544 Geological Society : Mr. Colthurst on Contortions 



in his paper read at Plymouth, respecting the mode of accumulation 

 of the bones. He states that these osseous remains cannot have 

 been derived from the emptying of some cave, because the mass of 

 superincumbent matter which has been removed from above the 

 beach proves that the bones must have been deposited where they 

 were found at a very ancient period, and long before they could have 

 been affected by human agency. There are also no known caves 

 containing bones sufficiently near. On the contrary, says Dr. 

 Moore, if the sea was at one time at the level indicated by the beach, 

 the Hoe must have been an island accessible by animals at low 

 water, and there appears no obstacle to the supposition that the 

 bears might have selected the beach to devour their prey ; and the 

 stranded whale may have added to the banquet. Whether the bones 

 were drifted or not, their occurrence on the top of the beach, and 

 not in it, prevents, the author says, any identity of time in their 

 origin ; but that the beach previously existed, and was of marine 

 origin, is proved by the resemblance of the deposit to a modern 

 beach, and its containing sea-shells of the existing period, although 

 few in number. 



That the deposit is not the result of glacial action, the author 

 observes, is probable from the want of any indication of such action 

 in the neighbouring district ; and though he does not presume to 

 assert that this may not be a cause of drift generally, and even of 

 the upper deposit in the same locality, yet he contends that the 

 dissimilarity in the composition of the lower deposit sustains him in 

 the supposition of its being of different origin, and really a deposit 

 from the sea. Lastly, Dr. Moore, in reference to the present posi- 

 tion of the beach far above any point attained by the sea during the 

 greatest storms, states that the deposit must have been elevated by 

 natural causes ; and that, however uncertain the exact period of such 

 an event, it seems to have occurred at a time probably more recent 

 than the epoch when the extinct animals disappeared. 



Appended to the paper, is a notice of a specimen of perforated 

 limestone taken from the Hoe Lake quarries, eighty- five feet above 

 the present level of high water, and Dr. Moore maintains his belief 

 that the perforations were formed by Pholades, and not by snails. 



A paper was next read, entitled " An Account of the Contortions 

 and Faults produced in the Strata underneath and adjacent to the 

 great Embankment across the Valley of the Brent, on the Great 

 Western Railway," by J. Colthurst, Esq. ; communicated by George 

 Bellas Greenough, Esq., F.G.S. 



The author was induced to lay this paper before the Society, be- 

 cause he conceives, that, in the phenomena exhibited by the sub- 

 sidence in the Brent embankment, there may be found the cause of 

 many of the contortions, faults and dislocations of strata, especially 

 among sedimentary rocks, and which are commonly attributed to 

 the agency of forces acting from below rather than to pressure from 

 without. 



The embankment is fifty-four feet in height, and rests on vegetable 

 soil, beneath which are four feet of alluvial clay ; then occurs a bed 



