| 
+ _* This catastro: 
_ Plishment ; yet it was disastrous to the living tribes over the whole sphere, 
J. D. Dana on American Geological History. ‘ 331 
_ From this epoch to the close of the Cretaceous, there were no 
contemporaneous revolutions, as far as we can discover. But 
the Cretaceous Period terminates in an epoch of catastrophe 
which was the most universal on record, all foreign Oretaceous 
ste having been exterminated, and all American, with a few 
oubtful exceptions.* This third general revolution was the 
prelude to the Mammalian Age. But there is no time to do this 
subject justice, and I pass on,—merely adding, on account of its 
interest to those who would understand the first chapter of 
Genesis, that there is no evidence whatever in Geology, that the 
after its completion, passed through a chaos and a six 
days’ creation at the epoch immediately preceding man, as Buck- 
land, in the younger days of the science, suggested, on Biblical, 
not on Geological, ground. No one pretends that there is a fact 
or hint in Geology to sustain such an idea: on the contrary, it 1s 
utterly opposed to it. 
Il. The question of the existence of a distinct Cambrian sys- 
tem is decided adversely by the American records. The Mol- 
in all their grand divisions appear in the subdivisions of 
the Lower as well as Upper Silurian, and the whole is equally 
and alike the Molluscan or Silurian Age. The term Cambrian, 
therefore, if used for fossiliferous strata, must be made subordin- 
ate to Silurian. : 
The Zuconic system of Emmons has been supposed by its au- 
thor to have a place inferior to the Cambrian of Sedgwick, or 
else on a level with it, But the investigations of Hall, Mather, 
and Rogers, and more lately of Logan and Hunt, have shown 
that the Taconic slates belong with the upper part of the Lower 
Silurian, being, in fact, the Hudson River shales, far from the 
bottom of the scale. ; ss 
TIL The American rocks throw much light on the origin of 
coal. Professor Henry D. Rogers, in an able paper on the 
been ages in accom- 
phe may not have been violent ; it may have fe 
