THE MICROSCOPE 



AND 



MICROSCOPICAL METHODS 



CHAPTER I 



THE MICROSCOPE AND ITS PARTS 



APPARATUS AND MATERIAL FOR THIS CHAPTER 



A simple microscope (§ 2, 11) ; A compound microscope with nose-piece (Figs. 

 70-80); eye-shade (Fig. 60), achromatic ($20), apochromatic ($22), dry (§17), 

 immersion ($ 18), unadjustable and adjustable objectives ($ 23, 24) ; Huygenian or 

 negative (I 38), positive ($37) and compensation oculars ($39) ; stage microme- 

 ter (Ch. IV) ; homogeneous immersion liquid (§18) ; mounted letters or figures 

 (£53) I ground-glass and lens paper (J 53). 



A MICROSCOPE 



§ I.- 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 

 object 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 (§ 11). 

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

 way to facilitate its use (Figs 17-20). 



