HENRY CAVENDISH 105 



mable and common air are exploded in a proper proportion, almost all 

 the inflammable air, and nearly one-fifth of the common air, lose their 

 elasticity, and are condensed into dew. And by this experiment it 

 appears, that this dew is plain water, and consequently that almost all 

 the inflammable air and about one-fifth of the common air, are turned 

 into pure water. 



In order to examine the nature of the matter condensed on firing a 

 mixture of dephlogisticated and inflammable air, I took a glass globe 

 holding 8,800 grain measures, furnished with a brass cock and an 

 apparatus for firing air by electricity. This globe was well exhausted 

 by an air-pump, and then filled with a mixture of inflammable and 

 dephlogisticated air, by shutting the cock, fastening a bent glass tube 

 to its mouth, and letting up the end of it into a glass jar inverted into 

 water, and containing a mixture of 19,500 grain measures of 

 dephlogisticated air, and 37,000 of inflammable ; so that, upon opening 

 the cock, some of this mixed air rushed through the bent tube, and 

 filled the globe. The cock was then shut, and the included air fired 

 by electricity, by which means almost all of it lost its elasticity. The 

 cock was then again opened, so as to let in more of the same air, to 

 supply the place of that destroyed by the explosion, which was again 

 fired, and the operation continued till almost the whole of the mixture 

 was let into the globe and exploded. By this means, though the globe 

 held not more than the sixth part of the mixture, almost the whole 

 of it was exploded therein, without any fresh exhaustion of the globe. 



As I was desirous to try the quantity and test of this burnt air, 

 without letting any water into the globe, which would have prevented 

 my examining the nature of the condensed matter, I took a larger 

 globe, furnished also with a stop cock, exhausted it by an air-pump, 

 and screwed it on upon the cock of the former globe ; upon which, by 

 opening both cocks, the air rushed out of the smaller globe into the 

 larger, till it became of equal density in both ; then, by shutting the cock 

 of the larger globe, unscrewing it again from the former, and opening 

 it under water, I was enabled to find the quantity of the burnt air in 

 it ; and consequently, as the proportion which the contents of the two 

 globes bore to each other was known, could tell the quantity of burnt 

 air in the small globe before the communication was made between 

 them. By this means the whole quantity of the burnt air was found 

 to be 2,950 grain measures; its standard was 1.85. 



