362 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
surface. Tie whole drawing eye-piece is fixed to the body-tube of the 
Microscope by a clamp and screw (fig. 63 e). The prism has a different 
torn in the two eye-pieces. Fig. 64 shows the form of the prism of fig. 62, 
Fig. 63. Fig. 64. 
f 
and fig. 65 that of the prism of fig. 61. The dotted lines indicate the 
path of the light-rays coming from the drawing surface. As seen from 
tigs.. 64 and^ 65, with the eye-piece fig. 62 the drawing surface must be 
inclined 12°, while with the eye-piece fig. 61 it must be inclined 45°, 
Fig. 66. 
or rather the Microscope must be inclined 45°, while the table on which 
the instrument stands is used as a drawing-board. 
The simplicity of the apparatus, and the fact that nothing about it 
needs adjustment, are great advantages. 
