Page:Popular Science Monthly Volume 45.djvu/125

Rh demonstrate here this correlation, which nobody has till now pointed out.

It is known that the receipts of therapeutics and materia medica have been preserved in a parallel way by practice, which has never ceased, in the Receptaries and other Latin treatises; these treatises, translated from the Greek during the period of the Roman Empire, and compiled in the first and second centuries, passed from hand to hand, and were copied frequently during the earlier portions of the middle ages. The transmission of the military arts and of fire-producing formulas, particularly, was carried on from the Greeks and Romans through the barbarous ages. In short, the necessity of the applications has always caused the subsistence of a certain experimental tradition of the arts of ancient civilization.

The oldest technical treatises in Latin of the middle ages on subjects in chemistry with which we are acquainted are the Formulas for Dyeing (Compositiones ad tingendo), of which we have a manuscript written toward the end of the eighth century, and the Key to Painting (Mappæ clavicula), the oldest manuscript of which is of the tenth century. The Formulas for Dyeing is not a methodical work, but a book of receipts and documents collected by a dyer for use in his art and intended to furnish him with working processes and information concerning the origin of his prime materials. It concerns such subjects as the coloring or dyeing of artificial stones for mosaic work; gilding and silvering and polishing them; making of colored glass in green, milky white, various shades of red, purple, yellow—the colors being both deep and superficial, and often brought out by the aid of simple varnishes; coloring of skins in purple, green, yellow, and various reds; dyeing of woods, bones, and horns; notices of minerals, metals, and earths used in goldsmiths' work and painting. Curious ideas are set forth on the function of the sun and of heat, peculiar to certain warm earths in the production of minerals endowed with corresponding virtues; while a cold earth produces minerals of weak quality. This reminds us of the theories of Aristotle on dry exhalation as opposed to moist exhalation in the generation of minerals—theories that made an important figure in the middle ages. The author distinguishes a feminine and light lead mineral as against a masculine and heavy mineral; a distinction like that mentioned by Pliny between male and female antimony, the male and female blue of Theophrastus, and many others. Minerals were continually likened in the chemistry of the middle ages to living beings.

We read likewise in this work of articles developed in certain operations, such as the extraction of mercury, lead, the roasting of sulphur, preparations of white lead with lead and vinegar, of