Prof. Norton on Molecular Physics. 283 



should. In this second problem a nearer approach is made to 

 a definite algebraic solution than in the other ; but as the rela- 

 tion between x and y is not deducible by integration from that 

 between s andy, the value of y as a function of x can only be 

 obtained in a series which is not a development of a definite al- 

 gebraic expression. 



Cambridge, September 18, 1866. 



XXXVI. On Molecular Physics. By Prof. W. A. Norton. 



[Concluded from p. 212.] 

 Chemical Action. 



THE general nature of the process of combination of two dissi- 

 milar molecules has already been considered (vol. xxx. p. 109). 

 We must now contemplate it more in detail, and take note of 

 certain distinctions and possible differences of result. We have 

 seen that two dissimilar molecules have an affinity for each other 

 when their unequal molecular forces are so related that under 

 their mutual action the atmospheres become polarized — that is, 

 the electric sether accumulates upon one of the two contiguous 

 sides, and is partly expelled from the other, so that the former 

 will be positive and the latter negative. The attraction that 

 results from this disturbance of the electric equilibrium consti- 

 tutes, as we conceive, the proper force of affinity or chemical at- 

 traction. It ordinarily comes into operation beyond the outer limit 

 of the molecular attraction proper (i. e. beyond c, fig. 1, p. 203, 

 vol. xxviii.), and draws the particles nearer together until they 

 come within the range of this attraction, which then determines 

 their complete and permanent union. The force of electrical 

 attraction or affinity thus brought into play should ultimately 

 diminish, if not pass off entirely, by reason of the electric dis- 

 charge that would ensue between the particles. Heat or the 

 electric spark may increase the natural force of affinity by aug- 

 menting the natural polarization that the molecular forces may 

 have initiated. Ln fact all the various circumstances upon 

 which the union of two dissimilar molecules depends are but 

 so many different circumstances under which the molecules 

 become polarized by their natural mutual action more or less 

 modified. 



We have seen (vol. xxx. p. 99) that a compound molecule, when 

 formed, becomes invested with its own proper atmosphere, and 

 so comes into special relations with other molecules, whether 

 simple or compound, similar or dissimilar. The density and 

 extent of such an atmosphere may vary widely with the degree 



