92 TWENTIETH ANNUAL REPORT ON THE STATE CABINET. 



would Avarm fust in April. As, however, the ground is not warm 

 far below the surface, but on the contrary is veiy cold only a few 

 inches down, it cools very rapidly during the night. In May the 

 earth becomes warmed to a greater depth. In July the difference 

 between morning and evening temperature is again about as great 

 as in April. This is perhaps to be explained on the ground that 

 the hotter any body, the more rapidly it radiates heat and cools 

 by radiation. 



2. The second phenomenon worthy of comment is the fact that 

 our average for the year is but 47.20 deg.. whereas it ought to 

 be, considering our latitude, about 10 i\eg. more. I have already 

 hinted at the explanation of this deficiency. It is scarcely 40 deg. 

 of lonoitude from the northeastern termination of the o^reat old- 

 world mountain range in the promontory of Xavarin to the point 

 at Avhich tne great Xorth Arnerican chain commences. From the 

 direction in which these mountain ranges run, it is not probable 

 that they exert much influence upon the winds or the temperature 

 in the Pacific ocean. But they approach within about 90 deg. 

 of longitude as between Cape Finisterre, on the Spanish coast, and 

 the highlands of Texas ; and thus three-fourths of all the polar cur- 

 rent is forced to pass through this w^ind gap of about one-fourth 

 of the earth's circumference, and by consequence each place within 

 this region has about three times as much of the cold polar winds 

 as it ought, and is, moreover, deprived by the same cause of a 

 portion of the amount of the w^arm return current to which it is 

 entitled. 



Xor is this all. From the direction of the polar current from 

 northeast to southwest, in a rhomb or loxodromic curve, the influ- 

 ence of this conformation of the surface is felt much more severely 

 on the westerly side of this gap than on the easterly side, that is, 

 in the United States, than on the Atlantic ocean. This we see 

 in the direction of the isothermals. The isothermal of 50 deo^. 

 for the year, for example, leaves Santa Fe, in New Mexico, lati- 

 tude 35.41 deg., and passes so much to the north of east on its 

 w^ay across the American continent and the Atlantic ocean, that it 

 meets Great Britain in lat. 52 deg. or 53 deg. So also of the 

 other isothermals. 



This difference, however, between our average for the year and 

 that which is due to our latitude, is felt rather in the winter than 

 in the summer, as will be seen from the following comparison of 

 places in nearly the same latitude, selected on both continents : 



