CHAPTER VI. 
USEFUL MICROSCOPE ACCESSORIES, LABORATORY 
EQUIPMENT, WORK TABLES, RADIANTS. 
Drawing Cameras (Camera Lucidas). — It is very frequently 
the case that sketches, relative proportions of structural details, 
or actual measurements of component parts of preparations 
being studied must be entered into notebooks. Free-hand draw¬ 
ing is tedious, difficult, and if a sketch to scale is required, as is 
usually the case, an exceptionally good judgment of proportion 
is essential. To obviate these difficulties a drawing camera may 
be employed. Although there are many types of these devices 
upon the market, the chemist is usually restricted to those forms 
which permit employing the micro¬ 
scope in a vertical position. 
The most convenient of these 
drawing cameras are shown in Figs. 
62 and 63. 
If, after attaching one of these 
devices to the tube of the micro¬ 
scope above the ocular, the worker 
looks into the instrument, he is 
able to see simultaneously both the 
preparation and the page of the notebook. 
In the forms shown in Figs. 62 and 63, known as Abbe prism 
camera lucidas, there is placed above the ocular a cube of glass 
which has been cut diagonally, the surface of one-half being 
silvered and cemented again in place, after a central oval per¬ 
foration has been made through the silvered surface. This oval 
aperture allows the image-forming rays of the microscope to reach 
the eye while the silvered surface reflects from a mirror the image 
of the notebook page or drawing paper. Fig. 64 shows diagram- 
matically the path of the light rays, the dotted lines indicating 
127 
Fig. 62. Small Abbe Drawing 
Camera. 
(Bausch & Lomb Optical Co.) 
