262 



It seems probable tbat the speed of the ion might be calculated from 

 the relative deflection of a similar form of discharge under influence of the 

 magnetic and electrostatic fields separateh\ The distance between the 

 points was the same in both cases and therefore the potential at the points 

 would, no doubt, remain of the same order, even though there was some 

 change. On the photographs a line may be drawn directly between the 

 points, and a second line drawn through the exti-emity of the negative 

 electrode perpendicular to the first line. If then a third line is drawn 

 from the positive point in the direction of the deflected stream and extended 

 to meet the sec-ond line, the distance to the intercept of the second and third 

 lines from the extremity of the negative electrode should be propoi'tional 

 to the deflection. Taking the distance to this intersection for the upward 

 deflec'tion. we have : 



He V ^ K tan G:, in case of the magnetic effect where H is the magnetic 

 field strength in gausses, e the charge on the ion, v the speed of the ion, 

 01 the angle of deflection, and K is a constant which depends on the poten- 

 tial drop along the path of discharge. 



In case of the electrostatic deflection, X e ^ K tan 02 where X is the 

 potential gradient between the electrostatic plates and 02 the angle of 

 deflection. 



Solving each equation for K we have 



Hev Xe 



K 



tan0], tan02 

 If the hi and h^ are the distances from the negative point to the inter- 

 cept in the two cases, and 1 the distance between the points, we have 



Hvh, Xhi hjX 



(Hv tan 02 ^ X tan 0i) , = , and v = 



1 1 h^H 



Since the discharge does not always pass directly between the points 

 when no transverse field exists, it would probably be more accurate to take 

 the average value of h for the upward and downward deflection. Making 



