of the more refrangible rays of Light. 329 



via, had both failed in obtaining any magnetic effect from vio- 

 let light, and as M. Berard, a most skilful experimenter, had 

 observed only casual indications of magnetism, the discovery 

 of Morichini was brought into considerable discredit, both in 

 France and England. 



Fortunately, however, for the reputation of the Italian 

 physician, his experiments were performed both before Sir 

 Humphry Davy, and Professor Playfair, — before the former 

 in 1814, and before the latter in 1817. Sir Humphry Davy, 

 whom we had the pleasure of meeting at Geneva in 1814, on 

 his return from Italy, mentioned to us that he had paid the 

 most diligent attention to one of Morichini's experiments, and 

 that he saw with his own eyes an unmagnetised needle render- 

 ed distinctly magnetic by violet light. 



When Professor Playfair was at Rome, he saw the experi- 

 ment performed by Dr Carpi, in the absence of Morichini, 

 before a party of English and Italian gentlemen. The fol- 

 lowing account of the experiment was drawn up from a con- 

 versation which the writer of this notice had with that dis- 

 tinguished philosopher, and was afterwards submitted to him 

 -for his approbation. 



" The violet light was obtained in the usual manner, by 

 means of a common prism, and was collected into a focus by 

 a lens of a sufficient size. The needle was made of soft wire, 

 and was found, upon trial, to possess neither polarity nor any 

 power of attracting iron filings. It was fixed horizontally 

 upon a support, by means of wax, and in such a direction as 

 to cut the magnetic meridian at right angles. The focus of 

 violet rays was carried slowly along the needle, proceeding 

 from the centre towards one of the extremities, care being 

 taken never to go back in the same direction, and never to 

 touch the other half of the needle. At the end of half an 

 hour, after the needle was exposed to the action of the violet 

 rays, it was carefully examined, and it had acquired neither 

 polarity, nor any force of attraction ; but after continuing the 

 operation twenty-five minutes longer, when it was taken off 

 and placed on its point, it traversed with great alacrity, and 

 settled in the direction of the magnetical meridian, with the 

 end over which the rays had passed turned towards the north. 



