106 



MICROSCOPIC ILLUSTRATIONS. 



in an inclined position, or the finger-springs, fig. 19 

 which are suited to hold large aquatic live -boxes, &c. &c. 



Fig. 19. 



C o 



o 



An arm, c, is attached to the lower fixed plate, for car- 

 rying a small condensing lens, or reflector, for throwing 

 condensed light upon opaque bodies. 



In Mr. Tyrrel's arrangement two sockets were fixed 

 in the front at x, x : the one for holding the condensing 

 lens, and the other the forceps, instead of the studs ?/, y, 

 and the arm c. The objections to this plan were, that 

 the condensing lens was moved together with the object, 

 so that the illuminated spot did not remain under the 

 centre of the instrument. The necessary consequence 

 was, that a re-adjustment was to be made at every move- 

 ment. Also, the situation of the sockets was such as to 

 obstruct large plates of glass containing thin sections of 

 fossil wood, &c. &c. from being laid upon the stage. 

 These inconveniences are entirely obviated in the im- 

 proved stage. 



Fig. 20. 



The upper plate or moveable part of the stage has a 

 circular aperture, b, furnished with two angular notches, 



