RIVER SYSTEMS OF NEW HAMPSHIRE. 



327 



ature is unusually low for the latitude. The line of the same average 

 temperature for the year crosses Europe several hundred miles farther 

 north, corresponding to the mouth of the St. Lawrence and the southern 

 coast of Labrador. Thus while New Hampshire cannot be declared to 

 be cold in respect to comfortable habitableness and capacity of vegetable 

 production, it is so in a relative sense, and as compared with other coun- 

 tries no further removed towards the poles. 



This is mainly caused by the cold oceanic current already referred to, 

 which the Arctic sea pours forth upon the north-eastern shores of our 

 continent. This effect is exerted on so grand a scale that the whole 

 north-east portion of North America is constituted a geographic region 

 of relatively low temperature. The focus of this district is at the north- 

 east corner of Hudson's bay, its relative deficiency of heat being 13°. 

 The temperature of all adjacent regions is lower than that due to the 

 latitude in proportion to their proximity to this point. Thus, at Quebec 

 the deficiency is stated by Wells as nearly 7°, and at New York, 4°; 

 throughout New Hampshire it is therefore about 5 ".5, — that is, our mean 

 temperature is what might be expected were our geographic position five 

 degrees farther north. The temperature of Europe, on the other hand, 

 is much warmer than would be expected for the latitude, owing to the 

 warm current of the Gulf Stream, which is constantly pouring upon its 

 shores. 



This comparatively low temperature of our state largely increases the 

 volume of its streams. This is effected, first, by the condensation of a 

 large amount of moisture from the warm south and south-west winds, 

 inducing a more abundant rainfall than could be looked for in our lati- 

 tude and upon the lee side of the continent ; and, secondly, by diminish- 

 ing the waste of water from evaporation, preserving consequently a larger 

 proportion for removal by rivers. Having already noticed the conditions 

 which are concerned in the first of these results, it remains to speak here 

 of the relation of evaporation to water-power, and the modification of 

 this influence from our comparatively low temperature. 



Of the total rainfall of the state, probably sixty per cent, is removed 

 by evaporation from our surface before it reaches the sea. In the case 

 of various reservoirs, where an exact measurement of this proportion 

 could be taken, the evaporation from the drainage area has been found 



