Ch. VI] 



DRAWINGS FOR PUBLIC \TH'\ 



187 



and a substage condenser in addition to the condenser of the lantern 

 or small lamp (fig. 49, 114), or light of sufficient aperture will not 

 be supplied to the microscope. In using the highest powers it is 

 also well to connect the substage condenser to the slide by homo- 

 geneous liquid, as described in § 113. The large or small arc light 

 is the only really satis- 

 factory radiant (for erect 

 images see § 283). 



If one has a drawing 

 room, a large or small arc 

 lamp, and direct current, 

 the arrangements shown 

 in fig. 109 are best, but 

 if direct current is not 

 available, excellent results 

 can be obtained by using 

 the small arc lamp on the 

 alternating current house 

 electric lighting system 

 and the microscope, as 

 shown in fig. 113-114. 



The light supplied to 

 the substage condenser 

 should be approximately 

 parallel. This is attained 

 with the small lamp by 

 putting the arc at the 

 focus of the condenser (fig. 



Fig. 113. Drawing Microscope with Small 

 Arc Lamp on tile House Lighting System. 



(From Optic Projection). 



S, Sp The lamp socket and separable attach- 

 ment plug. 



Rh The rheostat not allowing over 5 amperes 

 of current to flow. 



Lamp The small arc lamp (fig. 49), at right 

 angles to the microscope. 



Mirroscope The microscope on a block (B). 



»ir, mr The mirror of the microscope and the 

 mirror over the ocular to reflect the li^ht directly 

 downward. 



Image The picture of the microscopic object 

 reflected down upon the drawing paper. 



Sh Opaque shield to screen the light from the 

 drawing surface. 



49). With the large lamp 



one should use a long focus lens for the condenser, as shown in fig. 1 15. 



In all cases the substage condenser should be shifted up and down 



slightly until the best effect is produced. The substage condenser 



should of course be carefully centered before commencing to draw 



(§ 104). 

 §298. Drawings for publication. -The inexpensive photographic 



processes of making cuts for the printing press bring within the reach 



