no 



DRA WING WITH THE MICROSCOPE. 



[CH. V. 



(B) By a camera lucida reflecting the rays of light from the drawing 

 paper, etc., so that their direction when they reach the eye coincides 

 with the direction of the rays from the microscope (Fig. 57, 60). In 

 all of the camera lucidas of this group, the rays from the paper are twice 

 reflected and no inversion appears. 



The better forms of camera lucidas (Wollaston's, Grunow's, Abbe's, 

 etc.), may be used for drawing both with low and with high powers. 

 Some require the microscope to be inclined (Fig. 105), while others are 



Fig. 103. 



Fig. 104. 



Fig. 102. 



Fig. 102. Abbe Camera Lucida with the 

 mirror at 45°, the drawing- surface hori- 

 zontal, and the microscope vertical. 



Axis, Axis. Axial ray from the mi- 

 croscope and from the drawing surface. 

 A B. Marginal rays of the field on the 

 drawing surface, a b. Sectional view of 

 the silvered surf ace on the upper of the tri- 

 angular prisms composing the cubical 

 prism ( P). The silvered surface is shown 

 as incomplete in the center, thus giving passage to the rays from the microscope. 

 Foot. Foot or base of the microscope. 



G. Smoked glass seen in section. It is placed between the mirror and the prism 

 to reduce the light from the drawing surface. 



Mirror. The mirror of the camera lucida. A quadrant (Q) has been added to 

 indicate the angle of inclination of the mirror, which in this case is 45 . 



Ocular. Ocular of the microscope over which the prism of the camera lucida is 

 placed. 



P, P. Drawing pencil and the cubical prism over the ocular. 



Fig. 103. Geometrical figure showing the angles made by the axial ray with the 

 drawing surface and the mirror. 



A B. The drawing surface. 



Fig. 104. Ocular showing eye-point, E P. It is at this point both horizontally 

 andverhcally that the hole in the silvered surface should be placed (<S 173). 



