Page:Popular Science Monthly Volume 18.djvu/856

836 the other senses, but not that of sight. This is proved by the sensations of sound, heat, and smell, which must be produced by matter, for to give rise to the feeling of touch is the essential property of matter and of matter alone. This property is what he calls an officum corporis—that is, a “function of substance”; another which he mentions afterward is weight, or the tendency to proceed downward. He also demonstrates the presence of aqueous vapor in the air by the phenomena of absorption and evaporation. A quotation of his language at this point will give a fair idea of his logic and his style: “In short, garments hung on the surf-beaten shore grow moist, but if spread out in the sun they become dry again. Yet we have not seen how the moisture of the water made its way in, nor how it vanished beneath the heat. The water, then, is scattered into minute parts, which the eyes can in no way behold.” He employs arguments that are in use nowadays in physics to prove the smallness to which matter can be subdivided. The most solid bodies, such as rings upon the fingers and the very stones beneath our feet, are worn away by constant rubbing. “But,” as he goes on to say, “the nature of sight has enviously shut off the view of those portions of the substance which disappear at any one time.”

The arguments which he uses in this connection form an additional proof of the scientific tendency of Lucretius’s mind. In his time the inductive and experimental methods were imperfectly understood and little practiced. He himself does not appear to have attained to them, he was bound by the false philosophical notions of the Greeks; yet often, as here, he traces the cause from various effects with considerable sagacity. He has in several cases, though generally on insufficient evidence, anticipated some of the results of modern research. It is easy to see how his opinions would have been strengthened, and what added breadth and vigor of reasoning he would have gained, if he had stood on our vantage-ground and had known all that we now know. As it is, we feel surprised at finding that he accomplished so much with such imperfect material for his work.

We do not intend to follow the entire development of his theory, but merely to trace his relations to science and the scientific spirit. The rest of the first book and the whole of the second are taken up with a description of the action and properties of the primitive atoms, of which he supposes all things to be composed. Amid some arguments that appear reasonable, he brings forward a striking fallacy. “If,” says he, “matter is infinitely divisible, the greatest and the least, consisting equally of an infinite number of parts, must be equal.” In other words, a mile and an inch are equal, for they each consist of an infinite number of equally small parts. The mathematical imagination among the ancients must have been very little developed, if such an argument passed muster with minds trained to the investigation of abstract truth.