15 
On a new Combined Binocular mid Single Microscope. 
By F. H. Wenham. 
(Read December 12th, 1860.) 
At the meeting of tMs Society in June last,, I exhibited 
and described an improved binocular microscope, on the 
principle of dividing the image by means of a thin achromatic 
prism fixed close behind the object-glass. The improvement 
on a former instrument (which had the defect of being 
pseudoscopic) consisted in refracting the right and left hand 
sections into the opposite eye, and by this transposition 
obtaining a true orthoscopic effect by an arrangement equally 
simple as before. Having since still further advanced the 
definition, by a modification in the construction of the prism, 
the performance was so superior to anything that preceded it, 
that several were made for parties who had seen the results, 
and which instruments proved satisfactory to their owners. 
It appearing evident that the use of the binocular micro- 
scope was likely to become general, I have directed my 
attention once again to its improvement, and come before you 
this evening on the same subject, to announce the attain- 
ment of a degree of success in respect to convenience, sim- 
plicity, and improved definition, that, considering the nature 
of the principle, could not have been anticipated. 
It is, perhaps, scarcely requisite to urge the advantage of 
being able to view minute organisms with the aid of both 
eyes together ; for it is admitted that the single microscope 
affords but little appreciation of undulations of surface or 
bulk. We have even now a vivid recollection of looking 
through the microscope for the first time, as exhibited at the 
Society of Arts five and twenty years ago, by our member, 
Mr. Cornelius Varley. The objects were the wheel ani- 
malcule and the sap circulation in the Chara. Not having, 
at that time, the least knowledge of the instrument or objects, 
we formed no idea of bulk; but observing a moving object 
in a field of light, supposed the effect similar to the repre- 
sentations of a magic lantern, the then familiar toy of our 
youth. 
The living organisms revealed by the microscope still 
possess a charm for us beyond all others, for herein can be 
traced the first links in the chain of creation. Quickly pass- 
ing from the simple vital plant-cell to higher grades of deve- 
