Abstract
II. ELECTRIC force pervades all matter. Our planet and the atmosphere surrounding it are vast storehouses of electrical energy in a constant state of unstable equilibrium. Electricity is one of the forces of nature, and may be developed in various ways and under various conditions. The aurora, the thunderstorm, and the earth's magnetism, are each grand displays of electrical force upon a vast scale. Electrical energy may be excited by chemical action, friction, heat, induction, magnetism; and currents of electricity so obtained may be employed for telegraphic purposes. Thermo-electricity, as the name implies, is that generated by electric currents in metallic bodies by the disturbance of the equilibrium of temperature, the essential conditions being, that the extremities of the dissimilar metals should be in opposite states as regards temperature. The discovery of thermoelectric currents is due to Seebeck of Berlin in 1821; the generation of electric currents by the application of heat to a pile or series of dissimilar metals, however, remained in abeyance until the researches of Nobili and Melloni, who constructed the thermo-electric pile, consisting of alternate parallel bars of bismuth and antimony placed side by side. Fig. 10 is a representation of the thermo-electric pile as arranged by Melloni. The brass frame on the left contains the compound bars, the wires from the antimony and bismuth poles being connected to a galvanometer, shown on the right-hand side; the quantity of electricity passing from the poles of the pile (regulated according to the difference of temperature of the bars) causes the needle of the galvanometer to be deflected. With thermo-electric currents the quantity of electricity developed depends upon the difference of the temperature of the two poles of the dissimilar metals; the currents may be so delicate that a difference of temperature equivalent to 18/2200 part of a degree may be measured.
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The Progress of the Telegraph * . Nature 11, 450–452 (1875). https://doi.org/10.1038/011450a0
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DOI: https://doi.org/10.1038/011450a0