By examining these substances we obtain ideas of all the principles which enter into the composition of Vegetable and Animal bodies; that is, of those substances that are capable of fermentation: this enables me to treat of fermentation in general; of its three different degrees or kinds, the spirituous, acetous, and putrid; and of the products of those fermentations, ardent spirits, acids analogous to those of vegetables and animals, and volatile alkalis. The order in which I treat of all those substances being different from that in which they are obtained from compound bodies, I give, in a distinct Chapter, a general idea of Chymical Decomposition, with a view to shew the order in which they are separated, from the several bodies in the composition whereof they are found. This brings them a second time under review, and gives me an opportunity of distinguishing those which exist naturally in compound bodies, from those which are only the result of a new combination of some of their principles produced by the fire. The succeeding Chapter explains the late Mr Geoffroy's Table of Affinities; which I take to be of great use at the end of an Elementary tract like this, as it collects into one point of view the most essential and fundamental doctrines which are dispersed through the work. I conclude with an account of the Construction of such Vessels and Furnaces as are usually employed in Chymistry. In this Part I say nothing of any manual operations, or the several ways of performing Chymical processes; reserving these particulars for my Treatise of Practical Chymistry, to which this must be considered as an Introduction. CONTENTS. Elements of the THEORY of CHYMISTRY. CHAP. I. _Of the Principles of Bodies_ Page 1 Sect. 1. Of Air 2 Sect. 2. Of Water 3 Sect. 3. Of Earth 4 Sect. 4. Of Fire 5 Sect. 5. Of the Phlogiston 7 CHAP. II. _A general View of the Relations or Affinities between Bodies_ 9 CHAP. III. _Of Saline Substances in general_ 11 Sect. 1. Of Acids 12 Sect. 2. Of Alkalis 14 Sect. 3. Of Neutral Salts 15 CHAP. IV. _Of the Several Sorts of Saline Substances._ Sect. 1. Of the Universal Acid 18 Sect. 2. Of the Nitrous Acid 22 Sect. 3. Of the Marine Acid 25 CHAP. V. _Of Lime_ 29 CHAP. VI. _Of Metallic Substances in general_ 34 CHAP. VII. _Of Metals_ 37 Sect. 1. Of Gold _ib._ Sect. 2. Of Silver 39 Sect. 3. Of Copper 44