Page:Somerville On the Magnetizing Power of the More Refrangible Solar Rays.djvu/1

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X. On the magnetizing power of the more refrangible solar rays.

By Mrs. M. Sommerville. Communicated by W. Sommerville, M. D. F. R. S. Feb. 2. 1826.

Read February 2, 1826.

In the year 1813, Professor Morichini of Rome discovered that steel, exposed to the violet rays of the solar spectrum, becomes magnetic. His experiments were repeated by Professor Configliachi at Pavia, and also by Mons. Berard, at Montpellier, without success. I am not aware of any one having attempted them in this country, perhaps from the belief that experiments which had sometimes failed in Italy, were not likely to succeed in our more northern climate. The unusual clearness of the weather last summer, however, induced me to try what could be accomplished in this country. Accordingly, in the month of July, an equiangular prism of flint glass, the three sides of which were each 1,4 by 1,1 inches, was fixed in a slit made to receive it in a window-shutter: by this prism a coloured spectrum was thrown on an opposite panel, at the distance of about five feet. I used for the subject of experiment, a very slender sewing needle an inch long, having previously ascertained that it was quite free from magnetism, by repeated exposure of both ends of it to the north and south pole of a very sensible magnetic needle, when it was found equally to attract either pole in every instance. The magnetic needle employed as a test in this experiment, is made of a sewing needle mag-