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Rh date, even were it only the date of their copies. This source of facts is already known as to antiquity. It is not wanting as to the middle ages, although it seems to have till now escaped the erudite persons who have written the history of science, and it permits us to reconstitute that under a new form and with a new precision. By the aid of those documents I shall attempt to show, concerning myself especially with chemical industries, what knowledge, practical or theoretical, subsisted after the fall of ancient civilization, and how the traditions of the shop maintained those industries, almost without new inventions, but at least at a certain level of perfection.

The history of physical science in antiquity is very imperfectly known to us. There existed then no methodical treatise for the purpose of teaching, such as we have in the principal civilized states. Hence, except as to the medical sciences, we have only insufficient notions respecting the processes employed in the arts and trades of the ancients. The experimental method of the moderns has associated those practices into a body of doctrines, and has shown close relations between them and the theories for which they served as basis and confirmation. This method was almost unknown to the ancients, at best as a general principle of scientific learning. Their industries had little connection with theories, excepting in measures of length, surface, or volume, which were deduced immediately from geometry and in goldsmiths' receipts, which were the origin of the theories, partly real and partly imaginary, of alchemy. It has been even asked if industrial formulas were not formerly preserved by purely oral tradition and carefully held back for the initiated. Some scraps of the traditional lore may have been transcribed into the notes which have been used in the composition of Pliny's Natural History and the works of Vitruvius and Isidore de Seville, not without a considerable mixture of fables and errors. But a more thorough examination of the works that have come down to us from antiquity, a more attentive study of the manuscripts, at first neglected because they did not relate to literary or theological studies or to ordinary historical questions, permits the affirmation that they were not so. We are all the time discovering new and considerable documents which show that the processes of the ancient industrials were then, as now, inscribed in workmen's note-books or manuals intended for the use of the tradespeople, and that they were transmitted from hand to hand from the most remote times of ancient Egypt and Alexandrine Egypt, to those of the Roman Empire and the middle ages. The discovery of these note-books offers all the more interest because the use of the precious metals with civilized peoples goes back to the highest antiquity; the technique of the ancient goldsmiths and jewelers is not revealed to us all at once except