ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
327 
distance between them 2 in. So we have here a most complicated form 
of Huyghenian eye-piece, consisting of no less than four lenses. 
A short distance from the end of the nose-piece we have an equi- 
convex lens of 5J- in. focus ; this, as was stated before, is really the 
back lens of all the objectives ; for when the power is changed it is only 
the front lens of the objective that is altered. These front lenses, which 
are six in number, are mounted in a well-made and convenient rotating 
nose-piece, (A rotating nose-piece of a cumbersome form was made by 
Adams in 1746, and was fitted to his “ Universal Double Microscope.”) 
This compound Microscope consists therefore of six lenses, the largest 
number probably ever fitted to a non-achromatic Microscope. 
There is another piece of apparatus of much interest, viz. a ring 
with a bar fixed at right angles to it. This can be used for either sub- 
stage or superstage illumination. For substage illumination a biconvex 
lens, of 2 in. focus, is burnished into a short piece of tube which screws 
into the ring ; the bar attached to the ring slides through a socket in 
the stage (see fig. 73), the whole forming a crude substage condenser 
capable of being focussed. When superstage illumination is required, 
the lens and its tube are removed, and a lieberkuhn substituted for 
them ; the rod is inserted in the socket in an opposite direction, so 
that the lieberkuhn is brought immediately over the object on the 
stage. It will be noticed that the one lieberkuhn 
is made to do duty for all the powers (fig. 74). 
This combined sub- and superstage illuminator 
was employed by Jones in his “ Most Improved 
Compound Microscope,” and is figured in the 1798 
edition of Adams on the Microscope, but this is 
the earliest example yet recorded of it. The 
pivoted superstage, with three holes in it, which 
was fitted to all Benjamin Martin’s Microscopes, 
and which was also adopted by Adams and Jones, 
is unfortunately missing, but a place is fitted to receive it in the packing 
in the box. 
Some possessor of this instrument has been trying to compensate the 
non-achromatism of the objective by the use of a screen ; for there is a 
piece of green glass roughly cut to fit the tube of the substage condenser. 
This must be a very early, if not the earliest, instance of a screen. 
The Microscope presented to the Society by Dr. Dallinger is full of 
interest, and is the earliest example of a rackwork limb Microscope in 
its collection. 
Ross’s Hew Model Medical School and Educational Microscope. — 
This instrument (figs. 75 and 76) has been specially designed for the use 
of demonstrators, teachers, and medical, dental, veterinary, and pharma- 
ceutical students. It is a modification of the well-known Boss Eclipse 
stand, and is intended to provide students, at the outset of their career, 
with a^ thoroughly good instrument at a small initial outlay, but ad- 
mitting of subsequent addition of parts without structural alteration, 
and rendering it ultimately capable of doing the most advanced work. 
Its construction is substantial, and all its different parts are well fitted, 
and it will be found perfectly steady in all positions, even wdien used 
with the highest power objectives. The stage is sufficiently large to 
Fig. 74. 
