of Steel Needle -Points in Aii 



299 



Extrapolating for a distance between the plates of ^ X 10~ 8 , 

 the field between them comes to be 4 x 10 8 . This would induce 

 a still higher charge (8 x 10 -9 ) on a spherical molecule ; but 

 it must be remembered that these data are much further 

 removed from molecular dimensions than mine. 



On the other hand, there is a case accessible of what may 

 perhaps be called discharge between plates, which takes place 

 actually within molecular dimensions : I mean the passage of 

 electricity at the cathode of a voltameter. Here, if a step 

 of potential of, say, 1 volt be assumed, and if/ stand for the 

 corresponding field between the liquid and the metal of the 

 cathode, 



/X \ 10 " 8= 3^0' or /= I X ° 6 E ' S - units - 



This is capable of inducing on a spherical molecule charges 

 of 1*5 x 10~~ n E.S., a number which cannot be distinguished 

 from the ionic charge. Moreover, no reduction is necessary 

 here as the data of calculation are from measurements made 

 direct on single molecules. 



Taking, then, these three calculations together, and having 

 regard to the fact that the nearer the conditions of experiment 

 approach molecular arrangement the closer are the results to 

 the value of the ionic charge, I cannot help thinking that they 

 furnish strong grounds for supposing that electrified atoms in 

 gases are associated with the same quantity of electricity as 

 m electrolysis. 



As regards the third possibility of molecular cohesion (c) 

 mentioned above, that it is due to a combination of (a) and 

 (6), it is impossible, without knowing the relative values of 

 the two forces at work, to get any idea of the atomic charge 

 from the value of/. AH that can be said is that it will be less 

 than the value calculated for atoms held together by electrical 

 attraction only. Even in this case, therefore, there is nothing 

 to negative the presence of ionic charges in gaseous conduction. 



Effect of Pressure. 



§ 7. If the conclusions arrived at above be correct, one 

 may picture a metal point on the verge of discharging as a 

 smooth curved conducting surface studded all over with 

 Grotthuss chains standing up on it like bristles. The density 

 of charge upon it will thus be far from uniform. It will reach 

 a maximum at the root of each chain, the quantity collected 

 there being constant for a given gas, independent of the length 

 of the chain, and equal perhaps to the ionic charge of the gas 

 atoms. In between the chains the density will be much less. 



X2 



