AGES OF ROCKS, etc. 627 
The RED SANDSTONE OF RocKLAND COUNTY AND New-Jersey, has been shown by trains 
of evidence to be almost certainly the “ new red sandstone.” (Vide pp. 293, 294.) 
The TRAP ROCK OF THE Palisades has been shown to be older than the quaternary and 
drift deposits, and newer than the red sandstone of Rockland and New-Jersey, and was pro¬ 
bably erupted at the epoch of the marl and green marl deposits of New-Jersey. (Vide pp. 
1.79, 202, 282, 284, 285.) 
The Long-island division is shown to be probably equivalent to the New-Jersey marls 
and potter’s clay formations of Prof. Rogers’ final geological report of New-Jersey, covered 
perhaps by tertiary in some places. (Vide pp. 246, 272, 273.) 
The drift deposits, and the main effects of the drift epoch, have been showm to have 
preceded the epoch of the quaternary of the Hudson, Champlain and Mohawk valleys, and 
the superior deposits of Long island, and to have succeeded those included in the Long-island 
division. (Vide p. 168, and many places described on Long island and in the Hudson valley, 
where the drift is covered by the quaternary ; and p. 248 et seq. where they rest on the strata 
of the Long-island division, and perhaps on the tertiary.) 
The QUATERNARY DEPOSITS of the Hudson and Champlain valley, and of Long island, 
have been shown to have succeeded the drift, and may perhaps be considered as the effect of 
a continuation of the same causes that produced the drift, but modified in intensity, some 
boulders and pebbles being deposited in the clay beds of the quaternary. 
The UPPER DRIFT is the last epoch of deposition preceding the alluvial causes. (Vide pp. 
123, 135, 136, and 158.) 
The METAMORPHic ROCKS have been discussed in this volume, and referred to the period 
of the Champlain division. (Vide pp. 439, 463-4, 466 to 476, 486.) 
The slate rocks are mica slate, argillo-micaceous slate, talcose slate, chlorite slate, talco- 
argillaceous slate, and argillaceous slate. The mica slate and argillo-micaceous slate pre¬ 
dominate, but in some places pass gradually into the others by insensible changes in short 
distance, so as to render it obvious that they are contemporaneous. Where the mica slate 
comes in contact, or nearly in contact, with limestone, the latter is almost always crystalline, 
dolomitic, and frequently white; but when the talc sZaie is. near the limestone, the latter is 
subgranular and generally grey; and generally the more argillaceous and less altered the slate 
rocks are, the less altered are the limestones, and they approach nearer to the compact and 
sparry limestones of the Champlain and Taconic rocks. 
The quartz rock is not visible in very numerous localities in New York. Some have been 
described. Professors Hitchcock and Dewey have described it in various parts of Berkshire 
county, Mass., as connected with gneiss and mica slate.* It occurs also in New-Jersey (For¬ 
mation No. 1, of Prof. Rodgerst), in Pennsylvania and Virginia. 
The limestones of Westchester and New-York counties are like those of Putnam and 
Dutchess counties in New-York, Litchfield and Fairfield counties in Connecticut, Berkshire 
* Vide Final Geological Report of Massachusetts, 1842, p. 587, 583. American Journal of Science, vol. ix, p. 16. 
t Final Geological Report of New-Jersey, 
