ZOOLOGY AND BOTANY, MICROSCOPY, fc TC . 



227 



Microscope magnifies 10 diameters. The Microscope having been ar- 

 ranged, the preparation is moistened with some strongly refracting 

 liquid and hand-centred ; the iris rotated to cut off all superfluous 

 light so that only the preparation to be measured is visible through the 

 Microscope. Whether the object is viewed from above or below it is 

 well to illuminate it with the usual mirror. When the loup is removed 

 the limiting angle is viewed with the telescope. 



.-si: ■: 



Fig. 44. 



The general appearance of the instrument is shown in fig. H. In 

 the stage-plate, carried on a pillar set on the horseshoe foot, is a rotatory 

 horizontal circle graduated in .degrees. Above, it bears a perforated 

 prolongation on which the hemisphere H is situated. The screws z and 

 j respectively centre and adjust the hemisphere. Sp is the mirror for 

 the under illumination. In the tube P, just above the mirror, is the 

 nicol polariser adjustable, by means of its sleeve, in the three positions 

 of 0°, 45°, 90°. The vertical circle V, on which the telescope (or 

 Microscope) is affixed, is graduated into half degrees, and by means of 



Q 2 



