never failing to communicate to the public, by fome channel or other, the refult obfervations. of my In the publication of this work, I have thought that it would be agreeable to my readers to preserve, in fome measure, the order of hiftory, and therefore I have not thrown together all that I have observed with respect to each kind of air, but have divided the work into two parts; the former containing what was published before in the Philofophical Tranfactions, with fuch observations and corrections as fubfequent experience has fuggested to me; and I have referved for the latter part of the work an account of the experiments which I have made fince that publication, and after a pretty long interruption in my philofophical purfuits, in the course of the laft fummer. Befides I am fenfible that in the latter part of this work a different arrangement of the fubjects will be more convenient for their mutual illuftration. Some Some perfons object to the term air, as applied to acid, alkaline, and even nitrous air; but it is certainly very convenient to have a common term by which to denote things which have fo many common properties, and thofe fo very ftriking; all of them agreeing with the air in which we breathe, and with fixed air, in elasticity, and transparency, and in being alike affected by heat or cold; fo that to the eye they appear to have no difference at all. With much more reafon, as it appears to me, might a perfon object to the common term metal, as applied to things fo very different from one another as gold, quickfilver, and lead. Befides, acid and alkaline air do not differ from common air (in any respect that can countenance an objection to their having a common appellation) except in fuch properties as are common to it with fixed air, though in a different degree, viz. that of being imbibed by water. But, indeed, all kinds of air, common air itself not excepted, are capable of being imbibed by water in fome degree. Some Some may think the terms acid and alkaline vapour more proper than acid and alkaline air. But the term vapour having always been applied to elastic matters capable of being condenfed in the temperature of the atmosphere, efpecially the vapour of water, it seems harsh to apply it to any elastic fubftance, which at the fame time that it is as tranfparent as the air we breathe, is no more affected by cold than it is. As my former papers were immediately tranflated into feveral foreign languages, I may prefume that this treatise, having a better title to it, will be translated also; and, upon this prefumption, I cannot help expreffing a wifh, that it may be done by perfons who have a competent knowledge of the subject, as well as of the English language. The mistakes made by some foreigners, have induced me to give this caution. London, Feb. ADVERTISEMENT, THE weights mentioned in the course of this treatise are Troy, and what is called an ounce measure of air, is the fpace occupied by an ounce weight of water, which is equal to 480 grains, and is, therefore, almoft two cubic inches of water; for one cubic inch weighs 254 grains. THE CONTENT S. THE INTRODUCTION. Section I. A general view of PRECEDING DISCOVERIES relating to AIR Page 1 Sect. II. An Account of the APPARATUS with which the following Experiments were made 6 PART I. Experiments and Obfervations made in, and before the Year 1772. 23 Sect. I. Of FIXED AIR 25 Sect. II. Of AIR in which a CANDLE, or BRIMSTONE, has burned out Sect. III. Of INFLAMMABLE AIR Sect. IV. Of AIR infected with ANIMAL RESPIRATION, or PUTREFACTION C 43 55 70 Sect. |