A Treatise on Painting/Chapter 175
Chap. CLXXV.—The Course of Study to be pursued.
The student who is desirous of making great proficiency in the art of imitating the works of Nature, should not only learn the shape of figures or other objects, and be able to delineate them with truth and precision, but he must also accompany them with their proper lights and shadows, according to the situation in which those objects appear.