J.D. Dana on the origin of the Earth’s Features. 253 
mung, making a dislocation of at least 16,000, and probably of 
20,000, feet. And yet the Trenton limestone and Hudson River 
shales are not metamorphic. Some local cases of alteration 
occur there, including patches of roofing slate; but the greater 
art of the shales are no harder than the ordinary shales of the 
ennsylvania Coal formation.’ 
At a depth of 16,000 feet the temperature of the earth’s crust, 
allowing an increase of 1° F. for 60 feet of descent, would be 
about 330° F.; or with 1° F. for 50 feet, about 880° F.—either 
of which temperatures is far above the boiling point of water; 
and with the thinner crust of Paleozoic time the temperature at 
this depth should have been still higher. But, notwithstanding 
this heat, and also the compression from so great an overlying 
mass, the limestones and shales are not crystalline. The change 
of parts of the shale to roofing slate is no evidence in favor of 
the efficiency of the alleged cause; for such a cause should act 
uniformly over great areas. 
In Southern Virginia, between Walker’s Mountain and the 
Peak Hills, the Trenton rocks, as Lesley observes, are brought 
mh by means of a fault, to a level with the Lower Carboniferous. 
The amount of the fault by the lowest estimate is 15,000 feet. 
Notwithstanding the depth at which the Trenton beds had been 
ying previous to the faulting, the limestones are not granular 
marbles, but ordinary stratified limestone. 
Again, in the great Nova Scotia section, at the Joggins, 15,000 
feet of rock are exposed to view out of the 16,000 feet or more 
of the whole Carboniferous formation ; and the lower strata of 
these 15,000 feet consist of shales and sandstones, and fossilif- 
erous limestone, without metamorphism. . 
at is the natural inference from these data? . Can we as- 
* In a recent conversation with Mr. Lesley, he confirmed these statements, and 
said that the upturned rocks are so situated that the srerelenate thickness of the 
Series is easily ascertained. The facts are briefly alluded to in my Manual of Ge- 
ology, on page 707. 
Am. Jour. Sc1.—Szconp Szrizs, Vou. XLII, No. 125.—Szpr., 1966. 
33 
