SIK G. G. STOKES, BART,, ON THE EONTGEN RAYS. 19 



of the first tube, be they of residual gas, or alnraiuium, or 

 platinum, might fall upon the thin aluminium plate which 

 forms a wall between the two tubes, separating the one from 

 the other, and that that would give rise to molecular dis- 

 charge in the second space, although the actual moving 

 molecules never passed through the wall. As I say, that is a 

 rough illustration — rather a gross and material illustration — 

 to enable you to understand more clearly the vicAv I have 

 to bring before you. 



I have said that the so-called cathodic rays are easily 

 deflected by a magnet. Now we know from other experi- 

 ments that if a body sufficiently charged with electricity is 

 in rapid motion, and that motion takes place in a magnetic 

 field, the body tends to be deflected. This looks, therefore, 

 very much as if these cathodic rays are actually streams of 

 molecules, which being highly charged electrically, and of 

 almost inconceivable minuteness, would be deflected by a 

 slight magnetic force. Now, if these highly-charged mole- 

 cules come to strike on the aluminium wall which separates 

 the two tubes (which are end to end) from one another, it 

 may be that an electrical action goes on which resembles 

 very much what electrolysis is supposed to be according to 

 the views of Grrotthuss, I shall not have time to enter into 

 an explanation of that now, for it would lead me too far 

 from the subject ; but several present will no doubt under- 

 stand what I mean when I refer to the views of Grotthuss. 

 The molecules then impinge on the wall, and give rise to 

 a projection of molecules from the second side of the wall, 

 but the latter are not the same molecules which impinged on 

 the first side of it. Whether the molecules projected in the 

 second tube come from a very minute quantity of residual 

 gas, or whether they are derived from the aluminium wall 

 itself, from which they are torn, as it were, does not signify 

 for my purpose. We have here, you see, a conceivable mode 

 of emitting these so-called rays in this way, simulating the 

 transmission of a ray of light through a plate of glass, though 

 it is no ray at all that we are dealing with. 1 confess I 

 think that that is the true view of the action which takes 

 place. But Lenard himself believed that the cathodic rays 

 were, as he said, processes in the ether. By means of the 

 first tube used alone, as was done in the first instance, but 

 closed with a " window " of somewhat thicker aluminium 

 foil, so as to sustain the atmospheric pressure, he was able to 

 receive the cathodic rays which came from the second surface 



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