LOCAL CLIMATOLOGY. 73 



bergeii, and produces winters at the North cape of Norway, hiti- 

 tude 70, no colder than our own ; so that the winters of Iceland 

 are scarcely colder than those of Lombardy. 



But inside of this Gulf Stream, alone: the Canada and New-Ensr- 

 land coast, there is a cold stream passing from the Polar sea 

 towards the equator. The seasons are perceptibly retarded, espe- 

 cially in the spring, by this cold sea current along their coast. It 

 gives rise also to those cold northeast storms and winds which 

 are so disagreeablo through the spring and early summer. These 

 winds and storms are felt as far inland as Central New York, and 

 in some instances still farther. 



IV. The fourth cause named as affecting temperature, is, situa- 

 tion in reference to the great mountain ranges. 



The atmosphere presses upon the earth with a pressure of 15 

 pounds per square inch, or a weight equal to a stratum of water 

 about 30 feet deep. 



In consequence of the unequal distribution of heat and the rota- 

 tion of the earth on its axis, there is always a current called " the 

 jpolar cuiTent^''^ moving towards the equator, and another called 

 *' tJte return current,''^ moving in the opposite direction, or from 

 the equator to the poles. Sometimes the polar current is " the 

 surface current ^^^ as it is called ; that is, it blows next to the sur- 

 face of the earth, and the return current blows above it in the 

 other direction ; and at other times the order is reversed, and we 

 can always distinguish them by two signs : (1) The return cur- 

 rent blows in the northern hemisphere from a southerly direction ; 

 and (2) is warmer than the polar current, which blows from a 

 northerly direction. 



Now, when either of these winds, as surface current, meets with 

 a mountain range or other obstruction of the kind, it does, as a 

 stream of water would, turn around it, if it be higher than the 

 upper surface of the wind. Take, for example the Alps, and in 

 fact the great Eastern range extending from the Atlantic coast as 

 Pyrennees and reaching the Pacific coast as Altai. Starting from 

 the Atlantic coast at latitude about 40 deg., it stretches across the 

 continent with but few gaps, and reaches the Pacific coast at lati- 

 tude nearly 60 deg. ; and thus it is in just the latitude where 

 the polar and the return currents usually change position. The 

 consequence is, that the polar current is seldom if ever felt south 

 of this mountain range, while an undue share of the return cur- 



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