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SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. y-] 



a large change of temperature in middle latitudes. The maximum 

 occurs on zero day, that is, on the day of the solar observation, 

 v^^hile at Nev^r York the maximum difference is 7° F. three days 

 after the solar observation, showing that the temperature changes 

 like the pressure changes move from the interior of the continent 

 to the eastern coast. It should be noted, however, that atmospheric 

 pressure is found highest with high solar radiation, while the highest 

 temperature is found with low solar radiation, the two being inverted 



Fig. 19. — Differences between mean temperatures with low and high solar 

 radiation, winter half-year, 1918-1922. 



to each other, and showing secondary maxima and minima at the 

 same intervals apart. The range from the maximum difference at 

 Winnipeg at zero day to a minimum difference at four days is 5.1° F., 

 while at New York the range from a maximum difference at three 

 days to a minimum difference at five days is 3.4° F. In summer the 

 maximum dift'erences at Winnipeg and New York came several days 

 later than in winter. 



The observations of the Astrophysical Observatory show not only 

 that the solar heat radiation varies materially from day to day, but 

 also show that the monthly mean values vary at times as much as 

 2 per cent from the normal. 



