J. D. Dana—Origin of the Rocks of the Cortlandt Series. 115 
Cortlandt noryte or augite-noryte, as occurring forty miles west 
the Hudson on the east slope of the Kittatinny Mountains, 
not far west of Libertyville and Deckertown (between c and d 
on the map, Plate 1x, in this Journal for last November) ; and 
and several miles long, coming in between the Hudson River 
slate and the overlying Oneida Conglomerate, and conforming 
to them in strike. In a recent letter to the writer he observes 
that the question as to whether eruptive or not he does not 
consider as settled, the debris of the region having prevented 
satisfactory examination. The adjoining slates are stated to be 
modified, as if from the influence of the mass, for 3,000 feet to 
the eastward—a distance so great that the effects can hardly be . 
all due to contact. The further study of that region may throw 
light on the Cortlandt rocks. 
(3.) ARCHHAN DETRITUS, SUPPLEMENTED BY MATERIALS FROM THE OCEAN, 
The chief stony materials which the ocean’s waters have to 
contribute are: (1) the calcareous—calcium carbonate mainly 
through the secretions (shells, corals, etc.) of its living species, 
and calcium chloride ; (2) the magnesian, from the magnesium 
chloride and sulphate; and (8) the soda, through the sodium 
chloride or common salt. 
he calcareous and magnesian materials of the oceanic 
waters have been of immense importance in rock-making. The 
limestones of the world have originated from the former. Be- 
sides this, few muds or neers sand beds have been made 
since the first Rhizopods Linas that have not contained 
more or less disseminated calcareous material ; and this material, 
in the course of the metamorphism of those beds, has been often 
employed in producing some of the new combinations constitut- 
ing metamorphic rocks. So, also, the ocean has been the chief 
source of the magnesia used for making dolomite, or magnesian 
limestone, and for other purposes. In the case of the limestone 
of Westchester County, which is dolomitic, pe magnesia was 
taken from the sea-water, according to the most generally ac- 
cepted view, while the process of consolidation was going on 
in great marshes of concentrated saline waters. 
into silicates, such as tremolite, white pyroxene, and other 
species; or, when iron cha also been present, into other related 
silicates of Tight or 7 ae gee tints, = hornblende, actinolite, 
green pyroxene so into other magnesian minerals 
through other ay of the limes ne. 
Thus the magnesia of the ocean’s waters has beyond doubt 
