ZOOLOGY AND I50TANV, MICROSCOPY, ETC. 95 



MICROSCOPY. 



A. Instruments, Accessories, &c* 

 (1) Stands. 



Beck's Imperial Microscope. — This instrument has been designed 

 for critical work of the most advanced type. At the same time it is com- 

 pact, and does not stand too high from the table to be comfortably used 

 in a vertical position. In its complete form it is provided with coarse 

 focussing adjustment, double speed fine adjustment with graduated 

 head, full size eye-pieces, rack-and-pinion focussing draw-tube, gradu- 

 ated, additional slidins; draw-tube, graduated clamp to joint, graduated 

 concentric rotating stage, rack-and-pinion movement to rotating stage, 

 centring screws to stage, graduated vertical and horizontal stage motion, 

 coarse focussing sub-stage adjustment, fine focussing sub-stage adjust- 

 ment, centring sub-stage adjustment, swinging and sliding mirror. 



The stand is made upon two models ; the English tripod foot, and 

 the Continental base and pillar. In the English or tripod model there 

 is a splay between the front feet of 8.j in., and 9 in. from front to 

 back. A long lever clamp is provided to fix the Microscope at any 

 inclination, and the latter is limited in its motion in the exact horizontal 

 and vertical positions. The Continental model stand is unusually 

 large and steady ; the base measures 6 j in. in length by 4^ in. in 

 width, and is provided with a similar clamp to the joint. The limb 

 of the Microscope is pierced with a square hole and clamp screw, in 

 which an illuminator for opaque objects may be held. 



The body-tube of tho Microscope is 2 in. in diameter, and 3*6 in. 

 long, but with the nose and draw-tubes in their closed position it 

 measures 140 mm. or 5^ in. The nose-piece and draw-tubes may be 

 removed, and a photographic lens mounted in the centre of this short 

 and large diameter-tube allows of the use of a wide angle for low-power 

 photomicrographic work. The draw-tube is provided with a rack-and- 

 pinion adjustment, and has a ring fitting at its lower extremity, which 

 carries the object-glass screw-thread. An additional sliding draw-tube 

 is supplied, and both are graduated in millimetres ; a total extension of 

 tube with the two draw-tubes of 260 mm. is obtained. The diameter of 

 tho tube is that of the No. 4 largest Royal Microscopical Society's 

 standard gauge, 1*41 in., and an adapter is supplied to take tho 

 !No. 1 size, '917 in. Low-power and orthoscopic eye-pieces may be 

 made of the full size, which give a much larger field of view than can 

 be attained with the small size eye-piece. A small size body, with 

 sliding graduated draw-tube with a range of length of 140 mm. to 

 200 mm., is supplied to the simpler forms of the instrument. 



The coarse focussing adjustment is by means of a spiral rack-and- 



* This subdivision contains (1) Stands; (2) Eye-piecos find Objectives; (3) Illu- 

 minating and other Appiiratus; (4) Photomicrography; (5) Microscopical Optics 

 and Manipulation ; (6) Miscellaneous. 



