A HISTORY OF SCIENCE 



mometer is hydrogen gas. The principle by which it 

 is utilized does not differ, in its rough essentials, from 

 that of ordinary thermometers, but the details of its 

 construction are much too intricate to be elaborated 

 here. 



But if you would see the most wonderful things in 

 this laboratory or rather, to be quite accurate, I should 

 say, if you would stand in the presence of the most 

 wonderful things you must go with Professor Ram- 

 say to his own private laboratory, and be introduced 

 to some little test-tubes that stand inverted in cups 

 of mercury decorating a shelf at one end. You would 

 never notice these tubes of your own accord were you 

 to browse ever so long about the room. Even when 

 your attention is called to them you still see nothing 

 remarkable. These are ordinary test-tubes inverted 

 over ordinary mercury. They contain something, since 

 the mercury does not rise in them completely, but if 

 that something be other than ordinary air there is 

 nothing about its appearance, or rather lack of ap- 

 pearance, to demonstrate it. But your interest will 

 hardly fail to be arrested when Professor Ramsay, in- 

 dicating one and another of these little tubes, says: 

 " Here you see, or fail to see, all the krypton that has 

 ever been in isolated existence in the world, and here 

 all the neon, and here, again, all the zenon." 



You will understand, of course, that krypton, neon, 

 and zenon are the new gases of the atmosphere whose 

 existence no one suspected until Professor Ramsay 

 ferreted them out a few years ago and isolated them. 

 In one sense there should be nothing mysterious about 

 substances that every air-breathing creature on the 



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