[43] I do not find that Boyle quotes Mayow, though their labours in the same field were contemporary. But Boyle in his hidden qualities of the air published in 1674 has an observation that looks as if derived from Mayow. “And this undestroyed springiness of the air, with the necessity of fresh air to the life of hot animals, suggests a great suspicion of some vital substance if I may so call it, diffused through the air, whether it be a volatile nitre or rather some anonymous substance, sidereal or subterraneal, though not improperly of kin to that which seems so necessary to the maintenance of other flames.” The following is an analysis of Mayow’s essays, so far as relates to his chemical Philosophy. CHAP. _1st. Of Nitre._ The air is impregnated with a vital, igneous, and highly fermentative spirit of a nitro-saline nature, p. 1. Nitre is a salt consisting of an acid and an alkaline part, as appears by the Analysis, and by the generation of nitre; for if this salt be deflagrated with sulphur, the acid spirit will fly off, and may be collected by means of a tubulated retort and a receiver: and so if it be deflagrated with tartar, the residuum will be equal in weight to the tartar employed, though much of that, is of a fœtid oily nature. This appears also from the composition of nitre, by the addition of spirit of nitre to an alcali, p. 2-4. The fixed part of nitre is obtained from the earth; pure earth being probably a compound of salt and sulphur. p. 8. CHAP. _2d. On the aereal and fiery spirit of nitre._ The air seems to contain an acid, as appears from the regeneration of vitriolic acid after the calcination of Vitriol, and from the rusting of steel filings in a moist air; p. 10. A component part of the acid of nitre, is derived from the air, which evidently contains something necessary to the support of flame. But this aereal pabulum of flame, is not air itself, for air remains when the confined taper is extinguished: nor is it as vulgarly supposed, the salt called nitre, p. 12. But that these fire-air particles exist also in nitre is evident, since this salt will support the combustion of sulphur in vacuo. Fill a tube with gunpowder slightly moistened, and it will burn out in vacuo, or with its mouth inverted over water. Hence the aereal part of nitre, is the same with the fire-air particles of the atmosphere, and is one component part of the acid spirit of nitre: the other being (like the fixed part) obtained from the earth, p. 17. 18. The fiery particles thus common to nitre and to the air, he denominates nitro-aereal. It is these that give causticity to spirit of nitre, and occasion the red fumes observed in distilling it, p. 18. They do not take fire of themselves in nitre, because they are inveloped with moisture; but when combined with salt of tartar, and thrown on the fire in a dry state they inflame, p. 20.