306 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 20. 



rian stage, and an equally distinct middle Devonian stage. The 

 lithological and paleeontological characters of the several groups of 

 strata were then treated of in succession ; their resemblances and dif- 

 ferences, in these respects, being carefully noted. From the consi- 

 deration of the stratigraphical details contained in this and the pre- 

 ceding paper, Dr. Bigsby deduces two main conclusions ; namely, 

 1 . That, from the Potsdam sandstone to the summit of the Carboni- 

 ferous rocks, these strata were laid down in comparative quiet ; sub- 

 ject to occasional, vertical, variable, secular oscillations, which led to 

 considerable superficial changes. 2. That their elevation, foldings, 

 fractures, and metamorphism were effected after the deposition of 

 the whole ; in a single prolonged transaction, and principally in a 

 N.E. and N.W. direction, along the present Appalachian ridges and 

 their continuation from Labrador to near the Gulf of Mexico. The 

 evidences on which these two propositions rest were next detailed ; 

 and the views of the Professors Rogers on these points, and the 

 author's objections, were stated in full. 



