32 



had not completed to his entire satisfaction, is to be found in a MS. 

 constituting a " Mh part " of liis celebrated experiments on factitious 

 air. This unpublished paper, written for the Royal Society, probably 

 in 1766 or 1767, and consisting, with a "digression on air" which 

 accompanies it, of twenty-six pages, commences with a series of expe- 

 riments on the air produced from animal and vegetable substances in 

 distillation, the animal matter employed being hartshorn shavings, the 

 vegetable substances, wainscot and tartar: the inflammable gases 

 from these he finds nearly similar to each other, but so different in spe- 

 cific gravity, and explosive power, from the inflammable gas yielded by 

 metals, that he determines them to be of a different kind : he then 

 examines the caput mortuum of the distillation by deflagrating it with 

 nitre, and finding, contrary to expectation, that the weight of the fixed 

 air produced is greater than that of the charcoal consumed, leaves off 

 abruptly, in doubt whether the experiment is incorrect, or whether part 

 of the fixed air is to be ascribed to the nitre. We see from the state- 

 ment which I have mentioned as having been communicated by him to 

 Dr. Priestley before 1772, that by that time he had acquired clearer 

 ideas of the generation of fixed air. 



From this account of experiments which Cavendish never chose to 

 publish, I pass to those of which he delayed the publication till he had 

 completed them, though in their progress he made no secret of them 

 to his friends. They fill a volume of unsewn and single, but paged and 

 indexed octavo sheets, in his own hand, bearing dates from February 

 1778 to May 1785, in the following proportions: in 1778 thirty-three 

 pages, in 1780 thirty-six, in 1781 seventy-five, in 1782 forty-five, in 

 1783 fifty-three, in 1784 forty-four, in 1785 thirty-three. I found 

 them in a packet entitled " Experiments on Air." 



These very numerous and laborious experiments all bear on the so- 

 lution of one question, namely, what becomes of the lost air in the va- 

 rious chemical processes, in which it is now known that oxygen passes 

 into fixed combinations? Scheele in 1777* had stated this question 

 thus : " It appears in the transition of what is called injiammahle prin- 

 ciple into the air a considerable part of the air is lost. But whether 

 the phlogiston which is lost from the substance still remained (in his 

 before- mentioned experiments) in the residuum of air in the bottle, or 

 whether the lost air was united and became fixed with the substances of 

 liver of sulphur, oils, &c., is a question of great importance. It would 

 follow on the first supposition that phlogiston has the power of de- 



* Scheele's work on air was written in 1775, but not published till 1777- 



