PHYSICAL CONDITIONS. 



11 



The temperatures at noon showed some important differences 

 (fig. 3). The temperatures of the soil surface were highest hi the 

 open air (sec. 6) and lowest hi the deepest shade (sec. 1). The 

 soil temperature was practically uniform hi the bed without the fan. 

 In the bed with the fan the soil temperature was relatively low hi the 

 deeper shades, probably as a result of increased evaporation due to 

 the ail movement. 



BED 



B£D B 







ji//p 







s. 



*"->.. * 



'*?...- 









jc!l&££- 



4££^- 



^l 







&QL 



r 60**^0- 









I 













yd/i" 









35°C 



30° C 



25° C 



20 ° C 123456123456 

 Fig. 3.— Diagrams showing temperatures at noon, averaged for the entire period of the experiments. 



The air temperatures in sections 1 to 4 were noticeably higher in 

 bed B than in the corresponding sections in bed A. These differences 

 in air temperature were less clearly expressed hi the averages for the 

 entire period of the experiments than they otherwise would have been, 

 because of the occurrence of a number of dark or rainy days. The 

 absolute maximum temperatures of the air recorded at noon for the 

 period of experimentation bring out clearly the fact that higher tem- 

 peratures prevailed in the bed without the fan. 



Table III.— Absolute maximum temperatures during the experiments. 





Bed. 



Section. 





1 



2 



3 



4 



5 



6 



A (with fan i 



°C. 



34.0 

 38.0 



° C - . 

 35. 5 



36.0 



32.2 

 34.5 



°C. 

 32.5 

 33.5 



°C. 

 33 

 33 



°C. 



32 



B (without fan) 



32 







The important facts here shown are the comparative uniformity of 

 air temperatures in all of the different sections of bed A, and the rela- 

 tively great variation in bed B. 



The temperatures of the air, of the soil at the surface, and of the 

 soil at a depth of 8 inches at 6 p. m. show only slight chfferences (fig. 4). 

 In bed A the temperatures of the soil at the surface and at the depth 

 of 8 inches were comparatively low in the deeper shades, as a result of 

 the wind movement and the increased evaporation caused by the fan. 



The temperatures of bed A show remarkable uniformity in the dif- 

 ferent sections at all hours of observation. The only important 

 differences are to be found in the slightly lower temperatures of the 



279 



