[Illustration: Plate V.--Drawing of three figures--Lord Lansdowne, Mr. Lloyd George, and Mr. Asquith--showing how an illusion of size may be produced in a picture. The figure of Mr. Asquith is of the same actual vertical measurement as that of Lord Lansdowne, viz. two inches and one eighth. Yet owing to the position in which the three figures are placed and the converging lines--suggesting perspective--the drawing of Mr. Asquith does not merely represent a much taller man than does that of Lord Lansdowne, but actually gives the impression, at first sight, that the little black figure representing Mr. Asquith is longer and bigger altogether than that representing Lord Lansdowne. Yet the figures are of the same dimensions. It is owing to illusion of the same nature that the disc of the low moon appears larger than that of the high moon.] The theatrical scene-painter has another kind of difficulty with the low moon and the setting sun. He can never be right for more than one row of seats--one distance--in the theatre. Here there is no peep-hole, no frame or picture-plane. The observer is _in_ the picture. If the moon is represented by an illuminated disc of one foot in diameter, it will, when looked at at a distance of 115 feet, have the same visual size as the moon itself, but if your seat is nearer the scene it will look too large, if further off it will look too small. There is no getting over this difficulty, as the standard of actual Nature is set up on the stage by the men and women appearing on it at a known distance. It used to be asked in classical times by ingenious puzzle-makers--"What is the size of the moon?" A true answer to that question would be "that of a plate a foot in diameter seen at a distance of a hundred and fifteen feet." To a large extent the painter, like other artists, has to produce things which do not shock common opinion and experience, and must even consciously concede to that necessity, and make the sacrifice of objective truth, in order to secure attention for his higher appeal to the sense of beauty, to emotion, and sentiment. Approved departures by the artist from scientific truth are those which are deliberately made in order to give emphasis--as, for instance, in the huge, but tender hand of the man in the emotional masterpiece, "Le Baiser," by the great sculptor Rodin. Another departure from objective truth which is justified, is seen in Troyon's picture in the Louvre, where the false drawing and exaggerated size of the leg of a calf advancing towards the observer suggest, and almost give the illusion of, movement.