undulatory theory of light, we see that both involve the same Idea ;—the Idea of a Medium acting by certain mechanical properties. The question there is, what is the true view of the mechanism of the Medium ? The other example of Aristotle's failure in physics, given in p. 82, namely, his attempted explanation of the round image of a square hole, is a specimen rather of indistinct than of inappropriate ideas. In the first edition I had not accurately represented Aristotle's statement. The geometrical explanation of this phenomena, which I have inserted in the text, was given by Maurolycus, and before him, by Leonardo da Vinci. Ναρθηκοπλήρωτον δὲ θηρῶμαι πυρὸς Prom. Vinct. 109. I brought to earth the spark of heavenly fire, Concealed at first, and small, but spreading soon Among the sons of men, and burning on, Teacher of art and use, and fount of power. BOOK II. HISTORY OF PHYSICAL SCIENCE IN ANCIENT GREECE. INTRODUCTION. N order to the acquisition of any such exact and I real knowledge of nature as that which we properly call Physical Science, it is requisite, as has already been said, that men should possess Ideas both distinct and appropriate, and should apply them to ascertained Facts. They are thus led to propositions of a general character, which are obtained by Induction, as will elsewhere be more fully explained. We proceed now to trace the formation of Sciences among the Greeks by such processes. The provinces of knowledge which thus demand our attention are, Astronomy, Mechanics and Hydrostatics, Optics and Harmonics; of which I must relate, first, the earliest stages, and next, the subsequent progress. Of these portions of human knowledge, Astronomy is, beyond doubt or comparison, much the most ancient and the most remarkable; and probably existed, in somewhat of a scientific form, in Chaldea and Egypt, and other countries, before the period of the intellectual activity of the Greeks. But I will give a brief account of some of the other Sciences before I proceed to Astronomy, for two reasons; first, because the origin of Astronomy is lost in the obscurity of a remote antiquity; and therefore we cannot exemplify the conditions of the first rise of science so well in that subject as we can in others which assumed their scientific form at known periods; and next, in order that I may not have to interrupt, after I have once begun it, the history of the only progressive Science which the ancient world produced (E). |