Electrolytic Theory of Dielectrics. 477 



more directly to each molecule, without depending so much 

 on the positions of its neighbours, and is therefore more 

 constant in amount. Hence, owing to both these causes, the 

 above value of g is too large. 



The source of error discussed above under specific inductive 

 capacity, which is due to the resistance of a body to electrical 

 stress being greater than that to mechanical stress on account 

 of pairing, is as negligible here for solids as it probably was 

 there. Indeed, even in the case of liquids it is not nearly so 

 important a factor in the calculation as before ; for the true 

 value of T (for electrical stress) is also affected by the same 

 cause, and it is the ratio of M to T which enters into the 



expression for q ; and, in fact, if instead of the ratio -=, we 



write the ratio of the volume of a liquid to the change of its 

 volume when strained to the breaking-point under tension, 

 not only does this source of error become negligible, but the 

 one which depends on the fact that M is less than M disappears 



M 



altogether. For the above ratio and -^ are by definition the 



same. There are, however, two minor sources of error still 

 remaining in the case of liquids. One arises from the experi- 

 mental difficulty of ascertaining the maximum extension that 

 a pure liquid will bear without breaking ; the measured 

 values being almost certainly too low in consequence of 

 foreign matter in solution. The other is due to the fact that 

 the molecules of a liquid are able to move about among them- 

 selves. This property will enable them, when the field of 

 force is very strong (as it is just before disruption occurs) to 

 fall into line with it and form chains — a tendency which must 

 also exist in solids, but is probably almost unsatisfied on 

 account of their rigidity. Now a chain of alternately oppo- 

 sitely electrified molecules is a line of high specific inductive 

 capacity, and the formation of a large number of such lines 

 through the liquid may easily raise the value of K by an 

 appreciable though unknown amount. Hence, as these two 

 remaining sources of uncertainty tend to compensate, and it 

 is impossible to say which will preponderate, it will be fairer 

 to substitute the sign £ for < in the equation of q for 

 liquids. 



A few experiments on sparks in liquids, due to a very 

 sudden rise of potential between platinum electrodes, are in 

 fair agreement with the formula when viewed in the light of 

 the above. 



Phil. Mag. S. 5. Vol. 34. No. 211. Dec. 1892. 2 L 



