THE 
MONTHLY MICROSCOPICAL JOURNAL. 
AUGUST 1, 1870. 
I—On an Erecting Binocular Microscope. By J. W. SteeHen- 
son, F. RAS. F.R.MS., Actuary to the Equitable Assurance 
Society. 
(Read before the Roya Microscopican Society, June 8, 1870.) 
Puate LVII. 
Brrore I describe the instrument which is on the table before me, 
it is perhaps desirable that I should briefly point out the purpose 
for which it was devised, without however dwelling on the great 
benefits which have unquestionably been derived trom binocular 
vision when low, or moderately low, powers are used. 
The inefficient working of the ordinary erector, when monocular 
mstruments alone were known, became more obviously unsatisfac- 
tory when Mr. Wenham’s beautiful invention was given to the 
world, for then, not only had we the optical defects and lowering 
of the magnifying power, which we had previously experienced, but 
we had in addition, whenever it became necessary to manipulate an 
object on the stage either in the way of dissection, selection or ad- 
justment, to revert to the old form of instrument, and to make the 
change necessary in its optical arrangements in consequence, whilst 
the altered circumstances under which the object was viewed, not 
unfrequently rendered its recognition difficult, if not impossible. 
My aim, then, has been to produce a binocular which, by in- 
version of the object, both laterally and longitudinally, shall act as 
an erector, and under which an object can therefore be dealt with 
without any change in the conditions under which it is originally 
EXPLANATION OF PLATE LVIL. 
Fic. 1.—The two lower prisms, showing the division and lateral inversion of the 
cone of light on leaving the objective. 
2.—The upper prism, showing the longitudinal inversion of the laterally- 
corrected image. 
», 3.—The three prisms as arranged in use—the two lower being rounded to fit 
into the arm which carries the object-glass. 
4,.—The microscope in its entirety, 4rd of actual size. 
VOL. IV. F 
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