388
DO AND DO NOT IN DRAWING
ICe. X
liable to cause confusion. If the mirror is silvered on the face or
if a prism is used there will be no doubling of the reflected image.
(8) Inverted images. One must follow carefully the directions
or there is liable to be an inversion of the projected image (§ 512-
526).
(9) In printing and photographing with projection apparatus
the difficulties likely to be met with in photography are sure to come
in. Knowledge of the principles underlying photographic pro¬
cesses will help one to overcome the troubles.
§ 549. Summary of Chapter
Do
i. Have a suitable room or a
suitable shield around the draw¬
ing to keep out stray light
(§ 453-455)-
2. Draw in the evening if a
proper room is not available in
the day time (§ 453).
3. Use an arc lamp for light
if possible (§ 461-462, 486-487).
4. Always use a rheostat with
an arc lamp, large or small
(§ 487, fig. 182, 185).
5. One can draw images pro¬
jected by all forms of projection
apparatus (§452).
X:
Do Not
1. Do not try to draw with
the drawing surface flooded with
stray light. Only the light
from the specimen should reach
the drawing surface.
2. Do not forget that it is
dark in all rooms in the evening
and, therefore, that is a good
time to draw.
3. Do not use a weak light
for drawing if you can have an
arc light.
4. Never try to use an arc
lamp, large or small, without a
rheostat in series with it.
5. Do not forget that it is
possible to draw the images
projected by any form of appar¬
atus.