132 DRAWING WITH THE MICROSCOPE [CH. V 



micrometer were y 1 th millimeter, then the enlargement would be 

 25 -3- yf^ = 500. That is, the image was drawn at a magnification of 

 500 diameters. 



If the micrometer scale is added to every drawing, there is no 

 need of troubling one's self about the exact distance at which the 

 drawing is made, convenience may settle that, as the special magnifi- 

 cation in each case may be determined from the scale accompanying 

 the picture. It should be remembered, however, that the conditions 

 when the scale is drawn must be exactly as when the drawing was 

 made. 



187. Drawing at Slight Magnification. Some objects are of 

 considerable size and for drawings should be enlarged but a few diame- 

 ters, 5 to 20. By using sufficiently low objectives and different ocu- 

 lars a great range may be obtained. Frequently, however, the range 

 must be still further increased. For a moderate increase in size the 

 drawing surface may be put farther off, or, as one more commonly 

 needs less rather than greater magnification, the drawing surface may 

 be brought nearer the mirror of the camera lucida by piling books or 

 other objects on the drawing board. If one takes the precaution to 

 draw a scale on the figure under the same conditions, its enlargement 

 can be readily determined ( 186). 



A very satisfactory way to draw at low magnifications is to use a 

 simple microscope and arrange a camera lucida over it as over the ocular. 

 In this way one may get drawings at almost any low magnification. 



If one has many 

 large objects to draw at a 

 low magnification, then 

 some form of embryo- 

 graph is very conven- 

 ient. (Jour. Roy. Micr., 

 Soc., 1899, P- 223.) The 

 writer has made use of 

 a photographic camera 

 and different photo- 

 graphic objectives for the 

 purpose. The object is 



FIG. 1 1 8. Camera lucida for drawing objects natural size. (H. Bausch 

 Jour. Applied Microscopy, vol. Hi (/<%>, p. 801). 



illuminated as if for a photograph and in place of the ground glass a 

 plain glass is used and on this some tracing paper is stretched. Noth- 



