NEW-YORK SYSTEM. 
299 
times depositing sandstone, sometimes slate, limestone, etc., varying at intervals; and we 
can perceive no origin from which such a vast amount of mineral matter can have been 
abraded and washed away, as we see forming this immense accumulation of detritus, unless it 
has been brought by the equatorial and polar currents in their ceaseless flow through all time 
since the ocean has occupied the surface of the earth. 
Some of the strata of this system are more fully developed in the west, and gradually thin 
out and finally disappear, or are represented by a thin layer on the southern flank of the Mo¬ 
hawk valley, or on the western flank of the Hudson valley; but generally the reverse is true, 
and the maximum development is found in the angle between these two valleys ; and these 
depositions seem to have been formed in a kind of eddy, produced by the meeting of the flow 
of warm water of the Gulf stream through the Mohawk valley, with the cold Polar current 
through the Champlain and Hudson valley.* 
The cold northern current flowing through the Champlain and Hudson valley, would offer 
a satisfactory explanation of the rarity of the remains of organic existence in these rocks in 
that valley; while they abound in depositions of the same mineralogical characters, which 
are, in fact, the continuation of the same strata, on the flanks of the Mohawk valley, and 
throughout the southern part of New-York west of the Schoharie kill. In the latter case, 
they were exposed to the genial influences of the equatorial current; in the former, to the 
chilling cold of the polar stream. 
The strata of the New-York system will be considered under the following general di¬ 
visions, viz: 
I. CATSKILL DIVISION. 
Upper members of the Catskill mountain series of the Geological Reports for 1840 and 1841. Mon¬ 
trose sandstone, and Oneonta sandstone of Geological Reports of New- York. Old red sandstone, 
probably, of Europe. Nos. 9, 10, Hand 12, of the Pennsylvania Geological Reports. Old red 
sandstone. No. 9 Mr. Conrad's arrangement.] 
The Catskill division of rocks consists of coarse and fine grits, with various shades of red, 
brown, grey, greenish, and mottled red and green, which lie thick bedded with the oblique 
laminae of deposition strongly marked (vide Plate 6, figs. 1, 3 and 4);| conglomerates of 
* The reasons for and evidences of those currents have been traced in the article on the drift deposits, in the latter part of the 
second chapter. 
+ Geological Report of New-York, 1839, p. 62. 
t Vide also Wood-cut No. 8. 
