JOHN, AND ISAAC HOLLANDUS.
HEY were two brothers, both of them of great parts and ingenuity, and wrote on the dry topics of chymistry. They lived in the 13th century, but this is not assured. The whole art of enamelling is their invention, as is also, that of colouring glass, and precious stones, by application of thin metal
plates. Their writings are in the form of processes, and they describe all their operations to the most minute circumstances. The treatise of enamelling is esteemed the greatest and most finished part of their works: whatever relates to the fusion, separation, and preparation of metals, is here delivered. They write excellently of distillation, fermentation, putrefaction, and their effects; and seem to have understood, at least, as much of these matters as any of the moderns have done. They furnish a great many experiments on human blood; which Van Helmont and Mr. Boyle have since taken for new discoveries. I have a very large work in folio, under their name, of the construction of chymical furnaces and instruments. Their writings are as easily purchased, as they are worthy of perusal, on account of valuable secrets in them, which may pave the way for greater discoveries. See BOERHAAVE, p. 21.