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FIEST CLASS OF OBJECTS FOR THE SUBJECT. 81
(according to Gothe s perfectly correct and true theory of
colours), and also of the growing indistinctness of all out
lines. In Italy, where the atmosphere is very transparent,
this datum loses its power and is apt to mislead : Tivoli,
for instance, seems to be very near when seen from Frascati.
On the other hand, all objects appear larger in a mist,
which is an abnormal exaggeration of the datum ; be
cause our Understanding assumes them to be further
from us.
Finally, there remains the estimation of distance by
means of the size (known to us intuitively) of intervening
objects, such as fields, woods, rivers, &c. &c. This mode
of estimation is only applicable where there is uninter
rupted succession : in other words, it can only be applied
to terrestrial, not to celestial objects. Moreover, we have
in general more practice in using it horizontally than ver
tically: a ball on the top of a tower 200 feet high appears
much smaller to us than when lying on the ground 200
feet from us ; because, in the latter case, we estimate the
distance more accurately. When we see human beings in
such a way, that what lies between them and ourselves is
in a great measure hidden from our sight, they always
appear strikingly small.
The fact that our Understanding assumes everything it
perceives in a horizontal direction to be farther off, therefore
larger, than what is seen in a vertical direction, must partly
be attributed to this last mode of estimating distances, inas
much as it only holds good when applied horizontally arid
to terrestrial objects ; but partly also to our estimation of
distances by atmospheric perspective, which is subject to
similar conditions. This is why the moon seems so much
larger on the horizon than at its zenith, although its visual
angle accurately measured that is, the image projected by
it on to the eye is not at all larger in one case than in the
other ; and this also accounts for the flattened appearance of
,