122 Professor Julius Wilhelm Brilhl [May 26, 



WEEKLY EVENING MEETING, 



Friday, May 26, 1905. 



His Grace the Duke of Northumberland, K.G. D.C.L. F.R.S., 



President, in the Chair. 



Professor Julius Wilhelm Brijhl, Ph.D. Sc.D. Hon. 3fem. R.I., 

 Professor in the University of Heidelberg. 



The Development of Spectro-Chemistry . 



Associated as I am with Great Britain in my capacity as a Member 

 of the Royal Institntion, it is a special pleasure to me this evening to 

 sketcli to you the development of a branch of scientific study, the 

 early history of which was enacted in this country — a country to 

 w^iich for many years I have been bound by close ties of sympathy. 

 Many of you know already, and the others will see this evening, that 

 I am in especial measure indebted to the science of this country for 

 stimulus and encouragement in my own studies. It is a som*ce of 

 deep satisfaction to me to testify here to the gratitude which I owe 

 to British science. 



I. 



§ 1. Last August it was my privilege to attend the Meeting of 

 the British Association on the classic ground of Cambridge, and one 

 sunny afternoon I found my way into that peculiarly effective example 

 of collegiate architecture, the Chapel of Trinity College. The 

 organ was playing Bach's Passacaglia, and I sat down quietly at the 

 foot of the marble statue which bears the inscription : 



Newton. 

 Qui genus humanum i?igenio superavit. 



The empty chapel was filled with harmony and with memories of 

 the great man who once had sojourned there. And my thoughts 

 wandered back to the past. 



In 1666, almost two-and-a-half centuries ago, Isaac Newton, then 

 a young bachelor, liad decomposed a beam of sunshine, discovered 

 the diverse refrangiljility of the coloured rays, and explained the 

 phenomena of dispersion. 



The founder of scientific optics was also the first to perceive a 

 connexion between difi'erences in the composition of various natural 

 bodies and their power of transmitting light. 



Newton observed that oils, amber, sulphur, and other combustible 

 bodies possess great refractive power, and he made the remarkable 



