1869.] 293 [Whittlesey. 



The extremity of the peninsula of Cape Ann, near Rockport, ex- 

 hibits hundreds of acres of rock surface nearly destitute of vegetation, 

 and completely covered with blocks of stone which have been sepa- 

 rated from the mass beneath by the action of frost working in fractures 

 of the concentric character above described. Should the glacial sheet 

 ever return to this surface it would find an immense amount of mate- 

 rial jirepared for transportation. 



It Avill naturally occur to the reader that possibly this concentric 

 fracture may be due to the action of water bringing about the decay 

 of the rock, and that these concentric sheets are only great exfoliations 

 of disintegrated material. An examination however will convince 

 the observer that these great sheets of rock which are sejaarated by 

 these fractures are not penetrated by decay; moreover the exfoliation 

 caused by chemical change is generally observable on the same masses 

 in the form of obscure scales, rarely producing sheets more than 

 an inch or two in thickness, while the sheets of rock separated 

 by the concentric fractures are from one to three feet in thickness. 

 AVhen the position of the rock exposed to weathering is such that 

 neither waves nor frost can at once profit by the fracture and lift the 

 separated rock from its bed, then the agents of decay enter into the 

 fissure and proceed slowly to widen it upwards and downwards so 

 that the disintegrating agents have thrice the surface to work upon 

 that they would have if the decay Avere confined to the outer surface 

 of the z'ock alone. 



It is evident that this tendency to concentric fracture must tend to 

 produce dome-like forms wherever masses of unstratified rock are ex- 

 posed to weathering, and it is probable that we must attribute most 

 of the rounded bosses of rock which cover New England and other 

 regions where such domes abound, to the action of this agent. I am 

 inclined to think that glacial action has in most cases done little more 

 than round and smooth the domes previously formed by the operation 

 of this mode of decay. 



The Secretary read a paper by Col. Charles Whittlesey of 

 Cleveland, Ohio, upon the Physical Geology of Eastern Ohio. 



This paper embodied some of the results reached by a long series 

 of observations upon the exact dip, thickness and mass of the car- 

 boniferous and devonian rocks of eastern Ohio. The work was 

 commenced by Col. Whittlesey thirty years ago, while engaged, under 

 the late Professor Mather, upon the State Geological Survey, and has 



