ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



359 



objectives, bottles for stains, Horder's storage box for cover-glass pre- 

 parations, and the special aluminium frame to carry the latter. 



Mineralogical Microscope.* — This is shown in fig. 58, and is a 

 strongly constructed model, inclinable, with a stage 85 mm. square. 

 The Nicol's prisms have rectangular surfaces ; the polariser can be 

 removed, and the analyser behind the objective inside the tube can be 

 easily slipped to one side. The object under examination does not 

 turn : the Nicol's prisms being turned together by means of cog-wheels 

 worked by a screw-button ; this arrangement is something like the 

 Allan-Dick model made by Swift. A graduated circle, with a vernier 

 reading to one minute, indicates the position of the polariser with 

 regard to the object. Rapid change of parallel light into converging light 

 is effected by lenses mounted on a slide. The variation of the focus pro- 

 duced by the Nicol's prism is corrected by a lens. There is an opening 

 behind the objective for the introduction of mica or quartz lamellae, etc. 



Fig. 159. 



Fig. 59a. 



The instrument has the quick-changing nose-pieces. The position of the 

 oculars with respect to the Nicols is determined by shades. 



The lenses for this series of Microscopes are all supplied by Messrs. 

 Seibert and Kraft, of Wetzlar. 



Travelling Microscope.t — This is shown in fig. 50. It is described 

 as "large size," but is reduced to a small bulk by the easy dismounting 

 of its component parts. The instrument can also be used as a simple 

 Microscope for dissection (fig. 59a). The present form seems an im- 

 provement on the earlier model, which was described in this Journal.! 



* Catalogue Soc. Genevoise pour la construction d'instruments, de physique et de 

 me'canique, No. 2485 (1900) p. 102. 



t Op. cit., No. 2430 (1900) p. 101. X Journal E.M.S., 1884, p. 437. 



