ALLUVIAL DIVISION. 5 
much more rapidly for a few years past, than at any former period since observations have 
been made. This is caused principally by the increased quantity of land brought under tillage, 
and from which every shower removes more or less earthy materials in the streams, far more 
than when the soil was covered by its native forests. The small streams deposit the greater 
portion of the coarser earthy materials washed into them ; but much of the finer portions is 
carried in suspension into the Hudson, and finally deposited more or less remote from its 
source. The coarser materials washed down the Hudson are deposited at and near the Over¬ 
slaugh, where the river current is checked in ordinary stages of the river by the flood-tide. It 
is only during freshets, that the river current is sufficient to overcome the tidal flow, so as to 
carry its coarse alluvion farther down the stream. This has caused serious obstruction to 
navigation in time of low water in summer and autumn, and science and art have been put in 
requisition to overcome this natural impediment to navigation. Large sums of money have 
been expended to make a channel of sufficient width and depth to accommodate the various 
interests concerned in the navigation of the river, and keep it open. The best means have 
been employed to obviate the difficulty, and the system employed is the only one that would 
be permanently useful; but it must be kept constantly in operation, the piers elongated every 
few years, and a dredging machine frequently employed in seasons when the river is very 
low. In low water, sand accumulates between the piers ; and in a higher stage of water, much 
of the sand is washed through the channel, and deposited in the eddies and still water beyond 
them ; so that in places where the water was before of considerable depth, sandbars and shoals 
form, and eventually obstruct the navigation. The dredging machine or an elongation of the 
piers then becomes necessary, so as either to deepen the channel, or cause an acceleration of 
the current to effect the same object. Large quantities of additional matter, in the form of 
sand and mud, are continually washed down the river from above ; so that the difficulty is a 
permanent one, and will continue as long as fields are cultivated and water flows. A perma¬ 
nent fund ought to be established to provide for the necessary annual dredging, and the occa¬ 
sional elongation of the piers. 
The soils of the flats and islands in the Mohawk valley, and in that of the Hudson below 
Lansingburgh, have long been celebrated for their fertility. They all contain some lime mixed 
with argillo-siliceous apd organic matter. 
The alluvions of the Hoosick are similar to those of the Mohawk, in consequence of the 
water flowing for a considerable distance over argillaceous and calcareous rocks, which are 
similar in composition to those of the Mohawk. 
The alluvial deposits of the Batten kill are much smaller, and not as good soil as the others. 
These alluvions are more siliceous, in consequence of the great quantity of siliceous gravel, 
pebbles, and boulders of granular quartz, brought down from the Green mountains during 
freshets. There is a striking difference in the productiveness of the alluvions of the Batten 
kill in the eastern part of Washington county, and those of the neighboring small streams 
that flow over and derive their alluvial materials from the argillaceous and argillo-calcareous 
rocks of this part of the same county. The Batten kill alluvions of this part of its course 
are mostly formed of sand, gravel and pebbles, derived from the granular quartz of the Green 
