32 



to the Essex County Natural History Society, and was 

 received from the Banks of Newfoundland. 



Prof. Rogers called the attention of the Society to a 

 geological problem, namely, — the cause of the want of 

 symmetry in the curves of the earth's strata, as seen in the 

 great mountain chains of America and Europe. Prof. 

 Rogers suggested, as the explanation of the phenomenon, 

 the forward pressure of the lava wave beneath, which he 

 supposed to have produced the curve, in the progress of an 

 earthquake. If a horizontal stratum were acted upon by a 

 perpendicular force from within the earth, it would be 

 raised in a symmetrical arch ; but if this force had a hori- 

 zontal as well as a perpendicular action, the result would 

 be the formation of a curve such as is really found to exist. 

 A railroad bar breaking under the weight of a passing train 

 is fractured towards the extremity farthest from that on 

 which the pressure commences, and in the same way the 

 points of fracture in the curves of upheaved strata are at 

 the most abrupt portion of the curve, towards the termina- 

 tion of the wave. The point of fracture in the railroad bar 

 is nearer to its remote support in proportion to the speed of 

 the passing train. Prof. Rogers supposed that there is a 

 horizontal thrust acting upon the bar through the principle 

 of adhesion in addition to the perpendicular action of 

 gravity. 



Mr. Desor stated, as an illustration of the rapid progress of 

 geological science, that the plication theory, which was hardly 

 known fifteen years ago, is now almost universally adopted. 

 This result he thought was due chiefly to the investigations of 

 the Profs. Rogers in the Alleghany chain. In Europe the plica- 

 tion theory had been first practically illustrated by Prof. Studer 

 in the Jura range, and it was by nnistake that the credit of it 

 had been Liven in this country to another Swiss geologist. 



As to the cause of the plication, several theories had been 

 proposed besides that of Prof. Rogers. Prof. Studer thought 

 that the plication of the Jura was the result of a lateral press- 

 are, caused by the upheaval of the Alps. M. C. Prevost ascribed 



