THE CONQUEST OF NATURE 



virgin one, but was nevertheless relatively unexplored: 

 and Mr. Hewitt was, therefore, for the most part obliged 

 to depend upon his own researches and experiments. 

 In these experiments hundreds of gases were examined, 

 some of them giving encouraging results, but most of 

 them presenting insurmountable difficulties. Finally 

 mercury vapor was tried, with the result that the light 

 just referred to was produced. 



The possibilities of mercury- vapor gas had long been 

 vaguely suspected suspected, in fact, since the early 

 days of electrical investigation, two centuries before. 

 The English philosopher, Francis Hauksbee, as early 

 as 1705 had shown that light could be produced by 

 passing air through mercury in an exhausted receiver. 

 He had discovered that when a blast of air was driven 

 up against the sides of the glass receiver, it appeared 

 " all round like a body of fire, consisting of an abundance 

 of glowing globules," and continuing until the receiver 

 was about half full of air. Hauksbee called this his 

 "mercurial fountain," and although he was unable to 

 account for the production of this peculiar light, which 

 he remarked "resembled lightning," he attributed it 

 to the action of electricity. 



Between Hauksbee's "mercurial fountain" and 

 Hewitt's mercury-vapor light, however, there is a wide 

 gap, and, as it happened, this gap is practically unbridged 

 by intermediate experiments, for Mr. Hewitt had 

 never chanced to hear anything of Hauksbee's early 

 experiments, or of any of the tentative ones of later 

 scientists. But this, on the whole, may have been 

 rather advantageous than otherwise, as, being ignorant, 



