LAPLACE 219 



also when very young, to membership of the Academy. 

 During his Hfe, which coincided with France's most change- 

 ful and fateful years, Laplace, who had ambitions in the 

 direction of leading activity in the state, always managed to 

 ingratiate himself with the coming holder of power. Thus 

 his influence increased, independently of the fate of his 

 people, right into his old age. 



Laplace's achievements as a man of science are above all 

 concerned with the first advances towards full understanding 

 of molecular forces in liquids. He is the founder of the 

 theory of capillarity, by which name much more is desig- 

 nated than an understanding and quantitative knowledge of 

 the rise of liquids in narrow tubes, which Leonardo had 

 recognised as of especial interest. To this category, for 

 example, also belongs the formation of drops, indeed every- 

 thing connected with that self-acting assumption of shape 

 which is a peculiarity of liquids, and which is most strikingly 

 shown in the case of small quantities of liquid, where the 

 force of gravity plays a less part, as Galileo also fully recog- 

 nised. Laplace opened the road to an understanding of all 

 these phenomena from the quantitative point of view, by 

 referring them to the attractive forces of the parts (mole- 

 cules) of all bodies, which forces act only over very small dis- 

 tances, and had already been recognised by Newton as dis- 

 tinct from gravitation.^ He thus arrives for the first time at a 

 complete explanation of the inverse proportionality between 

 the capillary rise in tubes and the diameter of the latter, a 

 fact already known from observation on the rise of water, 

 Laplace's explanation depending upon the effect of the 

 molecular forces. Attention had hitherto been diverted 

 from this by Newton's idea of the very small range of 

 action of these forces; but it was only possible to make use of 

 this idea by the application of the greatest mathematical 

 skill, which Laplace possessed, using the infinitesimal 



1 This is to be found in the fourth volume of his Mecanique celeste. 



