ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



583 



any position by means of a milled head and screw. The condensers, 

 light filters, iris diaphragms, cooling chambers, lenses, mirrors and 

 prisms (figs. 84, 85, 86, 87, 88, 89) are so made that when in position on 



Fig. 83. 



the rail their centres are in alignment on the optic axis. The illuminat- 

 ing apparatus, arc, incandescent gas or paraffin lamp, fits on the bench, 

 and is provided with an adjustment for altering its position. 



Fig. 84. 



Fig. 85. 



Fig. 86. 



The platform upon which the Microscope is placed is provided with 

 a tilting movement by which the optic axis of the instrument may be 

 inclined up or down. The platform runs on three sets of steel rails ; 



