14 NEW HAMPSHIRE AGRICULTURE. 



FRESHETS. 



The tillage portion of the First Minister's Farm, as before re- 

 marked, is a section of Merrimack River interval. 1 For one 

 hundred and twenty-two rods, the river forms a part of its 

 northern boundary. As one stands upon its bank, some fifteen 

 feet above its surface, when at its summer level, and looks up 

 and down its course, it seems a peaceful stream, and its quiet 

 flow suggests only the gentle lapse of the later years of a well- 

 spent life. Its channel has a width of some five hundred feet, 

 and its depth rarely exceeds fifteen. Unless ruffled by the wind, 

 its surface is as smooth as a mirror and reflects the trees and 



shrubs and flowers which line its wav. 



j 



But it is not always thus. At times, it rises in its might some 

 five, ten, fifteen and even twenty feet ; like a tawny giant from 

 his sleep, increasing its volume and accelerating its flow. So 

 long as it keeps within its banks, its current, though strong, is 

 comparatively harmless. 



When, however, swollen by the waters of excessive rains, 

 particularly if these be combined with those of melting snows, 

 it overflows its channel, its course is capricious, impetuous and 



1 The formation of the Concord interval is clearly revealed upon a careful ob- 

 servation of the adjacent territory. When, in a prehistoric age, the great ice 

 cap, which covered the northern part of this continent, receded from the Mer- 

 rimack valley, it left behind it a bed of glacial drift extending from one side 

 to the other of it. Upon the middle portion of this was subsequently laid an- 

 other of modified drift, through which the river has pursued its devious way, 

 cutting away its banks on alternate sides, all the while deepening its channel 

 and emptying its sand-laden waters into the ocean at Newburyport. This it 

 continued to do until the rocks of the underlying formation arrested its de- 

 scent. Since then, its depth has not been changed, but its channel has all the 

 while been moving laterally easterly and westerly, until it has passed over 

 the entire interval time and again. 



Most of these lateral movements have been gradual. Some of them, however, 

 have been violent and extensive. The September freshet of 1828 severed along 

 tongue of land of some thirty acres, from the east side of the river and trans- 

 ferred it to the west side and by a new channel then made converted it into an 

 island, since known as Bradley's Island. Again, in January, 1831, the river cut 

 off Hale's Point, near by, and transferred it from its west to its east side. 



These changes have generally resulted from natural causes. But several have 

 been made by other agencies. In 1846, or thereabouts, the Northern Railroad 

 turned all the water of the river at Sewall's Island into its eastern channel, 

 which it has since broadened at the expense of much valuable land. At about 

 the same time, this railroad cut a new channel across the base of Goodwin's 

 Point, thereby transferring a large tract of land to its west side and making it 

 an island. 



