CHE extended this inquiry, and deter- mined the difference between fixed and azotic air, another species of suffocative gas, which cannot be respired by animals, nor is it misci- ble with water, and therefore by some called mephitic, or phlogisti- cated air. This azotic air consti- tutes about seventy-two parts in the hundred of the common atmo- sphere, and therefore deserves par- ticular attention : it was discovered by Dr. Priestley, and arises from the changes which atmospheric air undergoes in every process of com- bustion, putrefaction, and respira- tion ; in short, it is of the same nature as that contained in the air- biadder of the carp, and other fish. Bein^, much lighter than the air of the atmosphere, the az,ote instantly extinguishes burning tapers, and rapidly destroys the life of animals immersed in it. The most splendid and important discovery of Dr. Priestley, how- ever, is that of vital air, or oxygen, to which he was accidentallv led, in August i//4, and which will transmit his name to posterity. This aerial fluid, which he deno- minates dephlogisticated air, be- cause he supposed it to be deprived of ail its phlogiston, also forms a considerable part of our atmo- sphere, so that it has been ascer- tained, by experiment, to exist there in the proportion of about 27 or 28 parts in 100. Thus, the composition of that boundless element in which we breathe and move, was, at length, discover- ed, and though Bergmann and Scheele, in Sweden, as well as Lavoisier, in France, claimed an equal or coeval merit with Dr. PRiESTLEY,having, about the same period, in their experimental re- gearches on this subject, obsen ed CHE t>7 similar phenomena ; yet, we be- lieve, the last mentioned philoso- pher is justly entitled to the honour of being called the author of this great discovery. The manner in which it was made, is foreign to our purpose ; and we shall there- fore briefly state, that the inge- nious and noble Lavoisier, who fell a sacrifice to the ambition and tyranny of Robespierre, of infa- mous memory, established a new and more plausible system ot che- mistry upon the ground -work of this contested discovery, bv which the component parts of the atmo- sphere were clearly and indubitably determined. In contradistinction to the exploded doctrine of phlogis- ton, the theory adopted by La- voisier, and supported by Ber- THOLLET, MoRVEAU, ADET,HAS- SENFRATZ, De L PlACE,MoNG£, Chaptal, Fourcroy, and others, was now termed the Antiphlogistic System. The principal feature ot the new French system is, that the air is a compound body, and that metals, in general, are simple sub- stances. We cannot, in this place, enter into farther particulars ; and therefore only recommend to the juvenile reader, the perusal and study of such elementary works as afford a rdain and accurate expla- nation of that admirable and highly useful science ; without a compe- tent knowledge of which, he ill ever reme.in in a state of infancy, at least with respect to the num- berless, phenomena taking place in the physical world. We regret, however, that a publication calcu- lated completely to answer the ex- pectations of an ordinary reader, is still a desideratum ; though there have been published within the last twenty years, a great variety of instructive books on this subject. The
