2 HOW TO USE THE MICROSCOPE 



on the part of the reader. But I shall treat him as 

 one knowing but the barest facts, yet desiring to 

 have a more practical knowledge of microscopy. 

 In point, I write for the beginner who wishes to 

 know how to begin and how to proceed, in a simple 

 and relatively inexpensive way. 



The word " microscope " is derived from two 

 Greek words (mikros, httle ; skopein, to look at), 

 and a microscope is an instrument which presents 

 to the eye a magnified image of the object examined. 

 The simplest form of microscope is an ordinary 

 magnifying lens, whether in the form of a reading- 

 glass or a pocket magnifier ; while a compound 

 microscope is an instrument provided with at least 

 two lenses, one of which is called the "objective," 

 and the other the " eye-piece." The objective and 

 eye-piece are fixed in the opposite ends of a tube, 

 and the object is placed in focus under the objective, 

 which forms an image of a certain magnification ; 

 this image is again magnified by the eye-piece. 

 The fuial magnification depends upon the power of 

 the objective, the power of the eye-piece, and the 

 length of the tube. Taking an objective which 

 magnifies 15 diameters, an eye-piece magnifying 5 

 diameters, and having a tube of standard length— 

 10 inches — we have a final magnification of 15x5 = 

 75 diameters. 



Beginners are cautioned against statements issued 

 by vendors of cheap lenses as to their magnifying 

 powers. A microscope may be advertised as 

 capable of magnifying thousands of times. Those 

 " times " are the square of the standard diameters. 

 Thus 2,500 times is really the square of 50 diameters 



