By the late eighteenth century, scientists had discovered certain types of gas, such as 'fixed air' (carbon dioxide), but their composition was little understood. Relatively few investigations into gases had taken place, and so the polymath Joseph Priestley (1733–1804) was able to make major breakthroughs in the field using a range of experimental techniques. While living near a brewery, he found that it was possible to outline the shape of the gas above fermenting beer with smoke, and that fire would burn with varying strength depending on the composition of the air. This three-volume collection first appeared between 1774 and 1777. Following the international interest and new discoveries prompted by the publication of its predecessor, Volume 2 - reissued here in its corrected 1776 second edition - includes accounts of further experiments, Priestley's paper on the conducting power of charcoal, and, most significantly, notes on what he calls 'dephlogisticated air' (oxygen).