CH. X] DRAWING FOR PUBLICATION 373 



If the observer faces the light the object on the stage will appear 

 like a printed page upside down (fig. 212). 



(B) For a drawing shelf, the mirror or prism being close to the 

 ocular and the draughtsman sitting with his face toward the light 

 (fig. 183, 187), the object is placed on the stage facing the objective 

 and right edge up. 



The image will be erect on the drawing surface (fig. 211). 



The object on the stage will also appear erect (fig. 211). 



525. For a translucent screen. For this the object is simply 

 turned around so that it faces in the opposite direction in each case 

 but remains the same edge up. 



526. For erect images on a horizontal drawing surface with 

 apparatus like Edinger's (fig. 202). In this case no mirror or 

 prism is necessary. The position of the object on the stage for 

 erect images is precisely the same as for a horizontal microscope 

 and a vertical screen ( 518). 



This has the disadvantage of requiring one to turn the cover- 

 glass away from the objective, which prohibits the use of high 

 powers. If the cover-glass is turned toward the objective the 

 drawing will be like a mirror image (fig. 213). 



DRAWINGS FOR PUBLICATION BY THE AID OF PROJECTION 

 APPARATUS 



527. Projection apparatus can give much assistance in pro- 

 ducing the outlines and main details of drawings for publication. 

 The outline drawings should be made on good drawing paper with a 

 medium lead pencil. When the ink, air-brush, or crayon work is 

 added for the finished drawing, the pencil lines will be covered or 

 they may be erased. The finishing must be done free-hand and 

 constant reference made to the actual specimen, to the image on 

 the screen, or as looked at through a microscope. The finishing 

 cannot be done successfully with the image of the specimen pro- 

 jected on the drawing paper as one cannot tell how the drawing 

 looks with the image projected upon it. By means of a suitable 

 screen the image may be cut off of part of the drawing surface while 

 doing the finishing. By removing the screen the image can be 



