1875.] 97 [Rogers. 



may often in future, as he was wont to do in former years, 

 grace our meetings by his presence and instruct us by his 

 wise and eloquent contributions. 



Geological Notes. By Prof. William B. Rogers. 



Art. I. On the Newport Conglomerate. 



It will be remembered that in a communication to the American 

 Association in 18G0, and in fuller detail in a paper on " The Meta- 

 morphism of Conglomerates," published in Silliman's Journal the 

 following year, the late distinguished Geologist, Prof. Edward 

 Hitchcock, endeavored to show that the generally elongated form and 

 closely fitting arrangement of the pebbles in the Newport conglom- 

 erate were due to the influence of heat or other agencies softening 

 the rock, combined with a continued pressure and tension, by which 

 the pebbles were squeezed and drawn out in their semi-plastic con- 

 dition. 



To this view I objected, on the ground that such an action applied 

 on a large scale must have had the effect not only of flattening 

 the pebbles in a uniform direction, but of developing a cleavage 

 or lamination of them, all parallel to tbeir flat sections as they lie in 

 the mass. For this and other reasons set forth in the Proceedings of 

 the Society, in a paper communicated the same year, I main- 

 tained that the forms and arrangement of the pebbles were those 

 which had resulted from the wearing action of the tides and cur- 

 rents, by which they had been originally moulded in the process of 

 their deposition and accumulation; not doubting, however, that in 

 some metamorphic districts conglomerate rocks are to be found, 

 which have sustained great internal changes through the effects of 

 heat, chemical action and violent pressure. 



At a subsequent meeting of the American Association (18G9), the 

 plastic theory was again brought forward, and an argument in its favor 

 was drawn from the then recent experiments of Prof. Tresca of the 

 Conservatoire des Arts et Metieres, on what he calls the " flow of 

 solids," and this argument seems hitherto to have passed unchallenged. 

 When, however, we refer to the results of these experiments, we find 

 the fact that in all cases the solid subjected to the moulding force 

 exhibited a striking alteration of its structure ; a bar of metal, for 

 example, thus forced through a contracted opening, being reduced in 



PROCEEDINGS 15. S. N. H. — VOL. XVIII. 7 OCTOBER, 1875. 



