ANNIVERSARY ADDRESS OF THE PRESIDENT. IxXl 



corresponding with that at which it could stand relatively to the sphe- 

 roidal mass of which it is considered to have formed the upper part. 



The amount of separation between the original beds, supposing no 

 contraction in that part of the earth's surface, would correspond with 

 the difference which the folding and crumpling of the beds would 

 make in the length of the section across them prior and subsequent 

 to their contortion. If we assume a fracture from tension along a 

 line of 1300 miles, and the section across the beds so broken through 

 to be one-sixth less now than prior to their movement, and 1 50 miles 

 their present measurement, after contortion, on both sides, we should 

 have an opening of sixty miles between the edges of the first fracture, 

 if there be no evidence of fractures parallel to the first. Now in the 

 case of the Appalachian region the facts would appear to show thai 

 the force had always been exerted in the S.E. for at least the mean 

 breadth of 150 miles, and hence the tension-fractures, — considering 

 them to have been repeated, and thus to have produced waves of 

 translation more and more bending up the beds, so as even to throw 

 them over -s^dth folds dipping towards the force employed, — would 

 have to be made in the mass of matter occupying the space between 

 the edges of the original great rent. We should thus have to con- 

 sider it as from time to time consolidated in such a manner as to offer 

 resistance and be fractured by tension in the manner required. 



After carefully considering the facts brought forward by the Pro- 

 fessors Rogers, for which the best thanks of geologists are due to 

 them, it appears to us that lateral pressure, not from the mere injec- 

 tion of some liquid and molten matter, which, as Professor Rogers 

 observes, could scarcely produce the effects observed, when such molten 

 matter is considered to form a portion of a general mass beneath, but 

 from the pressure of masses of the crust of the earth against other 

 masses along great lines of fracture on the surface, has been the cause 

 of these flexures. Under any hypothesis, the sliding of a portion of 

 the earth's crust would appear to be essential, as also a flexibility of 

 the component beds sufficient to admit of folding and contortion. 

 The greater the power for both, the less the necessity for the rise of 

 the squeezed mass into mountains. Under the hypothesis of lateral 

 pressure, considering that to have been exerted with an uniform in- 

 tensity for 1300 or more miles, and the thickness and resistance of 

 the crust sufficiently uniform also, we do not perceive anything to 

 prevent the general mass from sliding over a fluid body beneath, 

 and being crumpled and folded as in the Appalachian region. 



The visit of our colleague Professor Henry Rogers to Europe was 

 for the more especial purpose of comparing other contorted, ridged 

 and furrowed regions with that which had afforded to the labours ot 

 himself and brother those facts. Examining the structure of the 

 Devonian formation on the Rhine, he considers that the entire re- 

 gion of the Devonian and carboniferous rocks exhibits the same laws 

 of flexure and plication observable in the Appalachians, and he points 

 to a section from S.E. to N.W., either through the Taunus to West- 

 phalia ; or by the Rhine from Bingen to Remagen, or from the Hunds- 

 ruck to the coal region of Liege, as showing an almost universal 



