J. D. Dana— Origin of the Rocks of the Cortlandt Series. 111 
augite-noryte of Cortlandt in mineral constitution, cover wide 
regions; and the same kinds may have formerly existed in the 
Highlands north of the Cortlandt region, although they have 
not. yet been discovered there; and this is somewhat i oe 
Further: chrysolite, hone common in igneous pecan is 
also common as a metamorphic product, and occurs 
chloritic and mica schist and other ks as should be: ex- 
pected from its composition and gi ee heed by heat. 
Doubts with regard to Archean detritus as the only source 
of these Cortlandt rocks come from the ver abrupt transitions 
which exist between the hornblendic or augitic rocks and the 
ordinary mica schists and gneiss, so strongly exemplified in the 
Verplanck region; in the almost exclusive occurrence over so 
found in a similar way over any other part of Westchester 
County, the material of whose rocks, the limestones excepted, 
s 
sey Bightands (that of Greenwood Lake on the map, page 106), 
or on their western border, where sedimentary beds of High- 
land origin were extensively formed. The = border of 
the Archean in New Jersey is under Triassic beds, so that 
scarcely anything is known of the Lower Siaria strata directly 
southwest of Stony Point. 
2. IGNEOUS EJECTIONS ALONG WITH MORE OR LESS ARCHHAN DETRITUS. 
In favor of igneous ejections as a chief source, there are the 
following facts. 
The larger part of the rocks are much like i igneous rocks. 
They resemble them (1) in mineral constitution; (2) in their 
soda-lime feldspars; (8) in the abundance of hornblende or 
poner and (4) in the feeble proportion of quartz. The noryte, 
though containing hypersthene, offers no objection to the view. 
a chrysolitic feature of the rocks of some parts of the region 
a frequent voleanic characteristic. 
ut while such resemblances to the igneous rocks exist, it is 
a striking fact (1) that nowhere in the region are the rocks col- 
umnar like those of the Palisades and many regions of augitic 
— rocks ; (2) that,no vents orjdikes have been {found to 
indicate the places of their ejection ; (3) that sometimes mix- 
tures of two or three kinds oecur—as hornblendyte, pyroxen- 
yte and augite-noryte—which were not combinations made 
separate ejections but are merely irregularities of constitution in 
a single large mass of rock; and occasionally Be noryte and 
