Page:Popular Science Monthly Volume 19.djvu/544

528 the moment. The effect of idiosyncrasy is excellently illustrated by the "Number forms," where we saw that a very special sharply defined track of mental vision was preferred by each individual who sees them. The influence of the mood of the moment is shown in the curves that characterize the various emotions, as the lank, drooping lines of grief, which make the weeping-willow so fit an emblem of it. In constructing fire-faces it seems to me that the eye in its wanderings follows a favorite course, and notices the points in the pictures at large that coincide with its course. It feels its way, easily diverted by associations based on what has just been noticed, and so, by the unconscious practice of a system of "trial and error," at last finds a track that will suit—one that is easy to follow, and that also makes a complete picture. The process is essentially the same as that of getting a clear idea from out of a confused multitude of facts. The fancy picture is dwelt upon, all that is incongruous with it becomes disregarded, while all deficiencies in it are supplied by the fantasy. These latest stages are easily represented after the fashion of a diorama. Three lanterns are made to converge on the same screen. The first throws an image of what the imagination will discard, the second of that which it will retain, the third of that which it will supply. Turn on the first and second, and the picture on the screen will be identical with that which fell on the retina. Shut off the first and turn on the third, and the picture will be identical with the illusion.

Visions, like dreams, are often mere patchworks built up of bits of recollections. The following is one of these:

Recollections need not be joined like mosaic-work; they may be blended, on the principle I described two years ageago [sic], of making composite portraits. I showed that if two lanterns were converged upon the same screen, and the portrait of one person was put into one and that of another person into the other, the portraits being taken under similar aspects and states of light and shade, then on adjusting the two images eye to eye and mouth to mouth, and so superposing them as exactly as the conditions admitted, a new face will spring into existence. It will have a striking appearance of individuality, and will bear a family likeness to each of its constituents. I also showed that these