86 
physik, 1881, p. 298; Journ. of the R. Micr. Soc. 1881, p. 203). 
The division of the pencil of rays emerging from the objective to 
produce two separate images is effected at the upper end of the 
tube by partial reflexion at a thin stratum of air between two 
juxtaposed glass prisms a and h. The direct rays proceed to an 
eye-piece B, arranged in the axis of the tube, the reflected rays 
undergo another reflexion through a prism h' in a second eye-piece 
B' placed excentrically so as to make its axis and that of the 
tube include an angle of 14". Both eye-pieces give images of 
equal magnification. The excentric eye-piece may be adjusted by 
a screw D to suit the inter-ocular width of the observer. Bisection 
of the pencil for producing stereoscopic effects is made by ad- 
justable semi-diaphragms above the eye-pieces; without these the 
apparatus gives binocular non-stereoscopic vision. Available with 
low or high power objectives (only achromatic) on any of the 
large stands provided with rackwork coarse adjustment and which 
permit of the body being shortened to at least 140 mm. (Fig. 43.) 
In case 
In ordering this binocular apparatus for any microscope 
it will be necessary to send a sharp sealing-wax impression 
of the upper end of the tube. 
Reversing Prism after NACHET (p r i s m e r e d r e s s e u r), 
for obtaining erect images when using the compound microscope 
as a dissecting microscope. With plate mount to rest on No. 2 
eye-piece 
*Diffraction Plate after abbe, for demonstrating the effects 
of diffraction in the formation of microscopical images (Monthly 
Micr. Journ., Febr. 1877, p. 82; Dippel, Mikroskop p. 144). 
— Three cover-glasses silvered at their lower surfaces, with 
traced groups of parallel and crossed lines, cemented on a glass 
slip; in case 
