Davis.] 
322 
[Nov. lS, 
river for brick -making. The bricks from these clays, the flag 
stones from the Hudson river series and the winter ice-crop from 
the river itself constitute the chief geological products of this 
great water way. 
The Champlain clays are well known as the product of a late 
glacial or post-glacial submergence of the valley, allowing a long 
estuary to connect the Hudson, the basin of Lake Champlain and 
the St. Lawrence, leaving New England and the Provinces cut 
off as an island. The deposition of the clays directly on glaciated 
rock surfaces may be seen at various points ; for example just 
north of the bridge over the Kaaterskill at Belfast Mills, a mile 
west of Catskill ; and on the gravels in the pits in Catskill, 
above mentioned. Their fine texture and even bedding indicate 
comparatively deep and quiet water ; and the sands lying on their 
surface should probably be interpreted as a deposit made as the 
land was rising from its depressed position. 1 Before the recent 
elevation of the land, by which the further accumulation of es- 
tuary clays was stopped, the clays formed a covering of even 
surface, F, fig. 2, but of variable depth in the Hudson trench 
and its deeper lateral branches ; they were essentially bottom de- 
w c 
Fig. 2. 
posits, not littoral ; and taken alone they would give no clear indi- 
cation of the amount of depression of the land during their 
formation. This amount must be determined by the associated 
littoral deposits, of which more below. Since the recent eleva- 
tion, the even surface of the clays has been greatly cut away by 
the Hudson and to a considerable extent by its tributaries. All 
stages of valley growth can here be traced ; and of these none' are 
more interesting than those in which the streams have unwit- 
tingly sunk their channels on buried rocky ledges, thus producing 
water-falls by superimposition ; as is the case with the Kaaterskill, 
at Belfast Mills, above mentioned ; the Esopus at Saugerties ; the 
l Merrill interprets these sands as indicating a difference in the materials carried 
into the estuary by the lateral streams (Amer. Journ. Science, xli, 1891, 463), and sug- 
gests that the absence of sands while the clays were forming might be explained by so 
great a submergence that the streams then had little surface drainage, and hence little 
volume and carrying power. 
