182 Mr Wilson , On the Magnetic Deflection of Cathode Rays. 
Metal forming 
Cathode 
Atomic 
weight 
Deflection 
(d) 
Spark 
length 
Potential 
Difference 
(V) 
djV 
Aluminium 
27 
mms. 
23 
mms. 
2-0 
28-0 
122 
Iron 
56 
20 
2*5 
33-4 
116 
Copper 
63-6 
18 
3 0 
39-0 
113 
Zinc 
65 
16-6 
4-5 
54*2 
122 
» 
— 
10 
11-0 
110 
105 
Silver 
108 
18 
3-0 
390 
113 
Tin 
118 
17 
3-6 
45-3 
114 
Platinum 
195 
16 
4-0 
49-3 
112 
)> 
— 
16 
4-0 
49-3 
112 
)) 
11 
10-0 
j 1050 
113 
Lead 
207 
18 
3-0 
39*0 
113 
>> 
— 
15 
5*0 
59-0 
115 
Mean... 114*2 
The P. D.’s corresponding to the spark lengths are taken from 
Paschen’s tables ( Wied . Ann. 37, p. 79, 1889) for sparks between 
spheres of 1 cm. radius. 
These results show clearly that d V V is nearly a constant 
quantity whatever the metal of which the cathode is composed 
and potential difference used to produce the discharge. The 
variations from the mean value are not greater than can be readily 
accounted for by experimental errors. It thus appears that — is 
the same for the cathode rays proceeding from each of the eight 
metals tried. 
These experiments were carried out at the Cavendish Labora- 
tory and my best thanks are due to Prof. Thomson for advice 
during the course of the work. 
