SUBDUCTION, in arithmetic, the same as Subtraction.
THE reader will recollect, that the article CHEMISTRY, in this Supplement, was divided into four parts; of which only the first three, comprehending the elements of the science, were given under the word CHEMISTRY. The fourth part, which was entitled an examination of bodies as they are presented to us by nature in the mineral, vegetable, and animal kingdoms, naturally subdivides itself into three parts, comprehending respectively, 1. Minerals; 2. Vegetables; 3. Animals.
The first of these subdivisions, which has been distinguished by the name of MINERALOGY, we have treated of already in a former part of this Volume. As the other two subdivisions have not hitherto received any appropriate name, we have satisfied ourselves with the word SUBSTANCE, by which chemists have agreed to denote the objects which belong to these subdivisions. This SUPPL. VOL. II. PART II.
name, it must be acknowledged, is not unexceptionable; but we did not consider ourselves as at liberty to invent a new one.
The present article, then, seems to divide itself into two parts: the first part comprehending vegetable; the Division of second animal substances. But there are certain animal and vegetable substances distinguished from all others by being used as articles of clothing. It is usual to tinge these of various colours, by combining with them different colouring matters for which they have an affinity. This process, well known by the name of DYEING, is purely chemical; and as it belongs exclusively to animal and vegetable substances, it comes naturally to be examined here. We shall therefore add a third part, in which we shall give a view of the present state of DYEING, as far, at least, as is consistent with the nature of a supplementary article.