HELMHOLTZ IN KONIGSBERG 



lished paper of Maxwell was a letter to Dr George 

 Wilson, to be found in the Transactions of the Royal 

 Society of Arts for 1855, but he had before this date 

 been experimenting with his well-known colour top, 

 and the results of his experiments are recorded in 

 the Transactions of the Royal Society of Edinburgh, 

 vol. xxi., p. 185. As already mentioned, in 1852, 

 Helmholtz published his first paper. 



To appreciate the work of these distinguished 

 men, and more especially the part taken by Helm- 

 holtz in placing the theory of colour on a sound 

 basis, let us go back for a little to fundamental 

 ideas regarding light, gradually accumulated before 

 they appeared on the scene. It was once held 

 that a luminous body shoots out from itself minute 

 particles, which, passing to the observer's eye, give 

 rise upon impact to the sensation of light. This 

 corpuscular theory, while it satisfactorily explained 

 many of the facts, failed in an explanation of others, 

 and it has now been entirely disproved. Its place is 

 taken by the undulatory theory, first suggested by 

 Huygens in 1690, reconciled to some extent with the 

 discoveries of Newton by Euler, advocated by Hartley, 

 and finally established by a study of the phenomena of 

 interference by Thomas Young and by Fresnel. This 

 theory gives a complete explanation of all the pheno- 

 mena of light. According to this view, light, objec- 

 tively considered, is simply a mode of motion of a 

 substance called the luminiferous ether which pervades 

 H 



