RIVER SYSTEMS OF NEW HAMPSHIRE. 315 



wich. Iii consequence of this geographic position, almost equidistant 

 between the equator and the pole, the amount of evaporation in New 

 Hampshire is only that clue to a moderate temperature ; the moisture of 

 the soil is not burned away by long continued and excessive heat, nor 

 are the sources of water supply wholly cut off by long and uninterrupted 

 cold. For the same reason the winds are variable, not constant as 

 within the tropics, but coming throughout the year from every quarter of 

 the compass, rarely for more than two or three days from the same point, 

 bringing heat and cold, moisture and dryness, in succession. It follows 

 also from this geographic position, that the precipitation of moisture is 

 non-periodic. It occurs in the form of either rain or snow at all seasons, 

 tending to make the volume of streams constant throughout the year. 

 Its fall is usually gentle, often occupying several days for the deposition 

 of a single inch of water. On this account sudden and great inunda- 

 tions are of rare occurrence. It is generally attended, also, with a pro- 

 tracted continuance of cloud, fog, or mist, which lessens evaporation, 

 and, in consequence, increases the volume to be removed by drainage. 



The continental position of New Hampshire has the further effect to 

 produce a larger rainfall and a smaller amount of evaporation than the 

 average for this latitude. It is situated on the coast, and is constantly 

 visited, therefore, by currents of air directly from the ocean, tending to 

 produce a more equable temperature, increased rainfall, and a humid 

 atmosphere. It lies directly in the current of the south-west winds from 

 the Gulf of Mexico. This great inland sea is noted for its remarkably 

 high temperature, to which it presents an evaporating surface of 800,000 

 square miles in area. The prevailing course of our storms being from 

 the west and south-west, it is to a very large extent from this source that 

 their vapor is derived. This is precipitated upon us in our so-called 

 north-easterly storms, the moisture being brought in large measure by an 

 upper current whose course is opposite to that experienced below. 



This deposition, also, is relatively more abundant here than farther 

 south, because of the colder currents of air which these storms encoun- 

 ter here, after uniting with which their combined capacity for retaining 

 moisture becomes greatly diminished, the excess necessarily falling in the 

 form of rain. The whole circulation of the Arctic ocean, including all 

 the waters which are brought in by the currents through Behring's strait, 



