I could mention instances within my own experience in which the visualizing faculty has become strengthened by practice; notably one of an eminent engineer, who had the power of recalling form with unusual precision, but not color. A few weeks after he had replied to my questions, he told me that my inquiries had induced him to practice his color memory, and that he had done so with such success that he had become quite an adept at it, and that the newly acquired power was a source of much pleasure to him.
The memories we should aim at acquiring are chiefly such as are based on a thorough understanding of the objects observed. In no case is this more surely effected than in the processes of mechanical drawing, where the intended structure has to be portrayed so exactly in plan, elevation, side view, and sections, that the workman has simply to copy the drawing in metal, wood, or stone, as the case may be. It is undoubtedly the fact that mechanicians, engineers, and architects possess the faculty of seeing mental images with remarkable clearness and precision.
A few dots like those of the Bushmen give great assistance in creating an imaginary picture, as proved by our general habit of working out new ideas by the help of marks and rude lines. The use of dolls by children also testifies to the value of an objective support in the construction of mental images. The doll serves as a kind of skeleton for the child to clothe with fantastic attributes, and the less individuality the doll has, the more it is appreciated by the child, who can the better utilize it as a lay figure in many different characters. The art of strengthening visual as well as every other form of memory lies in multiplying associations; the healthiest memory being that in which all the associations are logical, and toward which all the senses concur in their due proportions. It is wonderful how much the vividness of a recollection is increased when two or more lines of association are simultaneously excited.
It is a mistake to suppose that a powerful exercise of the will can vivify a faint image. The action of the will is negative, being limited to the suppression of what is not wanted and would be in the way. It can not create thought, but it can prevent thoughts from establishing themselves which lead in a false direction; so it keeps the course clear for a logical sequence of them. But, if appropriate ideas do not come of their own accord, the will is powerless to evoke them. Thus, when we forget a familiar name, it is impossible to recall it by force of will. The only plan in such cases is to think of other things, till some chance association suggests the name. The mind may be seriously dulled by over-concentration, and will only recover its freshness by such change of scene and occupation as will encourage freedom and discursiveness in the flow of the ideas.
All that remains to be said refers to the utility of the visualizing faculty, and may be compressed into a few words. A visual image is
