494 Dr. H. Arctowski on Normal Anomalies of 



67° ( = 50 + 17) amplitude would represent the variation 

 corresponding to the coefficient of perfect atmospheric trans- 

 parency* at the latitude of Nertchinsk, the lowest tempe- 

 rature of January must be considered 6°*5 too high, and the 

 highest July temperature 11°'5 too low, since the extreme 

 daily mean temperatures should be —37° and +30°. 



Thus it may be that, in this case, the decrease in amplitude 

 is in close connexion with the annual variation of atmospheric 

 moisture. During the summer months, the greater amount 

 of aqueous vapour diminishes the coefficient of atmospheric 

 (thermal) transparency very much more than during the 

 winter months, and so it is evident that the summer tempe- 

 ratures differ more from what they should be than the 

 temperatures observed during the winter. 



This leads to the question whether the steps of the 

 Nertchinsk temperature curve, and perhaps also the steps of 

 the curves of several other stations, are not partially due to 

 a rhythmical transport of atmospheric moisture. 



In the ascending part of the curve of Barnaoul the de- 

 pressions following the crests generally precede by 2 to 

 4 days the corresponding details of the curve of Nertchinsk. 

 The inflexions of the isotherms characteristic for these 

 changes progress therefore across Siberia from the W. 

 towards the E. 



But, as a result of the International Balloon ascents of 

 May 13th, 1897, Hergesell has shown that the typical 

 decrease of temperature observed then in Central Europe was 

 very much more accentuated at high altitudes than it was 

 near the ground "j*. Similar observations have been made 

 since. In consequence, the inflexion of the isotherms must be 

 more pronounced at an altitude of 10,000 m. than it is at the 

 surface of the earth's crust. . After each step of the ascending 

 temperature curve the entire air-mass above the station where 

 the step has been observed is changed. The work of the 

 progressive heating of the ground by solar radiation and the 

 heating of the air-mass above by convection currents, must, 

 to a certain extent, be begun anew, and probably under 

 different conditions. 



Evidently, to reach a definite conclusion it would be 

 necessary to study the records of individual years and the 

 weather maps as well. But the real difficulty, and at the 

 same time the great interest of the study of these normal 



* A. Angot, Ann. Bur. Centr. Met. France, vol. i. p. B. 121 (1883). 

 t Meteor. Zeii. vol. xvii. p. 1 (1900). 



