THE MICROSCOPE 



AND 



MICROSCOPICAL METHODS, 



CHAPTER I. 



THE MICROSCOPE AND ITS PARTS. 



APPARATUS AND MATERIAL FOR THIS CHAPTER. 



A simple microscope (§ 2, 9) ; A compound microscope with nose-piece (Figs. 

 6S-80), eye-shade (Figs. 59-60), achromatic (<! 18), apochromatic (? 20), dry (§ 15), 

 immersion (§ 16), unadjustable and adjustable objectives (§ 21, 22), Huygenian or 

 negative (§ 35), positive (ji 34) and compensation oculars (<S 36), stage microme- 

 ter, homogeneous immersion liquid (§ 16, Ch. IV), benzin and distilled water ({! 103- 

 108). Mounted letters or figures (§ 49) ; ground-glass and lens paper ($ 49). 



A MICROSCOPE. 



\ 1. A Microscope is an optical apparatus with which one may obtain a clear 

 image of a near object, the image being always larger than the object ; that is, it 

 enables the eye to see an object under a greatly increased visual angle, as if the ob- 

 ject were brought very close to the eye without affecting the distinctness of vision. 

 Whenever the microscope is used for observation, the eye of the observer forms an 

 integral part of the optical combination (Figs. 16, 21). 



\ 2. A Simple Microscope. — With this an enlarged, erect image of an object 

 may be seen. It always consists of one or more converging lenses or lens-systems 

 (Figs. 16-20), and the object must be placed within the principal focus ({! 9). The 

 simple microscope may be held in the hand or it may be mounted in some way to 

 facilitate its use (Figs. 17-20). 



