DRAWING TO SCALE FROM MICROSCOPE 



281 



pencil can be seen distinctly enough but the outline of the object 

 becomes too dim. In the camera lucida of Fig. 151 there are 

 two revolving diaphragms with handles at K, with a series of 



Fig. 152. — Convenient drawing board for use with camera lucida. 



openings, all but one of which in each series are covered with a 

 graduated series of different intensities of smoked glass. With 

 this provision one can decrease the light entering the eye from the 

 drawing paper or from the object until the object and the point 



