CHAPTER VIII WHAT GLASSES DO TO US
T HE Florentines were doubtless mistaken in sup posing that their fellow citizen (see page v) was the inventor of the lenses now so commonly worn to correct errors of refraction. There has been much discussion as to the origin of these devices, but they are generally believed to have been known at a period much earlier than that of Salvino degli Armati. The Romans at least must have known something of the art of supple menting the powers of the eye, for Pliny tells us that Nero used to watch the games in the Colosseum through a concave gem set in a ring for that purpose. If, how ever, his contemporaries believed that Salvino of the Armati was the first to produce these aids to vision, they might well pray for the pardon of his sins; for while it is true that eyeglasses have brought to some people im proved vision and relief from pain and discomfort, they have been to others simply an added torture, they always do more or less harm, and at their best they never im prove the vision to normal.
That glasses cannot improve the sight to normal can be very simply demonstrated by looking at any color through a strong convex or concave glass. It will be noted that the color is always less intense than when seen with the naked eye; and since the perception of form depends upon the perception of color, it follows that both color and form must be less distinctly seen with glasses than without them. Even plane glass low ers the vision both for color and form, as everyone knows who has ever looked out of a window. Women who wear glasses for minor defects of vision often observe