ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



437 



Geneva Company's Travelling Microscope. — This is a very inge- 

 niously constructed instrument, shown set up in fig. 51, and as folded 

 for travelling in fig. 52. 



To fold it, the narrow curved support between the base and the 

 uprights is turned back within the latter. 

 Fig. 51. a pin which fixes it in position (not shown) 



being first withdrawn from the base. The 

 uprights are then brought down to meet 

 the base, the body-tube, stage, and mirror 



Fig. 52. 



being at the same time swung so as to be 

 horizontal. The base consists of an open 

 frame only, but is heavy enough to give 

 complete steadiness. 



The milled head seen on the right of 

 the body-tube clamps the socket of the 

 latter between the uprights, so as to pre- 

 vent it altering its inclination. The fine 



adjustment is effected by tilting the stage at one end by the screw 



beneath it. 



When folded, the instrument measures 7^ X 3 in. x 1| in. 



Eeichert's Microscope with modified Abbe Condenser. — 

 C. Eeichert, of Vienna, with his medium stand (No. III.) supplies a 

 modified form of Abbe condenser, shown in fig. 53, with which may 

 be contrasted the original form by Zeiss (fig. 54). 



The optical combination, consisting of three lenses with an 

 aperture of 1-30 N.A., is screwed in a ring a attached to an arm d. 

 This arm revolves on a pivot beneath the stage, so that it can be 

 turned away from the stage, as shown in the figure. The fitting c of the 

 lower lens has inner grooves to receive the diaphragm slide b, which 

 can be drawn out entirely, for changing the five diaphragm-stops which 

 drop into an aperture at e, or partially (to the right or left), so that 

 the aperture may lie eccentrically to the optic axis for oblique illumina- 

 tion. A spring-pin falling in three holes marks the central or extreme 

 lateral positions of the slide. The lenses with the diaphragm slide 

 can be rotated in the ring, so that all azimuths of obliquity can be 

 obtained. The pin / fits into a hole beneath the stage when the 

 condenser is centered. 



A slide beneath the stage for the ordinary cylinder diaphragms 

 can be used when required on the condenser being turned aside. 



