to obtain the sharpest focus to bring out details. Do 

 not expect too great a range in the fine adjustment. It 

 is even more dangerous to focus down to any extent with 

 the fine adjustment than with the coarse adjustment, 

 because any impact of the front of the objective on the 

 cover cannot be as easily felt. \Vhile moving the speci- 

 men about to observe different parts of it, it will be 

 necessary to continually work the fine adjustment to 

 keep the object in focus. It is always well to move the 

 specimen when trying to get a focus, for without the 

 movement one may be trying to focus upon a point 

 where there is no object, and again, the moving object 

 is more apt to be noticed as the lens comes into focus. 



It will be noticed during this movement that the 

 microscope reverses the image, and that the specimen 

 seems to move in the direction opposite to that in which 

 it is moved. This, along with the fact that the micro- 

 scope magnifies the movement as well as the specimen, 

 is perplexing at first and makes it difficult to move the 

 specimen just where it is wanted, and no farther. With 

 practice comes the delicacy of movement which enables 

 one to put the specimen just where he wants it. 



The beginner should always use the low power objec- 

 tives and oculars first. The low power objectives have 

 longer working distances and are not so apt to be in- 

 jured. They always show a larger portion of the speci- 

 men and thus give one a better idea of the general 

 contour. After obtaining this general idea the higher 

 powers can be used to bring out greater detail in any 

 particular part. If the objectives are par-focalized and 

 centered on a nosepiece as described on page II, the 

 change of objectives is made by simply turning one 

 objective out of the optkal axis and the other into it 

 without the necessity of re-focusing (except for a slight 

 turn of the fine adjustment) and again hunting up the 

 15 



