1913] on the Method of Positive Rays 595 



you is tlie use of it for the discovery and investigation of a new sub- 

 stance. I have in previous lectures said that sometimes there 

 appeared on the plates a line corresponding to a particle with an 

 atomic weight 3 ; this mnst either be a new element of a polymeric 

 modification of hydrogen, represented by H3. The other possibility 

 that it is a carbon atom with four charges is put out of court by the 

 fact that it frequently occurs when the carbon line is exceedingly 

 faint, and when there is not a trace of a carbon atom with even two 

 charges, though the doubly-charged carbon atom occurs readily 

 under certain conditions. In addition to this, the carbon atom para- 

 l)ola never approaches the vertical near enough to allow of its having 

 four charges. I thought the study of the substance producing this 

 line would be of interest, and I have for some time been working at 

 it ; and although the research is by no means completed, I have 

 obtained some results which 1 should like to bring before you. 



At first I was greatly hindered by not knowing the conditions 

 under which the line occurred ; although it appeared from time to 

 time on the plates, its appearance was ahvays fortuitous, and some- 

 times for weeks together the plates would not show a trace of the 

 line. The line sometimes appeared, but why it did so was a mystery, 

 and I could not get it when I wanted it. I began an investigation, 

 which proved long and tedious, to find the conditions under which 

 the line appeared. I tried filling the discharge-vessel with all the 

 gases and vapours described in the books on chemistry without 

 success. At last I tried bombarding various substances with cathode 

 rays. Under this treatment the substances give off considerable 

 quantities of gas the greater part of which is hydrogen, carbonic acid 

 or carbon monoxide. When I came to analyse by the positive rays 

 the gases given off in this way, I found that with a large number of 

 substances these gases contained the substances giving the three lines, 

 so that I was now in a position to get tliis line whenever I wanted it, 

 and investigate the properties of the gas to which it owes its origin. 

 The question of the gases absorbed and given off by solids is an ex- 

 tremely interesting one, and a considerable number of investigations 

 have been made on it. In all these, as far as I know, the method has 

 been to heat the solid to a high temperature, and then measure and 

 analyse the very considerable amount of gas which is driven off by 

 the heating. As far as I know, no experiments have been made in 

 which the gases were driven off by bombardment with cathode rays. 

 This treatment, however, will cause the emission of gas even when 

 ordinary heating fails to do so. 



Belloc, who has recently published * some interesting experiments 

 on this subject, after spending about six months in a fruitless attempt 

 to get a piece of iron in a state in which it would no longer give off gas 



* Ann. de Chimie et de Physique [8], xviii. p. 569. 



