162 THE USE OF THE MICROSCOPE 



is not needed; if there is, as there should of course be, an 

 arrangement with the microscope for regulating the 

 intensity of the light. The writer finds that yellow-green 

 light in the microscope, and white light on the drawing 

 paper are comfortable. The ring of neutral glasses round 

 the prism must be carefully adjusted, so that the light 

 from the drawing surface is reduced to the proper intensity. 

 The mirror of the camera should be kept at 45 degrees, 

 where there is usually a stop; and the object to be drawn 

 should be put at the center of the field. A large object 

 can be drawn piecemeal, by shifting both slide and paper, 

 keeping the mirror at 45 degrees. Bristol board and an F 

 drawing pencil are good. If the lead of the pencil is cut 

 with flat facets, the pencil can be held so that one of the 

 facets reflects the light and shows up bright in the image. 

 When the camera is used on the monocular microscope, 

 the left eye should be shielded by a ground-glass disc. 

 When the drawing camera is attached to the monobjective 

 binocular with parallel tubes, it is possible, with practice, 

 to use both eyes with comfort. Or, as a rule, a small disc 

 of ground glass (or ordinary waxed paper) may be put 

 on the left eyelens. 



The Abbe drawing camera can be made with a half- 

 silvered Swan cube, in place of the Abbe cube with perfo- 

 rated reflector. (It is now made in this form by the Spencer 

 Lens Company.) 



Use of a Binocular Magnifier. — The writer draws only 

 the outline and the coarser details with the camera, taking 

 especial care to trace this outline accurately. Then he 

 puts the card with the drawing under a binocular magnifier, 

 amplifying three and one-half times, placed close to the 

 right of the microscope; removes the camera, and draws 

 in all the fine details. The drawing is then inked in under 

 the binocular with a fine pen, and India ink. It is good 

 sometimes to ink in strongly only the important parts, 

 such as chromosomes, or particular chromosomes, and 

 leave all else in outline, or merely dotted in. 



