112 



TABLES 103-110.- 



-COOLING BY RADIATION AND CONVECTION 



TABLE 103.— AT ORDINARY 

 PRESSURES 



According to McFarlane the rate of loss of 

 heat by a sphere placed in the center of a 

 spherical enclosure which has a blackened 

 surface, and is kept at a constant temperature 

 of about 14° C, can be expressed by the 

 equations 



e = .000238 + 3.06 X lO" 8 / - 2.6 X 10" 8 / 2 , 



when the surface of the sphere is blackened, or 



e = .000168 + 1-98 X 10" 9 / - 1.7 X 10" 8 r 2 , 



when the surface is that of polished copper. 

 In these equations, e is the amount of heat 

 lost in cgs units, that is, the quantity of heat, 

 small calories, radiated per second per square 

 centimeter of surface of the sphere, per de- 

 gree difference of temperature t, and t is the 

 difference of temperature between the sphere 

 and the enclosure. The medium through 

 which the heat passed was moist air. The 

 following table gives the results. 



TABLE 104.— AT DIFFERENT 

 PRESSURES 



Experiments made in Tait's Labora- 

 tory show the effect of pressure of the 

 enclosed air on the rate of loss of heat. 

 In this case the air was dry and the 

 enclosure kept at about 8°C. 



SMITHSONIAN PHYSICAL TABLES 



