Page:Memoirs of the Geological Survey of Great Britain, Volume 1.djvu/471

458 458 INFLUENCE OF VOLTAIC ^BLECTEICITT

tricity which decomposes, and that which is evolved by the decompoeitioii of a certain quantity of matter, are alike.* We are, therefore, led to the conclusion, that the electricity engaged in this decompoution is due to some peculiar action upon the crust of the earth by some of the radiant forces, and that the electricity measured, or capable of being measured, in the experiments on the electricity of mineral veina, is an exact representative of the amount of chemical action going on within the mineral vein or lode itself.

62. That there is a very striking relati(m between the electriaty thus evolved, and magnetism, is shown from the following experiment. Two pieces of copper pyrites were connected by copper wires with a Daniell's battery, and placed in a mass of clay in a moist state. Hie day dried very slowly, and when quite dry presented sundry cracks, all radiating, somewhat irregularly, from around the wires. The ores had changed, as in the case already described (58). On breaking the clay, it was found that it was arranged in curved lines ; those from the north pole being exactly at right angles to those produced by the action from the sou^ pole.

63. It would be very premature to attempt, at this period of the in- vestigation, to explain the phenomena which have presented themselves. Many things remain to be proved, and although we have seen that mag- netism and electricity are capable of producing the same effects, we have yet to add that link to the chain which will prove the relations existing between the forces of chemical affinity and magnetism.

64. The experiments on the temperature of mines, &c., suffidently prove some source of heat beneath the sur&ce of the earth, which, by acting at considerable depths, must be capable of producing upon a given mass of matter certain effects analogous to those of a thermo- electric bar. At the same time, we have the action of radiant forces on the sur£BU», to which possibly the magnetism of the earth may be due. Professor Airy is disposed to refer it to the influence of the solar calorific radiations ;t but it may probably be due to the influence of the actinic power, or that force which is active in producing chemical change, particularly as we must refer to it those effects on magnetic needles observed by Mr. Christie and others.];

65. From the results of the experiments which have been now de- scribed, a most intimate relation is indicated between the crystalline and molecular forces, and magnetism and electricity. This relation, it would appear, must also be extended to the phenomena of chemical


 * • ExperimenUl Besearchefl in Electricity/ toI. i. p. 256.

t * ETcning Lecture on Magnetism at the Meeting of the British Association at Cam- bridge/ reported in the <^then»um.' X < Philosophical Transactions/ 1826, p. 219.

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