552 THE POPULAR SCIENCE MONTHLY. 



geysers. The memoirs which he published on the subjects of these 

 studies contain the analyses of the volcanic rocks occurring in the 

 island, which led him to the theory that all the eruptive rocks that 

 reach tlie surface consist either of an acid or a basic silicate, or a 

 mixture of the two, that has been formed and crystallized within the 

 interior of the earth. Other papers relate to the formation of various 

 crystalline minerals by the joint action of heat, acid gases, and moist- 

 ure, on the rocks, and the theory of the geysers. 



With the aid of his battery, Bunsen performed the electrolysis of 

 some of the rarer metals. He began with magnesium, which he pre- 

 vented from taking fire as soon as it came to the surface by the ingen- 

 ious device of catching the metal as it rose in a cup, which he formed 

 in his carbon pole for the purpose, while it was still under the salt. 

 He then proceeded to the reduction, in conjunction with the late Dr. 

 Matthiessen, of the alkaline-earth metals, and, with Hillebrand and 

 Norton, of the metals of the cerium group. Apj^lying metallic mag- 

 nesium in photo-chemical researches and in comparison of the light of 

 its flame with that of the sun, he gave the impulse which induced the 

 undertaking of the commercial preparation of the metal. 



Other researches, with which his name is connected, are those of 

 Kolbe on the electrolysis of the fatty acids, of Kolbe and Frankland 

 on the isolation of the organic radicals, the explanation of a new 

 method of determining vapor densities, the investigation and correc- 

 tion of Dalton and Henry's law of absorption of gases in water, experi- 

 ments on laws of gaseous diffusion, on applications of gaseous diffusion 

 in gasometric analysis, on the phenomena of the combustion of gases, 

 and on the temperature of ignition of gases ; all of which were per- 

 formed by himself or his pupils, or both. 



In analytical chemistry Bunsen has contributed something valuable 

 to the solution of nearly every important problem, and the best meth- 

 ods in complicated laboratory processes like those of the analysis of 

 silicates and mineral waters, methods for the estimation of nitrogen 

 and sulphur, and a method of volumetric analysis, which, though re- 

 quiring considerable time for its completion, leaves little to be desired 

 in point of accuracy and simj^licity of manipulation. He introduced a 

 general method for the separation of the rare earths, by which he for 

 the lirst time prepared pure yttria and erbia, and by which several 

 new metals have been discovered by other chemists. 



In connection with his investigations on the measurements of the 

 chemical action of light. Professor Roscoe, who was associated with 

 him, speaks admiringly of his untiring energy and wonderful manipu- 

 lative power, and says that, in all the difficulties and perplexities by 

 Avhich the experimental investigation of such a subject is beset, he 

 never .knew Bunsen discouraged, or at a loss for an expedient by which 

 an obstacle could be overcome. "Cheerful and self-reliant under the 

 most depressing circumstances, he never gave up hope, and thus it was 



