Dr. G. Gore, F.R.S., has invented an improved thermopile for
measuring small electromotive forces. It consists of about 300 pairs
of horizontal, slender, parallel wires of iron and German silver, the
former being covered with cotton. They are mounted on a wooden frame.
About 1½ in. of the opposite ends of the wires are bent downward to a
vertical position to enable them to dip into liquids at different
temperatures contained in long narrow troughs; the liquids being
non-conductors, such as melted paraffin for the hot junctions, and the
non-volatile petroleum, known as thin machinery oil. The electromotive
force obtained varies with the temperature; a pile of 295 pairs having
a resistance of 95.6 ohms at 16 deg. Cent. gave with a difference of
temperature 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.