105 
07 i Nachet’s Stereo-pseudoscopic Binocular Microscope, 
and on Nachet’s Stereoscopic Magnifier; with 
Remarks on the Angle of Aperture best adapted to 
Stereoscopic Vision. By W. B. Carpenter, Esq., 
M.D., F.B.S., &c. 
(Read June 12th, 1867.) 
Nachet’s Stereo-Pseudoscopio Binocular Microscope. — 
An ingenious modification of Mr. Wenham’s arrangement 
has been introduced by MM. Nachet, which has the attri- 
Fig. L 
Arrangement of Prisms in Nachet’s Stereo-pseudoscopic Binocular: — 
1, for Stereoscopic ; 2, for Pseudoscopic, effect. 
bute, altogether peculiar to itself, of giving to the image 
either its true Steoreoscopic projection, or a Pseudoscopic 
“ conversion of relief,’’ at the will of the observer. This is ac- 
complished by the use of two prisms, one of them (Fig. 1, a) 
placed over the cone of rays proceed- 
ing upwards from the objective, and 
the other (B)at the base of the secondary 
or additional body, which is here placed 
on the right (Fig. 2). The prism a 
has its upper and lower surfaces paral- 
lel ; one of its lateral faces inclines at 
an angle of 45°, whilst the other is ver- 
tical. When this is placed in the 
position 1, so that its inclined surface 
lies over the left half (/) of the cone ot 
rays, these rays, entering the prism per- 
pendicularly (or nearly so) to its infe- 
rior plane surface, undergo total reflec- 
tion at its oblique face, and, being thus 
turned into the horizontal direction, 
emerge through the vertical surface at 
right angles to it. They then enter the Nachet’s Stereo-pseudo- 
vertical face of the second prism b ; and scopic Microscope. 
