SKETCH OF ROBERT WILHELM BUN SEN. 553 



that these somewhat intricate and difficult investigations were brought 

 to a successful close." 



Perhaps none of his labors are more distinguished than the experi- 

 ments with which he and Kirchhoff laid the foundation of the new 

 science of spectrum analysis. Among his own most important trans- 

 actions in this work was the discovery, by means of the spectrum 

 lines, of the metals caesium and rubidium. He first saw the caesium 

 lines, says Professor Roscoe, in a few milligrammes of the alkaline resi- 

 due obtained in an analysis of the Diirkheim mineral waters, and the 

 discovery of a second new metal (rubidium) soon followed that of the 

 first. " So certain was he of the truth of his spectroscopic test, that he 

 at once set to work to evaporate forty tons of the water, and with 16*5 

 grammes of the mixed chlorides of the two new metals which he thus 

 obtained he separated the one metal from the other (no easy task) and 

 worked out completely their chemical relationship and analogies ; so 

 much so, that the labors of subsequent experimenters have done little 

 more than confirm and extend his observations." Another research in 

 this direction was that on the spark spectra of the metals contained in 

 cerite and other rare minerals, which he carefully mapped in such a 

 manner as to make the sej^aration and identification possible. 



Bunsen's name is identified with two instruments which he has 

 devised, which have come into general use in science and the arts ; the 

 Bunsen gas-burner, which is almost indispensable in laboratories and in 

 many processes of manufacturing, and is used in many households ; 

 and the Bunsen pump for accelerating filtration, which those who em- 

 ploy it could likewise hardly do without. 



His published writings are many. Most "of them are special papers 

 relating to the subjects of investigation that have been already men- 

 tioned ; others embody more general results of his studies. His visit to 

 Iceland gave rise to several papers on the various physical, geological, 

 and volcanic phenomena of the island ; his studies in metals to a num- 

 ber of monographs ; his spectroscopic studies to " Chemical Analy- 

 sis based on Observations of the Spectrum," published by him and 

 Kirchhoff. Besides these, we may mention "Researches on Chemical 

 Affinity " ; " On a New Volumetric Method " ; and " A Treatise on Gas 

 Analysis." 



Concluding his notice in " Nature," from which we have drawn 

 liberally in the preparation of this article. Professor Roscoe says : 

 " The many hundreds of pupils who, during the last half-century, have 

 been benefited by personal contact with Bunsen will all agree that as 

 a teacher he is -without an equal. Those who enjoy his private friend- 

 ship regard him with still warmer feelings of affectionate reverence. 

 All feel that to have known Bunsen is to have known one of the truest 

 and noblest -hearted of men." 



