Of chemistry, in the modern scientific sense, the ancients knew almost nothing. Empirically they were aware of certain properties exhibited by substances, and could perform certain manipulations; but, like moderns down to a very recent time, they had no real understanding of the quantitative or qualitative relations of elements. Long ago Greek philosophy, followed by the Epicurean school, had set forth an "atomic theory," which on the surface is surprisingly like the modern chemical hypothesis; but this contained strange and illogical features and had no connection with actual practice. In this department the chief proficiency of the world of this date lay in metallurgy, in which the processes empirically discovered, chiefly by Egyptians and Phoenicians, were closely similar to those now employed. They thoroughly understood the smelting of ores, but could render no scientific account of the processes. Botany was in a very crude condition, scarcely extending beyond such knowledge as was required on the one hand for farming and horticulture, and on the other for the vegetable medicines used by contemporary physicians. The doctoring of the time was also, of course, largely empirical, but assuredly hardly more so than it was a century or so ago, and distinctly more rational than it became in the Middle Ages. We cannot conceive of a reputable doctor at Rome prescribing the nauseous mediaeval absurdities. Practical surgery must have been surprisingly advanced, and there is scarcely a modern surgeon who does not exclaim in admiration of the instruments discovered at Pompeii and now preserved in the Naples Museum (see FIG. 69). In physic it is, of course, tolerably certain that many of the remedies or methods of treatment were of the sound and simple kind discovered by the long experience of mankind and often put in use by our grandmothers. The defect contemporary medicine was that it was almost wholly empirical. The ancient surgeon could doubtless perform ordinary operations--amputations and excisions--with neatness, and the ancient physician knew perfectly well what to do with the ordinary complaints--the fevers and agues, the bilious attacks, the gout, or the dropsy--but he was baffled by any new conditions. Moreover, if he could diagnose and cure, he could seldom prevent, inasmuch as he had little understanding of the causes of maladies. He had everything to learn in regard to sanitation and the preventing of infection. A plague would sometimes kill half the people in a town or district, and the loss of 30,000 persons in the metropolis would probably appear to most Romans as a visitation of the gods, nor is it certain that the doctors would generally disagree with that view. Though there were many quacks, it is not the case that the reputable medical men--most of them Greek, some of them Romans, who borrowed a Greek name because it "paid"--lacked the scientific spirit or such knowledge as the time afforded.