Lightens and destroys detail — Another effect which is difficult
for the student to see is that the light often partially or wholly hides
detail which is known to exist. Thus in Fig. 15, on the left-hand
part of the leaf, we find between the outer edge and the midrib
representations of veins which extend continuously, but which are
seen only at their central parts. Similar effects are found in Fig.
18, and these figures illustrate the common case in which continu-
ous detail in the object is situated so as to receive the light at differ-
ent angles, and be visible for part of its length only. The student
who sees the central part of a detail whose form he knows, is very
apt to think he sees it all, and represents its entire length ; he is
esp'^cially apt to draw the whole when he sees the two ends of a
detail whose central part cannot be seen, and he must be very care-
ful to draw no more than he sees, for without the careful observation
which notes every place in which the light obliterates the detail, an
artistic drawing cannot be made.
