Chase.] 



312 



[February. 



omitted such records as extended over a period less than from three 

 to five years. The compari-son is confined to the extra-tropical regions, 

 because the double maxima in the torrid zone would have compli- 

 cated the results too much for my present purpose. The differences 

 are counted from January in the Northern, and from July in the 

 Southern hemisphere. The first series of ratios for the Northern 

 hemisphere is computed from the monthly averages at 217 stations, 

 recorded in Dove's V. table, '< Abweichungen, 1845-1855, bezogen 

 auf Mittel langerer Reihen." At 206 of the stations the observa- 

 tions covered periods of from ten to seventy-seven years, the general 

 average period of the entire table being upwards of twenty-two years. 

 The second series is obtained by combining the more limited ratios 

 of the several countries, a method which gives undue weight to the 

 European observations. The third series is based on the respective 

 European, Asiatic, and North American averages, allowing to each 

 grand division a weight corresponding to the portion of its area 

 which is embraced in the temperate zone. The ratios of the South- 

 ern hemisphere (where the stations are few in number, and confined 

 to the sea-coast), are calculated by the first method. 



General and Local Eatios of Monthly Temperature- 

 Differences. 



» Mean of Dove, Coffin, and Quyot. 



