THE BINOCULAR MICROSCOPE. 165 



APPLICATION OP BINOCULARITY TO THE MICROSCOPE. 



The application of this principle to microscopic pur- 

 poses seems to have been tried as early as 1677, by a 

 French philosopher, le Pere Cherubin, of Orleans, a Capu- 

 chin friar. The following is an extract from the description 

 given by him of his instrument : " Some years ago I 

 resolved to effect what I had long before premeditated, to 

 make a microscope to see the smallest objects with the 

 two eyes conjointly ; and this project has succeeded even 

 beyond my expectation, -with advantages above the single 

 instrument so extraordinary and so surprising, that every 

 intelligent person to whom I have shown the effect, has 

 assured me that inquiring philosophers will be highly 

 pleased with the communication." 



This communication long slumbered and was forgotten, 

 and nothing more was heard of the subject until Professor 

 Wheatstone's very surprising invention of the stereoscope, 

 when it again attracted the attention of this philosopher, 

 who applied to both Eoss and Powell to make him a 

 binocular instrument. But this was not done ; and during 

 the year 1853 a notice appeared in Sillimaris American 

 Journal of a binocular instrument constructed by Professor 

 Riddell of America, who had contrived a binocular micro- 

 scope in 1851, with the view "of rendering both eyes service- 

 able in microscopic observations." ct Behind the objective," 

 he writes, "and as near thereto as possible, the light is 

 equally divided and bent at right angles, and made to 

 travel in opposite directions, by means of two rectangular 

 prisms, which are in contact by their edges somewhat 

 ground away, the reflected rays are received, at a proper 

 distance for binocular vision, upon two other rectangular 

 prisms, and again bent at right angles, being thus either 

 completely inverted for an inverted microscope, or restored 

 to their first direction for the direct microscope." M. 

 Nachet also constructed a binocular microscope, upon the 

 same principle as his double microscope, with the tubes 

 placed vertically and 2i inches distant. This even had 

 disadvantages and inconveniences, which Mr. F. H. Wenham 

 ingeniously succeeded in modifying and improving. 



