88 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



observations will not only be more directly comparable with the 

 observations on high mountains than those used here for such a 

 comparison, but they will also furnish a basis for studying the 

 variations in a dry atmosphere and the influences by which these 

 variations are affected. Further, the study of the radiation of the 

 upper air layers is as yet very incomplete and ought to be extended 

 by means of continuous observations on high mountains or, perhaps 

 better, from balloons. My observations indicate that the " perfectly 

 dry atmosphere " has a radiating power as great as 50 per cent of the 

 radiation of a black body at the temperature of the place of observa- 

 tion. The upper air layers — the stratosphere — must therefore have 

 a considerable influence upon the heat economy of the earth as a 

 whole. Observations at high altitudes of the absorption and radia- 

 tion of the atmosphere are therefore very desirable. 



Finally, means must be found to study the effective radiation 

 during the daytime in a more systematic way than has been done 

 in this paper. The effective temperature radiation — that is, the dif- 

 ference between the total effective radiation and the access of scat- 

 tered skylight — can evidently be obtained by measuring these two last 

 named quantities simultaneously ; measurements that do not seem to 

 involve insurmountable difficulties. 



