M2 Ua^jjeriments of Morichini, Kidolfi and others^ 
the South of France, having repeated at an early period the 
experiments of Morichini without success, was induced, by Mr 
Playfair’s account of them, to re-examine the subject with great 
attention. On the 18th October 1817, about % o’clock in the 
afternoon, when the external thermometer stood at 14°, the one 
in his chamber at 15° and 15° S, and Saussure’s hygrometer at 
41°, he admitted the sun’s direct rays through an aperture 
three-fifths of an inch in diameter. A prism placed behind 
this aperture formed the solar spectrum upon a piece of card per- 
forated so as to allow only the violet rays to pass. A lens was 
fixed behind this perforation ; but instead of making the focus 
of the violet rays pass over the needle, he found it easier to 
make the needle pass through this focus always in the same di- 
rection. After continuing this process for an hour, the needle 
being nearly in the direction of the meridian, he could not dis- 
cover that the slightest degree of magnetism was communicated 
to it. 
The connection between light and magnetism, which appears 
to be indicated by the preceding results, has been supposed to 
exist to a still greater extent. In a paper published by Colonel 
Gibbs in Professor Silliman’s Journal he goes so far as to 
consider light as the great source of magnetism. In 1 81 7 he 
had visited the mine of magnetic iron at Succassanny, and was 
informed, that the ore in the upper part of the bed was magne- 
tic, while that which was raised from the bottom acquired it on- 
ly after exposure to the influence of the atmosphere. This ef- 
fect he ascribed, without any sufficient reason, t© the influence 
of light. 
In support of this opinion, Colonel Gibbs attempted to ascer- 
tain by direct experiment, the influence of light upon a magnet. 
For this purpose he determined the power of his magnet, as 
it had been shut up in the dark for a long time, and lying 
down. He then exposed it to the rays of the sun, also lying 
down, and remote from the iron support, and he found that it 
had gained 12 oz. power in forty minutes, and 14 oz. power 
only in five hours -f.” 
A very remarkable analogy between the phenomena of mag- 
nets and of glass, either transiently or permanently crystallised, 
* American Journal of Scknccy No. 1. p. 89. f Id. No. p. 20^^ 
