298 Mr, A. P. Chattock on the Electrification 



values might thus be calculated in terms of/ if the geome- 

 trical conditions were known. This, however, is not the case 

 under the conditions of actual experiment ; but by arranging 

 that the chains shall consist of single molecules only, it is 

 possible to get an idea of the magnitude of the charge in 

 question. Reduce in imagination the discharging-point to 

 molecular dimensions ; and find, by what is rather violent 

 extrapolation, the corresponding value of/ at discharge from 

 the constant in Table II. The Grotthuss chains will have 

 been reduced to single molecules by the reduction of the 

 point, and by supposing them to be spheres the + and — 

 charges induced on their opposite sides may be calculated. 

 These charges will then represent in the case of (a) half, and 

 in the case of (b) the whole of the atomic charge. 



Taking the diameter of a molecule as ^ x 10~ 8 centim^ the 



value of/ at the centre of a molecule opposite the point is 

 (from Table II.) 



/= ip x (£ 10- 8 J =3-1 x 10 7 E.S. units, 



which will induce on a conducting sphere of the same dimen- 

 sions equal and opposite charges of 



Iff 10 " 8 )/= 6 x 10 ~ 10 E - S - units - 



This number is greater than the atomic charge (or than half 

 the atomic charge) because it is calculated from measurements 

 on chains of many molecules, which, as was pointed out above, 

 are not conductors, but only lines of high S.I.O. Now the 

 most probable value of the ionic charge of oxygen is 10~ n , 

 which, considering the extent of the extrapolation and the fact 

 that the above number is too great, is in sufficiently striking- 

 agreement with it. It is at any rate satisfactory that the ex- 

 perimental number is the larger of the two. 



It is interesting to see whether a similar result is to be got 

 from measurements of sparks between plates. Taking Dr. 

 Liebig's numbers above referred to, I find, following Prof. 



J. J. Thomson, that the formula /= j + 150 expresses the 



results for the smallest spark-lengths in air fairly well, con- 

 sidering that the numbers for that part of the curve are rather 

 irregular. The values of a lie between 1*9 and 1*4 for the 

 five smallest spark-lengths (I =0*0066 to 0*0245 centim.). 



