CH. V\ DRAWING WITH THE MICROSCOPE 129 



and in the same direction, that is, so the end of the drawing board 

 shall be in a plane parallel with the stage of the microscope. The 

 mirror must have its edges in planes parallel with the edges of the 

 drawing board also (Figs. 115, 116.) 



FIG. 115. Arrangement of jo" 

 the drawing board for using the 

 microscope in an inclined position 

 with the Abbe camera lucida (de- 

 signed by Mrs. S. P. Gage, 1887.) 



185. Drawing with the Abbe Camera Lucida. (A) The 

 light from the microscope and from the drawing surface should be of 

 nearly equal intensity, so that the image and the drawing pencil can be 

 seen with about equal distinctness. This may be accomplished with 

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

 of the microscope with white paper when transparent objects are to be 

 drawn. For high powers it is best to use a substage condenser. Often 

 the light may be balanced 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 micro- 

 scopic image will be obscure. 



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

 reflected light ( 63), 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 (Fig. 53). 



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 

 ra} 7 s from the mirror (Fig. 109 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 excellent plan to blacken the end of the drawing pencil with carbon 



