RECORD OF TESTIMONY AND STATEMENTS IN RELATION TO 197 



NECESSITY FOR DISTRICTING PLAN 



of heat the sun's direct rays are beneficial or prejudicial according to cir- 

 cumstances. Heat is absorbed by walls of brick, stone or concrete, with the 

 consequence that the air near them is heated; heat is also transmitted 

 through building walls to the' rooms. In winter this is an advantage in 

 this climate, but in summer it may be a disadvantage. Walls shaded from 

 the direct rays of. the sun tend to make houses cooler. In summer this is 

 desirable but in winter undesirable. The direct rays of the sun influence 

 the moisture of the air as well as its temperature. The evaporation of 

 water is increased, but as the capacity of air for holding moisture is also 

 increased by heating the relative humidity may be decreased. At all events 

 the sum total of the effect of sunlight is to raise the sentient temperature, 

 that is, the temperature shown by the wet bulb thermometer. It is this sen- 

 tient temperature coupled with air movement which affects the health and 

 comfort of human beings. 



Sunlight likewise causes movements of the air. This is due to unequal 

 heating in different places. The air currents thus set up are gentle and 

 desirable. Places which never receive the sunlight are more likely than 

 others to contain stagnant air. 



Considered from the standpoint of light, the sun's rays profoundly 

 affect the lighting of rooms. This is a matter of common knowledge, but 

 quantitative relations have been shown by many photometer tests made at 

 points located at different distances from windows, and by similar tests 

 made at the windows of different stories in tall buildings the exterior light- 

 ing of which is influenced by adjoining buildings. The sun's rays are re- 

 flected in various ways from exterior surfaces of buildings so that the 

 exterior conditions materially influence the interior lighting, and the nearer 

 the buildings are together the greater is the importance of this factor. 



The sun's rays have an effect on vegetation, as will be mentioned later. 

 Sunlight tends to remove moisture from particles of dust in the air thereby 

 improving a foggy atmosphere. It tends to dry pools of water which might 

 otherwise become breeding spots for mosquitoes. The sun's rays have a 

 marked disinfecting action and prevent the growth of molds and fungi, 

 thereby eliminating odors of certain kinds. They also destroy bacterial life, 

 whether the bacteria are floating in the air, or are attached to the exposed 

 surfaces of pavements, floors, or walls. To the extent to which this occurs 

 the danger of infection from certain disease germs is lessened. Sunlight 

 has both a physiological and a psychological influence on human beinsfs. To 

 these may be added the aesthetic effect of light and' shade produced by sun- 

 light. In these various ways sunlight is desirable for the health and comfort 

 of human beings, while the complete absence of sunlight is correspondingly 

 detrimental. 



Daylight 



By daylight is meant the indirect lighting from the sun, that is, lighting 

 received from the sky or clouds and reflected from various surfaces. While 

 it is possible for human beings to exist without direct sunlight and even 

 without daylight, it is the experience of the race that both sunlight and 

 daylight m sufficient amounts are highly desirable. Daylight is necessary 

 not only for the health and comfort but for economic reasons. Too little 

 light causes eye-strain with its train of physiological disturbances, and de- 

 creases the productiveness of work. It unfavorably influences the mental 

 condition. Light promotes cheerfulness, while gloomy rooms depress 

 vitality. Lack of daylight limits the length of the working day in some 



