522 OF THE PHYSICAL STRUCTURE 



or fifty feet of change of level. Here there was a decided arching 

 of the surface, by which the river had been displaced from its 

 ancient valley. Occurring in Chili, in a country so frequently 

 visited by earthquakes, there can be little doubt as to the origin of 

 this local anticlinal flexure in the earth's crust. 



We are inclined to regard the XJUah Bund as another example 

 of an anticHnal axis formed in modern times by an earthquake. 

 According to the description and map furnished by Mr. Lyell, in 

 his admirable account of earthquakes contained in his Principles, 

 this is a long elevated mound, extending from east to west across 

 the eastern arm of the Indus, near the fort and village of Sindree. 

 It is upwards of fifty miles in length, and runs parallel to a line 

 of subsidence, along which the previously low and perfectly level 

 plain around Sindree became permanently flooded. It is con- 

 jectured to be, in some parts, sixteen miles in width, and to have 

 a height above the original level of the delta, of ten feet, which it 

 seems to preserve very uniformly. 



Of the Date of the Appalachian Axes. 



It has been stated already, that, excepting in one or two local- 

 ities, the Appalachian formations constitute an unbroken succes- 

 sion of conforming strata, from the lowest members of the system, 

 which repose immediately on the primary or metamorphic rocks, 

 to the highest of the carboniferous strata. ^Ye must therefore 

 conclude, that the elevatory actions, which lifted the entire chain 

 above the level of the ancient sea, and impressed upon it those 

 symmetrical features of structure which we have described, could 

 not have begun, at least with any degi-ee of intensity, until the 

 completion of the carboniferous formation. That the principal 

 movement immediateli/ succeeded the termination of this period 

 of gradual operations, or more properly arrested the further prog- 

 ress of the coal-formation, is, we think, clearly proved, by the fact, 

 that nowhere do we meet with any strata, referable to the next 

 succeeding or new red sandstone period, overlying the highest 

 rocks appertaining to the coal ; and it can scarcely be supposed, 

 that throughout so vast an area, embracing several enormous 



