In Dr. Herz's opinion, the telephone is not to remain a single apparatus, varied only as to form, but, on the contrary, must be actually modified according to the purposes for which it is designed. He thinks that a telephone operating at great distances must differ from a city apparatus, and that an instrument for transmitting song can not be absolutely the same as one for conversational purposes. So he has endeavored to create types that shall prove appropriate for these different applications.
DECISION OF THE CONGRESS OF ELECTRICIANS ON THE UNITIES OF ELECTRIC MEASURES.
For these measures there are adopted the fundamental unities—centimeter, gramme, second, and this system is briefly designated by the letters C., G., S. The practical units, the ohm and the volt, will retain their present definitions; the ohm is a resistance equal to 109 absolute unities (C., G., S.), and the volt is an electromotive force equal to 108 absolute unities (C., G., S.). The practical unit of resistance (ohm) will be represented by a column of mercury of 1 square mm. in section at the temperature of 0°C. An international commission will be charged with ascertaining for practice, by means of new experiments, the height of this column of mercury representing the ohm. The name ampère will be given to the current produced by the electromotor force of 1 volt in a circuit whose resistance is 1 ohm. Coulomb is the quantity of electricity defined by the condition that in the current of an ampère the section of the conductor is traversed by a coulomb per second. Farad is the capacity defined by the condition that a coulomb in a condenser, whose capacity is a farad, establishes a difference of potential of a volt between the armatures.
SECONDARY BATTERIES.
By J. Rousse.
In order to accumulate electricity for the production of light or motive power, the author has arranged secondary batteries, which differ from those of M.G. Planté. At the negative pole he uses a sheet of palladium, which, during the electrolysis, absorbs more than 900 times its volume of hydrogen. At the positive pole he uses a sheet of lead. The electrolyzed liquid is sulphuric acid at one tenth. This element is very powerful, even when of small dimensions. Another secondary element which has also given good results, is formed at the negative pole of a slender plate of sheet-iron. This plate absorbs more than 200 times its volume of hydrogen when electrolyzed in a solution of ammonium sulphate. The positive pole is formed of a plate of lead, pure or covered with a stratum of litharge, or pure oxide, or all these substances mixed. These metallic plates are immersed in a solution containing 50 per cent. of ammonium sulphate. Another arrangement is at the negative pole, sheet-iron; at the positive pole a cylinder of ferro-manganese. The electrolyzed liquid contains 40 per cent. ammonium sulphate.