LOWELL. — TEMPERATURE OF MARS. 663 



For the earth in its entirety M = o and N = o, since what is lost hy 

 convection in one place is gained in another. 

 Applying this same formula to the case of Mars we have similarly — 



ai = .40 approximately, 



A 1 = , ,^ „ (1 —.17 X .32) = whole spectrum — albedo of its air X 

 1.524'' 



visible portion 



.946 



1.524' 

 fii = ai approximately, 

 vi = 1 — .13 = .87 



Whence for the earth under a clear sky 



^^^ A(l +v — va) 

 yd + v-^O' 



and similarly for Mars, substituting its values for A, a, and /?. 



Since in both a = ^ and yi = y approximately, we have Ti for Mars, 

 which gives 



r* A' 



But the earth is .50 cloud-covered, and the transmission of cloud 

 being not more than .20 (the value he takes), we have finally 



Ti* ^ Ai .99 



T ~A .60' 

 whence 



T, =^ .974 T, 



and 7" being 519.4° Abs. on the Fahrenheit, 



Ti = 505.7°, that is, 46.3° F. or 8° C. 



a result substantially the same as we have deduced. 



Had we assumed (3 to be .70 and to be in like proportion to a for 

 Mars, we should have had 



T*= 1.140- 



y 



and 7\*= 1.101—, 



71 



