have submitted these views to a close consideration, and the test of
accordance with observation, and, where applicable, with experiments
also, I will do myself the honour to bring them before the Royal
Society.'

Two elaborate memoirs are then devoted to the subject of Atmospheric
Magnetism; the first sent to the Royal Society on the 9th of October,
and the second on the 19th of November, 1850. In these memoirs he
discusses the effects of heat and cold upon the magnetism of the
air, and the action on the magnetic needle, which must result from
thermal changes. By the convergence and divergence of the lines of
terrestrial magnetic force, he shows how the distribution of
magnetism, in the earth's atmosphere, is effected. He applies his
results to the explanation of the Annual and of the Diurnal Variation:
he also considers irregular variations, including the action of
magnetic storms. He discusses, at length, the observations at
St. Petersburg, Greenwich, Hobarton, St. Helena, Toronto, and the
Cape of Good Hope; believing that the facts, revealed by his
experiments, furnish the key to the variations observed at all these
places.

In the year 1851, I had the honour of an interview with Humboldt, in
Berlin, and his parting words to me then were, 'Tell Faraday that I
entirely agree with him, and that he has, in my opinion, completely
explained the variation of the declination.' Eminent men have since
informed me that Humboldt was hasty in expressing this opinion. In
fact, Faraday's memoirs on atmospheric magnetism lost much of their
force--perhaps too much--through the important discovery of the
relation of the variation of the declination to the number of the
solar spots. But I agree with him and M. Edmond Becquerel, who