48 L. Smith, Esq., on a Comparative Examination 



of the spectrum. But to magnetize them under envelopes of dyed 

 silk is quite a different experiment, and if I do not much mistake, 

 the effect in this case will hinge on the chemical change wrought in 

 the silk and its dye hy the solar rays ; consequently, to repeat the 

 experiments hereafter, it will be necessary to attend to the materials 

 used in the dyeing. 



In concluding this inquiry I may repeat, that I view the nature 

 of the connection between colour and magnetism to be, that there 

 are forces which act in common on the magnetism and the power of 

 the body in transmitting or reflecting light. Faraday and Plucker 

 have previously shewn the intimate connection between the crystalline 

 and the magnetic force ; while the tendency of my experiments has 

 been to shew that the colour, a property much more strongly attached 

 to a body than its crystalline force, is likewise connected with the 

 magnetism. When a number of bodies are grouped together the 

 connection is seen clearly enough ; but when single cases only are ex- 

 amined, apparent contradictions are not unfrequent. This appears 

 to me to indicate that colour and magnetism are mixed up with other 

 qualities derived from the forces of aggregation, together giving the 

 varied properties possessed by the bodies by which we are on every 

 side surrounded, while the further knowledge for the unfolding of 

 these may demand the labour of countless ages to come. 



A Comparative Examination of the Objective Glasses of Micro- 

 scopes^ from Mr Boss of London, Mr Spencer of America, 

 and M, Nachez of Paris. By J. Lawrence Smith, Esq. 



Having had an opportunity a short time since, while at 

 Paris, to examine the comparative merit of the lenses of 

 these makers, it might not be uninteresting to microscopists 

 to know the result of my examination, particularly as it was 

 made under peculiar circumstances — namely, by adapting 

 alternately the objectives to the same mounting, and regard- 

 ing the same object under the same illumination. 



The glasses used were considered by their makers as among 

 their best. That made by Ross was in the possession of M. 

 Rutherford of U. S. Spencer's was owned by Dr Burnet of 

 Boston, and had just been brought by him from Spencer. 

 That of Nachez belonged to Dr Bigelow of Boston, now in 

 Europe, engaged in microscopic research very creditable to 

 himself. Their magnifying powers varied from thirteen 



