CH. VI] DRAWING WITH A CAMERA LUCID A 169 



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 is obscure. 



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

 reflected light (fig. 21, 34), like dark colored insects, etc., are to 

 be drawn, the light must usually be concentrated upon the object in 

 some way. The microscope may be placed in a very strong light 

 and the drawing board shaded, or the light may be concentrated upon 

 the object by means of a concave mirror, or a bull's eye condenser 

 or the small arc lamp (fig. 49) may be used. 



If the drawing surface is too brilliantly illuminated, it may be 

 shaded by placing a book or a ground-glass screen between it and 

 the window, also by putting one or more smoked glasses in the path 

 of the rays from the mirror (fig. 100). If the light in the microscope 

 is too intense, it ma^ be lessened by using white paper over the mirror, 

 or by a ground-glass screen between the microscope mirror and the 

 source of light (Piersol, American Monthly Microscopical Journal, 

 1888, p. 103). It is also an excellent plan to blacken the end of the 

 drawing pencil with carbon ink. Sometimes it is easier to draw on a 

 black surface, using a white pencil or style. The carbon paper used 

 in manifolding letters, etc., may be used, or ordinary black paper 

 may be lightly rubbed on one side with a moderately soft lead pencil. 

 Place the black paper over white paper and trace the outlines with 

 a pointed style of ivory or bone. A corresponding dark line will 

 appear on the white paper beneath (Jour. Roy. Micr. Soc., 1883, 



P- 423)- 



(i) It is desirable to have the drawing paper fastened with thumb 

 tacks, or in some other way. (2) The lines made while using the 

 camera lucida should be very light, as they are liable to be irregular. 

 (3) Only outlines are drawn and parts located with a camera lucida. 

 Details are put in free-hand. (4) It is sometimes desirable to draw 

 the outline of an object with a moderate power and add the details 

 with a higher power. If this is done it should always be clearly 

 stated. It is advisable to do this only with objects in which the 

 same structure is many times duplicated, as a nerve or a muscle. 



