238 TABLES 245-247. 



RADIATION CONSTANTS. 

 TABLE 245. Radiation Formula and Constants for Perfect Radiator. 



The radiation per sq. cm. from a " black body " (exclusive of convection losses) at the temper- 

 ature T (absolute, C) to one at / is equal to 



/= ff ( T* /*) (Stefan-Boltzmann) ; 



where <t= i.277Xio~ 12 gramme-calories per second per sq. centimetre. 

 = 7.66 X lo- 11 " minute " 



= 5.32 X io~ 12 watts per sq. centimetre. 

 The distribution of this energy in the spectrum is represented by Planck's formula : 



where / A is the intensity of the energy at the wave-length X (X expressed in microns, ju) and e is 

 the base of the Napierian logarithms. From Kurlbaum's value of the difference of the total 

 energy radiated from black bodies at 100 C and o C,/ioo /o = 0.0731 watts per square cen- 

 timetre (whence the above value of a) and \ aua T==2g^o (the mean of Paschen's and Lummer's 

 values), the following constants have been calculated (see Planck, Ann. d. Phys. 4, p. 562, 1901) : 



Ci = 8.813 X io 8 for/ in 

 C 2 = 14550 for X in microns 

 /max = 2.869 X io~ 16 T 5 for/in 

 X m 7'= 2930 for X in microns (ft) 



= *-200 X io- 16 7' & for/in 



TABLE 246. Radiation in Gramme- Calories per 24 Hours from a Perfect Radiator at to an abso- 

 lutely Cold Space (-273 0). 

 Computed from the Stefan-Boltzmann formula (Ekholm, Met. Z 1902). 



TABLE 247. Values of J A for Various Temperatures Centigrade. 



Ekholm, Met. Z. 1902, used Ci = 8346 X io and C 2 = 14349, and for the unit of time the day. 

 For 10, the values for J\ have been multiplied by io, for the other temperatures by 100. 



SMITHSONIAN TABLES. 



