492 Albert P. Mathews 



that the range of the cohesive forces is necessarily of the 

 order T/K." T is the surface tension and K the internal 

 pressure. Lord Rayleigh, in his revision of Maxwell's classical 

 account of capillarity in the new edition of the Encyclopaedia 

 Britannica and in his many splendid writings on this subject, 

 does not seem to have considered this question. All other 

 writers whom I have consulted seem to have followed Laplace's 

 lead and assumed, without evidence, that cohesion does 

 penetrate matter like gravitation. 



Thus, Gauss, 1 who introduced clear ideas of surface 

 energy and the potential energy of fluids, writes as follows 

 in 1830: "The ordinary attraction which is proportional 

 to the square of the distance, and which permits the repre- 

 sentation of all motions in the heavens with such good agree- 

 ment, can be used in the explanation neither of capillary 

 phenomena nor of adhesion and cohesion; a correctly carried 

 out computation shows ' dass eine nach diesem Gesetze wirk- 

 ende Anziehung eines beliebigen Korpers der zur Ausfuhrung 

 von Experimenten geeignet ist, d. h., dessen Masse im Ver- 

 gleich mit der der Erde vernachlassigt werden kann, auf 

 einem beliebig gelegenen, sogar den Korper beriihrenden 

 Punkt, im Vergleich mit der Schwere verschwinden muss. 

 Wir schliessen hieraus dass jenes Anziehungsgesetz in den 

 kleinsten Abstanden mit der Wahrheit nicht mehr iiberein- 

 stimmt, sondern dass es eine Modification erfordert. ' In 

 other words, the particles of the body exert, besides the at- 

 tractive force of gravitations, still another force which is notice- 

 able only , in the smallest distances. All appearances show 

 uniformly that the second part of the attractive force (the 

 molecular attraction) is not noticeable in the smallest meas- 

 urable distances. On the other hand, in unmeasurably small 

 distances it may greatly surpass the first, which is propor- 

 tioned to the square of the distance. 



1 Gauss: "Allgemeine Grundlagen einer Theorie der Gestalt von Fliis- 

 sigkeiten," Ostwald's "Klassiker der exakten Wissenschaften," No. 135, p. i. 

 "Commentationes societatis Regiae Scientiarium Gottingensis Recentiores," vii, 

 1830. 



