116 J. D. Dana—Origin of the Rocks of the Cortlandt Serves. 
supplemented that of detritus in determining the constitution 
of metamorphic rocks, and has led especially to the production 
of different varieties of hornblende and pyroxene, the darker 
kinds resulting when the all-pervading ‘ingredient, iron, was 
present. ‘ 
Further, the ocean has been one of the sources of soda in 
rock-making. e contributions of this nature to sedimentary 
deposits, are, as is well known, common and extensive. Beds 
of rock salt, sometimes of great thickness, occur in formations of 
various ages, from the Silurian to the present time; and mag- 
nesian salts, derived, directly or indirectly, from the same sea- 
waters that afforded the rock salt, are also frequently present. 
Moreover, brines from deep borings are common. It is-not 
necessary here to give details. I mention two American 
cases only, one relating to the Lower Silurian formation, and 
the other pertaining to the vicinity of the region under dis- 
cussion. 
The boring at the St. Louis Insane Asylum, reported upon 
by Mr. G. C. Broadhead, State Geologist of Missouri,* which 
netrated through Carboniferous and Lower Silurian strata 
nto the Archwan, reached a depth of 3,84384 feet. ‘Salt 
water” was obtained in the Lower Silurian (Magnesian lime- 
stone) at a depth of 1,220 feet and below. At 2,256 feet, the 
water contained 3 per cent of salt; at 2,957 feet, 44 per cent; 
at 3,293 feet, 2 per cent; and below 3,545 feet, 7 to 8 per cent. 
Prof. G. H. Cook, State Geologist of New Jersey, states in 
his Report for the year 1880, that from a boring in the Triassic 
sandstone at Patterson in that State (which is in the same geo- 
graphical region with the Cortlandt area, it lying to the east of 
the Archean Highlands) the water obtained at 2,050 feet af- 
forded, per gallon, 408°46 grains of sodium chloride, with 
109-44 of magnesium chloride and 278°32 of calcium chloride 
—which shows the presence of about half the proportion of 
salt contained in sea-water, and of a much larger proportion of 
magnesium and calcium chlorides than sea water contains ; 
and Prof. Cook adds: “the questions suggested by finding the 
salt water must remain for the present unanswered, though the 
fact that the rock-salt of Kurope is found in rocks of the same 
age as this raises the question whether it may not also be 
found here.” 
Rocks containing salt in beds or brines have undoubtedly 
undergone metamorphism, and under conditions as to superil- 
cumbent formations which permitted of no escape of the so- 
dium, and which therefore would have forced it into chemical 
combination with the other materials present. And if it has 
entered into any minerals the feldspars must be among them, 
* Report on'the Geological Survey of Missouri for 1873-1874, 8vo, p. 32. 1874. 
