70 PROCEEDINGS OF THE ASSOCIATION OF 



markings on the surface of rocky strata in New York and other 

 places." 



Association adjourned to half-past three o'clock, p. m. 



Friday^ 3^ o'clock, p. m. — Prof. Silliman in the chair. The 

 following gentlemen were announced by the standing committee 

 as the local committee for next year. Dr. T. Romeyn Beck, Prof. 

 E. Emmons, Albany, and Mr. W. C. Redfield, New York. 



A letter from Mr. James T. Hodge, relative to the distribution 

 of State Reports, was read by the secretary. 



A paper was read " on the Structure of the Appalachian chain, 

 as exemplifying the laws which have regulated the elevation of 

 great mountain chains generally;" by Prof. Henry D. Rogers, 

 and Prof. William B. Rogers. 



The authors divide their paper into two parts ; Part I, being a 

 description of the phenomena : Part II, a theory of the flexure 

 and elevation of the strata deduced from the preceding features 

 of structure. 



Part I, embraces the following heads : 



1st. A sketch of the physical featm-es of the Appalachian chain, 

 from New England to Alabama. 



2nd. Predominance of southeastern dips, with an historical sketch 

 of the previous explanations offered by other geologists. 



3rd. Of the character of the flexures of the strata, and the law of 

 their gradation in crossing the chain northwestward. Two or three 

 new terms are here proposed for designating conditions of structure. 

 The several prevailing forms of structure are then exemplified: (a,) 

 normal flexures; {h,) folded flexures and inversions; (c,) flexures 

 broken or passing into faults. 



4th. Of the distribution of the axes in groups; remarkable paral- 

 lelism of the axes in each group ; great length of some axes ; bending 

 of axes ; increasing interval between the axes as we advance towards 

 the northwest. 



5th. Descriptions of a series of sections across the chain, with a 

 table of the northwest and southeast dips which they disclose. 



Part II, treats of the following theoretical topics : 



1st. The force producing the flexure and elevation of the strata, 

 was compounded of a wave -like oscillation of the crust, and a tan- 

 gential pressure towards the northwest. 



2nd. Theory of the origin of the supposed subterranean undula- 

 tions, and of the manner in which the strata became permanently 

 bent. 



3rd. Identity of the undulations of the crust with the wave-like 

 motion of the earth in earthquakes. This latter shown to result 

 from an actual billowy oscillation of the surface of the subterranean 

 fluid lava. 



