exertions having for their object the discovery of the direct relation of light and electricity. These ineffectual exertions could not remove my strong persuasion, and I have at last succeeded.” He describes the phenomenon in somewhat figurative language as the magnetisation of a ray of light, and also as the illumination of a magnetic curve or line of force. He has no sooner got the effect in one case, than he proceeds, with his characteristic comprehensiveness of research, to test the existence of a like phenomenon in all the substances available. He finds that not only heavy glass, but solids and liquids, acids and alkalis, oils, water, alcohol, ether, all possess this power; but he was not able to detect its existence in any gaseous substance. His thoughts cannot be restrained from running into curious speculations as to the possible results of the power in certain cases. “What effect,” he says, “does this force have in the earth where the magnetic curves of the earth traverse its substance? Also what effect in a magnet?” And then he falls upon the strange notion that perhaps this force tends to make iron and oxide of iron transparent, a phenomenon never observed. We can meet with nothing more instructive as to the course of mind by which great discoveries are made, than these records of Faraday’s patient labours, and his varied success and failure. Nor are his unsuccessful experiments upon the relation of gravity and electricity less interesting, or less worthy of study.
Throughout a large part of his life, Faraday was possessed by the idea that gravity cannot be unconnected with the other forces of nature. On March 19th, 1849, he wrote in his laboratory book,—“Gravity. Surely this force must be capable of an experimental relation to electricity, magnetism, and the other forces, so as to bind it up with them in reciprocal action and equivalent effect?”9 He filled twenty paragraphs or more with reflections and suggestions, as to the mode of treating the subject by experiment. He anticipated that the mutual approach of two bodies would develop electricity in them, or that a body falling through a conducting helix would excite a current changing in direction as the motion was reversed. “All this is a dream,” he remarks; “still examine it by a few experiments. Nothing is too wonderful to be true, if it be consistent with the laws of nature; and in such things as these, experiment is the best test of such consistency.”
He executed many difficult and tedious experiments, which