A HISTORY OF SCIENCE 



despite Hutton's clear prevision, of these marvellous 

 slow revolutions through which, as Lyell taught us, 

 the earth's crust had been built up! Not even Jen- 

 ner could foresee a century ago the revolution in sur- 

 gery which has been effected in our generation through 

 the teachings of Lister. 



And what did Rumford and Davy know of energy in 

 its various manifestations as compared with the knowl- 

 edge of to-day, of Crookes and Rayleigh and Ramsay 

 and Kelvin? What would Joseph Priestley, the dis- 

 coverer of oxygen, and Cavendish, the discoverer of 

 nitrogen, think could they step into the laboratory of 

 Professor Ramsay and see test-tubes containing argon 

 and helium and krypton and neon and zenon ? Could 

 they more than vaguely understand the papers con- 

 tributed in recent years to the Royal Society, in which 

 Professor Ramsay explains how these new constituents 

 of the atmosphere are obtained by experiments on 

 liquid air. "Here," says Professor Ramsay, in effect, 

 in a late paper to the society, "is the apparatus with 

 which we liquefy hydrogen in order to separate neon 

 from helium by liquefying the former while the helium 

 still remains gaseous." Neon, helium, liquid air, 

 liquid hydrogen these would seem strange terms to 

 the men who on discovering oxygen and nitrogen 

 named them " dephlogisticated air" and "phlogisti- 

 cated air" respectively. 



Again, how elementary seems the teaching of Her- 

 schel, wonderful though it was in its day, when com- 

 pared with our present knowledge of the sidereal 

 system as outlined in the theories of Sir Norman Lock- 

 yer. Herschel studied the sun-spots, for example, with 



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