202 F. W. Very— On the Solar Constant. 



If the supposition were correct that A == 21 + J a , the solar 

 constant would have to be much larger than 4, since, as I have 

 shown by the reduction of an observation by Yiolle,* a. value 

 of I as great as 2*86 is reached at the altitude of 13*7 km. 

 Twice this would be 5*72 without including anything for J a .f 



For his second method, Bigelow employs that of spectro- 

 bolographic energy-curves and the determination of the effec- 

 tive solar temperature from the maximum ordinate. This 

 method, which I have discussed recently in this Journal, £ 

 seems to me the one least open to objection. Here Bigelow 

 has obtained ratios by dividing the summed ordinates of the 

 energy-curves by that for a temperature of 6900° Abs. C. 

 These ratios are compared with those for J a /A, which are quite 

 similar, and the author concludes that " this shows that the 

 energy lost in bolometer spectrum is the same as J a , and it is 

 absorbed in the lower levels " (op. cit., p. 281). This conclu- 

 sion involves the assumption that all of the depletion suffered 

 by the solar rays is produced by that atmospheric absorption 

 on which J a depends. This assumption is certainly incorrect, 

 since a large part of the lost radiation is reflected and does not 

 enter into the thermodynamic equations of the atmosphere in 

 any way. It is true that if the losses by reflection and by 

 absorption were proportional at every level in the atmosphere, 

 the above ratios would be the same as if the whole process 

 were absorptive, and the indications are that there is such an 

 approximate proportionality ; but the proportionality need not 

 be exact, and the approach to exactness probably varies with 

 the season. The following are the observed ratios : 



Station Washington 



Altitude above sea-level 64 m 



Ratio from the bolometer spectrum -363 

 " by thermodynamic theory.. *362 



About 2/3 of the atmosphere remain above Mt. Whitney 

 and also 2/3 of the depletion ; hence there is no evidence that 

 the depletion takes place a in the lower levels," except in the 

 general sense that the atmosphere itself exists principally at 



* " A High-level Measurement of Solar Radiation," Astrophysical Journal, 

 vol. xxxvii, pp. 25-30, January, 1913. 



f My determination has been criticised by Mr. Abbot in the Astrophysical 

 Journal for March. 1913. Only one objection is relevant, namely, that con- 

 cerning the rate of cooling of black copper, and this is not justified, as would 

 be evident if my investigation of the theory of the observations could be 

 given in full. Unfortunately, this would require a lengthy discussion, and 

 I have not behind me the power of a great institution, which can afford to 

 publish such work in extenso. 



|" Solar Eadiation," this Journal (4), vol. xxxvi, December, 1913, cf. 

 especially pp. 610-614. 



b. Wilson 



Mt. Whitney 



H80 m 



4420 m 



•258 



•236 



•287 



•225 



