474 Mr. A. P. Chattock on an 



discrepancy is far greater: K= 1-00054, M = l'l x 10 6 , and 

 <i-=5*3 xl0~ 8 , 



? = 8xl0~ 15 . 



The following considerations, however, seem to me to show 

 that these results are just wdiat they should be, on the view of 

 initially charged particles. According to that view, the 

 oppositely charged particles tend to pair more and more as 

 the temperature rises. When the pairing has gone on to a 

 certain extent the body becomes liquid (provided, of course, 

 the critical pressure is not overstepped), the bonds holding 

 the paired particles together having been strengthened at the 

 expense of the others to such an extent that the latter are no 

 longer capable of holding the particles in relatively fixed 

 positions. At a still higher temperature they have become so 

 weakened that the paired particles fly off in the form of 

 vapour. 



Now- Young's Modulus expresses the difficulty experienced 

 in bringing the particles of a body nearer together. When a 

 body is compressed it yields chiefly at those places where the 

 particles are furthest apart. Hence, in the case of a body 

 composed of partially paired particles, the yielding will chiefly 

 occur where the pairing is least, i. e. betw r een the particles B 

 and C, D and E, &c. in fig. 1. The same is of course true of 

 tension. 



When, however, the body is strained electrically the case is 

 different. The electrostatic field takes hold, as it were, of all 

 the + charges throughout the dielectric, and urges them past 

 all the — charges, which it pulls in the opposite direction. 

 The resistance to this straining will obviously depend prin- 

 cipally on the firmness with which the paired particles hold 

 together. It will be determined, therefore, by the forces 

 between the particles A and B, C and D, &c, and will 

 consequently be greater than M. 



From this it follows that as the particles become more and 

 more paired (i. <?., as they pass from the solid to the gaseous 

 condition) M will get less and less, as it is known to do, wdiile 

 the resistance to electrical strain will probably not differ much 

 from the value it possessed in the solid state. And, in fact, if 

 for M in the above three cases of fluids we substitute the value 

 2 x 10 12 , which is fairly representative of M for the most 

 elastic solids (it is necessary to take a high value, since, 

 by what has just been said, low elasticity only applies to 

 mechanical strain in bodies where pairing is pronounced), 

 we obtain for q : — 



