444 Sir Henry Boscoe [June 1, 



the changes which these gases effect on the volcanic rocks with which 

 they come into contact. Eleven more days were given to the investi- 

 gation of the phenomena of the geysers, and at the end of August 

 Bunsen left the island, having in the short space of ahout three 

 months collected a mass of material the working up of which, as he 

 writes to Berzelius, "will tax all my energies for some length of 

 time"— a prediction which was subsequently fully realised. 



To enlarge upon this research is beyond the province of the 

 present discourse. Suffice it to say that Bunsen's original investigation 

 lies at the foundation of modern petrology, and has opened out an 

 unbounded field for research, the cultivation of which has already 

 yielded great results and will in future yield still greater ones. 

 Tyndall's remarkable experimental illustration of Bunsen's geyser 

 theory will be remembered by many of the older members of this 

 Institution. 



Of all Bunsen's researches the one which will undoubtedly stand 

 out pre-eminent as time rolls on is that on spectrum analysis. The 

 most important discovery made by Bunsen during the short duration 

 of his residence in Breslau was, as I have said, the discovery of 

 Kirchhoff, who was then Professor of Physics in that University, and 

 whose great ability the elder man at once recognised. No sooner had 

 Jolly removed to Munich, in 1854, than Bunsen took care that Kirch- 

 hoff should be his successor in the Heidelberg Chair of Physics. 

 And thus came about that great twin research which has made the 

 name of these men known through the wide world. To dilate upon 

 the importance of the discovery is unnecessary ; to follow out the 

 growth of this branch of science in its height and depth and breadth 

 is here impossible. All that is now possible is to remind you of 

 Kirchhoff 's great discovery — namely, the full explanation of Fraun- 

 hofer's lines in the solar spectrum, pointing the way to a knowledge 

 of the chemical composition of the sun and fixed stars — and that of 

 Bunsen's application of the principles of spectrum analysis to the 

 examination of terrestrial matter. 



On March 1, 1861, I had the honour of bringing before a Royal 

 Institution audience the results of these discoveries — viz., those of 

 Kirchhoff and Bunsen, made in the autumn of 1859 ; those of Bunsen, 

 in 1860 and 1861. In that discourse I gave an account of the two 

 new metals caesium and rubidium. I ventured to say whilst these 

 researches were in their earliest infancy, that the dawn of a new 

 stellar and terrestrial chemistry had been announced, thus opening 

 out for investigation a bright prospect of vast fields of unexplored 

 truth. And the subsequent work of forty years, and of many investi- 

 gators, has not falsified this prediction. 



In a letter to me dated April 10, 1860, Bunsen writes as 

 follows : — 



" Do not be annoyed with me, dear Boscoe, that I have done nothing 

 with our light investigation. I have left everything untouched, be- 

 cause 1 have obtained full certainty, by means of spectrum analysis, 



