278 
GEOLOGY OF THE FIRST DISTRICT. 
“ Px)st Tertiary. By this term, Mr. Lyell designates a group of organic remains which 
not only embraces a less percentage of extinct species than the Newer Pliocene, but they 
are of a more arctic character than the recent group of the same parallels of latitude. In 
this series must be included the tertiary deposits on the borders of Lake Champlain, described 
by Professor Emmons; as they are identical with those of the St. Lawrence, described by 
Capt. Bayfield, and which Lyell refers to his Post Tertiary. The shells of the St. Lawrence 
are the same with those of the Champlain beds; and not only so, but Lyell has found them 
to be nearly all the same with the post-tertiary species of Scotland, Denmark, Norway and 
Sweden, and there is less than one per cent of species unknown in a living state.”* 
n. TRAPPEAN DIVISION. 
Extent of these Rocks. 
These rocks in New-York, except dykes and those classed among primary rocks, are entirely 
confined to Rockland and Richmond counties. They exhibit a bold rocky bluff along the right 
bank of the Hudson, from near Haverstraw to the New-Jersey line ; and thence it extends in 
an uninterrupted ridge, with a rude columnar front called the Palisades, to near Hoboken, 
opposite the city of New-York. There are several parallel ranges more or less interrupted 
in New-Jersey; and like those of Rockland county, some of them are more or less curved and 
hook-shaped. The same rocks are found connected with the red sandstone formation in Penn¬ 
sylvania, Virginia, Maryland, and North-Carolina to the south-southwest; and with those of 
Connecticut, Massachusetts, and Nova-Scotia on the northeast; and in the plains east of the 
Rocky mountains, described by Long and others ; those of the Polar circle, between McKen¬ 
zie’s river and Cape Turnagain ;t and on the south coast of Lake Superior. 
The trap region of Rockland county occupies much less of the surface of this county than 
one would suppose in passing along the Hudson river. It forms a narrow belt on the shore 
of the Hudson, from the New-Jersey line to near Haverstraw, where it ranges off to the north¬ 
west and then west, and finally southwest near the base of the Highlands, where it disappears. 
A branch of it strikes off about two miles north of Nyack in a westerly direction, and extends, 
with perhaps some interruptions, to near the Highlands. These ranges of trap rock are nar¬ 
row, from one-fourth to one mile, and in some places perhaps one and a half to two miles 
broad. Along the Hudson, and on the north front of the range extending west from Haver¬ 
straw, the trap rock forms high mural columnar escarpments, of three hundred to eight hun¬ 
dred feet in height, with a steep slope of debris, which have been crumbled off from the cliffs 
Geological Report of New-York for 1841, p. 47. 
t American Journal of Science, Vol. 17, pp. 1,10. 
