388 



DO AND DO NOT IN DRAWING 



[CH. 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 X : 

 Do 



i . Have a suitable room or a 

 suitable shield around the draw- 

 ing to keep out stray light 

 ( 453-455)- 



Do NOT 



i. 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. 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,%. 182,185). 



5. One can draw images pro- 

 jected by all forms of projection 

 apparatus (452). 



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. 



