i6 



COMPOUND MICROSCOPE AND ITS PARTS 



[Ch. I 



Fig. 17. Tripod Magnifier. 



§ 16. Mounting of simple microscopes. — Magnifiers are arranged 

 in mountings to be held in the hand; for example, reading glasses 



and pocket magnifiers. The tripod 

 magnifier (fig. 17) may be held in the 

 hand or supported by its legs over the 

 object to be seen. Sometimes there is 

 a special support with arrangements 

 for focusing as well as holding the 

 magnifier in any desired position (fig. 

 19). This arrangement is especially 

 desirable when magnifiers are used for 

 dissection. For the purposes of dis- 

 section and examining objects under 

 a small magnification, binocular ar- 

 rangements like spectacles are very 

 convenient, as one can move the head and bring the object into view 

 at will (§ 145). 



Compound Microscope 



§ 17. This, as shown in fig. 3 and 20, and explained above, aids 

 the eye in obtaining an enlarged retinal image by two steps, viz. the 

 formation of a large real image by 

 the objective and a retinal image 

 of this real image by means of the 

 microscope ocular, and the cornea 

 and crystalline lens of the eye, the 

 ocular acting in general Hke a simple 

 microscope (§ 3). 



For holding the objective and oc- 

 ular and focusing the microscope, 

 there are a number of mechanical 

 arrangements necessary. For illu- 

 minating the object there is usually 

 a mirror and often a condenser. It 

 is customary and convenient to divide the parts of a compound micro- 

 scope into two groups: (i) the optical parts, and (2) the mechan 

 ical parts (fig. 25). 



Fig. 18. Tripod Magnifier with 

 A Section Removed to Show the 

 Two Component, Convex Lenses 

 AND Intervening Diaphragm. 



