n6 



DRA WING WITH THE MICROSCOPE. 



[CI I. V. 



low powers (16 mm. and lower objectives) by covering the mirror with 

 white paper when transparent objects are to be drawn. For high pow- 

 ers it is best to use a substage condenser. Often the light may be bal- 

 anced by using a larger or smaller opening in the diaphragm. One 

 can tell which field is excessively illuminated, for it is the one in which 

 objects are most distinctly seen. If it is the microscopic, then the image 

 of the microscopic object is very distinct and the pencil is invisible or 

 very indistinct. If the drawing surface is too brilliantly lighted the 

 pencil can be seen clearly, but the microscopic image will be very ob- 

 scure. 



Fig. hi. Drawing Board for the Abbe Camera Lncida This diaiuing board, 

 devised by the Bausch & Lomb Optical Co., is adjustable vertically, and the board 

 may be inclined to prevent distortion. It is also arranged for use rvith an inclined 

 microscope by having the base board hinged. Microscope and drawing surface 

 are then inclined together. The camera lucida has a graduated arm to bear the 

 mirror and a graduated quadrant at the mirror joint so that the angle of the mir- 

 ror may be accurately determined. {See also Fig. /oj: (From the Bausch & 

 Lomb Optical Co.) 



When opaque objects, that is objects which must be lighted with re- 

 flected light (§ 59), like dark colored insects, etc., are to be drawn the 

 light must usually be concentrated upon the object in some way. The 



