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 the 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 moisture, 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 prevented from taking fire as soon as it came to the surface by the ingenious 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. Applying metallic magnesium 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 correction of Dalton and Henry's law of absorption of gases in water, experiments 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 performed 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 methods 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 requiring considerable time for its completion, leaves little to be desired in point of accuracy and simplicity of manipulation. He introduced a general method for the separation of the rare earths, by which he for the first 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 manipulative power, and says that, in all the difficulties and perplexities by which 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