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This eBook from the Gutenberg Project consists of approximately 107 pages of information about Scientific American Supplement, No. 312, December 24, 1881.

Nor has the speaking condenser been neglected.  As regards this, efforts have seemingly been made toward finding a convenient arrangement and a regular mode of construction, the good working of these apparatus being absolutely dependent upon the care with which they are set up.

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.

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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 10^{9} absolute unities (C., G., S.), and the volt is an electromotive force equal to 10^{8} 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 deg.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 ampere 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 ampere 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.

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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.  Plante.  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

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