Drawing Apparatus. 
*Camera lucida after Abbe. The drawing surface is made 
visible b}^ double reflection, from a large plane mirror and from 
the silvered surface of a small prism in the eye-point of the eye- 
piece. The microscopic image is seen directly through an aperture 
in the silvering of the prism. By the concentricity thus obtained 
of the pencil of rays reaching the eye from both the microscope 
and the paper, the image and pencil are seen coincidently without 
any straining of the eyes. With this ai)paratus moreover drawings 
may be made on a horizontal surface without perceptible distortion. 
The brightness of the paper is regulated by smoke-tinted glasses 
which fit into the prism casing. The apparatus is adjusted for 
the No. 2 Huyghenian and the compensating eye-pieces 4 and G, 
but can also be used with very low amplifications, and also with 
the 6 and 10 dia. aplanatic lenses (No. 79) on the large dissect- 
ing stand I ; if to be used on dissecting stand III it requires a 
special fitting (which we supply for M. 8. — ) 
