Page:Popular Science Monthly Volume 70.djvu/425

Rh chromatuphlosis. However, technical terms often lead the philologist to express the same opinion of them that the devil is said to have used of the Ten Commandments, "They are a queer lot." In the language of the Psalmist, "They are fearfully and wonderfully made." Generally speaking, animals make less use of sight than man; all those that have been domesticated select their food by the sense of smell and not by sight. The test may be readily made with blind horses, which are unfortunately not as rare as they ought to be. Birds, on the other hand, depend wholly on the sense of sight, which is remarkably acute. In ancient accounts of battles, sieges and pestilence, those gruesome birds that live on corpses are never absent. It may be taken for granted that the problem, How do we see? exercised the ingenuity of the ancient thinkers a great deal. It need not surprise us that they were wide of the mark, seeing that there is as yet no universally accepted theory of vision. But the moderns have learned that color is subjective, whereas the ancients regarded it as objective. Lucretius, who follows the teachings of some of the Greek philosophers, probably of Empedocles, affirms that very thin films are detached from the visible object and impinge upon the eye to produce sight. Aristotle was convinced that there must be some medium between the organ of sight and the object seen by which the sight-process is mediated. Lucretius says that persons afflicted with jaundice see everything yellow because so many atoms of that color fill the orb of sight. He compares the casting away of films or effigies to the cicada that casts off its tunic, or the snake that sheds its glossy vesture and to fire that emits smoke. Much later Locke says: "Since the extension, figure, number and motion of bodies of an observable bigness may be perceived at a distance by the sight, it is evident that some singly imperceptible bodies must come from them to the eye." Lucretius seems to have observed natural phenomena with unusual care for a Soman, but it was rather their more violent aspects, such as thunder and lightning, earthquakes and waterspouts and floods. The phenomena of rain, hail and snow could of course not escape his attention. It has been shown above that the ancients, particularly the Greeks, had a very defective perception of colors and that they had very poor eyes for the beauties of nature as displayed in scenery. It may be interesting to trace briefly the growth of this last sentiment, since it is one of the latest phases of evolution. The Greeks were eminently a social people. They laid