76 Royal Society : — Anniversary Address of the President : 



lished during the last thirty years of his life, made this department 

 of mathematical science, and more particularly whatever related to 

 the action of molecular forces, pre-eminently his own. They compre- 

 hend the theory of waves and of the vibrations of elastic substances, 

 the laws of the distribution of electricity and magnetism, the pro- 

 pagation of heat, the theory of capillary attraction, the attraction 

 of spheroids, the local magnetic attraction of ships, important pro- 

 blems on chances, and a multitude of other subjects, which the 

 time allowed for this notice will not permit me to mention. His 

 well-known treatise on Mechanics is incomparably superior to every 

 similar publication in the clear and decided exposition of principles 

 and methods, and in the happy and luminous combination of the 

 most general theories with their particular and most instructive ap- 

 plications. 



Poisson was not a philosopher who courted the credit of propound- 

 ing original views which did not arise naturally out of the immediate 

 subjects of his researches ; and he was more disposed to extend and 

 perfect the application of known methods of analysis to important 

 physical problems, than to indulge in speculations on the inven- 

 tion or transformation of formulae, which, however new and elegant, 

 appeared to give him no obvious increase of mathematical power in 

 the prosecution of his inquiries. His delight was to grapple with 

 difficulties which had embarrassed the greatest of his predecessors, 

 and to bring to bear upon them those vast resources of analysis, and 

 those clear views of mechanical and physical principles in their most 

 refined and difficult applications, which have secured him the most 

 brilliant triumphs in nearly every department of physical science. 



The confidence which he was accustomed to feel in the results of 

 his analysis — the natural result of his own clear perception of the 

 necessary dependence of the several steps by which they were de- 

 duced — led him sometimes to accept conclusions of a somewhat 

 startling character : such were his views of the constitution and finite 

 extent of tiie earth's atmosphere, which some distinguished philoso- 

 phers have ventured to defend*. It is not in mathematical reason- 

 ings only that we are sometimes disposed to forget that the conclu- 

 sions which we make general are not dependent upon our assumed 

 premises alone, but are modified by concurrent or collateral causes, 

 which neither our analysis nor our reasonings are competent to 

 comprehend. 



The habits of life of this great mathematician were of the 

 most simple and laborious kind ; though he never missed a meet- 

 ing of the Institute, or a lecture, or an examination, or any other 

 public engagement, yet on all other occasions, at least in his later 

 years, he denied access to all visitors, and remained in his study 

 from an early hour in the morning until six o'clock at night, when 

 he joined his family at dinner, and spent the evening in social con- 

 verse, or in amusements of the lightest and least absorbing ciiarac- 

 ter, carefully avoiding eveiy topic which might recall the severity of 



[• Noticed by Mr. (now Sir John W.) Lubbock, in L. E. & D. Phil. Mag. 

 vol. xvii. p. 469. — Edit.] 



