ERRORS CONCERNING THE MICROSCOPE. 39 



Of late years the Microscope has not only become 

 indispensable to the scientific student, but a delight to 

 the amateur. Nevertheless certain popular errors still 

 deter many from its employment ; and now that it is 

 no longer the costly instrument it used to be, those 

 errors should be combated. A very general belief of 

 its ''injuring the eyes" will be found even among 

 microscopists. On evidence the most conclusive, I 

 deny the accusation. My own eyes, unhappily made 

 delicate by over-study in imprudent youth, have been 

 employed for hours daily over the Microscope without 

 injury or fatigue. By artificial light, indeed, I find it 

 very trying ; but by daylight — which on all accounts is 

 the best light for work — it does not produce more 

 fatigue than any other steadfast employment of the 

 eye. Compared with looking at pictures, for instance, 

 the fatigue is as nothing. Nor should any uneasiness 

 be felt at the musccB volitantes, which may be ob- 

 served for the first time after using the Microscope. 

 Few eyes are altogether without them, and it is erro- 

 neous to attribute them to the Microscope, because 

 they may not have been previously observed. The 

 student should early learn to keep the unoccupied eye 

 open, not to screw it up, and distort his countenance, 

 because the sight of other objects confuses him. In a 

 little while he will learn to attend only to the eye look- 

 ing through the Microscope ; and his studies will be 

 greatly relieved thereby. 



It is further said that microscopic observation is apt 

 to be very erroneous, and that we can see whatever we 

 wish to see. Undoubtedly men often do see what they 



