14 Tlie Microscope. 



you cannot ascertain what you want with the lower 

 power, you must be content to see but a small portion 

 of the object clearly "in focus/' and cultivate the 

 habit of disregarding the rest. 



The beginner will not probably succeed in finding 

 anything nearly so well suited for observation with the 

 high object-glasses as some of the beautiful micro- 

 scopic preparations supplied by opticians. In these, 

 the object is placed on the centre of a slip of glass, 

 measuring three inches by one, and covered by a little 

 piece of thin glass manufactured for the express pur- 

 pose, and securely joined to the thicker slip. You 

 will do well to have a few of these at hand, both to 

 assist you in learning the use of your microscope, and 

 because if you wish to prepare objects for yourself, 

 the ready-made ones will show you what your own 

 work ought to resemble. 



A single scale of a moth, like that at fig. 8, 

 Plate I., would be suitable for looking at with a 

 powerful object-glass; and a small group of such scales 

 will easily be procured. Let the microscope incline 

 backward to whatever height is most convenient as 

 you sit at your table. Arrange the light properly,* 

 and place the slide upon the stage the slide, I 

 should explain, means the slip of glass with its pre- 

 pared object. There will be some sort of ledge on 

 purpose to support it in the inclined position of the 

 microscope. Find the object's place while the least 



* A very complete article on the illumination of objects will be 

 found in the " Intellectual Observer," for January, 18G3. Its title 

 is " The Eye and the Microscope," by H. J. Slack, Esq. 



