THE METHOD OF POSITIVE BAYS 



5 2 7 



raising the temperature, however, fresh water of crystallization is given 

 off. Something of this kind seems to take place in the case of gases ab- 

 sorbed in metals, and there seem to be indications that there is some 

 kind of chemical combination between the gas and the metal. This ab- 

 sorbed gas may influence the behavior of the substance. For example, 

 an ordinary carbon filament gives off, when raised to a white heat, large 

 quantities of negatively electrified corpuscles; but Pring and Parker 3 

 have shown that when great precautions are taken to get rid of the ab- 

 sorbed gas, the emission of these corpuscles falls to less than one mil- 

 lionth of their previous value. It is in the gases given off by certain 

 metals when they are bombarded by cathode rays that I have found an 

 unfailing source of the substance, which I shall denote by X 3 , giving 

 the line corresponding to the atomic weight 3. The arrangement I 

 have used for investigating the presence of this gas is shown in Fig. 4. 



Ca-mera. 



Fig. 4. 



A is a vessel communicating with the bulb B in which the positive rays 

 are produced by two tubes, one of which is a very fine capillary tube, 

 while the other one is five or six millimeters in diameter; taps are in- 

 serted so that one or both of these vessels can be closed, and the vessels 

 A and B isolated from each other. A is provided with a curved cathode 

 such as are used for Eontgen ray focus tubes, and the cathode rays 

 focus on the platform on which the substance to be bombarded is placed. 

 [It is not absolutely necessary to focus the cathode rays in this way, 

 but it makes the supply of the gas X 3 more copious.] After the metal 

 or other solid to be examined has been placed on the platform, the taps 

 between A and B being turned so as to cut off the connection between 



3 Phil. Mag., XXIII., p. 192. 



