X

PREFACE.

larger bulk than they had before ■, and, contrariwise, oftwo being contracted into less bulk than even one of themoccupied by itself.

To render the process anywise to be depended on, ac-'tual mixtures of the respective bodies ought first to bemade, in different proportions, and examined hydrostati-cally, that the quantity of contraction or dilatation inparticular cafes may be known and allowed for. By thusborrowing from both sciences, we are furnished withmeans of discovering the proportions of the ingredients inmany mixtures, provided the ingredients themselves areknown, with tolerable certainty: in some mixtures, asof lead and tin, this method is more commodious, andperhaps more exact, than any which pure chemistry hasafforded.

In this manner the mechanical and chemical sciences(concur, and require the assistance of one another, in theirown operations, and in almost all the manual arts. Inthe greater number of the arts the chemical prevails, andmany are no other than direct branches of practical che-mistry, as the arts of dying and staining, the runningdown of ores, the refining and compounding of metals,the making and colouring of glass, enamel, porcelain, &c.making wines, vinegars, spirits, &c. preparing indigo,smalt, Prussian blue, vermilion, lakes, and other coloursfor the painter. It is in those arts, and in those branchesof arts, which are strictly chemical, that the most impor-tant and most numerous discoveries are to be expected :chemistry having hitherto been the least cultivated, though

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