of the more refrangible rays of Light. 331 



Mrs Somerville now applied the same method to pieces of 

 clock and watch springs, about \\ inches long, and from \ to 

 \ of an inch broad,* and they were found to receive a strong- 

 er degree of magnetism from the violet rays, an effect which 

 was attributed to their blue colour, and their greater extent of 

 surface. Bodkins were not affected. When the violet ray 

 was concentrated by a lens, the magnetic influence was impart- 

 ed to the needles in a shorter time. 



In order to give additional confirmation to these results, Mrs 

 Somerville exposed magnetised needles, half covered as former- 

 ly, to the sun's rays transmitted thi-ough glass coloured blue 

 by cobalt, and they were distinctly magnetised as before. 

 Needles exposed under green glass received the same property. 



Mrs Somerville now inclosed unmagnetised needles in pieces 

 of blue and green ribband, one half of each being covered 

 with paper, and after they had hung a day in the sun's rays 

 behind a pane of glass, they had acquired magnetic polarity, 

 the exposed ends being north poles, as in the former experi- 

 ments. When red, orange, or yellow ribband was used, no 

 magnetic influence was imparted. 



In performing these experiments, Mrs Somerville found 

 that the most favourable time of the day was from ten to one 

 o'clock ; and that, as the season advanced, the magnetism ac- 

 quired was less permanent, as the needle required a longer ex- 

 posure to acquire the same degree of magnetic virtue. 



Although Mrs Somerville has thus established a most 

 important fact in science, yet the subject is by no means ex- 

 hausted ; and we would recommend to her attention the zeal- 

 ous prosecution of it, in reference to the examination of the 

 other physical properties of the solar spectrum. 



More than twelve years ago, Dr Brewster communicated to 

 the Royal Society of Edinburgh a paper, in which he endea- 

 voured to show, that there existed visible rays beyond the 

 spectrum, and possessing a high degree of refrangibility ; and 

 that each homogeneous colour of the spectrum was accompani- 

 ed with rays of greater refrangibility. This increased refrangi- 

 bility was ascribed to a change produced upon the light by 



* When these possessed any magnetism, it was removed l>y beating. 



