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As a final study three mg. of radium bromide were placed beneath the 
points, in an attempt to change the form of discharge, as described by 
A. E. Garrett®, for discharges between blunted wires. The radium, which 
was contained in an unstoppered glass tube, was held by an ebonite rod so 
that both « and ? particles might reach the air in the path of discharge. 
No effect was observed except that which could be produced by a glass rod 
in the same position. 
SUMMARY OF RESULTS. 
A summary of the results, as given in this and the previous report, is: 
(1) The positive stream between the points for a spark or brush 
discharge was deflected by a magnetic field as low as 1,000 gausses, and 
both positive and negative streams for glow, spark and brush discharge 
were deflected by a magnetic field of 6.400 gausses. In all cases the 
direction of deflection was in accordance with electro-dynamical laws. 
(2) In most cases a change of type of discharge, and an increase of 
potential between the points was caused by excitation of the magnet. 
(3) The direction of the photographed stream for a spark discharge 
as it leaves the point is the same as the visible direction of the spark. 
(4) The size of the stream at the points (measured with a microm- 
eter microscope between the outer edges of the central dark band) is 
independent of the potential between the points. 
(5) The stream was deflected by an air current, the negative being 
deflected more than the positive. 
(6) The stream for the richer spark (i. e., for the higher speeds of 
the machine) increased in width as the distance from the point increased, 
while the stream for the glow discharge retained its original size as far as 
it could be traced. 
(7) The stream was deflected by an electrostatic field, in which case 
it was shorter and more scattered than in case of the magnetic deflection. 
(8) Values for the speed of the ion were calculated from the angle 
of deflection, in magnetic and electrostatic fields, and by placing the two 
fields in opposition. The average of these was 1.6x10*° cm. per second. 
(9) From the kinetic energy of the moving ion and the product of 
e 
the potential between the points and the charge on the ion values for —— 
m 
are calculated, the average value found being 1.8x10"*. 
6A. EH. Garrett, B. Se—The Phys. Soc. of London Proceedings, Dec. 1909, 
page 643. 
