rSfjr.J 
323 
[Da vis. 
Fishkill at Matteawan ; and elsewhere. All these falls are em- 
ployed for water-power, and a number of them have determined 
the sites of villages. 
The depth of the Hudson channel, G, in the clays, allowing 
tidal oscillations up to Troy, 150 miles from New York, and the 
same estuary-like features at the mouths of many of the lateral 
streams, seem to indicate a slight and recent depression of the 
land since the clays were cut by the streams; and this is a 
change of great value in the development of the Empire State, 
from the increase of navigable waters thus gained. The Hudson 
is not a large river, if measured by the area of its basin or by the 
amount of water that it discharges ; but as a result of the slight 
depression that its basin has lately suffered, its course below 
Albany has been transformed from a river of moderate size into 
a navigable tidal estuary, H, fig. 2, somewhat shallow and more 
or less encumbered now with islands and bars in its northern part, 
but deep and broad further south, except where locally narrowed 
in the passage through the hard rocks of the Highlands. The 
very recent date of this dejn-ession is inferred from the small 
delta-growth at tide-level in the tributary streams. 
It should not be imagined that the earlier stages of the history of 
the Hudson were free from the smaller oscillations here mentioned 
as characterizing the last chapter in its life ; small oscillations pre- 
sumably occurred at all times as frequently as recently, but the 
records of the more ancient of these trifling changes are merged 
into average results. The Jurassic- Cretaceous denudation of the 
ancient lowland, now a dissected highland, must not be regarded as 
accomplished while the land stood absolutely still ; but the oscil- 
lations of level during this great denudation were averaged into 
a general baselevel, AB, fig. 1, down towards which the antece- 
dent land mass was eroded. So with the valley lowland ; its roll- 
ing surface, so finely displayed in bird’s-eye view from the cliffs 
of the Catskill mountain front, presumably represents the aver- 
age of many oscillations during Tertiary time, none of great value. 
For all we can say, the trenches below its general surface were 
begun in some of the higher oscillations of that series, and com- 
pleted to their present form in the post-Tertiary cycle. They 
may have several times been filled with clays like those they now 
contain, and as often cleaned out again; for it is manifest that 
such episodes are short-lived. 
