ANODE RAYS AND THEIR SPECTRA. 125 
Fig. 1 shows an anode-ray tube. x is an ordinary cathode of 
aluminium ; the anode is formed by a stick a of a mixture of a halo- 
gen salt and graphite which is surrounded by a glass tube; through 
this tube passes a copper wire, which conducts the current to the salt, 
so that the surface of the salt mixture serves as the anode. 
If the current passes through the tube the surface of the salt, for 
‘instance Lil, gets melted and develops vapour of iodine, which pro- 
motes a high fall of potential; the positive lithium ions on the surface 
of the melted salt get their velocity in this field and appear in the tube 
as anode rays. These rays show the spectrum of lithium; they pro- 
duce on the glass the yellow fluorescence characteristic of positive rays ; 
they are emitted at right angles to the surface from which they come; 
they are deflectable by electric and magnetic fields in the sense of positive 
charged particles. 
Sodium rays are yellow, Ca rays violet, barium and strontium rays 
blue; about the spectra I will speak later on. If one had a sufficient 
Fie. 1. 
quantity of Ral. or RaBr., I think, there would be no difficulty in 
making Ra rays—that is, rays of positively charged Ra-atoms. 
We measured the velocity and the relation between charge and 
mass of these rays. The following table shows that the velocity 
of these rays, which depends on the electric field at the anode, is about 
the same as that of canal rays, and that it appears correct to assume 
that these rays consist of positively charged atoms :— 
Atomi 
a caw & sec < cay my Weight 
Sodium F A 1:76 x 10’ 0°40 x 103 23 23 
Lithium - f 2°40 x 107 1:15 x 10° 8:3 7 
Strontium . : 1:08 x 10’ 0°21 x 10° 90 88 
