so that the projecting ends shall all be equal among themselves, then these bars will bend under the influence of the first, only touching at the ends, and all taking exactly the same circular curve.

The parts of the bars projecting from the points of support, will equally bend in arcs of a circle, if care be taken to give them the form of solids of equal resistance starting from the points of support.

This reasoning applies equally to blade springs, bound together of equal radii, and which are straightened by a load.

Mr. Blacher lays down

First, That the flexure is proportional to the load: that is to say, that at each partial and constant addition to the load, there is a corresponding partial and constant flexure throughout the whole extent of the flexure.

Second, That the flexure is in inverse ratio to the number of springs: that is to say, that for a double load there is needed (all other things being alike) a double number of springs.

Third, That the flexure is proportional to the cube of the length developed by the spring.

Fourth, That the flexure is in inverse ratio of the width and of the cube of the springs or plates.

He con

M. La Salle concluded with some observations of his own. sidered that for a steel spring of the first quality, it ought not to be subjected to a tension greater than would cause an extension of substance of in length. At least, this is his opinion, until further experience determines within what limits elasticity can be maintained. He likewise observed, that the new system of springs, called "compensation springs," has been lately tried in France; these springs being composed of a small number of plates which, in proportion as they bend, spread out on a rigid bar. These springs, which at first sight appear lighter than common springs, are under bad conditions of solidity and durability, because the steel is worked to its utmost limits, and most frequently to a lengthening of, so soon as the middle begins to spread out under the influence of a load. If they wished they could work steel as much in common springs, and could considerably reduce their weight, which would then come out much lower than compensation springs. In his opinion, the principle of compensation springs was not rational. He found in them a radical vice, inasmuch as their sensibility diminished just as the load they bear increases-that is to say, that they lose their flexibility precisely at the moment when it should be as great as possible..

M. Polonceau, who has made some experiments lately on the two systems, explained that the new springs spreading out on a rectilinear bar, and shortening by all the length applied on this bar, offer a leverarm shorter and shorter as they go on bending. At first sight, it had seemed to him, as to everybody else, that under a given load these springs ought to act much in the same way as a common spring, shorter by the whole quantity in contact on the rigid bar: experience has, however, proved that compensation springs exhibit extraordinary elasticity. For the present he had no wish to prejudge the question, as he was engaged in ascertaining the working of the new springs; but he would give an account of his experiments to the society when completed.

M. La Salle is of opinion that the characteristic which essentially distinguishes the two systems is flexibility. In common springs the flexibility is proportionate to the load; in compensation springs, on the other hand, the flexibility decreases rapidly just as the lever-arms diminish under the influence of an increase of load, since the flexure is in inverse ratio to the cube of the length. In the experiments made on the Orleans Railway, they endeavored to load, first, each of the springs under experiment with a steady load of 5000 lbs., then with an additional load of 2000 lbs.; which, being taken off all at once at a given time, caused a reaction of the spring, which was shown by more numerous shakings or oscillations in the compensation spring than in the common spring. Hence it was drawn that the first was more elastic; but it must be said that the common spring, being composed of a greater number of plates, has to overcome greater friction, and that, consequently, its oscillations will stop sooner. To his mind the friction of the plates is of advantage when not carried too far, since it exactly prevents the oscillations from being kept up. A spring should not be absolutely elastic. The principal condition is, that it should be flexible; and as to friction, it absorbs beneficially a part of the force developed by the shock.

A member is not of the same mind as to friction, for if M. La Salle is right, the old springs are best of all; and that cannot be. Springs ought to have a great flexibility; they ought to bend much when heavily laden; and friction must certainly lessen its flexibility.

M. La Salle answered, that if friction is useful within certain bounds, it need not be so excessive as in the old springs. To be easy, a spring ought to be flexible, and produce oscillations of given fullness; and it was not, therefore, to be held out that the friction would be considerable enough to destroy the flexibility of the spring. For ease, it is desirable to make the springs as long as possible, because these being capable of being composed of a smaller number of plates, afford less surface for rubbing. He held, too, there are cases wherein too much elasticity is hurtful. For carriers and diligences he had made springs composed of five or six plates of 0.4 inch thickness. These springs were very easy under heavy loads, but they were less so when the carriages were empty; and in both cases caused them great swaying. Since then, he had put, instead of these springs, other springs made up of a greater number of thinner plates, which afforded much the same flexibility and the same weight. These latter, which showed much more friction, were preferred.-Proc. of Soc. Civ. Eng., Paris.

Water Pipes.*

Messrs. Neilson of the Hyde-park foundry, are at present under contract to supply about 30 miles of cast iron pipes to the town of Liverpool, for bringing the water from the Pike. They are 3 ft. 10 in. in diameter, the iron of which they are made being 13 inches thick. Each length measures fully 12 feet; and in every one of these there are nearly 4 tons of iron. Upwards of 1200 have already been delivered and shipped for Liverpool. The average number of lengths turned out does From the London Architect for August, 1851..

not exceed five per day, which involves a consumption of nearly 20 tons of iron. Every pipe before leaving the foundry is subjected to a severe test by hydraulic pressure. The moulds, which stand about 13 feet high, are sunk into the ground, bringing the top of the cylinder nearly on a level with the surface. The liquid metal weighing, as already stated, about 4 tons, is brought by means of a steam crane from the melting furnace, and poured into the mould.

On the Conduction of Electricity through Water. By MR. F. C. BAKEWELL.*

This paper gave the results of some experiments on the conduction of electricity by water, made with a view to prove that an electric current may be transmitted for a considerable distance through unprotected wires immersed in water. The experiments were conducted on Saturday, June 28th, in one of the Hampstead ponds. A thin copper wire (No. 20), 320 feet long, was stretched across the pond, and two copper plates, 10 inches square, to which wires were soldered, were immersed to serve as conducting plates for the return current. A Smee's battery of two pair of plates was used; and when the eonnexion was made with a galvanometer on the opposite bank, a steady deflexion of 30° was maintained, and a strong blue mark was produced by a steel electrode on paper moistened with a solution of prussiate of potass in diluted muriatic acid. In this experiment the conducting plates were placed close to the wire and on opposite sides of it, so that the return current passed diagonally across the exposed wire. The water in this case appeared to act as a conductor and as a non-conductor at the same time, in proportion to the surfaces exposed to its influence. In the next experiment the wire was doubled, and a current of electricity from the same battery was transmitted through the wires, both being immersed in the water. In this case the deflexion of the needle was more powerful, and it continued steady at 45°. From these experiments, which Mr. Bakewell stated were a confirmation of those undertaken by Mr. Bain and Lieut. Wright with a different object in 1841, he inferred that the exposure of a large surface, as the electric telegraph wires from post to post, presented greater opportunity for the dispersion of electricity in moist atmospheres than the points of connexion with the posts.

Proceedings of the Stated Monthly Meeting, September 18, 1851. Francis Grice, Esq., President pro tem., in the chair.

Isaac B. Garrigues, Recording Secretary.

The minutes of the last meeting were read and approved.

Letters were read from The Royal Geographical Society, London; and J. Erricsson, Esq., New York.

Donations were received from The Royal Institution of Great Britain; The Royal Geographical Society, and the Royal Astronomical Society,

From the London Architect for August, 1851.

London; Thomas Ewbank, Esq., Commissioner of Patents, Washington City, D. C.; Simeon Borden, Esq., Fall River, Mass.; J. Erricsson, Esq., New York, and Robert Smith, Esq., George W. Smith, Esq., and Prof. John F. Frazer, Philadelphia.

The Periodicals received in exchange for the Journal of the Institute were laid on the table.

The Treasurer's statement of the receipts and payments for the month of August was read.

The Board of Managers and the Standing Committees reported their minutes.

New candidates for membership in the Institute (7) were proposed, and the candidates (6) proposed at the last meeting were duly elected.

Dr. Rand, Chairman of the Committee on Meetings, presented several specimens of iron coated with copper, a new article sent to the Institute by Mr. Ebenezer G. Pomeroy, of Cincinnati, Ohio, and for which he has taken out a patent. His process is as follows::

Immerse the iron in dilute sulphuric acid, for the purpose of cleansing the surface of the article which is to be coated; and thus cleansed, submit the iron to a brisk heat to dry it; when dry, immerse the article in a mixture of clay and water, and again dry it so as to leave a thin coating of the clay on its surface; it is then to be immersed in a bath of melted copper, and the length of time requisite for the iron and copper to form a union, will depend on the thickness of the article under operation. The object of the clay is to protect the copper from oxidation during the process of alloying or coating, and to reduce it to the required thickness it is passed between rollers. The result of this annealing process will be a smooth surface, fully equal to the brightness of pure copper.

The specimens presented to the Institute had all the appearance of pure sheet copper, and are considered by the patentee applicable to the same purposes.

Dr. Rand also exhibited specimens of cotton fibre which had been immersed in a cold solution of caustic soda, after the method of Mr. Mercer, by which the fibre had undergone condensation. The amount of this change was stated to be one-fifth to one-third of the original volume of cotton employed, increasing its fineness by a chemical union with the soda. By this process the strength of the fibre was also stated to be increased in the proportion of 20 to 13; and certain colors are much brightened. (Vide Report of the British Association in London Atheneum, for July,-Journal of the Franklin Institute, present Vol. p. 204.) This subject will again be brought before the Institute.

Mr. G. W. Smith brought before the meeting an interesting specimen of flax cotton, made after the process of C. Claussin, and gave an account of his method.

The next subject of interest was an exhibition of the operation of one of Phillips' Patent Fire Annihilators, which was kindly loaned for the occasion by Mr. Sandford, of Adams' Express of this city, and put in operation by Dr. Hall, one of the patentees in this country. The portable apparatus is sixteen inches in height by eight inches in diameter, and consists of a machine composed of two thin iron cylindrical cases within. one another, the central case containing a brick composed of charcoal, sulphate of lime, and nitrate of potassa, and in the centre of this brick a

bottle containing a mixture of chlorate of potassa, in which is contained a portion of sulphuric acid. This deflagrating compound fires the inside by a pin being pressed down from the top so as to break the vial and ignite the brick, which creates a great amount of heat, sufficient to generate steam in the bottom of one of these cylinders, which unites with the gases evolved so as to produce a large jet of white vapor, without any suffocating odor; it was exhibited in a room in which there were not less than fifty persons, without producing cough or any disagreeable impression. The apparatus was merely exhibited in order to show its construction and mode of operation. A trial to test its practical merits was announced to take place in a few days.

COMMITTEE ON SCIENCE AND THE ARTS.

Report on Wm. C. Grimes' Steam and Water Indicator.

The Committee on Science and the Arts, constituted by the Franklin Institute of the State of Pennsylvania for the Promotion of the Mechanic Arts, to whom was referred for examination, a "Steam and Water Indicator," invented by Wm. C. Grimes, of Philadelphia, Penna.-REPORT:

That the instrument of Mr. Grimes, which is intended to indicate continually the height of the water, and pressure of the steam in a boiler, at any required place at whatever distance from the boiler, consists in two metallic tubes which are inserted, the one into the steam space, the other into the lower part of the water space of the boiler, and extend from the boiler to the place at which the indications are required to be made, where the ends of the tubes are brought side by side and connected together by a bent glass tube, one end of which enters each of the metallic tubes. In the simplest form, (which is described for the purpose of explaining most simply the theory of the apparatus,) the tube connected with the steam space (which may be called the upper tube) enters the boiler at the water line and runs for some distance horizontally, or a little inclined downwards, when it again bends downwards for some inches, and then runs in any convenient direction to the glass tube. The object of this arrangement is to allow the steam to condense in this part of the tube, and to keep the water which fills it always at the proper water level of the boiler. Each of the tubes is provided with a stopcock near the boiler, and on each of them immediately below the glass tube there is a small hole, (called by Mr. Grimes the air-hole,) which may be closed by a screw. In order to put the apparatus in working order, the boiler is filled to above the water line, the stop-cocks of the tubes being closed, and a small pressure of steam raised; the stop-cock of the upper tube being then opened a little, the water will enter the tube, and expelling the air before it through the air-hole, will finally begin to run through this hole; the stop-cock of the upper tube is then closed and the plug of the air-hole screwed in. The lower tube is then filled with water in a similar manner. The apparatus then contains water in the metallic tubes, and air in the glass tube or gauge. If now the stop-cocks on the tubes be opened, and the pressure of the steam increased, the air in the gauge will be compressed proportionably, and the water will rise to an equal height in each branch of the tube; in this way the gauge may be graduated by direct experiment. But the fall of the water level