300 



OUR PHYSICAL WORLD 



elements so as to free the image from distortion and fringes of 

 color. 



The telescope is very much like the microscope, except that 

 the object to be examined is a long way off, but the objective 



--"RACK a PINICN 

 COARSE ADJUSTMENT. 



^^ 



GRADUATED SHORT SLIDE . 



HEVOLV 



STAGE 

 ADJUSTABLE 



SPRING FINGER 



CONDENSER; MOUNTING ON,. 

 DROP SWNG ARM'""" 

 LOWER IRIS DIAPHRAGM-' 



FOR OeUftUE Ll6HT. 



STACE CENTERING 

 MIRROR 



MIRROR FORK 

 MIRROR BAR 



"RflCK & "PiNION 



BUTTON. 



FIG. 147. A compound microscope. (Courtesy of the Spencer Lens Co.) 



still forms an image of the object which is examined by the eye- 

 piece that magnifies it (Fig. 148). So that this image may be 

 as large as possible, the tube of the telescope is often very long 

 (see Fig. 149). In both telescope and microscope the tube is 

 not essential, but it is convenient to shut out the light from 



