RONTGEN RAYS. 
197 
and Professor Rontgen has practically “ topped,” in the popular phrase, 
the other people’s work by the hnal touch—“ success.” 
Varley, in 1871 (he is dead and gone), knew that the cathode dis¬ 
charge formed shadows of interposed bodies ; if he had only placed a 
photographic plate under the interposed bodies he would have produced 
chemical action on the film—it was this that Professor Rontgen did. 
Professor Crookes’s work in. the direction of high vacuum phenomena 
and the invention of his tube, undoubtedly made the road easier for the 
ultimate success attained ; but we are indebted to Mr. Jackson, of 
King’s College, for the focus tube, the best being manufactured in this 
country by Messrs. Newton, without which it would be impossible to 
have obtained the results of its successful and practical application. 
The Jackson tube, I am informed, was first made in 1894, and 
Rontgen’s discovery was announced in January of this year (1896), so 
you see the tube was in advance of the final work. I hope it is not 
invidious to say that it is highly gratifying to find that something not 
“ made in Germany ” is a success. (Loud applause). 
The discoveries made abroad during the last few months, of which 
one reads in the various papers, are merely repetitions of what has been 
done very largely at home—the quiet work of English scientists. 
Of course, in Germany, I am bound to say that the populace are in 
advance of us in knowledge, because help is given by their government, 
and we hear of many laboratories to which students can go free of 
charge for their scientific education ; whereas, in this country, you must 
pay very heavily. 
Captain Abney utilised what are known as the ultra-red, or heat rays 
of spectrum, which, you know, do not affect a photographic plate in the 
ordinary manner, and he was able to focus these rays and to photograph 
in a dark room a kettle of boiling water ; absolute proof of the extra¬ 
ordinary properties of rays that we cannot see. As Sam Weller said : 
“ My wision’s limited, I can’t see through a flight of stairs and a deal 
door.” But I am not so certain that some day we shall not be able to 
see some very queer things in that way ; that is to say we shall be able 
probably to see through materials which at the present time are 
impervious to light, but which I believe will ultimately prove to be just 
as transparent as glass ; in fact, I am told that one worker has been 
able to obtain a photograph through a foot of steel ; I have not seen the 
photograph, but I have no doubt that there is some truth in it. 
I will now show you the difference between a current in a vacuum 
and a current in the ordinary pressure of the atmosphere. (The lecturer 
experimented in the dark, showing the Electric Egg.) First, you see a 
discharge in air ; now in a partial vacuum, the character of the discharge 
being entirely altered. This is known as the Electric Egg—the 
phosphorescence on the glass represents the transparent shell, and the 
pink nucleus, in the centre, the yolk. (Applause). 
If I could get a sufficiently high vacuum you would not see that so- 
called yellow or pink yolk at all ; there would simply be a series of 
luminous striae. 
I lectured 24 years ago at a Working-men’s Institute and showed that 
very same apparatus. I then explained that beyond the fact that it was 
an exceedingly pretty and charming illustration of the discharge of 
electricity in a vacuum, there was no use for it ! Yet you see 24 years 
afterwards there is an important use found for the discharge in vacuo. 
A still higher vacuum will show a much better result in what is 
