of 100 deg.  Cent. an electromotive force of 0.7729 volts, or with 130 deg.  Cent. an electromotive force of 1.005 volt.  Each element, therefore, equaled 0.0000262 volt for each degree Cent. difference of temperature.  On having been verified with a standard voltaic cell the apparatus becomes itself a standard, especially for small electromotive forces.  It is capable of measuring the 1/34861 part of a volt.  For higher electromotive forces than a volt, several of these piles would have to be connected in series.  The fractional electromotive force is obtained by means of a sliding contact which cuts out so many pairs as is required.

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TELEPHONIC TRANSMISSION WITHOUT RECEIVERS.

The annual meeting of the French Society of Physics, the success of which is continually increasing, took place this year in the salons of the Observatory, which were kindly placed at the Society’s disposal by Admiral Mouchez.

There were three consecutive sessions, the one of Tuesday, April 15, being set apart for the members of the Association, the one of the 16th for the invited guests of Admiral Mouchez, and that of the 17th for the invited guests of the Society.  The salons were partially lighted by the Siemens differential arc, continuous current lamps, and partially by the Swan incandescent lamp supplied by a distributing machine that permitted of the lamps being lighted and extinguished at will without changing the normal operation of all the rest.  Many apparatus figured at this exhibition, but we shall on the present occasion merely call attention to those that presented a certain character of novelty or of originality.

Among the apparatus that we shall reserve a description of for the present was Messrs. Richard Bros.’ registering thermometer designed for the Concarneau laboratory, an instrument which, when sunk at one mile from the coast, and to a depth of 40 meters, will give a diagram of the temperature of the ocean at that depth; and Mr. Hospitalier’s continuous electrical indicators, designed for making known from a distance such mechanical or physical phenomena as velocities, levels, temperatures, pressures, etc.

Among the most important of the apparatus exhibited we must reckon Mr. Cailletet’s devices for liquefying gases, and those of Mr. Mascart for determining the ohm.  The results obtained by Mr. Mascart (which have been submitted to the Committee on Unities of the Congress of Electricians now in session at Paris), are sensibly concordant with those obtained independently in England by Lord Rayleigh.  Everything leads to the hope, then, that a rapid and definite solution will be given of this important question of electric unities, and that nothing further will prevent the international development of the C.G.S. system.

Mr. Jules Duboscq made a number of very successful projections, and we particularly remarked the peculiar experiment made in conjunction with Mr. Parinaud, that gave in projection two like spectra produced by the same prism, and which, through superposition, were capable of increasing the intensity of the colors, or, on the contrary, of reconstituting white light.