. On microscopical manipulation : being the subject matter of a course of lectures delivered before the Quekett Microscopical Club, January-April, 1869. ity drew increased attention to thesubje6t of binocular vision, but until a few years agono attempt seems to have been made to adapt theprinciple to microscopes. Owing to the short focallength of microscopical objectives, the use of tv\^oconvergent instruments would of course be im-pradlicable ; the only resource was to divide the pencilproceeding from the objedt-glass and convey half toeach eye. The earlier attempts resulted in theproduction
. On microscopical manipulation : being the subject matter of a course of lectures delivered before the Quekett Microscopical Club, January-April, 1869. ity drew increased attention to thesubje6t of binocular vision, but until a few years agono attempt seems to have been made to adapt theprinciple to microscopes. Owing to the short focallength of microscopical objectives, the use of tv\^oconvergent instruments would of course be im-pradlicable ; the only resource was to divide the pencilproceeding from the objedt-glass and convey half toeach eye. The earlier attempts resulted in theproduction of pseudoscopic instruments; that is, therelative positions of the objec5l viewed were reversed,projections being represented by depressions and thecontrary. This was found to be caused by the rays of light being conveyed to the wrong eyes, the rightc 2 20 MICROSCOPICAL MANIPULATION. side of the image entering the right eye, and the leftthe left eye, the effedl being that of a wronglymounted stereoscopic picture. It was found neces-sary that the right-hand image should be conveyedto the left eye, and vice versa, to produce a stereoscopic Fig. effedt; this was accomplished by M. Nachet of Paris,and Mr. Wenham by different methods, each havingtheir respective merits. As Mr. Wenhams is mostin use in this country, I will briefly describe it. Afour-sided prism of peculiar form (Fig. ii, A) is placed THE BINOCULAR MICROSCOPE. 21 in the body of the microscope, just behind the posteriorcombination of the objedt-glass (Fig. 11, B, a), which,when in position, it half covers. An additional body, l,is joined at a slight inclination to the left-hand side ofthe instrument, and the two bodies are furnished attheir upper extremities with draw-tubes, which supplythe means of making an adjustment for the varyingdistance between the eyes of different persons. Theimage formed by the left-hand half of the objedlivepasses up the straight tube to the right eye withoutbeing in any way interfered
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectmicroscopy, bookyear1
