ZOOLOGY AND P.OTAN, MICROSCOPY, ETC. 



395 



MICROSCOPY. 

 A. Instruments, Accessories, &c* 



(1) Stands. 



Bausch and Lomb's Petrographical Microscope Stand L C H.f — 

 This instrument (fig. GO) is intended to combine convenience of 

 manipulation with completeness of equipment. The excellence of the 

 same makers 1 L C stand included Nicols 

 of extra quality and size in addition to a 

 special illuminating device. The present 

 instrument combines these features with 

 the lever fine-adjustment and handle- 

 arm, the latter being so placed as to give 

 7'> mm. to the centre of the stage. The 

 stage itself is circular, and measures DO mm. 

 inside, and 102 mm. outside ; the gradu- 

 tions, which are in single degrees, are 

 read by convenient vernier. The stage- 

 plate lias a vulcanite top, and is pro- 

 vided with spring-clips and centring- 

 screws ; it has two scales at right angles 

 to each other, graduated in millimetres. 

 The plane-stage may be removed and 

 the revolving • mechanical stage substi- 

 tuted. This mechanical stage can be 

 completely rotated, and is graduated simi- 

 larly to the plane-stage ; it is designed to 

 carry the size of slides usually used in 

 petrographical work. The holders are 

 adjustable. Both movements are fitted 

 with verniers and graduations for record- 

 ing the field. The substage has a mount- 

 ing for the polariser or Abbe condenser, 

 and is focused by an accurate rack-and- 

 pinion of long range; the polariser may 

 be swung out of the optical axis when de- 

 sired. The body-tube is of fixed length and 

 lens, beneath which an iris diaphragm is mounted, so that the image 



Fig. 60. 

 is slotted for the Bertram! 



of 



* This subdivision contains (1) Stands ; (2) Eye-pieces and Objectives : (3) 

 Illuminating and other Apparatus ; (4) Photomicrography ; (5) Microscopical 

 Optics and Manipulation ; (6) Miscellaneous. 



t Bausch and Lomb Optical Co., Rochester, N.Y., Catalogue, Microscopes and 

 Accessories, p. 46. 



