40 NEW YORK STAT^ MUSEUM 



materials by winds blowing from the west. Their locations are 

 shown on the map. In other portions of the surface of the delta 

 there are occasional dunes, but in general the materials of the 

 delta are too coarse to be lifted by the winds. 



Alluvium. The Hudson river is bordered by broad valley flats 

 in its course from the northern edge of the sheet as far as Still- 

 water. The surface materials of these flats are the fine sediments ■ 

 or silts that have been deposited at times of high water when the 

 river overflowed its banks. From Stillwater south to the head of 

 tide water at Troy the work of the river in the recent epoch has 

 been rather to lower its bed by erosion than to build up a flood 

 plain. Some narrow areas of alluvial lands occur along the banks 

 and in the cuiwe of the river north of Lansingburg there are two 

 islands of alluvial origin. 



Along the Hoosic river the flats east and south of Schaghticoke 

 constitute an interesting physiographical feature. It is evident that 

 at a former time the river described a meander both on its right 

 and its left bank. A factor in this shifting of its course was the 

 rock barrier west of Schaghticoke which in times of flood held 

 back the waters, causing the river to overflow its banks and divert- 

 ing its currents against the valley slope. As this barrier was 

 gradually reduced through erosion, forming the present gorge, the 

 river straightened its course. The meanders were cut off from 

 the main channel leaving, however, as a remnant, the present 

 linked channels on the north flat. 



An extensive alluvial flat, representing a recent meander of the 

 river, occurs along the Hoosic in its lower course. As observed 

 on the left bank of the river, the soil of this area is an alluvium 

 with admixture of mold; it is of a high degree of fertility and is 

 cultivated for market gardening products. 



Swamps. Areas of swampy or partially drained lands, repre- 

 senting glacial lakes or ponds which have been filled in by sedi- 

 ments and overrun by vegetation, have been indicated on the map 

 as far as observed. 



