FOLDS AND FAULTING. 401 



regions, and gradually opened and flattened out as they 

 recede from such a centre. 



Whilst noticing cases of more ordinary transverse fault- 

 ing, they laid special stress on the occurrence of the greater 

 longitudinal overthrusts parallel to the main anticlinal axes, 

 which, owing to more or less compression, had snapped and 

 given way in the act of curving. It was found in South- 

 west Virginia that the youngest stratum first disappeared, 

 the older ones following in succession, until finally the 

 Lower Limestone of Cambrian or Lower Silurian age 

 comes to absolutely overlie the Carboniferous Limestone. 

 The strata thus engulfed represent a thickness of over 

 8000 feet, and the uninverted side of the wave had been 

 driven eighty miles over the more inverted portion. 



Those who are acquainted with the present condition of 

 this discussion will at once appreciate the solid basis upon 

 which the above conclusions were founded, and it is equally 

 to the credit of Professor Rogers that he came over to 

 Europe to test the accuracy of his conclusions in those 

 regions where similar results might be expected. The 

 Devonian strata of the Rhine, as also the Jura range, again 

 showed the passage from broad waving of the strata to that 

 of more complicated rlexuring, but, above all, in the Alps 

 he found the absolute comparison he was in search of. He 

 says : " We behold an exact counterpart, in the stratification 

 or structure of a single flank of the Alps, of that folding 

 with inversion, which characterises the Appalachian chain, 

 or that of the Ardennes, a single side of the Alps being the 

 equivalent of the whole of either of these zones ; it consists, 

 that is to say, of an undulation in one direction ". He con- 

 cluded that the flexure could only be due to the actual pul- 

 sation of fluid matter beneath the crust, propagated in the 

 manner of great waves of translation from enormous rup- 

 tures occasioned by the tension of elastic matter. The 

 various features observed were ascribed to the combination 

 of an undulating and a tangential movement, accompanied 

 by an injection of igneous veins and dykes into the fissures 

 occasioned by the bending. 



Sir Henry de la Beche (discussing Professor Rogers' 



