8b 



MICROSCOPE AND ACCESSORIES 



[_CH. I 



most conclusively that the eye is a part of the optical arrangement 

 when the microscope is actually used for observation, and that the 

 microscope with the eye is a different apparatus from the microscope 

 considered by itself. 



The diagrams, Figs. 16 A, B, are introduced to show under what 

 conditions both a virtual and a real image may be seen without 

 changing the position of the magnifier or the object. 



FIG. 17 A. Diagrams showing- the formation of real and of virtual images 

 and of the retinal image in using the simple microscope. See the explanation of 

 Figs. 14, 75, 16. 



Simple microscopes are very convenient when only a small mag- 

 nification (Ch. IV) is desired, as for dissecting. Achromatic triplets 

 are excellent and convenient for the pocket. For use in conjunction 

 with a compound microscope, the tripod magnifier (Fig. 17) is one of 

 the best forms. For many purposes a special mechanical mounting is 

 to be preferred. 



COMPOUND MICROSCOPE 



\ 12. A Compound Microscope. This enables one to see an enlarged, in- 

 verted image. It always consists of two optical parts an objective, to produce an 

 enlarged, inverted, real image of the object, and an ocular acting in general like 

 a simple microscope to magnify this real image (Fig. 21). There is also usually 

 present a mirror, or both a mirror and some form of condenser or illuminator for 

 lighting the object. The stand of the microscope consists of certain mechanical 

 arrangements for holding the optical parts and for the more satisfactory use of 

 them. (See frontispiece. ) 



\ 13. The Mechanical Parts of a laboratory, compound microscope are shown 

 in the frontispiece, and are described in the explanation of that figure. The stu- 



