296 PHYSIOLOGY. 



or white wall, if it can be avoided. White walls are likely 

 to injure the eyes. Choose a dark color for a covering for 

 a reading table. Sewing against the background of a white 

 apron has worked serious harm. Direct sunshine very 

 near the book or table is likely to do harm. 



2. Position in Reference to Light. Preferably have 

 the light from behind and above. Many authors say " from 

 the left," or "over the left shoulder." In writing with the 

 usual slant of the letters this may be desirable. But ver- 

 tical writing is now strongly advocated, as it enables one 

 to sit erect, and have the light from above and equally for 

 the two eyes. Sitting under and a little forward of a hang- 

 ing lamp will thus give the light equally to the two eyes 

 and send no light direct into the face. In reading by day- 

 light avoid cross-lights so far as possible. 



3. Electric Light. The incandescent electric light 

 has an advantage in being readily lighted, without matches, 

 and in giving out little heat ; but owing to its irregular 

 illumination (due to the shadow cast by the wire or fila- 

 ment), it is not well suited for study or other near work. 

 For this purpose an Argand gas or kerosene burner is 

 much to be preferred, since it throws a soft, uniform, and 

 agreeable light upon the work. 



4. Reading Outdoors. Reading out-of-doors is likely 

 to injure the eyes, especially when lying down. To try to 

 read while lying in a hammock is bad in many ways. Too 

 much light directly enters the eye, and often too little falls 

 upon the printed page. 



5. Reading Heavy Books. Do not hold the book or 

 work nearer the eyes than is necessary. " So far as possible 

 avoid continuous reading in large or heavy books by arti- 



