56 ELEMENTS OF APPLIED MICROSCOPY. 
be seen, and if, as more commonly occurs, the light from 
the paper is the strongest, the object becomes almost 
invisible. When the illumination is properly balanced, 
both object and paper should be clearly seen, and the 
point of a pencil on the paper may be made to trace the 
outline of the object with accuracy. Obviously this 
wr 
Ocular 
VLLLILMIATLLUHUAUTLILLILIY 
% 
Axis 
tie 
MMM zal 
EEE Saeed 
Fic. 27.—COuRSE oF Rays IN THE CAMERA Lucipa. (After Gage.) 
device, primarily intended as an aid to the making of 
drawings of microscopic objects, may be used in microm- 
etry. With a given arrangement of apparatus, the size 
of the drawing on the paper will depend upon the size of 
the object. By removing the latter and substituting a 
stage micrometer whose image will be superposed upon 
that of the drawing, the size of the original object may 
be read off directly. 
