322 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



it contained, if the air outside the bladder was removed by 

 means of the pump (Works, 1725, II. 413). Quantitative 

 measurements showed that air could be dilated in this way 

 to 9, 32, or 60 times its original volume; in an extreme 

 case, a " bubble of air possessing the space of but one 

 grain weight of water, ... by its own spring, was rarefied 

 to one hundred and fifty-two times its former dimensions ; 

 though it had been compressed only by the ordinary weight 

 of the contiguous air" (Works, 1725, II. 415). Analogous 

 experiments in which water was "freed from the pressure 

 of the atmosphere," revealed numerous little bubbles, pro- 

 duced by air lurking in the water, but gave no indication at all 

 " that water uncompressed, has an elastic power " (ibid., p. 428). 



A few years later Mayow showed that " air in which an 

 animal or a lamp had expired, possessed elastic force in an 

 equal degree with unimpaired air." He also experimented 

 with gases prepared artificially by the action of acids on 

 iron (Boyle, 1660; Works, 1725, II. 432), and "ascertained 

 that air of that kind expands to more than two hundred 

 times its volume ; and indeed if it had been relieved from 

 the pressure of the surrounding water, it would have ex- 

 panded twice as much. Nor will common air, when treated 

 in the same manner, expand more" (A.C.R. XVII. 115). 



By the experiments of Boyle and of Mayow, air was 

 shown to be typical of a group of " elastic fluids," which 

 differed from liquids in that they could expand in every 

 direction when the pressure acting upon them was reduced. 

 It was, however, left to Cavendish and to Priestley (p. 70) 

 to show clearly that the different gases or "airs" which 

 possess this remarkable property are distinct substances and 

 not merely different varieties of common air. 



Boyle's explanation of the "spring of the air." In 

 order to explain his observations, Boyle suggested : 



" That there is a Spring, or Elastical power in the Air we 

 live in. By which Spring of the Air, that which I mean is 



