GEOLOGY. 277 



The neat and clean manner in which the pebbles have been gen- 

 erally severed by the joints implies plasticity. For though occasion- 

 ally we meet with one that has a somewhat uneven surface, as if 

 mechanically broken, such cases are rare. Whatever may be our 

 theory of the agency that has formed the joints, the conviction is 

 forced upon every observer that the materials must have been in a 

 soft state after their original consolidation. There is no evidence 

 that the opposite walls have slid upon one another at all, as the op- 

 posite parts of the pebbles coincide. It seems as if a huge saw or 

 cleaver had done the work. 



These proofs of plasticity apply essentially though less forcibly to 

 the micaceous and talcose cement which has also been cut across by 

 these joints. Though generally small in quantity, it sometimes forms 

 layers of considerable thickness interstratified with the pebbles. 



Some have imagined that the elongated, flattened, bent, and in- 

 dented pebbles of this conglomerate may have been worn into their 

 present shape and brought into a parallel arrangement by the me- 

 chanical attrition of waves and currents. We feel sure that an ex- 

 tensive and careful examination of the localities, and of beaches 

 whero shingle is now being formed, will convince any one that they 

 cannot have had such an orhhi. 



In the conglomerates of Wallingford and Plymouth, Vermont, Pro- 

 fessor Hitchcock found that the process of elongating and flattening 

 the contained pebbles has been carried much further than at New- 

 port, R. I. Ho even inclines to the opinion that conglomerates in 

 these localities have been so operated on, while in a plastic state, by 

 mechanical agencies that they have been converted into schists, in 

 which these original rounded pebbles, flattened and elongated, formed 

 the thin quartzose lamina?. In regard to this theory Professor Hitch- 

 cock uses the following language : 



"It is not probably possible for us to convey a very clear and com- 

 plete idea of the evidence of this position. Would that our readers 

 could, as we have done, visit the localities and become familiar with 

 the striking specimens there by repeated and careful examination. 

 From our own experience it would not surprise us if the conversion 

 of the pebbles of conglomerates into the laminte of schist should 

 be pronounced preposterous by able geologists. So the idea seemed 

 to us at first, when the facts forced it upon our attention. But 

 as the facts compelled us to give up our scepticism, so we think it 

 will be with any candid mind. Looking at almost any specimen of 

 the talcose conglomerate schist, on the edge corresponding to the dip, 

 we should see nothing but alternating laminse of quartz and talc, or 

 mica, and pronounce it a good example of the rock which we have 

 called, and which is generally called, talcose schist. But a fracture 

 at right angles reveals the flattened pebbles, and shows us that the 

 edges are what we have regarded as laminee. Let the process of 

 flattening be carried a little farther, and no evidence will remain 

 that they ever were pebbles. Who knows how extensively the pro- 

 cess may have been thus carried through in the schists and gneiss of 

 the Green Mountains, and how large a part of them may once have 

 been conglomerate ? " 



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