Alluvium of Rivers. 



115 



Alluvium of Rivers. 



The deposits produced by the overflowing of rivers, are the most 

 common and familiar example of this stratum. They will, of course, 

 consist of that heterogenous mixture which a swollen and agitated 

 stream sweeps along. When first the river issues from the mountains 

 and begins to spread over the plains, coarse gravel and sand, and not 

 unfrequently large bowlders, will be deposited. The finer materials, 

 and most of the vegetable and animal substances, being lighter, will 

 float on farther before subsiding. So that the portion of an alluvial 

 tract which is nearest the mouth of the stream, will generally be most 

 valuable in an agricultural point of view, being made up of the finest 

 and richest loam. 



It is quite obvious that the power of rivers in depositing alluvium 

 must be lessened by every successive innundation ; since the more el- 

 evated the banks, the less frequently will the stream rise above them ; 

 and the less the amount of water thrown over the meadows. In some 

 places, along the Connecticut and its tributaries, the banks have al- 

 ready attained such an elevation, that it is only at long intervals that 

 the floods are high enough to surmount them : and yet they are ob- 

 viously the result of alluvial deposition. 



The Connecticut and its tributaries, the Deerfield and the Westfield, 

 furnish the only examples of river alluvium of much extent and im- 

 portance in the State. Some fine meadows of this description, how- 

 ever, occur on the Housatonic, in Stockbridge, Great Barrington and 

 Sheffield. Indeed, every river in the State, and every brook, present 

 limited tracts of this stratum. But only those along the Connecticut 

 and Housatonic were thought deserving of a place on the Map. In 

 some instances the deposition of the Connecticut, the Deerfield, and 

 the Westfield, is 15 or 20 feet thick. Logs, leaves, walnuts, butter- 

 nuts &c. are frequently imbedded at that depth, and but slightly chan- 

 ged. Relics of this kind, though of but little importance to the geol- 

 ogists of the present age, may be viewed with great interest in future 

 times, when this alluvium shall have become consolidated and other 

 formations shall be imposed upon it. 



The alluvial basin of Deerfield river, in Deerfield, is perhaps the 

 most remarkable example of this formation in the State. It is shut in 

 on all sides by high land, and the river is obliged to force its way to 

 the Connecticut through a narrow gorge in a high ridge of greenstone ; 

 and its direction where it empties, is almost opposite to the course of 



