MM. Reiss and Moser 07i the Magnetic Influence^ ^c. S25 



thorina are decomposed by a red heat, and leave the earth in 

 an isolated state, and they lose their acids more easily than 

 zirconia. 



Art. VI. — On the Magnetic Influence of the Solar Rays. By 

 MM. P. RiEss and L. Moser. 



The observations of Mrs Somerville, (published in this Jour- 

 nal, No. viii. p. 328,) tended to confirm the magnetic influence 

 of the violet rays. This action, discovered by M. Morichini 

 at Rome, and described by him a long time ago, had been 

 called in question by the natural philosophers of France, Ger- 

 many, and Italy. Yet the favourable result to which Mrs 

 Somerville had arrived, seemed to have so completely dissipated 

 these uncertainties, that, upon that discovery, various theories 

 have been started respecting the magnetism of the earth and 

 its annual and diurnal variation. It cannot be concealed, that 

 the magnetic action of the sun does not afford an easy expla- 

 nation of them. The labours of Baumgartner on the same 

 subject, — the observations of Mr Christie on the diminution of 

 the amplitudes of a needle osclllaling in the solar rays, which 

 seem to connect the magnetic action of the sun with a recent 

 discovery, — and, finally, an experiment of M. Zantedeschi at 

 Pavia, about to be published, have induced us to communi- 

 cate the results and researches which we have undertaken, to 

 illustrate so important a point. 



In limiting ourselves to a minute repetition of the methods 

 described by M. Morichini and his successors as the most fa- 

 vourable, we have, however, abandoned the methods which 

 they employed for appreciating the magnetic state of the 

 needles, and for measuring its intensity ; for anterior trials 

 had assured us that they were subject to errors almost una- 

 voidable. The most certain method of judging of the mag- 

 netism of a needle consists in making it oscillate ; and this is 

 the method which we have employed. The needles were of 

 soft steel. Their mass was very small, but they presented a 

 considerable surface to the action of the light. We were sa- 

 tisfied of the primitive state of these needles, as far as their 



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