116 APPLIED SCIENCE 



source of light, the sun, has been shut off in a great many 

 buildings. The result is that artificial illumination in the 

 daytime is a practical necessity. When such artificial 

 sources of light are used in place of sunlight they must 

 meet the needs of the eye and be installed with that aim 

 in view. 



Light should not shine directly into the eyes, but directly on 

 the object we wish to see. The paper that gives the great- 

 est amount of diffused reflection is white blotting paper. 

 Dirty paper does not diffuse light as well as a clean, white 

 board. White painted surfaces diffuse light well. Green, 

 red, and brown surfaces have low diffusive values. Color 

 on the walls of rooms and shops produces an effect upon 

 the color of objects within the room. Any strong color 

 on the wall will furnish a colored component of the total 

 light. 



Shades and reflectors are used either to modify the colors 

 of the radiating object or the brilliancy of the source, so 

 as to keep too bright a light out of the eyes, or to modify 

 the distribution of light so as to put it where it will be of 

 most service. 



117. Incandescent Lamps. The most common form of 

 electric lighting at the present time is the incandescent lamp. 

 It consists of a slender filament of some highly resisting 

 material prepared from carbonized paper or bamboo and 

 enclosed in a glass bulb. The ends of the filament are con- 

 nected to platinum or lead wires fused in the glass. One of 

 the wires is connected with the base of the socket, and the 

 other with its rim. The intervening space is filled with 

 white cement, which is a non-conductor. An attachment 

 is placed on the socket by which the current enters and 



