The portions of Scheele's Chemical Treatise on Air and Fire here reproduced in English are intended to form a companion volume to No. 7 of the Club Reprints, which contains Priestley's account of his discovery of oxygen. Not only have the claims of Scheele to the independent discovery of this gas never been disputed, but the valuable volume of Letters and Memoranda of Scheele, edited by order hold, which was published in 1892, places it beyond doubt that Scheele had obtained oxygen by more than one method at least as early as Priestley's first isolation of the gas, although his printed account of the discovery only appeared about two years after Priestley's. The evidence of this has been found in Scheele's laboratory notes, which are still preserved in the Royal Academy of Science in Stockholm.