CH. F.] DRAWING WITH THE MICROSCOPE. 117 



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 (Fig. 52). 



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. 102 G). If the light in the microscope is too intense, 

 it may 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, Amer. M. M. Jour., 1888, p. 103). It is also an excel- 

 lent 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 corre- 

 sponding dark line will appear on the white paper beneath. (Jour. 

 Roy. Micr. Soc, 1883, p. 423). 



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

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

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

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

 Details are put in free-hand. (D) 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. In such an object all 

 the different structures could be shown, and by omitting some of the 

 fibers the others could be made plainer without an undesirable enlarge- 

 ment of the entire figure. 



(E) If a drawing of a given size is desired and it cannot be obtained 

 by any combination of oculars, objectives and lengths of the tube of 

 the microscope, the distance between the camera lucida and the table 

 may be increased or diminished until the image is of the desired size. 

 This distance is easily changed by the use of a book or a block, but 

 more conveniently if one has a drawing board with adjustable drawing 

 surface like that shown in Fig. 1 1 1. The image of a few spaces of the 

 micrometer, will give the scale of enlargement, or the power may be 

 determined for the special case (§ 177-178). 



(F) It is of the greatest advantage, as suggested by Heinsius (Zeit. 

 w. Mikr., 1889, p. 367), to have the camera lucida hinged so that the 



