J. D. Dana— Origin of the Rocks of the Cortlandt Series. 109 
layers retain such ae Facts like these are not con- 
sistent with the theory of an eruptive origin. Moreover the 
schists are so firm rocks that the separation of vets by such 
means would be impossible. 
I add one additional fact with regard to these large inclu- 
sions. In the brownish-black chrysolitic pyroxenyte which 
occurs along the south side of Montrose Point, there is a 
layer of impure, mostly uncrystalline, gray limestone, eighty feet 
long (and probably much longer, as this is only the length of 
the exposure), and twelve to eighteen inches wide. It contains 
some gray-green tremolite or actinolite in the outer portion, 
and much disseminated pyrite, and owing to the latter is 
— rusted. ; 
s almost an Fon pdesibulity that a thin bed of limestone 80 
Phas log could by any means have got into the erupted roc 
and quite impossible that, if in, it should have held together, 
and retained from one end to the other, even approximately, a 
uniform strike and dip (N. 12° E., 70° W). 
(6.) At Verplanck Point, where what look like veins or 
dikes of pyroxenyte occur in the limestone, a4 are for the 
most part conformable to the limestone; as if they might be 
altered beds; and the more northern of these pseudo-veins 
consist of mica schist; further, these pseudo-veins of the Point 
are represented half a mile northeast in the line of strike b 
eds of mica schist or hornblendic schist. Such facts appear 
to show that the most of the “veins” are beds, metamorphosed 
spathic, hornblendic or augitic, is eee of eruptive origin. 
s heat and mOrsrre may convert siliceous sand- ers under 
numerous examples show, may convert, by the recrystallization 
attending metamorphism, well- bedded strata of hornblendie, 
augitic or feldspathic material into a massive rock, often undis- 
tinguishable even bebe pa from an eruptive rock, One 
example in proof is given in my paper in the June number of 
ee Journal (p. 428); and others in papers on the Helderberg 
ocks of Bernardston, Mass., and Vernon, Vt.* The layer of 
* This Journal, III, vi, 339, 1873 and xiv, 379, 1877. 
