5i8 THE POPULAR SCIENCE MONTHLY. 



are manifested. The diminution of light goes on almost unnoticed by 

 well-formed eyes, for it is compensated by the increase of the used 

 surface of the cornea. Less perfect eyes, on the other hand, not being 

 able to perform their functions with ease, have to make fatiguing 

 efforts to accommodate themselves to the situation, which tend to in- 

 crease existing defects or to induce short-sightedness. 



Adults are less liable than children to suffer injury from insufficient 

 light, for several reasons : 1. Their pupils being less dilatable, they 

 are obliged to desist from their work sooner when the light dimin- 

 ishes ; 2, They make more frequent use of glasses ; 3, They are less 

 often confined, like school-children, and compelled to continue their 

 labors after the light has become insufficient ; and, 4, The coverings 

 of their eyes are less extensible, and, if they have so far escaped 

 myopia, they have more chances of continuing free from it. 



A good management of the daylight is especially important with 

 regard to the construction of schoolhouses. It is not enough to lay 

 down a rule establishing the proportion which the surface of glass 

 should bear to the number of pupils ; attention must also be given to 

 the direction whence the light comes to each pupil. The darkest 

 point in the room must be light enough, and for this it is necessary 

 that each desk shall receive a sufficiency of light direct from the sky. 

 Every one who has practiced photography knows that the sky acts 

 more strongly than any terrestrial body upon the sensitive surface. 

 The least favored place in the room should be within the reach of this 

 light. Nevertheless, the direct rays of the sun should be avoided, for 

 they will dazzle. Where such an arrangement is otherwise practica- 

 ble, the advantage of a diffused light may be gained by opening win- 

 dows on the north side. Then, if the seats are placed perpendicularly 

 to the wall occupied by the windows, so that the pupils may receive 

 the light from the left side and from above, the result will be satisfac- 

 tory provided the width of the room does not much exceed the height 

 of the tops of the windows above the floor ; for, under this condition, 

 the least favored seat will still look upon about one twentieth of the 

 surface of the sky. With ceilings of the ordinary height, unilateral 

 lighting answers very well for rooms that do not exceed twelve or 

 thirteen feet in width. For larger rooms, windows may also be 

 opened on the other side, or behind the pupils, but never in front of 

 them. 



If we open windows in opposite sides of the room, we must arrange 

 it so that they shall not be on the south side, for that would let in the 

 glare of noon. For this reason it would be preferable to direct the 

 axis of the room north and south, in which case it may be expedient 

 to temper the forenoon and afternoon sunshine with transparent cur- 

 tains. This arrangement will also give us the advantage of a better 

 lighting in the morning and afternoon during the short days of winter. 

 A certain latitude in orientation is admissible, which may extend to 



