244 Magnetic Influence of Solar Light. 



well conducted experiments by MM. Moser and Riess have 

 again involved the whole question in its former obscurity, 

 they having failed completely in producing any change of 

 magnetic intensity in steel needles exposed to the solar 

 rays. The method of observation employed by them was 

 to count the number of oscillations performed in a given 

 time before and after the needle was submitted to the ac- 

 tion of the violet rays. So decisive were their results in 

 indicating the invariable intensity of the needles thus ex- 

 posed, and also so completely did they fail in verifying 

 the results of Baumgartner, formerly alluded to, that they 

 consider themselves entitled to reject wholly a discovery, 

 which for seventeen years has at different times disturbed 

 science. " The small variations," they observe, " which are 

 found in some of our experiments, cannot constitute a real 

 action of the nature of that which was observed by MM. 

 Morenchini, Baumgartner, &c. &c. &c. in so clear and 

 decided a manner." The latest authorities, as for instance 

 Prof. Turner, in the last edition of his Elements of Che- 

 mistry, coincide in this view of MM. Moser and Riess, so 

 that at present the discovery of the magnetic influence of 

 solar light is again considered more than doubtful. 



Such being the present aspect of the question of solar 

 magnetism, it ardently invites to farther enquiry; and as it 

 appeared to me that India offered several important advan- 

 tages for the investigation of such a subject, I resolved to 

 commence a series of experiments upon it, in the hope of 

 obtaining some interesting or decisive results. We have 

 here the command of a solar intensity both of light and 

 heat, far greater than observers in temperate regions can 

 avail themselves of, while the almost uninterrupted clearness 

 of the weather during certain seasons, enables us to pro- 

 secute our experiments from day to day with facility and 

 certainty. At the same time it must be remarked, that advan- 

 tages such as these, are far from being unalloyed, since all ex- 



