15 



On a new Combined Binocular and Single Microscope. 



By F. H. Wenham. 



(Eead December 12tli, 1860.) 



At the meeting of this 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 eflFect 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, 1 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 

 afi'ords 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- 



