350 



GENERAL SCIENCE 



motion of the waves. The nerves of the eyes are irritated, and this 

 irritation in turn is communicated to the nerves of the stomach. 

 The result is seasickness. Car sickness is caused in much the 

 same way. 



Abusing the Eye. Many people are very careless in the treat- 

 ment of their eyes. Some of the most common abuses are lying down 

 in a strong light or facing a bright light. Reading in a moving train 

 causes eye strain by trying to follow the unsteady type. Moving 



FIG. 230a. A far sighted eye at rest. The 

 rays of light meet behind the retina. 



FIG. 2306 represents rays of light from a 

 distant object focused on the retina by an 

 increased convexity of the lens, the increase 

 being obtained by the muscular effort known 

 as accommodation. In other words, one 

 who has such an eye has to use his accom- 

 modation for distant as well as near vision, 

 while the one with a normal eye can save 

 all his accommodation for near work. 



FIG. 230c represents the error corrected by a 

 convex glass, the necessity for distant ac- 

 commodation removed and accommodation 

 reserved for near vision. 



FIG. 230. 



pictures cause the muscles of the eye to do more work in ten minutes 

 than they would do in a week of ordinary usage. 



'Alcohol and tobacco may have very injurious effects on the eyes. 

 Tobacco smoke is very irritating to the lids and to the delicate outer 

 covering of the eyeball. 



Objections to Wearing Glasses. Many people object to wearing 

 glasses because they make them look old. If one has any trouble 

 with his eyes, he should go to an eye specialist and be properly 

 fitted to relieve the trouble; this saves a great deal of suffering for 

 the present, and possibly permanent injury to the eyes which can- 

 not be corrected later. 



