33 



the plication to a bulging up, caused by the depression of vast 

 areas. This was also the theory advocated by Mr. T. Dana. 

 Mr. Desor thought that whatever views are entertained as to the 

 real cause of this great feature of the earth's surface, the dynam- 

 ical illustrations which Prof. Rogei's had just adduced in support 

 of his theory were well calculated to hasten the solution of the 

 problem. 



Prof. Rogers said, his own and his brother's views in 

 regard to the upheaval of mountain ranges had been fully 

 confirmed in his own mind by visiting the Alps. He pro- 

 ceeded to give an account of the fan-like arrangement of 

 the strata of those mountains, illustrating it upon the black- 

 board. He gave it as his opinion that the Jura range was 

 raised by a force from the direction of the Vosges, as the 

 plications all lean towards the Alps, not from them, as 

 would be the case if they had been produced by a lateral 

 pressure caused by the weight of the latter, as supposed by 

 Prevost. 



In reply to a question from Prof. Wyman, Prof. Rogers 

 explained, that the upheaved strata preserve their shape by 

 means of trap dykes, and veins of greenstone and quartz, 

 which are always found in great numbers occupying the 

 fissures on the abrupt surface of the curve, and which fill- 

 ing these fissures in a liquid form, harden in cooling, and 

 act as keys and braces to prop up the bent strata. 



Mr. Desor read from a note from Mr. Logan, chief of 

 the Geological Commission of Canada, a statement of the 

 height of the Laurentian deposit, called by him drift, at 

 Montreal, as follows : — Height of Laurentian locality at 

 Montreal above the surface of the St. Lawrence, in Mon- 

 treal Harbor, summer level, 457.34 feet ; Fall to tide water 

 at Three Rivers, 12.75 feet; in all, 470.09 feet. 



Rev. Zadock Thompson presented specimens of wood 

 taken from a deposit at Burlington, thirteen feet below the 

 surface of the ground and two hundred feet above the level 

 of Lake Champlain. 



PROCEEDINGS B. S. N. II. 3 JULY, 1851. 



