VIEWS OF THE MICROSCOPIC WORLD. 



INTRODUCTORY CHAPTER. 



THE MICROSCOPE, AND THE MOUNTING OF MICROSCOPIC OBJECTS, 



MICROSCOPES are divided into two classes, single and compound. The single mi 

 croscope in its simplest form is a convex lens, and the magnified image of the object 

 passes at once to the eye of the observer ; the 

 object being magnified in the ratio of the focal 

 distance of the lens to the limit of distinct 

 vision, which varies from 5 to 10 inches in dif 

 ferent persons. A single microscope is repre 

 sented by Fig. 1, where A B is the lens; C D 

 an object placed in the principal focus of the 

 lens, at the distance H I ; and E F the magni 

 fied image, seen at the distance of distinct vision 

 by the eye at N. The image exceeds the ob 

 ject in length and breadth as much as N K is 

 larger than H I. 



The compound microscope must have at least 

 two lenses, viz., the object-glass and the eye-glass. 

 The office of the former is to produce a magrii- Fi - 



fied image of the object, which image is again magnified by the eye-glass, as if it was 

 an object ; the eye-glass being, in fact, a single microscope. The compound micro 

 scope is represented in Fig. 2, where A B is the object, D C the object-glass, 

 and F E the image of the object formed by the object-glass, so situated as to be 

 in the principal focus of the eye-glass 

 G- H. By this lens the divergent rays 

 of light proceeding from the image F E, 

 have their directions so changed, that 

 entering the e\ 7 e on the side of the lens 

 Gr P H, a second magnified image is 

 clearly discerned at K L, at the limit 

 of distinct vision. The entire mag 

 nifying power of the instrument is 

 e^ual to the combined effect of the two 

 glares, and is estimated as follows : 

 The imnge F E is as much larger than 

 the object A B, as its distance from 

 the centre of the object-glass C D ex 

 ceeds the distance of A B from the same Pig. 8. 



