ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



533 



ocular of approximately right-angled shape can be applied to the in- 

 strument ; it is placed in the sleeve of the horizontal tube (fig. 54, b). 

 A prism suitably placed deflects the rays to the ocular, and the operator 



F=Q>H^l4QM^l=^qDEEj 



Weg 1-2 =1-2' 



Fig. 54. 



can therefore make his observations in the ordinary microscopical atti- 

 tude. For the light-source either the incandescent gas-mantle, the 

 Nernst lamp, the limelight, or the electric arc-light may be used ; but for 

 photomicrography only the three last can be recommended. The arrange- 



Fig. 55. 



ment of the parts of the illuminating apparatus will lie understood from 

 figs. 5-4 and T>6. At a slight distance from the light-source L a re- 

 volver diaphragm J x limits the illuminating area. If the filter-screen K 

 is used it will be placed between Jj and the illuminating lens B. The 



