CH. /] 



MICROSCOPE AND ACCESSORIES 



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. 



FlG. 18. Figure to show that with 

 a simple microscope if the object is slight- 

 ly beyond the principal focus (F)a real 

 image will be formed at A' which can be 

 seen by an eye at E, and thai if a normal 

 or hyperopiceye is at E' a virtual image 

 can be seen without changing the posi- 

 tion of the simple microscope. The long- 

 sighted eye can see this image best as it 

 naturally focuses converging rays on the 

 retina. The myopic eye either sees no 

 image at all, or a mere blur, depending 

 upon the amount of myopia. A. object ; 

 A/ real image above the magnifier; 

 A." virtual image which can be seen 

 below the lens by an eye at E' ; E. eye in 

 position to see a real image ; E.' eye in 

 position to see A" a virtual image ; F. 

 principal focus of the magnifier. 



A" < 



FIG. fo. Tripod Magnifier 



The diagrams, Figs. 17, 18, 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. 



Simple microscopes are very convenient when only a small 

 magnification (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. 

 19) is one of the best forms. For many purposes a special mechan- 

 ical mounting is to be preferred. 



