THE MICROSCOPE AND ITS PARTS. 3 



nature studies, and a desire to know somewhat of the 

 beauties hidden from our unaided vision; for the sim- 

 plest glass shows the student unim- 

 agined charms in the petal of a flow- 

 er, the sand he walks on, and in the 

 green scum that floats on every sum- 



J Fig. 1. A Pocket-lens. 



mer pool and disgusts him until his 

 little lens reveals its purity and grace. It is always ready 

 for the examination of anything picked up in the fields 

 or woods, it is small, and it is easily carried in the pocket. 

 It can be obtained in a great variety of shapes, so far 

 as the frame that holds the lens is concerned ; it can be 

 had with but one glass, or with two or three of various 

 powers, to be used alone or combined ; it can be bought 

 with a large lens of low power in one end of the frame, 

 and a smaller glass of higher power in the other. But 

 whatever form the beginner selects, he must remember 

 that the larger the simple lens the lower, as a rule, will 

 be the magnifying power, and the longer the working 

 distance, or the space between the glass and the object 

 when in focus ; and the smaller the lens the more con- 

 vex it will be, the greater power it will have, the shorter 

 the working distance, and the less of the object it will 

 show at one view, and consequently the more trouble- 

 some it will be to use. The beginner is advised to pur- 

 chase a good pocket -lens with a working distance, or 

 "focal length" as it is sometimes rather incorrectly 

 termed, of one or one and one-half inches. This is all 

 that is really needed for the examination of botanical 



