BecKj on a New Stand for a Single Microscope. 3 
tion^ and in either case they admit a large pencil of light free 
from aberrations. 
Nearly all the spare room in the case is made use of, first, 
Pig. II. 
by a good-sized box, which fits between the four pillars, for 
dissecting instruments and apparatus ; and secondly, by a nar- 
row strip of wood which occupies the top right-hand corner of 
the case and receives the magnifiers. 
The binocular arrangement requires a few words of expla- 
nation. I find that in 1853 Professor J. L. Riddell, of New 
Orleans, described a form of binocular magnifier that could 
be made by using four reflecting prisms or pieces of silvered 
glass, and I believe a somewhat similar plan has been for some 
time adopted in France as an adjunct to the ophthalmoscope. 
But in these binocular arrangements there seems to have been 
the one idea that, if the rays passing through the lenses are 
to be divided, both halves must be similarly treated ; this is 
now proved by Mr. Wenham^s most successful construction 
of the binocular compound microscope, not only to be un- 
necessary, but really disadvantageous. 
In the single microscope, when the object is in focus, the 
rays emerge parallel from the magnifier, and there is nothing 
to prevent the use of both eyes — one close to the lens and the 
other some distance ofi"; the size of the object in each instance 
is the same, and the union of both images is perfect. 
This arrangement is shown in Figs. I and II : half the aperture 
of the lens proceeds direct to one eye, and the other half is 
reflected by two \_ prisms to the other eye ; the two fields of 
