THE LIMITATIONS OF SUBMARINE TELEGRAPHY.8

Vibrating Spherule Imbedded in an Elastic Solid.

Lastly, I must tell you about the color of the blue sky which was illustrated by the spherule embedded in an elastic solid. I want to explain to you in two minutes the mode of vibrations. Take the simplest plane-polarized light. Here is a spherule which is producing it in an elastic solid. Imagine the solid to extend miles horizontally and miles down, and imagine this spherule to vibrate up and down. It is quite clear that it will make transverse vibrations similarly in all horizontal directions. The plane of polarization is defined as a plane perpendicular to the line of vibration. Thus, light produced by a molecule vibrating up and down, as this red globe in the jelly before you, is polarized in a horizontal plane because the vibrations are vertical.

Here is another mode of vibrations. Let me twist this spherule in the jelly as I am doing it, and that will produce vibrations, also spreading out equally in all horizontal directions. When I twist this globe round, it draws the jelly round with it; twist it rapidly back, and the jelly flies back. By the inertia of the jelly the vibrations spread in all directions, and the lines of vibration are horizontal all through the jelly. Everywhere, miles away, that solid is placed in vibration. You do not see it, but you must understand that they are there. If it flies back it makes vibration, and we have waves of horizontal vibrations traveling out in all directions from the exciting molecule.

I am now causing the red globe to vibrate to and fro horizontally. That will cause vibrations to be produced which will be parallel to the line of motion at all places of the plane perpendicular to the range of the exciting molecule. What makes the blue sky? These are exactly the motions that make the blue light of the sky which is due to spherules in the luminiferous ether, but little modified by the air. Think of the sun near the horizon, think of the light of the sun streaming through and giving you the azure blue and violet overhead. Think first of any one particle of the sun, and think of it moving in such a way as to give horizontal and vertical vibrations and what not of circular and elliptic vibrations.

You see the blue sky in high pressure steam blown into the air; you see it in the experiment of Tyndall's blue sky, in which a delicate condensation of vapor gives rise to exactly the azure blue of the sky.

Now the motion of the luminiferous ether relatively to the spherule gives rise to the same effect as would an opposite motion impressed upon the spherule quite independently by an independent force. So you may think of the blue color coming from the sky as being produced by to and fro vibrations of matter in the air, which vibrates much as this little globe vibrates embedded in the jelly.

The result in a general way is this: The light coming from the blue sky is polarized in a plane through the sun, but the blue light of the sky is complicated by a great number of circumstances, and one of them is this: that the air is illuminated not only by the sun, but by the earth. If we could get the earth covered by a black cloth, then we could study the polarized light of the sky with simplicity, which we cannot do now. There are, in nature, reflections from seas, and rocks, and hills, and waters in an indefinitely complicated manner.

Let observers observe the blue sky not only in winter, when the earth is covered with snow, but in summer, when it is covered with dark green foliage. This will help to unravel the complicated phenomena in question. But the azure blue of the sky is light produced by the reaction on the vibrating ether of little spherules of water, of perhaps a fifty-thousandth or a hundred-thousandth of a centimeter diameter, or perhaps little motes, or lumps, or crystals of common salt, or particles of dust, or germs of vegetable or animal species wafted about in the air. Now what is the luminiferous ether? It is matter prodigiously less dense than air, millions and millions and millions of times less dense than air. We can form some sort of idea of its limitations. We believe it is a real thing, with great rigidity in comparison with its density, and it may be made to vibrate 400 million million times per second, and yet with such rigidity as not to produce the slightest resistance to any body going through it.

Going back to the illustration of the shoemaker's wax; if a cork will in the course of a year push its way up through a plate of that wax when placed under water, and if a lead bullet will penetrate downward to the bottom, what is the law of the resistance? It clearly depends on time. The cork slowly in the course of a year works its way up through two inches of that substance; give it one or two thousand years to do it, and the resistance will be enormously less; thus the motion of a cork or bullet, at the rate of one inch in 2,000 years, may be compared with that of the earth, moving at the rate of six times ninety-three million miles a year, or nineteen miles per second, through the luminiferous ether, but when we have a thing elastic like jelly and yielding like pitch, surely we have a large and solid ground for our faith in the speculative hypothesis of an elastic luminiferous ether, which constitutes the wave theory of light.

The weight of the conductors, says Henry Vivarez inLa Lumiere Electrique, plays an important part in submarine telegraphy, not merely as a heavy item in the outlay, but as one of the principal factors in laying down the lines, and in taking them up in case of damage. When the conductor is being raised, the grappling-irons which lift it have to resist not merely the vertical component of the weight of the cable, but also the considerable effects resulting from friction against the water. It thus frequently happens, when working at great depths, that the conductor may be exposed to a strain greater than it is able to bear, and we are forced to have recourse to stratagems to bring it to the surface. These artifices consist in the use of two or more ships in raising, which is done as shown in Figs. 2 and 3, or, in the most simple cases, with the aid of an auxiliary buoy, as in Fig. 4. In any event, we see that the difficulties, and of course the cost of raising, must be considerable.

Fig. 1.

Hence to decrease the weight of the cables would be an important step in advance. If the weight is in general very great, it is because the copper core does not take any part in the strain which the entire cable has to resist. We know, indeed, that copper cannot bear a breaking-strain greater, at most, than 28 kilos per square millimeter. Besides, it would be elongated by such a strain by a very considerable fraction of its initial length; and, if the core were made to take part in any manner whatever in the strain which the entire cable has to support, it would be drawn out beyond its limit of elasticity, and would remain permanently elongated, while the substances in which it is inclosed would return to their natural length. It would result that, being no longer able to find room in a sheath which had become too short, the copper wire would take a sinuous form in its gutta-percha envelope, and would occasion at certain points ruptures, the effect of which would be to decentralize the wire, to perforate the layer of insulating matter, and finally to open out a fault in the cable.

But there exists an alloy (silicium bronze) which can be drawn out into wires having a conductivity equal to that of copper, and a mechanical resistance equal to that of the best iron. The use of this alloy would render it possible to set free the coating of the cables from a part of the strain which it now has to resist, and to diminish, consequently, their dimensions and weight. Wires are now made of this alloy, having a conductivity of from ninety-seven to ninety-nine per cent. of the standard, which at 0°C., and with the diameter of a millimeter, have a resistance of 20.57 ohms per kilometer. These wires do not break with a less strain than from 45 to 48 kilos. per square millimeter, and, which is a very precious property, their increase in length at the moment of rupture does not exceed one or one and a half per cent.

Let us consider the deep-sea section of cable of the French company from Paris to New York—the so-called "Pouyer-Quertier" cable, constructed and laid in 1879 by Siemens Brothers of London.

The respective weight of each of its component elements is, per nautical mile, copper core, 220 kilos; gutta-percha, 180 kilos; hemp, or an equivalent, 80 kilos; 18 wires of galvanized iron of 2 millimeters in diameter, 860 kilos; external hemp and composition, 400 kilos; total, 1,740 kilos. Total diameter, 30 millimeters. Total mechanical strength, 3,000 kilos, the wires of the covering being supposed to be of iron. Weight under water, 450 kilos. It can support its own weight without breaking for a length of from six to seven miles.

Fig. 2.

The Atlantic presents from north to south, and at about an equal distance from each continent, a sort of longitudinal ridge, in which the depths vary from 300 to 400 meters. This ridge spreads out, in 50° north latitude, into the region which has received the principal wires connecting England and France with the United States. On both coasts there are depressions in which the bottom is at the depth of from 4,000 to 6,000 meters. The one on the east extends from the south point of Ireland to the latitude of the Cape of Good Hope, and its left-hand boundary follows the general outlines of the west coasts of Europe and Africa. The two others, the northwestern and the southwestern, form two basins, bordering respectively on the United States and the Antilles and South America.

In these depressions soundings have shown certain zones in which the depths exceed 6,000 meters, the principal of which are found to the west of the Canaries, to the south of Newfoundland, between Porto Rico and the Bermudas, and to the right of the Isle of Marten-Vaz.

Fig. 3.

The great depths of the Pacific are differently distributed. Between Japan and California, between 40° and 50° north latitude, there is the Tuscarora depression, which has depths of from 6,000 to 8,000 meters. Parallel to Japan and the Kuriles there is a depression in which has been found the greatest known depth—8,513 meters.

We see, therefore, that any new great submarine line, having to extend into another zone than that which has received the present Atlantic cables, must traverse depressions in which the bottom reaches a maximum depth of 4,000 meters. The possibility of raising a damaged cable would be very problematical under such conditions, and it would become certainly impossible in case of a cable from San Francisco to Japan.

Under these conditions, we are forced to conclude that the use of the present cables limits strikingly the progress of submarine telegraphy, which must remain confined to certain zones of the Atlantic, to inland seas, and to lines along the coasts. But if we consider the daily progress of applied science, and the constantly increasing demand for rapid communication between nations, it is certain that we must shortly undertake the study of new cables intended to traverse the greatest depths of the ocean for long distances. Necessity, therefore, compels us to investigate the new solutions of the problem, which may furnish us with light cables, easy to lay, and possible to repair.

Fig. 4.

A cable made by Mr. J. Richards is composed as follows: core of silicium bronze equal in weight to that of the Pouyer-Quertier cable, or, per nautical mile, 220 kilos; gutta-percha, 180 kilos; layer of hemp, 80 kilos. The sheathing is formed of 28 wires of galvanized iron of 1.25 millimeters in diameter, each covered with hemp, and all twisted into a rope around the dielectric; the wires, 500 kilos: the hemp covering them, 250 kilos. The weight of the cable is, therefore, 1,230 kilos in the air, and 320 kilos in the water. Its diameter is 25 centimeters, and its resistance to fracture 2,800 kilos, of which the core supports one-half. Under these conditions, the cable can support from eight to nine nautical miles of its length, and can be raised from the greatest depths. The results of this comparative examination are self-evident.

For an equal conductivity and an approximately equal mechanical strength, the new cable is in weight and bulk equal to about two-thirds of the Pouyer-Quertier cable. It would cost about $165 less per mile, and would require, for laying, a ship and engines of less power, and thereforecheaper. The reduced armature will suffice to resist friction and the attacks of animal life in the deep sea; but for the shore ends we must keep to the types generally employed. Such as it is, and although it may undergo modifications in detail from a more complete study and from experience, it merits the attention of competent engineers.

Our adjoining engravings illustrate the system of J. S. Williams, for working electrical torpedoes, launches, and torpedo boats, and the appliances be proposes for their equipment and his method of utilizing a system of electrical appliances for the defense of sea-ports, harbors, coast, and coaling stations. We use Mr. Williams' own words in describing this invention. Fig. 1 illustrates men-of-war or vessels attempting to force their way into a harbor defended by such means. The movable and controllable torpedoes are indicated by letters of reference, A, connected through the medium of paying-out electrical cables, G, with the base of operations upon the shore at C, and the launches and floating torpedo batteries or vessels, D. Several lines of torpedo defense or attack are shown, and illustrate the hostile vessels coming within the destructive radius of the movable and controllable torpedoes, which radius is limited only by the length of the paying-out cable, which length can be 1½ miles (more or less). These means secure an effective weapon at all times under command from the base of operations over a radius of 1½ miles, as against a radius of 50 ft., which is the estimated effective range of destruction for fixed mines containing an equal explosive charge.

The movable torpedoes operated from the shore can be supplied with electric power from the main circuits extending along the coast from the developing source, at any distance from the electric power station or base from which the movable torpedoes are operated or supplied. Any natural force, fuel, or other means can be employed for the development of the electric force, which can be transmitted through the main circuits with high tension or pressure to the power stations along the coast, or to the floating magazines, where electric accumulators are placed to hold a reserveof energy. The accumulators at such stations can be compounded so as to be at all times ready for supplying power, and being charged, except when the limit of storage is reached. Electric cut-offs are provided in the loop or derived circuits from the main to cut the magazines out of the circuit when such predetermined limit of energy is in reserve, and means are employed to prevent the backward flow of the current toward the source from the power stations supplied from the main or other circuit. Means are also employed to automatically regulate and prevent any excess of current passing through the circuit in which the accumulators are included. The discharging circuits from the reserve magazines can be connected at the will of an operator with an electric circuit, including electric magazines, forming part of the equipment of the launches, vessels, or torpedoes, so as to supply electric power thereto. This can be accomplished at the wharves or through the medium of a cable buoyed along the coast, so as to obviate the necessity of the launches or vessels returning or running into harbor. Signaling devices can extend from such buoy to the operator along the shore, who will close the circuit from the reserve or main supply circuit. Fig. 2 illustrates a sectional elevation of an electrical torpedo provided with mechanism at the stern for operating the rudder electrically, and the force is regulated by an automatic or manually operative variable resistance interposed in the electrical circuit at the switch board of the cable. A circuit reverser and variable resistance are arranged upon the switch board, so that the operator at the base can change the direction of the current, and regulate the force applied through the medium of the electrical cable in such a manner as to adjust the rudder to port or starboard, and, if so arranged, to maintain it at any angle by varying the resistance in the circuit. The rudder mechanism can be operated by the electric energy stored on board the torpedo through the medium of an electric circuit thereto from the electric accumulator provided with a circuit closer and variable resistance worked by the force passed through the paying-out cable. The force passing there through is regulated by a pressure regulator and controlled by a circuit reverser and variable resistance upon the keyboard. Means are also employed for indicating to the operator the position of the rudder at any moment, and such position will correspond to some defined resistance introduced at any given moment in the circuit. The mechanism combined with the rudder can consist of an arrangement of compound solenoids, the armatures of which are connected to a lever on the rudder head, or a small electric motor can be employed for operating worm gearing in, or combined with, the rudder head. The rudder is brought back to the midship or normal position by springs or counterbalance weights.

WILLIAMS' SYSTEM OF COAST DEFENSE BY ELECTRICAL TORPEDOES.

The motor of the torpedo, as illustrated, is composed of a number of disk-shaped armatures fastened on the shaft, combined with the screw propeller; the field magnets, being also of disk form, are arranged so that the armatures revolve within close proximity, but not touching the pole surfaces. This enables an exceedingly high efficiency and great power to be realized from a motor of light weight. This construction of motor is specially suitable for use in the equipment of torpedoes and launches, and permits an increase of the power of the motor in either of two directions, i. e., either by increasing the number of disks of a given diameter upon the shaft, or by increasing the diameter of the disks, both of these methods giving increased power in direct ratio to the increase of size. The accumulator or secondary battery, c, is especially designed to store the energy in a small space, and with light weight, and so as to command an amount of energy representing the power necessary for a speed of 25 miles an hour or more. In the electrical circuit, between the motor and accumulator, variable resistances and other governing devices are interposed, by which the current passing to the motor is regulated automatically in accordance with the speed of the motor, or with the electric pressure in the circuit from the accumulator. A circuit closer or variable resistance operating in the circuit is connected by the cable with a variable resistance at the switch board, and operated by the current controlled thereby. The force to the motor can be regulated, controlled, or stopped at the will of the manipulator at the switch board placed at the point from which the torpedo is dispatched. Signaling devices or guide rods, O, for indicating the position and direction of movement of the torpedo to the operator can be arranged to be raised and lowered, through the medium of electrical appliances, P, at will, by a current sent through the paying-out cable from the keyboard at the base of operations. Fixed means or sight rods can be used, and hooded incandescent lamps, O2, can be carried by the signal or sight rods, by which means at night or in the day the operator will be enabled to direct the torpedo to the object of attack in spite of adverse or cross currents, or a change in the position of the vessel under attack.

The body of the torpedo containing the machinery and explosive can be arranged to be any desired depth below the surface of the water, and be supported by a buoy as a shield, or be covered by a protection against shot, the displacement of the torpedo being regulated in accordance with the means employed for maintaining it the desired distance below the surface. The torpedo can be ballasted and provided with fins to offer the necessary resistance to the action of the propelling machinery. The electrical paying-out cable, G, is shown in a coil in proximity to the chamber at the bow, which is designed to carry the explosive charge in a fixed or detachable magazine, arranged when detachable to drop a determined distance, and to be fired electrically by the operator or automatically.

Fig. 6 illustrates an apparatus in which a dynamo is operated by a rotary engine having a throttling device controlled electrically by the current passing through the discharging circuit of the generator; the circuit of the generator is connected with the paying-out cable of the torpedo, through the medium of the key board, in which a variable resistance and regulating devices are employed for controlling the operation of the torpedo. Electric magazines are shown arranged to operate in the discharging circuit of the generator, and to be connected with the appliances forming part of the equipment of the torpedo through the medium of the paying-out cable, in conjunction with which is arranged the circuit-closing devices of the switch board under the control of the operator at the stations. Automatic electric pressure regulators are used in the circuit from the source, so as to reduce or regulate the pressure to some predetermined limit. The circuit controllers and manually operative variable resistances upon the switch or keyboard can have indicators connected with them. Under such conditions, with the circuits and appliances upon the torpedo constructed to a known standard, the control of such torpedo in all its movements and operations is easy and certain. Such appliances are especially designed for use upon men-of-war or steam or electric launches when the torpedo vessels are not equipped with electrical magazines. Fig. 5 illustrates a floating fort or battery equipped with machinery, electrical apparatus, and torpedoes, as illustrated in Figs. 2 and 6. The floating fort or battery equipped with electrical or other machinery for propelling can be anchored in suitable positions, or moved from place to place to be in torpedo range of a fleet, or in a suitable position for supplying torpedo launches with torpedoes, and electric or other means of power.

Fig. 3 illustrates a steam launch, and Fig. 4 an electric launch fitted with electrical appliances and compartments containing a means for carrying and discharging electrical torpedoes. By the employment of such means, and a well-organized system of coast defense, it will be practically impossible for hostile vessels to land troops, or to inflict a serious damage upon shipping or seaport towns. Any extent of coast or estuary can be thoroughly protected by launches, light vessels, and appliances operated from fixed electrical stations, supplied with power and means of operation from any point, however distant. For carrying such a system into practical operation, the cost will, it is claimed, be but a tithe of what would be required for placing an inefficient system of fixed mines and forts, or for building men-of-war for coast defense, as men-of-war are practically defenseless against a greater number of high-speed launches equipped with movable and controllable torpedoes, the reasons for which are obvious, as a sufficient number of such launches would cover a greater distinctive range than the vessel which depended upon the range of its guns, or those combined with uncontrollable torpedoes.

Let not the epithet "Perpetual," which the inventor applies to the little apparatus that we are about to describe, frighten the reader, for its only purpose is to indicate that the instrument in question is capable of operating indefinitely, without care and without there ever being any need of taking it apart.

Fig. 1—PERPETUAL GAS LIGHTER.

In this gas lighter the inflammation is produced by a small spark, but this latter, instead of being obtained by means of a pile, which, after a certain length of time, has to be mounted anew or entirely renewed, is secured by borrowing the energy produced by the operator pressing upon a button. It is, then, in reality, amechanicallighter in which electricity intervenes as an intermedium charged with the transformation of work into sufficient of a spark to produce inflammation. Thanks to this principle, and to the arrangement of the apparatus, there is secured cleanness, safety, and economy.

The lighting is reduced, then, to opening the cock and placing the extremity of the rod over the burner, or over the edge of the glass in burners provided with a chimney. Upon pressing the button and then freeing it, a spark leaps between the two points and lights the gas. (Fig. 1).

Fig. 2.—A, cylinder with lighting rod, G. B, movable cylinder fixed upon the axis, E. D, handle containing a rack actuated by a button, F.

The electric generator is a static induction machine of very small size, and the arrangement of which will be understood by reference to Fig. 1, which gives a general view of the apparatus with a portion removed in order to show the relative position of the different parts, and to Fig. 2, which shows the latter detached. A is an ebonite cylinder containing the entire machine, and closed above by a cap of the same substance upon which is screwed the lighting rod. The cap is traversed by conducting wires which end in two contact springs that establish an electric communication with the lighting tube.

Two inducting armatures of tin are cemented to the interior of the cylinder, A, and occupy, each of them, about a third of its circumference. The bottom of the cylinder, A, supports six contact springs, parallel with each other and constituting three distinct pairs which are properly connected, two by two, with the different parts of the rest of the apparatus.

The movable or induced cylinder, B, of ebonite is provided with six equidistant and insulated thin sheets of tin of a width nearly equal to the interval which separates them. This cylinder is given a rapid rotary motion by means of a system of rack and gearing every time the button, F, is pressed. During the revolution of the cylinder the six insulated plates come successively into communication with the six springs, and these put them successively in communication, two by two, first with the fixed inducting armatures, second, with the conductors connected with the two points between which the spark is to pass, and, third, with each other.

The apparatus operates, then, like Sir William Thomson's replenisher. It is only necessary for the armatures upon the cylinder, A, to be at the start at a difference of potential as small as desirable to suppose it, in order to have the play of the machine multiply the charge and soon give it sufficient tension to cross the interval that separates the two points fixed at the extremity of the lighting rod, G. From a technical point of view, the ingenious and new idea resides in the application of a multiplier of charges with which the priming and operation are always secured, provided the insulating parts are so dry that the losses due to dampness are inferior to the machine's power of production. This result, moreover, is easily attained by the use of a hermetically closed system, and of drying substances placed in that part of the cylinder which forms the handle of the apparatus.

From a mechanical point of view, the lighter contains a series of practical and simple arrangements which make it an apparatus at once convenient, strong, and sufficiently perpetual, as regards duration, to partially justify the name that has been bestowed upon it by its inventor, Mr. J. Ullmann.—La Nature.

In the accompanying cut we bring together a few figures of porcelain insulators for uncovered wires placed inside or outside of houses.

PORCELAIN INSULATORS FOR TELEGRAPH AND TELEPHONE LINES.

Figs. 1 and 2 represent simple and double channeled pulleys to be fixed against a wall, or upon a pole or a door post, by means of nails simply. Fig. 3 shows a pulley of larger dimensions for iron wires. Figs. 4, 5, and 6 show perforated insulators, that are quite convenient for holding and supporting a wire, but which are not convenient to put in position when the wire is of some length. Fig. 7 shows a device for protecting a wire that passes through a wall. Fig. 8 shows a support designed especially for small poles. It may be used either by passing the wires through the aperture or winding it around the neck of the bell. Fig. 8 shows a cleft insulator designed especially for fixing a wire in places where it must form an angle.—La Nature.

M. Brandt places alternately, in a continuous line, forty lamps of ordinary glass, forty of green glass, and forty of red glass, making a hundred and twenty lamps in all, at the foot of the stage. Each series of forty lamps forms a separate circuit. The three series can be lighted independently, or they may be combined, in order to obtain different effects of color. For example, a delicate rose hue may be produced by simultaneously lighting the red and the white lamps; a moonlight effect, by a combination of the white and the green lamps. In order to pass gradually from the latter to full daylight, it is only necessary to increase the resistance in the green circuit while strengthening the current in the white lamps. Moreover, the two sides of the stage may be lighted independently, because the 120 lamps are again subdivided into two circuits of sixty each. We may thus have a moonlight on one side of the stage, while the other side, at the moment when an actor enters with a torch in his hand, seems to be illuminated by the reflection from the torch. When the footlights are of gas, a current of hot air ascends above the whole line of lights, forming a sort of gaseous wall between the stage and the audience, which often makes it difficult to hear the actors. This inconvenience is suppressed by electric lighting, and the opera singers are agreeably surprised at the great improvement.—LumiereElectr.

It was not till 1867, on the occasion of the Universal Exhibition, that a dam was constructed at Suresnes that permitted of omnibus-boat service. The effect that this dam had was to raise the water 7½ feet up stream, and to consequently suppress the natural incline of the river between Paris and Suresnes. Its action made itself felt as far as to the Austerlitz Bridge in front of the Garden of Plants.

Between Suresnes and Lavallois the Seine is divided into two arms that are separated by the isles of Puteaux and Grande-Jabbe. The left arm was dammed at Suresnes, and here was established the sluice that allowed boats to cross the falls. The right arm was dammed at Levallois.

A law of April 6, 1878, decided the increase of the depth of the Seine between Paris and Rouen in order to allow boats of a draught of ten feet to reach Paris, and to bring thither, without transfer, English coal and Bordeaux wines. The Consul-General of the Seine having offered to contribute toward the expense, on condition that such boats might have it in their power to ascend as far as to Bercy, a law of July 21, 1880, decided that the Suresnes dam should be raised about three feet in order to increase the anchorage. To effect this, the dams of 1867 were entirely rebuilt, the new ones being located at Suresnes, across the two arms of the river. At the same time, the existing sluice was doubled by another one that was larger and deeper.

This great work was executed under the able direction of Mr. Boule, engineer in chief of roads and bridges, who has in charge the navigation of the Seine, outside of Paris, between Montereau and Poissy. The new sluice was constructed in 1880 and 1881, the dam to the left and the intermediate weir in 1882 and 1883, and the pass to the right in 1884. The width of the Seine at this point is about 820 feet, the length of the passes varies between 209 and 236 feet, and the two sluices occupy a width of 98 feet.

In the construction of the three passes there were established, up and down stream, dikes about 325 feet apart, thus giving considerable space for the installation of work yards, and much facilitating operations.

The new dam is closed by movable mechanisms of the kind invented by Engineer Poiret in 1834. The iron trestles that support the wickets are the largest that have ever been constructed, their height being nearly 20 feet and their weight 3,950 pounds. During freshets they are laid upon the bed of the sluice, and when the water subsides they are raised vertically. Upon these supports are placed swinging wickets, like those of mills, according to a system devised by Mr. Boulet in 1874, and which has been tried since then with success at thePort-a-l'Anglaisdam near Paris. This system has likewise been successfully applied upon the Moskowa, below Moscow, and upon the Saone, at the Mulatiere dam, near Lyons.9

The construction of the new sluice presented great difficulties, by reason of the fact that it was necessary to avoid obstructing navigation in the existing sluice, where the boats stood thirteen or fifteen feet above the laborers who were working at the side, behind simple dikes. Yet it became necessary to forbid the passage of the sluices for nearly a month each year. At Suresnes this was taken advantage of each time to keep the works in full blast during the whole night, the lighting being done by electricity. During these interruptions the boats accumulated at the sides of the dam, and gave the public an idea of what Paris would be as a sea port.

All the work is now finished. Its estimated cost is six millions, two of which were devoted to the construction of about half a mile of dock wall and of a long and wide sewer.

The sluices were opened for navigation on the 15th of September last. The new dams will be in operation in 1885, and next summer they will increase the height of water in Paris by one meter.—L'Illustration.

IMPROVEMENT OF THE RIVER SEINE.—THE NEW DAM AT SURESNES.

Mr. Fred. W. Brearey has been the honorary secretary of the Aeronautical Society of Great Britain ever since its establishment in 1866. In the course of his experiments, extending over some years, he found that if a serpentine action were imparted to a fabric it would propel an attached object many times its weight in the air. He records in his published magazine articles that he took the idea from watching the movements of a skate in an aquarium, which in swimming undulated its whole body.

BREAREY'S FLYING MACHINE.

In applying the principle to locomotion in air, it is of course impossible to undulate what may called the backbone of the whole structure in the manner of the skate. But a fabric may be so attached to a receptacle, and so worked from thence by a suitable motive power, that its undulations will propel and support a considerable weight, depending upon the energy with which such fabric is thrown into waves. He believes that the awning of a vessel can be made in this way to contribute to a ship's progress at the same time that it would cool the passengers.

Mr. Brearey argues that the instinct of the bird enables it to adapt itself instantaneously to varying circumstances; that in any arrangement for effecting flight by machinery—the adjustment of parts to meet sudden requirements being a matter requiring momentary thought—it is desirable, if practicable, to employ large surfaces for parachutic action, at the same time making this means of safety not an incumbrance, but an aid. The possession of instinct allows of the employment of the smallest surface in proportion to weight; the possession of forethought renders it necessary that intermittent action shall be safeguarded by large surfaces.

This requirement is fully met, the inventor says, by the arrangement advocated by him, and none but edge resistance is offered to the air, except the sharp lines of the necessary vehicle. The manufacture of such an apparatus upon a scale of utility would be as follows:

A flat-bottomed receptacle, somewhat of boat shape, would be fixed upon wheels. At the fore part of the boat a motor would from each side elevate and depress two wing-arms, each 15 ft. long. (See Figure.) Along the wing-arms is attached a fabric which would form the front part of a kite, which, being fastened in the center to the edge of the boat, would continue for 15 ft. to the rear, being extended about 6 ft. farther than the stern of the boat by a continuing spar. To a cross piece here would be fastened the tail end of the kite, which, however, instead of a point, would be about 5 ft. in width. From this again would extend a tail of about 12 ft., to which either a lateral, twisting, or a vertical movement could be imparted by cords in the hands of the operator in the boat for steering purposes. From the fore part of the boat would extend a bowsprit, from which cords would be attached to the two wing-arms to prevent the weight of the fabric from dragging them backward.

An important arrangement has been adopted by the inventor, which he calls the pectoral cord, which by its automatic action assumes the functions of the pectoral muscle of the bird. This is an India-rubber cord. It is attached by its two extremities to the under portion of each wing-arm, and in models passes underneath a central shaft—in this case the boat. Its degree of elasticity is regulated by the weight. When any model with wings is committed to the action of the air, the pressure of the air causes the wings to fly upward, and power is required according to the weight sustained to depress the wings against the weight. The strength of the cord, however, is such that it maintains the outstretched wings at that angle which is suitable for gliding upon the air without, in the case of the bird, any enforced muscular exertion. The contraction of this cord assists the power exerted in the downward stroke.

The wing arms would not be rigid throughout their length. They would consist of a number of rattans or canes firmly bound together by close wrapping, and tapered by cuttingoff one at intervals, this being practically unbreakable by any accident likely to occur. The portion next to the body for 5 ft. or 6 ft. might be stiffened by a steel tube, forming the center round which the rattans are wrapped. By this method of forming the wing-arms their length may be increased at pleasure.

A small model upon this principle, but without any motive power, was liberated as an experiment by Captain Templer, from a balloon which had risen 200 ft. or 300 ft. from Woolwich Arsenal, and it traveled back again to the arsenal half a mile against the wind uninjured.

The importance of such an apparatus might become manifest in any flight of a balloon from a besieged place over the heads of an investing army. The results of a rapid survey of the enemy's positions could be written and dispatched from a height against the same current which wafted the balloon, so as to fall within the lines of the besieged.

Given a light motive power, which it is hoped may soon be forthcoming, Mr. Brearey anticipates the action of the machine as follows:

A surface will be provided according to the weight to be carried, the supporting surface of a parachute being known. Upon being run down an incline the envelope will be inflated by the pressure of the air, and the wing arms raised to that point where their further elevation is restrained by the pectoral cord. The machine will then naturally float away from the incline, and the occupant must set his motor in action. The downward blow of the wing-arms will cause the fabric immediately attached thereto to imprison a mass of compressed air, and the following wave will force it along the under side of the fabric. This will cause propulsion.

The return or up stroke cuts off and diverts from the upper part that air which, but for the rise of the wing-arms, would flow over the back, and shunts it underneath, while that which is embraced in the concave fabric following the up-stroke is thrown off in a wave to the rear above the machine, and so on alternately.

During this energetic action the whole fabric is kept in a state of corrugation, and to such extent is rigid. It possesses all the properties of a plane, and superiority over a plane, inasmuch as it propels itself, and upon cessation of action assumes the functions of a parachute, the descent of which a man may regulate by a step backward or forward.

The latest invention which has been completed upon a full scale is the idea of Mr. H. C. Linfield, of Margate. It is really a plane-propelling machine, but the planes are compressed, it may be said, into small compass, being only two inches apart, and being of such number and extent as to present 438 square feet of strained and varnished linen in two frames, each five feet square. The dimensions of the machine are 20 ft. 9 in. in length, 15 ft. in width, and 8 ft. 3 ins. in height. It runs upon four wheels; the two front wheels are 6 ft. in diameter, the two hind wheels 3 ft. The frames before mentioned are fixed one on each outer side of the front wheel at an upward angle. The wheels have been tested to sustain a weight of 5 cwt.

The weight of the machine is 240 lb., and of its inventor 180 lb. He sits between the wheels and works two treadles, which actuate a nine-bladed screw 7 ft. in diameter, fixed in front of the machine, to which he can impart 112 revolutions per minute. This suffices to enable him to travel along a level road.

During the erection of the viaduct at Douarnenez—Department of Finistêre—over the river Pouldavid, one end of one of the heavy latticework girders dropped into the river, as shown in the upper one of the annexed cuts taken fromL'Illustration. The difficult problem to be solved was to remove the obstruction in as short a time as possible, and at the least expense; and the engineers came to the conclusion that it would be best to raise the fallen end, as the girder was intact, with the exception of those parts that struck the bottom of the river, and which could easily be replaced by others.

THE VIADUCT OF DOUARNENEZ.—THE POSITION OF THE FALLEN GIRDER.

THE VIADUCT OF DOUARNENEZ.—THE GIRDER RAISED.

The viaduct has three spans of 190 ft. each, and is 88 ft. above the surface of the water. While rolling the girders upon the piers, the pivot of one of the rollers broke, and a projecting length of 183 ft. of the girder dropped a vertical distance of 72 ft. That part of the girder that had to be raised was 183 ft. long, and weighed 145 tons, and the free end had to be moved a distance of 72 ft. in an arc the radius of which was 183 ft. Suitable scaffoldings were erected on the piers and below the fallen end of the girder; four strong and heavy double chains were connected with the lower end of the girder and passed over a scaffolding erected for this purpose, and the opposite ends of the chains were connected with a heavy box weighted with rails, and containing 2,700 cubic ft. of water. The upper end of the fallen girder was disconnected from the other parts of the structure, and a heavy steel pivot bar inserted, upon which the girder could turn. The box was so weighted that the fallen girder was somewhat heavier than the box, and then windlass chains were connected with the lower end of the girder, and wound upon windlass drums operated on top of the scaffolding. The weighted box thus merely acted as a counterbalancing weight, the raising being accomplished by means of the windlass. On the 1st of August the lower end of the girder was raised 17 inches, and remained in this position for twenty-four hours, during which time examinations were made which proved that the calculations were correct, and that all the parts worked perfectly. The operation was completed the next day with perfect success, and was witnessed by a great multitude, attracted by the novel sight.

The illustration represents a multiple wire tester, constructed for the Trenton Iron and Steel Company by Riehle Bros., of Philadelphia. It consists of a weighing mechanism (seen on the left, with a capacity of 4,000 pounds), two single or alternating pumps, a hydraulic jack, a patented three-way valve, and a rising and falling accumulator.

The weighing end of the machine, placed horizontally and secured by bolts to a foundation, is accurate, and will weigh the strain on one to six wires at a time. It is provided with self-adjusting grips to take in wires from No. 10 to No. 16, and hold them firmly. It can be adapted to take in a larger or smaller range of numbers when desired. There is a set of gripping appliances at both ends, and in the present instance they are 90 feet apart—one set at the scale end, and the other secured to head of piston. The jack is 5 feet in length, and lined with brass; its outside diameter is 3½ inches; its inside diameter, 2¼ inches. Like the scale end, it is firmly bolted down to its foundations.

The plunger has a stroke of 4 feet. It is supported and guided by three guides, the top one being a straight tube running on turned rollers. A three-way valve controls the movements of the jack and accumulator, and supplies water to the jack by a lever. When the lever is raised, the water is forced into the larger area of the jack, causing the plunger to move backward and bring a strain on to the wires or other specimens; when the lever is lowered, the water in the larger area of the jack only returns to the reservoir of the pump (to be used again). Now, without changing the position of the lever, the plunger will return automatically, without weight or counterbalance, with a steady, smooth, and uniform motion.

The pump has a slow motion, 60 revolutions per minute. It has two single action pistons, and the valves are so simple and readily accessible that an ordinary mechanic can examine and repair, when necessary, in a short time. The accumulator is so arranged as to overflow when it comes to its maximum height. The machine can be adapted to stretching and straightening wires in lengths to a given amount.

The weight on the scale and that on the accumulator is made to correspond, so that wires of a certain number or size can be quickly tested in quantities under exactly the same conditions, with only the movement of the lever.

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