TRANSITION ROCKS. 
233 
Kingston it changes its level, and begins to rise to a 
mountain height, forming the Indian ridge, which, 
although small when compared with the neighbour- 
ing Catskills, equals the Highlands in elevation. 
This ridge is produced into the Heldeberg, which 
passes to the northwest through Albany and Scho- 
harie counties. In the latter it paves a rich valley, 
and, rising again, encloses the valley of the Mo- 
hawk on both sides, and often with precipitous 
cliffs. At the Little Falls of the Mohawk it is cov- 
ered by the formation of red sandstone and gray- 
wacke ; but it is speedily seen again, forming the 
valley of West Canada Creek, and there rises into 
a table-land, whose southern slope presents the as- 
pect of a mountain ridge. In issuing from this 
ridge, Canada Creek forms Trenton Falls, and the 
formation is opened to a great depth. To the north 
of Trenton the formation extends to a great breadth, 
and may be traced to the northwest across the St. 
Lawrence and into Canada." 
Mr. M'Clure, who is probably better acquainted 
with the geology of the United States, from per- 
sonal observation, than any other individual, limits 
the field of transition rocks by the northwest boun- 
dary of the primitive formation, which we have al- 
ready described as extending from Lake Champlain 
to near the river Alabama. Of course it touches, on 
the northwest side, the southwest edge of the great 
secondary formation, in a line that passes consider- 
ably to the westward of the ridge which divides the 
eastern and western waters in Georgia, North Car- 
olina, and part of Virginia, and runs near it in the 
northern part of that state, and in the states of 
Pennsylvania and New- Jersey. This line of de- 
marcation runs between the Alabama and Tombig- 
bee rivers, to the west of the north fork of the Hol- 
stein, till it joins the Alleghany Mountains, near the 
White Sulphur Springs, in Green Brier county, and 
along that dividing ridge to Bedford county, in Peim- 
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