The trajectory of the two torpedoes is regulated by a cylindrical bellows, F, which gives entrance to the sea water.  The springs shown in the figure balance the hydraulic pressure.  The tension of these springs is regulated by the rod, H, according to the indications of the scale of depths, I.

When the torpedo reaches too great a depth, the action of the springs can no longer balance the increase of the hydraulic pressure, and the accumulation of the charge in the rear causes the front to rise toward the surface.  When the torpedo reaches the surface, a contrary action is produced.—­Revue Industrielle.

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THE FIRST STEAMBOAT ON THE SEINE.

[Illustration:  First steamboat built on the Seine.]

The accompanying engraving represents the remarkable steamboat that the unfortunate Marquis de Jouffroy constructed at Paris in 1816, after organizing a company for the carriage of passengers on the Seine.  De Jouffroy, as well known, made the first experiment in steam navigation at Lyons in 1783, but the inventor’s genius was not recognized, and he met with nothing but deception and hostility.  With the obstinacy of men of conviction, he did not cease to prosecute his task.  He assuredly had an inkling of the future in store for the invention that he was offering to humanity.

The paddle wheel boat that he constructed at Paris in 1816 did not succeed any better than its predecessors; it was remarkable nevertheless in appearance and structure.

The engine was forward, as shown in the engraving, which is copied from a composition of Dubucourt’s.

The company organized by the marquis was ruined, and, as well known, the unfortunate inventor himself died in poverty in 1832, at the age of eighty-one years.—­La Nature.

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THE ELECTRIC MOTOR TESTS ON THE NEW YORK ELEVATED RAILROAD.

The American Institute of Electrical Engineers at its last meeting of the season, held June 25, again considered the subject of electrical traction, the paper presented by Mr. Leo Daft being based upon some recent electrical work on the elevated railroads and its bearing on the rapid transit problem.  The Railroad Gazette gives the following abstract: 

He introduced the subject with a tribute to the efficiency of the elevated railroad system as it is now operated by steam, with special reference to that section of it known as the Ninth Avenue line, upon which his experiments with the electric motor have been conducted, over which passengers are now conveyed a distance of five miles in 26 minutes for five cents, which he considered the best and cheapest municipal rapid transit in the world, and which is operated with a higher degree of safety