What I wish you to understand is that an artist, who has the gift of composing tonal harmonies, employs them to express the abstract feelings or emotions that he has regarding his subject. A celebrated example is Whistler’s _Portrait of the Artist’s Mother_, that now hangs in the Luxembourg Gallery, in Paris. I expect you have seen photographs of it and remember that it represents an oldish lady, in a white lace cap and black gown, with her hands folded over a handkerchief on her lap. We see her figure seated in profile, in front of a grey wall. On it are two little black-framed pictures, and on one side hangs a dark green curtain.