OF GASES UNDER THE BECQUEREL RAYS. 
525 
III the first place, it will be seen that all the compounds examined gave very 
nearly the same values for the relative conductivities. There is, in fact, no clear 
evidence of any difference between them in this respect. This result naturally 
suggests the conclusion that all these substances give absorbable rays of the same 
physical nature. Secondly, it will be seen that the non-deflectable rays give some¬ 
what different results from the deflectable ones ; these differences being well outside 
the errors of experiment. For the former, the departure from the law of proportion¬ 
ality is decidedly more marked than for the latter. 
A reference to the table will show that these rays give results much closer to the 
deflectable rays than to the Rontgen rays. The very large conductivities charac¬ 
teristic of compounds of sulphur and the halogens under Rontgen rays are not met 
with in the case of Becquerel rays of any kind. 
It is now very generally agreed that the deflectable Becquerel rays consist of a 
stream of negative ions proceeding from the radio-active body with enormous 
velocities (Becquerel, ‘ CWiptes Rendus,’vol. 130, p. 109). But this theory gives 
no account of the nature of the other variety of Becquerel rays. I wish to make 
some mention of a possible solution of the question, indicating how far it appears to 
fall into line with the known facts. 
Let us, tlien, imagine that the absorbable rays consist of a stream of positive ions 
moving from the radio-active hod}"'. 
Now we know that the positive ions in gases carry tlie same charge as tlie 
negative, and that they have an enormously greater mass (J. J. Thomson, ‘ Phil. 
Mag.,’ vol. 48, p. 547). Unless, therefore, their velocity is smaller out of all 
proportion than the negative ions, it is to be expected that they will he mucli less 
easily deflected l)y the magnet. Tliis theory indicates, theii, that by apjfiying a very 
powerful field, the “ soft ” rays would be deflected. It would he well worth while to 
ex})eriment in this directimi. 
Next, it may l)e noticed that the smaller penetrating jwwer would be well 
accounted foi’ by the size of the positive ions, wliich would, of course, make more 
collisions with the molecules of the surrounding gas than the much smallei' 
negative ions. 
Lastly, the experiments described in this j^aper seem to indicate tliat the deflect- 
aide rays produce conductivity in gases by the same kind of process as the others— a 
process (piite diflerent from that by which the Rontgen rays produce conductivity. 
4'his is in accordance with the suggestion as to the nature of tlie rays, conductivity 
ijeing supposed to be produced in each case by the collision of the moving ions with 
the molecules, and the consequent splitting up of the latter into new ions. 
In this investisration I liave received much kind encouragement from Professor 
J. J. Thomson, and I wisli to express my best thanks to him. 
