21 



than the akiminium bronze, and the dull black, G percent, less than 

 the white paint. The recording apparatus receiving the reflection 

 of the dull black showed that 18 j^ercent. less light was reflected 

 than the aluminium bronze. 



Table VII showing the Amount of Light Lost from Reflection 

 from Sky, Etc. Average of three Experiments. Exposures, 

 three to six hours duration. 



In another single experiment in which boards were painted 

 with aluminium bronze, white and black paints, similar results 

 were obtained, although there was a difference in the percentage of 

 light reflected from various surfaces. Assuming that the light 

 from aluminium bronze was equal to 100 percent., the white board 

 gave 80 percent, and the black, only 58 percent. 



From these tests it is evident that there is quite a difference in 

 the various reflecting surfaces, and that something might be gained 

 by using substances reflecting the most light. In our experiment 

 house the iron posts and purlins are painted white, and the 

 steam pipes black. The cement walls, which are about 2 1-2 feet 

 high, have a coating of water paint, and the water pipes are dressed 

 with aluminium bronze. This possesses a high reflecting surface, 

 and might be used on exposed steam pipes, etc. to advantage. 



The light reflected from the sky and from adjacent buildings 

 is an important factor in the greenhouse light problem, and experi- 

 ments were made to learn how much light was reflected through 

 the roof glass on the north side of a greenhouse. Both exposures, 

 which were made about 10 inches from the roof glass, were entirely 

 protected on the south side, and received no direct sunlight. In 

 one case the reflected light from above was shut out, and in an- 

 other, not; although both exposures received reflected light from 

 a cement walk below. An average of results obtained from three 

 experiments is given in table VII. The experiments demonstrated 

 a marked difference in the amount of light received at each ex- 

 posure, all of which were made on bright days. A large brick build- 

 ing having considerable window surface was located about thirty 

 feet from the tubes, and some light was probably reflected from 

 this structure, although the apparatus was so placed that it did 

 not receive any direct reflection from the building. This test 

 showed that considerable reflected light entered the greenhouse 

 even on the northern slope of the roof. This was true also of the 



