"The experiments on air... supplied materials for four papers, besides leading to the observation of many phenomena which were never made public. ...In the interval which elapsed between the publication of Cavendish's first chemical papers and [these]... Priestley, the fourth of the great English pneumatic chemists, had appeared... while Scheele... and Lavoisier... besides other less distinguished observers had effected the discovery of nearly all the gases known to... the present... and their study engrossed the attention of every chemist."