xliv Annual Report of the Council. 



those who crossed swords with him in scientific controversy 

 found him a strenuous but always courteous opponent. 



Berthelot was elected an honorary member of this Society 

 in 1886. H. B. D. 



Ludwig Boltzmann was born at Vienna in 1844. He 

 studied at the University there under Stefan, and afterwards for 

 short periods at Heidelberg and Berlin, under Helmholtz and 

 Kirch hoff. He was called in succession to professorships of 

 mathematics or of theoretical physics at Graz (twice), Vienna 

 (twice), Munich, and Leipzig. He died on September 3rd, 

 1906. He had long been recognised as one of the leading 

 mathematical physicists of his time ; he was a foreign member 

 of the Royal Society, and had been an Honorary Member of 

 our own Society since 1892. 



Boltzmann's work bore mainly on the dynamical theory of 

 gases, and on electromagnetic theory. Although the inspiration, 

 always generously acknowledged, was in both cases derived from 

 Maxwell, the subsequent development was thoroughly inde- 

 pendent, and highly original. One result to which he was led 

 in the theory of gases, and which now goes by the name of 

 " Boltzmann's Theorem," excited the keenest interest and 

 admiration in Maxwell himself. Owing to the subtlety of the 

 reasoning on which it is based, and to its apparent inconsistency 

 with known numerical properties of various gases, it has been 

 the subject of a prolonged controversy, which is even yet, 

 perhaps, hardly completely determined. His earliest achieve- 

 ments in the field of electricity were the experimental deter- 

 mination of the dielectric capacities of various gases, and of 

 crystalline sulphur in various directions. Both investigations 

 were interesting and important as verifying the theoretical views 

 of Maxwell. At a later period he was occupied with the law 

 of radiation. 



Besides his scientific papers, Boltzmann published several 

 treatises. One of these was a course of lectures on Maxwell's 

 theory of electricity, designed to render the leading ideas of that 



