hird dimension, is
rendered much more clear.

[41] A striking example of this was given in a painting, by Andsell, of
a sportsman in the act of shooting, exhibited in the Royal Academy in
1879.

[42] This is at least true of all near objects.

[43] Helmholtz remarks _(op. cit._, p. 628) that the difficulty of
seeing the convex cast as concave is probably due to the presence of the
cast shadow. This has, no doubt, some effect: yet the consideration
urged in the text appears to me to be the most important one.

[44] _Populaere wissenschaftliche Vortraege_, 3tes Heft, pp. 71, 72.

[45] See, on this point, some excellent remarks by G.H. Lewes, _Problems
of Life and Mind_, third series, vol. ii. p. 275.

[46] To some extent this applies to the changes of apparent magnitude
due to altered position. Thus, we do not attend to the reduction of the
height of a small object which we are wont to handle, when it is placed
far below the level of the eye. And hence the error people make in
judging of the point in the wall or skirting which a hat will reach when
placed on the ground.

[47] I refer to the experiments made by Exner, Wundt, and others, in
determining the time elapsing between the giving of a signal to a person
and the execution of a movement in response. "It is found," says Wundt,
"by these experiments that the exact moment at which a sense-impression
is perceived depends on the amount of preparatory self-accommodation of
attention." (See Wundt, _Physiologische Psychologie_, ch. xix.,
especially p. 735. _et seq._)

[48] Quoted by Helmholtz, _op. cit._, p. 626.

[49] When the drawing, by its adherence to the laws of perspective, does
not powerfully determine the eye to see it in one way rather than in the
other (as in Figs. 5 to 7), the disposition to see the one form rather
than the other points to differences in the frequency of the original
forms in our daily experience. At the same time, it is to be observed
that, after looking at the drawing for a time under each aspect, the
suggestion now of the one and now of the other forces itself on the mind
in a curious and unaccountable way.

[50] _Ueber die phantastischen Gesichsterscheinungen_, p. 45.

[51] Another side of histrionic illusion, the reading of the imitated
feelings into the actors' minds, will be dealt with in a later chapter.

[52] In a finished painting of any size this preparation is hardly
necessary. In these cases, in spite of the great devia