53Q THE POPULAR SCIENCE MONTHLY 



acetate by putting a piece of zinc into the solution, and forming the 

 well-known lead-tree. When I bombarded this freshly precipitated 

 lead, I could get no trace of the X 3 line; the helium line, too, was 

 absent. I then tried another experiment. I took a piece of lead and 

 divided it into two parts. The first of these I bombarded by the 

 cathode rays: it gave the X 3 line quite distinctly. The other part I 

 dissolved in boiling nitric acid, getting lead nitrate. The nitrate was 

 heated and converted into oxide, and this was bombarded by the cathode 

 rays : it did not give the X 3 line, showing that the X 3 is not produced 

 by the bombardment, but is something stored up in the lead, which can 

 be detached from it when the lead is dissolved. I have tried several 

 samples of lead; the one which gave the X 3 line most distinctly was a 

 piece of lead from the roof of Trinity College Chapel, several hundred 

 years old. A sample of Kahibaum's chemically pure lead, which must, 

 I suppose, at no distant date have been subjected to severe ordeals by 

 fire and water, showed the line quite distinctly, though not so well as 

 the older lead. I have tried similar experiments with iron, and found 

 that iron which gave the three line very distinctly ceased to do so after 

 it had been dissolved in acid. 



As the most obvious explanation of X 3 is that it is H 3 , bearing the 

 same relation to hydrogen that ozone does to oxygen, and produced in 

 some way from the hydrogen dissolved in the metal, I tried if I could 

 produce it by charging metals with large quantities of hydrogen, and 

 then seeing if the hydrogen coming from the metal gave any traces of 

 H 3 . Thus, for example, I tested the hydrogen given off from hot 

 palladium, but found no trace of X 3 . I then charged nickel at a tem- 

 perature of about 355° C. with hydrogen in the way recommended by 

 Sabatier, but found no increase in the brightness of the X 3 over nickel 

 that had not been deliberately exposed to hydrogen. I tried if the 

 brightness of the line would be increased by adding hydrogen to the 

 bulb A, in which the bombardment took place, but found no effect. 

 I also tried adding oxygen to this bulb, thinking that if it was H 3 it 

 would combine with the oxygen, and thus be eliminated, but no great 

 diminution in the intensity was produced by this treatment. The gas 

 seems quite stable, at least it can be kept for several days without suf- 

 fering any diminution that can be detected; indeed, when once it has 

 got into a bulb, there is considerable difficulty in getting the bulb free 

 from it. It must be remembered, too, that by the method it is produced 

 the gas is subjected all the time to electric discharges which would 

 break it up unless it possesses very great stability. Thus if X 3 is a 

 polymeric modification of hydrogen, it must possess the following 

 properties : 



1. It must be very stable. 



2. It must resist the action of oxygen. 



