AGES OF ROCKS, CtC. 
629 
3. The next period of elevation and disturbance seems to have been subsequent to the 
deposition of the rocks of the Ontario division, and the effects of which are recognized from 
Green-pond rhountain through Bellevale mountain, Goose-pond, Sugar-loaf and Skunnemunk 
mountains. Pine hill, by Townsend’s iron mine, etc. where the rocks are vertical between 
the primary, and pitching under and resting on them; and along the Shawangunk mountains, 
where the same rocks are tilted to the west at high angles. This period may be the same as 
that next described, but is inferred to be different, from the fact that no rocks like those of 
the Erie and Catskill divisions are recognized among those above described. This evidence, 
however, is not deemed conclusive, as we have no evidence that any deposition of the mate¬ 
rials of the Catskill division were ever deposited on that side of the ancient Hudson valley 
and Walkill. 
4. The next period of elevation and disturbance of which certain evidence has been recog¬ 
nized, is subsequent to the deposition of the Catskill division, and even the coal formation, as 
it has disturbed all preexisting rocks in New-York east of the Delaware ; and the bending and 
wrinkling of the coal formation in Pennsylvania, Maryland and Virginia, is supposed to belong 
to this period. Its geological era is supposed to have been between the epochs of the coal 
formation and new red sandstone. This disturbance seems to have produced very marked 
effects in all the preexisting rocks, and particularly in the Highlands, the Hudson valley and 
its southern extension, the Mamakating and Walkill valleys, and still further along the 
“ Great valley” leading into Virginia and Tennessee. 
5. The next period of disturbance seems to have been at the end of the deposition of the 
Long-island division, by which its strata were disturbed before the drift and quaternary were 
deposited. This may, very possibly, have been at the time of the eruptions of the trappean 
rocks ; though we have no evidence, except that they belong to about the same geological 
period. 
6. Another period was between the drift and quaternary periods, by which the land in 
mass, and retaining its configuration, was partially elevated to about the level of the quater- 
ternary formations. (Vide discussions on the drift.) 
7. The last period of elevation seems to have been after the deposition of the quaternary 
system, by which a large portion of our country has been elevated above the waters of the 
ocean some hundred feet. (Vide discussions on pp. 148, 157, etc.) 
(C). Periods of metamorphic agency. 
This is a subject of much difficulty, and on which there is as yet little definite knowledge^ 
The following remarks may afford some glimmerings of light to those who may investigate 
this subject, which is one of the many important geological problems. 
It has been observed that where rocks have been most modified by metamorphic agenc)r, 
they are near granitic, sienitic, trappean, quartzose and metalliferous protrusions, masses, 
dykes and veins. 
1. It has been observed in the First geological district, that the trappean rocks intersect by 
Geol. 1st Dist. 82 
