8 MICROSCOPY TOR BEGINNERS. 



actors ; and when she returned it she said, " Thank you. 

 I don't like it much ; I can see a good deal better with- 

 out it." 



To " get the focus " it is not really necessary to close 

 one eye, although that is usually done. If both eyes 

 are open, the one looking through the lens becomes so 

 interested that the other sees nothing ; or, if you prefer, 

 you may say that the brain becomes so interested in con- 

 templating the image formed on the retina of the eye 

 examining the magnified object, that it fails to note the 

 retinal impressions of the other. But if one eye must 

 be closed, it can be done, after very little practice, with- 

 out clapping your hand over it. This applies equally 

 well to the use of the compound microscope. 



To focus a pocket-lens hold the object to be examined 

 in the left hand, and while looking through the glass 

 raise and lower it with the right hand until the magni- 

 fied object appears clear and distinct, the outlines sharp, 

 and without a fringe of color, and the surface rough or 

 smooth, rounded or concave, as it indistinctly appears to 

 the unaided eye. The focus cannot be obtained without 

 this experimenting every time the glass is used. A 

 good plan is to place the lens nearer the object than you 

 know to be necessary, but always without allowing the 

 two to come in contact, and then to slowly raise the 

 glass until the image is distinct, when it will be focussed. 

 Keep it steadily in that position and study the object. 



The compound microscope (Fig. 2) consists of the 

 stand, the eye -piece, and the objective, although the 



