of 'Electricity through Gases. 



195 



hood of his spheres. In the absence of any statement re- 

 garding the thickness of leads, we can attach no importance 

 to Bailie's results as far as his smallest spheres are concerned. 

 When their diameter is only one millimetre, we may take it 

 for granted that the effect of the wires conveying the charge 

 was considerable. 



Paschen has taken this point into consideration, and it 

 follows from the information he gives that with spheres of 

 5 millimetres in diameter and cylindrical leads of about 3 

 millimetres diameter the disturbing effect becomes apparent 

 when the sparking distance is greater than 5 millimetres. 

 The leads cannot be reduced in size beyond a certain point 

 with the usual arrangement of the experiments, as the spheres 

 are moved together by a micrometer arrangement, and must 

 of course be kept rigidly in their place. 



Making full allowance, however, for the possible effects of 

 leads and leakage, I cannot altogether resist the feeling that 

 the ultimate increase of potential with increasing distance is 

 not altogether due to these causes. My chief reason is the 

 good agreement between Paschen and Bailie's results in this 

 respect. 



For spheres having a radius of *5 centim. Bailie finds the 

 minimum of R to take place when the distance is about half- 

 way between *20 and -25 ; while Paschen finds the same dis- 

 tance almost exactly the same, though a trifle nearer to '25. It 

 seems difficult to believe that a disturbing cause should affect 

 both observers in exactly the same manner. For the smaller 

 spheres the distance at which the spark potential is a mini- 

 mum is equal to nearly half the radius of the spheres. This 

 is shown in the following Table : — 



Table VII. 



Radius of spheres. 



Explosive distance for smallest normal force. 



Bailie. 



Paschen. 



centim. 

 3 



1-5 

 10 



•5 



•3 



•25 



•175 



•60 

 •45 



•22 

 •17 



•10 



•42 



•25 



11 



