MICROSCOPIC OBJECTS. 



203 



ing apparatus. First, then, is fig. 3, consisting of a tube 

 containing either a rectangular prism or a plane metal, to 



Fig. 7. Fig. 9. 



Fig. 8. 



which the tube c, d, fig. 1 (p. 195), with its adjustment and 

 the object-glasses, is to be screwed at a, the end b being 

 adapted to the screw at the objective end of the body b, 

 fig. 1, which is then equipped for action in a horizontal 

 position ; only you must adjust it to the height of your 

 eye by drawing the rod m, fig. 1, up or dowoi, and then 

 fix it by means of the pinching- screw ; the height wiU of 

 course depend upon your own and that of the chair and 

 table you make use of, and also upon the focal length of 

 the object-glass employed. AU you want now is some- 

 thing to raise the stage up to the corresponding elevation, 

 and then everything wiU go on much as before. Now 

 this you shall have." You see that baU at c, fig. 4, (a 

 section of it is shown at fig. 6, p. 202) : it is an excellent sub- 

 stitute for a cradle-joint, and may be used instead of that 

 already described in fig, I, g ; it has three holes in it, 



T 2 



