480 ON THE PHYSICAL STRUCTURE 



well known town of KnoxviJle, il may be entitled the KnoxvUle 

 division. In this, as in the division last mentioned, the whole 

 disturbed space is comparatively naiTow. 



9. The last or ninth division of the chain extends from the 

 southern termination of the Knoxville section, near the mouth of 

 the Clinch river, to the neighborhood of Tuscaloosa, in the centre 

 of Alabama. This we propose to call the Alabama Division. 

 Unlike the district just preceding, it exhibits almost perfect straight- 

 ness in its axes ; the strike, which is about south tliirty-five west, 

 continuing unchanged until the strata disappear beneath the 

 horizontal formations of the cretaceous and tertiaiy systems of 

 middle Alabama. 



Predominance of Southeastern Dips. 



While the general direction of the Appalachian chain is north- 

 east and southwest, there is a remarkable predominance of south- 

 eastern dips throughout its entire length from Canada to Alabama. 

 This is particularly the case along the southeastern or most dis- 

 turbed side of the belt, where it is strikingly exhibited in the great 

 valley, and in the extensive mountain ridges that bound it on the 

 southeast. But, as we proceed towards the northwest, or from the 

 region of greatest disturbance, the opposite, or northwest dips, 

 which previously were of rare occurrence, and always very steep, 

 become progressively more numerous, and, as a general rule, 

 more gentle. 



Of the prevalence of this interesting general law throughout all 

 the part of the chain extending from western Massachusetts into 

 eastern Tennessee, we have convinced ourselves by a personal 

 examination of the entire tract, during the last six years, and have 

 partially announced it in various passages of our Reports on the 

 Geology of New Jersey, Pennsylvania, and Virginia. We learn 

 from Dr. Charles T. Jackson, and other sources, that the prevail- 

 ing southeastern dip extends to western Vermont, and the valley 

 of Lake Champlain. 



Upon the correct interpretation of this singular feature depends, 

 we conceive, the clear elucidation of whatever relates to the dy- 



