It seems probable that 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 separately. 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 extremity 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 second line, the distance to the intercept of the second and third 
lines from the extremity of the negative electrode should be proportional 
to the defiection. Taking the distance to this intersection for the upward 
deflection, we have: 
2 
H ev Xe 
Hev = K tan 0), 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, 
8; 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@, where X is the 
potential gradient between the electrostatic plates and 62 the angle of 
deflection. 
Solving each equation for K we have 
Hev Xe 
e—— = —- 
tan91, tan92 
If the h, and h, are the distances from the negative point to the inter- 
cept in the two cases, and | the distance between the points, we have 
Hvh, Xh, h,X 
—- = —, andy = 
l ] Jayog sb 
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 
(Hv tan 02 = X tan 91), 
