“Tho’ the force of its elasticity is so great as to be able to bear a prodigious pressure, without losing that elasticity, yet we have, from the foregoing Experiments, evident proof that its elasticity is easily, and in great abundance destroyed; and is thereby reduced to a fixt state by the strong attraction of the acid sulphureous particles which arise either from fire or from fermentation; and therefore _elasticity_ is not an _essential immutable property_ of air-particles; but they are, we see, easily changed from an elastick to a fixt state, by the strong attraction of the acid, sulphureous, and saline particles which abound in air. Whence it is reasonable to conclude that our atmosphere is a _Chaos_, consisting not only of elastick, but also of unelastick air-particles, which in plenty float in it, as well as the sulphureous, saline, watery, and earthy particles, which are no ways capable of being thrown off into a permanently elastick state, like those particles which constitute true permanent air. Since, then, air is found so manifestly to abound in almost all natural bodies; since we find it so operative and active a principle in every chymical operation; since its constituent parts are of so durable a nature, that the most violent action of fire or fermentation cannot induce such an alteration of its texture as thereby to disqualify it from resuming, either by the means of fire or fermentation, its former elastick state; unless in the case of vitrification, when, with the vegetable Salt and Nitre in which it is incorporated, it may, perhaps, some of it, with other chymical principles, be immutably fixt,--since then this is the case, may we not with good reason adopt this now fixt, now volatile _Proteus_ among the chymical principles, and that a very active one, as well as acid sulphur; notwithstanding it has hitherto been overlooked and rejected by chymists, as no way intitled to that denomination?” This quotation shows us how little Mayow’s shrewd reasoning and well-devised experiments had impressed the thinkers of his age. While Hales quotes frequently from Boyle’s and Newton’s works, his reference to Mayow is meagre; nor does he adopt any one of Mayow’s conclusions. One would have thought that, having prepared so many gases by means of apparatus well adapted to their purpose, and having observed that certain substances introduced into air produced contraction, he would have drawn the conclusion that such “airs” were essentially different kinds of matter. But the “Proteus” was too much for him; and he left the subject practically in the same state of “Chaos” in which he found it. [1] _Memoirs for a General History of the Air_; Shaw’s Abridgment of Boyle’s works, edition 1725, vol. iii. p. 26. [2] “Suspicions about some hidden qualities of the Air,” _ibid._ p. 77. CHAPTER II “FIXED AIR” AND “MEPHITIC AIR”--THEIR DISCOVERY BY BLACK AND BY RUTHERFORD