ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



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of D, so that when the plate is in position, and loaded with a weight, 

 L adjusts itself to parallelism with M, and the plate rests evenly upon the 

 two edges. The block K which carries L is not fixed, but is made to slide 

 along the bar D, and is clamped by the screw N ; in this way the distance 

 between the inner edges of L and M can be set to any length between 10 

 and 30 mm. Between L and M and beneath them is a totally reflecting 

 prism i, by which the light reflected into it by the glass plate on the rod h 

 passes vertically upwards through the upper horizontal face. The prism 

 is fixed on three screws, by which its upper surface may be adjusted to 



Fig. 7. 



parallelism with the plate, and it is slowly raised or lowered by a milled 

 head at the lower end of m. The prism is supported on the plate p, and 

 can always be brought into the middle of the space between L and M by 

 the screw n, and fixed by the clamps o o. The position of L, and con- 

 sequently the distance between L M, may be measured either by the micro- 

 meter-screw and index at G, or more conveniently by the Microscope z. 

 S is a horseshoe support, in which turns an axle bearing the pillar T and 

 clamped by s. Upon T are the two slides with micrometer-screws U V, by 

 which the Microscope z can be moved horizontally through measured dis- 

 tances, either parallel or perpendicular to the length of the bench ; z turns 

 about the axle x, which is clamped by the screw y. The Microscope itself 

 1887. L 



