246 ANNUAL OF SCIENTIFIC DISCOVERY. 



R. showed, by a series of figures on the black-board, the successive 

 features of an anticlinal, just when it forms a normal arch, then steep- 

 ening more and more on its western side, until it becomes a folded 

 axis. He then pointed out the passage from this latter into a fault, 

 by the fracture of the strata, and the folding down and engulfing of 

 some of the rocks belonging to the western half of the anticlinal. In 

 this way the rocks of the eastern side of the mountain are, in certain 

 cases, made to over-ride and lie upon the edges of the newer strata. In 

 other cases, as shown by the Professor, the dislocation, joined to subse- 

 quent denudation, has given the appearance of an unconformable depo- 

 sition of the newer upon the older rocks. Prof. R. referred to various 

 marked instances in the Appalachian belt, in which an anticlinal axis, 

 when traced longitudinally, passes by the gradations just described 

 into a fault. In some cases, the fault thus produced is continued for 

 a long distance, as in the great lines of dislocation which pass from 

 south-western Virginia into Tennessee, and are thus prolonged for several 

 hundred miles. In other cases, the line of fault, by a reverse order, 

 passes again into an anticlinal axis. Similar phenomena were described 

 in regard to synclinal axes. But in this case, the east side of the axis 

 or trough became engulfed. Prof. R. stated it as the law that, in the 

 Appalachian anticlinal axes, the fracture occurs always on the west side 

 of the axes' plane. In synclinal, it occurs on the east side. 



In conclusion, Prof. R. enforced the great importance of attending 

 to these phenomena of dislocation, and pointed out the fact that exten- 

 sive lines of unconformity, in the south-west and elsewhere, in the Ap- 

 palachian belt, which are clearly due to the fracture and movement 

 before described, are liable to be interpreted as lines of original uncon- 

 formability , and have been so regarded by other observers. Thus, along 

 the base of the Cumberland mountain, in south-western Virginia and 

 eastern Tennessee, the coal rocks are seen abutting against the steep 

 dipping lower Appalachian rocks, as if deposited after the disturbance 

 of the latter. Yet Prof. R. has actually traced these features into 

 an anticlinal axis. 



ON THE ORIGIN OF STRATIFICATION. 



THE following paper, on the " origin of stratification," by Mr. David 

 A. Wells, of Cambridge, was read at the meeting of the American As- 

 sociation, Albany : 



The general idea respecting the origin or cause of stratification, as 

 expressed in geological text-books, or as inferred from the writings of 

 geologists, seems to be this : that strata, or the divisions of sedimen- 

 tary matter, have been produced either by an interruption of deposition, 

 or a change in the quality of the material deposited. This idea is well 

 illustrated by the deposition of matter of tides or inundations, its sub- 

 sequent consolidation, and a renewed deposition on the plane of the 

 former deposit. That such is really the cause of stratification, in very 

 many or most instances, I do not dispute ; but that there are other 

 causes which tend to produce and have produced stratification, equally 

 extensive and varied, is, I think, clearly shown by the following obser- 

 vations. 



