heat and cold.

But there is the greatest possible difference in individuals in
this respect. Some persons have distinct images of things they
have seen, are good visualizers. Others are weak in this respect,
but have clear auditory images. And so as to all the various
kinds of sensory images.

This is a fact of comparatively recent discovery. The first
proponent of the idea was Fechner, but no statistical work was
done in this line until Galton entered the field, in 1880. In
his "Inquiries into Human Faculties," he says:

[Sidenote: _Investigations of Doctor Galton_]

"To my astonishment, I found that the great majority of the men
of science to whom I first applied protested that mental imagery
was unknown to them, and they looked on me as fanciful and
fantastic in supposing that the words 'mental imagery' really
expressed what I believed everybody supposed them to mean. They
had no more notion of its true nature than a color-blind man, who
has not discerned his defect, has of the nature of color. They
had a mental deficiency of which they were unaware and naturally
enough supposed that those who affirmed they possessed it were
romancing."

[Sidenote: _Investigations of Professor James_]

The investigations of Dr. Galton were continued by Professor
James, of Harvard University. He collected from hundreds of
persons descriptions of their own mental images. The following
are extracts from two cases of distinctly different types. The
one who is a good visualizer says:

"This morning's breakfast-table is both dim and bright; it is dim
if I try to think of it with my eyes closed. All the objects are
clear at once, yet when I confine my attention to any one object
it becomes far more distinct. I have more power to recall color
than any other one thing; if, for example, I were to recall a
plate decorated with flowers I could reproduce in a drawing the
exact tone, etc. The color of anything that was on the table is
perfectly vivid. There is very little limitation to the extent
of my images; I can see all four sides of a room; I can see all
four sides of two, three, four, even more rooms with such
distinctness that if you should ask me what was in any particular
place in any one, or ask me to count the chairs, etc., I could do
it without the least hesitation. The more I learn by heart the
more clearly do I see images of my pages. Even before I can
recite the lines I see them so that I could give them very slowly
wor