116 



Scientific Geology. 



the Connecticut. The Deerfield, being a mountain torrent, and of less 

 extent, is raised several hours earlier than the Connecticut after a rain. 

 It even begins to subside before the latter has risen much. But as 

 the Connecticut swells, it throws back the waters of the Deerfield over 

 the broad basin among the mountains, and sometimes retains it there 

 for three or four days, or even a week, until the very finest sediment 

 is deposited. The consequence is, a rapid growth of alluvium, and 

 great fertility of soil. 



It is interesting to observe in Deerfield meadows the numerous 

 changes in the bed of the river, that have taken place at no very re- 

 mote period; though none of much importance since the settlement of 

 the place by the whites. A map of these changes might be instruc- 

 tive as illustrating the operation of existing geological causes. But I 

 did not judge it expedient to construct one, since so many other cases 

 of more importance will require drawings. I remark, however, that 

 as the banks of this river are so easily Avorn away, constant changes 

 are taking place with much rapidity by the action of the stream, 

 that it must be a fine place for studying nuviatiie dynamics. 



Patches of river alluvium are represented on the map in Stock- 

 bridge, Sheffield, Great Barrington, Longmeadow, Springfield, West 

 Springfield, Northampton, Hadley, Hatfield, Whately, Deerfield and 

 Northfield. 



Coast Alluvium. 



This sort of deposition is of two kinds. The first is produced by 

 tides and currents in the ocean, which frequently transport large 

 quantities of soil from one place to another, and cause it to accumulate 

 in those situations where their force abates, or is destroyed. In the 

 southeastern part of the State, such cases are numerous : and I have 

 regarded the sandy accumulations of this kind in Provincetown ; op- 

 posite Chatham and Harwich; on the north shore of Barnstable ; and 

 in several places along the northwest coast of Nantucket, as of suffi- 

 cient extent to deserve a notice upon the map. Deposits of this kind 

 on a smaller scale are very common in the southeast part of the State. 



Salt Marsh Alluvium. 



Salt marsh alluvium results from the joint action of two, and some- 

 times three causes : 1. the decay of salt marsh plants; 2. the silt 

 brought over the marsh by the tides : and 3. from the alluvial soil 

 brought down by steams, when these happen to empty through those 



