48 



THE MICROSCOPE AND ITS REVELATIONS. 



Fro. 



supports. The advantages of this general design have now been satis- 

 factorily demonstrated by the large use that has been made of it ; but 

 the details of its construction (such as the height and slope to be given to 

 the hand-rests) may be easily adapted to individual requirements. 



47. Beck's Dissecting Microscope, with Nachet's Binocular. A sub- 

 stantial and elaborate form of Dissecting Microscope, devised by the late 

 Mr. K. Beck, is represented in Fig. 36. From the angles of a square ma- 

 hogany base, there rise four strong brass pillars, which support, at a 

 height of 4 inches, a brass plate 6-J- inches square, having a central aper- 

 ture of 1 inch across ; 

 upon this rests a circular 

 brass plate, of which 

 the diameter is equal to 

 the side of the preced- 

 ing, and which is at- 

 tached to it by a revolv- 

 ing fitting that sur- 

 rounds the central aper- 

 ture, and can be tight- 

 ened by a large milled- 

 head beneath ; whilst 

 above this is a third 

 plate, which slides easi- 

 ly over the second, be- 

 ing held down upon ifc 

 by springs which allow 

 a movement of 1^ inch in 

 any direction. The top- 

 plate has an aperture of 

 1-j- inch for the reception 

 of various glasses and 

 troughs suitable for containing objects for dissection; and into it can 

 also be fitted a spring-holder, suitable to receive and secure a glass slide 

 of the ordinary size. By turning the large circular plate, the object 

 under observation may be easily made to rotate, without disturbing its 

 relation to the optical portions of the instrument; whilst a traversing 

 movement may be given to it in any direction, by acting upon the smaller 

 plate. The left-hand back pillar contains a triangular bar with rack- 

 and-pinion movement for focal adjustment, which carries the horizontal 

 arm for the support of the magnifiers; this arm can be turned away 

 towards the left side, but it is provided with a stop which checks it in the 

 opposite direction, when the magnifier is exactly over the centre of the 

 stage-aperture. Beneath this aperture is a concave mirror, which when 

 not in use, lies in a recess in the mahogany base, so as to leave the space 

 beneath the stage entirely free to receive a box containing apparatus; 

 whilst from the right-hand back corner there can be raised a stem car- 

 rying a side condensing-lens, with a ball-and-socket movement. In addi- 

 tion to the Single lenses and Coddington ordinarily used for the purposes 

 of dissection, a Binocular arrangement was devised by Mr. K. Beck, 1 

 on the principle applied by MM. Nachet, about the same date, in their 

 Stereo-pseudoscopic Microscope ( 38). Adopting Mr. Wenham's method 

 of allowing half the cone of rays to proceed to one eye without interrup- 



Beck's Dissecting Microscope, with Nachet's Binocular 

 Microscope. 



" Transactions of the Microscopical Society," N. S., Vol. xii. (1864), p. 3. 



