



46 Dr. Forty on the Climate of the United States, $x. 



Vancouver, l^jjj; and in eastern America, at Council Bluffs, 

 «gg ; and at Fort Wolcott, Rhode Island, 32 °" 5i 



69° 06* 



The law, as established by Humboldt, that the same causes 

 which produce the greatest convexity of the isothermal line also 

 equalize the temperature of the seasons, has been already well 

 illustrated in the table tracing the isothermal line of 55°-40 

 around the earth. The same isothermal curve, according to 

 Humboldt, runs on the western coasts about six degrees of lati- 

 tude higher than on the eastern; but to illustrate the law that at 

 this convex point the seasons are most equalized, another table 

 becomes necessary. Thus the annual mean temperature being 

 equal to the fourth part of the total of the winter, spring, sum- 

 mer, and autumnal temperatures, the same isothermal line of 

 53° 60 shows 



Winter. Spring. Summer. Autumn. 



At the concave summit in ) 53 o. 60 _32 o -00+52°'30-f 75°-604-54^50 

 America, 74° 40' W, Ion. i ' 4 



At the convex summit in ) 5r . fi0 _40°-10-|-5r-80-f 68°-40-f54°-10 



Europe, 2° 20' W. Ion. i ' 4 



At the concave summit in > w rn _24°-80-f-54 o -70-f-80 o -60+54°-30 



Asia, 116° 20' E. Ion. I 4 " 



At the convex summit in i MO ..^_ 4r-33-f-48 o -00- t-65 o -00-f 52°-67 

 America, 122° 37' W. Ion. ) 4 



The first three results on the same isothermal line are furnish- 

 ed by Humboldt. Unable to obtain the same annual temperature 

 on our Pacific coast, it becomes necessary to take a lower iso- 

 thermal line, (that of Fort Vancouver in the "Army Meteorolo- 

 gical Register,") which of course gives a contrast in the seasons 

 correspondent^ greater. It is thus seen that on the western 

 coasts, where the isothermal curve rises, or is convex, the seasons 

 are much equalized, the difference between the mean tempera- 

 ture of winter and summer being only about one half as great 

 as on the eastern coasts, where the line sinks, or is concave. But 

 this may be better illustrated by a tabular arrangement. 



Diff between mean temp- 



IsoUirrmalline. of winter and summer. 



Asia, eastern coast, 53° -60 ( At depressions, . . . 55 D 80 

 America, eastern coast, 5.T-60 { " " ... 43°-60 



Europe, western coast, 53°-G0 ) At summits, . . . 28°30 

 America, western coast, 5P-75 T " « t % 23° 70 



