by Fig. III., which is a perspective view of a furnace adapted for the reduction of ores and salts of non-volatile metals and similar chemical compounds. Figs. IV. and V. are longitudinal and transverse sections, respectively,through the same, illustrating the manner of packing and charging the furnace.
The walls and floorsL L', of the furnace are made of fire bricks, and do not necessarily have to be very thick or strong, the heat to which they are subjected not being excessive. The carbon plates are smaller than the cross section of the box, as shown, and the spaces between them and the end walls are packed with fine charcoal.
The furnace is covered with a removable slab of fireclay, N, which is provided with one or more vents,n, for the escaping gases.
The space between the carbon plates constitutes the working part of the furnace. This is lined on the bottom and sides with a packing of fine charcoal, O, or such other material as is both a poor conductor of heat and electricity—as, for example, in some cases, silica or pulverized corundum or well-burned lime—and the charge, P, of ore and broken, granular, or pulverized carbon occupies the center of the box, extending between the carbon plates. A layer of granular charcoal, O', also covers the charge on top. The protection afforded by the charcoal jacket, as regards the heat, is so complete, that with the covering-slab removed, the hand can be held within a few inches of the exposed charcoal jacket; but with the top covering of charcoal also removed and the core exposed, the hand cannot be held within several feet. The charcoal packing behind the carbon plates is required to confine the heat and to protect them from combustion.
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.
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.
Fig. 23.Fig.23.
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.
Figs. 21 and 22.—FRONT VIEW AND LONGITUDINAL SECTIONFigs. 21 and 22.—FRONT VIEW AND LONGITUDINAL SECTION OF THE MANGIN PROJECTOR. (Scale 1/15). A. Elliptical mirror. B. Arm of the same. C. Nut for fixing the mirror. D. Support of the mirror. E. Occultator. F. Support for same. G. Lever for maneuvering the occultator. I. Support of the occultator rod. J. Screw for fixing the mirror support. K. Screw for fixing the support of the occultator rod. L. Screw for fixing the occultator support.
Figs. 21 and 22.—FRONT VIEW AND LONGITUDINAL SECTION OF THE MANGIN PROJECTOR. (Scale 1/15). A. Elliptical mirror. B. Arm of the same. C. Nut for fixing the mirror. D. Support of the mirror. E. Occultator. F. Support for same. G. Lever for maneuvering the occultator. I. Support of the occultator rod. J. Screw for fixing the mirror support. K. Screw for fixing the support of the occultator rod. L. Screw for fixing the occultator support.
Figs. 21 and 22.—FRONT VIEW AND LONGITUDINAL SECTION OF THE MANGIN PROJECTOR. (Scale 1/15). A. Elliptical mirror. B. Arm of the same. C. Nut for fixing the mirror. D. Support of the mirror. E. Occultator. F. Support for same. G. Lever for maneuvering the occultator. I. Support of the occultator rod. J. Screw for fixing the mirror support. K. Screw for fixing the support of the occultator rod. L. Screw for fixing the occultator support.
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.
Fig. 24.Fig.24.
These ingenious arrangements, which depend upon the state of the atmosphere, do not appear to have been imitated outside of the navy.
The system of optical communication proposed by Capt. Gaumet, and which he names theTelelogue, 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 signalsupon 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 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.
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.
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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Continued from page 8094.
Continued from page 8094.
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 theSelen-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 ordifferenzialrecorder. 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,aandawhen 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.
Fig. 1.Fig.1.
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 thedifferenzialrecorder. Opposite the two slits,aanda', there are two powerful converging lenses,landl', whose foci coincide with two sorts of selenium plate rheostat,zandz'. 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.
Fig. 2.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', andn'. 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 withz', 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 witha', had up to this moment been closed, and a luminous fascicle escaping throughawill 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.