The equation 



Molecular Attraction. 635 



L-E e 



= constant, 



and the above statement, are true, because the molecular 

 attraction varies inversely as the square of the distance apart 

 of the attracting particles and because the total amount of 

 attractive force possessed by a molecule is a constant. 



The author believes that the above statement and italicized 

 sentences express the physical reality represented by the 

 equation under discussion, 



\ = l x'CVd- VB). 



The true nature of the attractive forces is a subject which I 

 will not attempt to discuss in the present paper. 



Regarding the errors cited by Mr. Sutherland contained 

 in the earlier papers, I would say that I have never supposed 

 the molecular cohesive force and the attraction of gravitation 

 to be identical in the sense attributed to me by Mr. Sutherland. 

 In the first paper, p. 230, I state in italics, " the molecular 

 attraction appears to resemble the attraction of gravitation in 

 that it varies inversely as the square of the distance apart of 

 the attracting molecules and does not vary with the temperature. 

 It differs from the attraction of gravity in being determined 

 primarily by the construction of the molecule and not by its 

 mass. ,J I have never receded from the above view, and by 

 the statements made in the second and fifth papers, that the 

 molecular force obeyed the law of gravitation, I did not 

 intend to imply that the constant factor of the force was 

 identical in the two cases. 1 still believe that all attractive 

 forces may be identical in origin and character and obey the 

 same general law, but of course the constant factors of the 

 forces, in the usual sense of that term, are totally different. 

 The statements as I made them w T ere misleading, I admit. 



I did not at first understand the fact that the law of 

 gravitation extended to the molecular attractive force, made 

 the heat of vaporization vary, not as the mass, but as the 

 5/3 power of the mass. A realization of this fact and its 

 consequences caused me to publish, in the sixth paper already 

 cited (1907), a full discussion of the derivation of the 

 equation under discussion, and to express a belief which I 

 had long held, namely, that the numerator factor of Newton's 

 law of gravitation needed modification. A further statement 

 of my views upon this subject will shortly be published. 



Camden, S. C. 

 June 7th, 1910. 



