DISLOCATIONS OF THE COASTAL PLAIN STRATA. 7 



a number of isolated districts in wliicli identical phenomena are to be accounted 

 for on different hypotheses. It is also a theory which nothing in our previous ob- 

 servation or experience would cause us to doubt, and is one which has been ai)plied 

 to similar phenomena in Europe, especially in the islands of Moen and Rugen, in 

 Denmark. 



In discussing Mr Hollick's paper Acting President Shaler said : 



My objections to i\Ir Hollick's paper may be summed up as follows: On the 

 western end of the island of INIarthas Vineyard, a region which Mr Hollick has 

 not personally examined, series of Cretaceous and Tertiary rocks, having an aggre- 

 gate thickness of several hundred feet, are folded into extended anticlinals and 

 syuclinals, the average dips of which exceed 40° of declivity. The width of this 

 area of folded rocks is not less than five miles, extending entirely across the island. 

 The average amplitude of the folds })robably exceeds one thousand feet. The 

 amount of the disturbance is as great on the southern side of the island, the region 

 furthest removed from the main ice front, as it is on the northern side of the field. 

 Moreover, the axes of the folds are not at right angles to the path of the glacial 

 movement, but in a general way parallel to that course. 



On this field of profoundly dislocated rocks there remains in an almost unaltered 

 state the com})licated erosion topograjihy which existed when the region was in- 

 vaded by the ice of the last glacial period. Considerable areas are destitute of 

 erratic material. Scarcely any of the valleys have been so far obstructed by the 

 drift that their forms are not readily distinguishable. Moreover, on the northern 

 or shock side of the island there are many minor disturbances of the strata which 

 may be reasonably attributed to the thrusting of the ice-sheet, but these disloca- 

 tions greatly differ from the broad folds which characterize the other parts of the 

 district. They seem to me to be imposed upon the preglacial topography. 



Fur the reasons I have indicated, as well as for othei-s which cannot be briefly 

 stated, while granting that the horizontal thrusting of an ice-sheet may disrupt 

 strata, I do not believe that the foldings of the Marthas Vineyard section are due 

 to this cause. 



AFr Hollick replied : 



Professor Shaler is in error in regard to my not having personally visited and 

 examined the western end of the island. The question seems to resolve itself into 

 merely a difference of opinion as to the preglacial age of the to])ography. 



It was voted to adjourn the further discussion until after the noon 

 recess. 



Upon reassembling at 2.15 o'clock p ni J. AV. Spencer spoke U])on "Mr 

 Hollick's pa))er. 



The first paper read was entitled — 



REOOySl RUCTION OF THE AXTILLEAN CONTINENT 

 I5V J. \V. SI'ENTKK 



Remarks U])on this ])aper were made l)y W. B. Scott as to the Aiitil- 

 lean faunn^ and their hearing upon the former land connection; hy J. 



