386 DYNAMICAL GEOLOGY. 



sure, to which they were originally not adjusted; and the phenomena of 

 earthquakes, volcanic explosions, etc., may arrive." These results are 

 favored by the fact that the deposits were not half consolidated, and, there- 

 fore, little able to resist the pressure. 



In the consequent collapse from the continued pressure, the included 

 strata would be necessarily shoved up out of place, flexed in anticlines and 

 synclines, and traversed by great oblique fractures, as Daubree's experiments 

 illustrate, which would become the courses of displacements, all on a scale 

 of magnitude comporting with the thickness of the accumulated formations. 

 The flexures were not flexures of the earth's crust, but of the supercrust, or 

 the beds in the geosyncline. The work was slow in progress ; for the great 

 flexures in such mountain-making are produced without obliterating or seri- 

 ously obscuring the stratification. 



In the great forced movement, if the pressure on the two sides of the 

 trough was unequal, as was commonly the fact, the beds were shoved from 

 the side of strongest pressure, or thrust, toward the opposite. Consequently 

 the flexures became crowded and steepest on the former side, and the over- 

 thrust flexures and upthrust blocks were thrust toward the other side. 

 Hence the resulting mountain range and its flexures are inequilateral. In 

 the case of the Appalachians, the thrust was strongest on the side toward 

 the ocean. Further : on the side of least pressure, the mountain range 

 often declines into elevated plateaus, with feebly undulating or horizontal 

 stratification, as exemplified, on the landward side of the Appalachians, in 

 the Cumberland plateau and its continuation northward; in the Uinta 

 Mountains and the high plateaus of Utah on the landward side, and to the 

 south, of the Wasatch. In the narrow troughs of deposition of eastern 

 North America, the flexures often fail to indicate inequilateral pressure. 



After a mountain-birth there has commonly succeeded a time of relaxed 

 lateral pressure; and then occurred adjustments, largely by gravitation, in 

 the moved masses or faulted blocks making chiefly downthrow displace- 

 ments, besides producing new fractures and faults. Such displacements 

 have taken place especially in the region of mountain plateaus, where the 

 pressure was least. 



Illustrations of the steps in the contraction process of mountain-making 

 have been above derived mostly from the Appalachian Range. They may 

 be found almost equally apposite in most of the mountains of the world, as 

 the examples already given prove. The Taconic Eange, on the borders 

 between New England, and New York and Canada, has the same general 

 characteristics as the Appalachian, with the addition of the universal meta- 

 morphism of the beds of sandstone, shale, and limestone. Its preparatory 

 geosyncline was on a parallel line with the northern part of the Appala- 

 chian; and the two were deepening and taking in deposits together until 

 the close of the Lower Silurian, when the Taconic mountain-making crisis 

 came. The rocks of the range are, therefore, only those of the Cambrian and 

 Lower Silurian. It is probable that this mountain belt extends through 



