It was a long time before artists overcame the difficulty of representing this effect; and the first pictures in which it was accomplished were naturally regarded as wonders. Since it is not the purpose of this book to teach you to draw I will mention only one of the principles involved. It is the one we have already been discussing--the contrast of light and dark, or, as it is called, “chiaroscuro.” Artists soon discovered that, if an object has bulk, that part of it which is nearest to the light will reflect most light; the parts less near, less light; while the parts that are exposed to no light will appear dark. As this was how the artists saw the objects, it was so they tried to represent them. They learned to “model” the object, that is to say, to represent it as having bulk, by reproducing in their pictures the contrasts of light and dark. At first the contrasts were crude, chiefly of the very light and very dark, but by degrees the artists became more skillful and learned to represent also all the varying gradations of less light and less dark. By this time they were better able to surmount the difficulty of foreshortening.