Magnetic Influence of Solar Light. 



369 



The earlier experiments under this section, were the first 

 of the entire series, and the method of observation employed 

 by me throughout them, was the same I believe as that of 

 Mrs. Somerville. This remark is however made with some 

 reservation^ in consequence of my having been unable to 

 procure any detailed account of this lady's experiments, but 

 there is still sufficient in the brief and imperfect notices I 

 have had the opportunity of examining, to make me feel 

 tolerably certain on the point. Half of each experimental 

 needle employed was covered with several folds of thin 

 (quarter-tola) paper, and then exposed on a proper support 

 to the influence of the sun's light transmitted through the 

 medium employed. After exposure, the needle was remov- 

 ed to a room, and being there delicately suspended, a small 

 compass needle was carefully and gradually approximated 

 to it, and the nature of the action between the rwo observed. 

 To this mode of observation there are, in my opinion, in- 

 superable objections, but as these developed themselves only 

 in consequence of the experiments to be detailed, I shall 

 reserve all remarks upon this point until these details have 

 been given 3 since the reality of my objections will then be 

 much more readily felt and admitted. 



tion of the question of solar magnetism, and I will return to the subject 

 on the earliest opportunity. In ignorance of what may occur in the 

 interval, I will not however detain the third section by me, until such 

 an opportunity presents itself, lest I should be disappointed alto- 

 gether.— R. B, S. 



Aug. 4th, 1842. — Since the above note was written I have had the 

 pleasure, through the active kindness of my friend Mr. M'Clelland, of 

 receiving all the apparatus necessary for the composition of the second 

 series of these experiments. To the characteristic liberality of J. W. 

 Grant, Esq. C. S. (in this instance, the more grateful as shewn towards 

 a total stranger), I have been indebted for an excellent prism, well 

 adapted to my objects. The acceptable gift reached me however, only 

 the day before the rainy season regularly set in, and I have of course 

 been unable to bring it into use as yet. Unless circumstances should 

 interfere, the second section will be undertaken at the commencement 

 of the cold weather. 



3 B 



