TABLES OF DIFFERENCES OF MEAN TEMPERATURES. 165 



unsatisfactory results, for the reason that the distribution of Tieat passing into the 

 atmosphere directly and indirectly through surface radiation, evection, and conduc- 

 tion, and the amount parted with by radiation during the night, as well as the 

 modifying influence of the aqueous vapor, present far too complex phenomena to 

 be accounted for numerically. We have already seen that the absolute amount of 

 vapor and the relative humidity are among the causes sufiicient to impress a totally 

 different character upon the range of the daily fluctuation, from that we might 

 otherwise have expected from the meridian altitude of the sun and the length of its 

 diurnal arc. 



