the Earth* s Contraction from Cooling. 133 



bearing* layers bearing evidence, to the last, of oscillations in- 

 volving an intermittent but progressing subsidence. The syn- 

 clinorium, the resultant, was much less marked than that at the 

 close of the Devonian. 



6. During the Palaeozoic, along the sea-border, a more or less 

 perfect barrier was made by a geanticlinal uplift (anticlinorium), 

 which was a counterpart to the geosynclinal of the Appalachian 

 region*. 



7. The middle or close of the Jurassic period was an epoch 

 of displacements, and the making of a series of imperfect syn- 

 clinoria along the Triassico-Jurassic areas from Nova Scotia to 

 southern North Carolina, as sufficiently described. 



8. During the era of the Connecticut-river sandstone (Tri- 

 assico-Jurassic) a nearly complete sea-border anticlinorium ex- 

 isted, a counterpart to the progressing geosynclinal. Its exist- 

 ence is proved by the absence of all marine fossils from the 

 beds*. 



9. The era closing the Cretaceous, and that of the Tertiary, 

 witnessed but small uplifting and some local displacements of 

 the rocks of these eras on the Atlantic border. The principal 

 movement was geanticlinal ; and it involved probably the whole 

 Alleghany region. 



10. In the Quaternary there were extended movements of 

 geanticlinal and geosynclinal character, which need not be here 

 described. 



b. Mountain-making after Arclwan time on the Pacific border, 

 within the territory of the United States. 



1. At the close of the Lower Silurian, none yet known. 



2. At the close of the Devonian, none yet knownf. 



o. At the close of the Carboniferous age, or the Palaeozoic, 



* In nry ' Manual of Geology ' the probable existence of such a barrier is 

 recognized, in connexion with the remarks on the geography of the Trenton 

 period in America ; and it is particularly dwelt upon and illustrated by a 

 map in the chapter on the Triassic; but it is not spoken of as connected in 

 origin \yith the geosynclinal that was in progress to the west of it. Evi- 

 dence with regard to this anticlinorium is given in the following part of 

 this memoir. 



f Although no case of unconformability between the Carboniferous and 

 the underlying Palaeozoic is yet distinctly made out in the Sierra Nevada, 

 the Great Basin, or the Wahsatch, such occur further south, according to 

 Mr. J. W. Powell, in the vicinity of the Grand Canon of the Colorado (see 

 Amer. Journ. Sci. 3rd ser. vol. v. p. 45/). The fact that Whitney has 

 found no rocks lower than Carboniferous in the Sierra may be a conse- 

 quence of the same unconformability beneath these mountains. But in the 

 region of the Canon, the Carboniferous, Triassic, Jurassic, Cretaceous, and 

 Tertiary beds are all conformable. The epochs of mountain-making over 

 the Pacific slope south of the latitudes of the Wahsatch range, and also of 

 that to the north, were different from those within these latitudes.. 



