Mr. Trimmer on Pipes or Sandgalls in Chalk. 521 



elusion, that when these were originally deposited hold rocky moun- 

 tains existed in close proximity to the present site of Calcutta ; and 

 taking his data from the results of personal observation on the trans- 

 porting power of rapid currents, he estimates the distance of these 

 mountains at not greater than twenty or thirty miles. Resting on 

 the bed of coarse conglomerate, the entire depth of which is un- 

 known, although it cannot be less than eighty feet, the bore having 

 pierced it to that extent, there are beds of carbonaceous matter and 

 lacustrine clay bearing the clearest evidence of having been quietly 

 deposited on a marshy surface clothed with vegetation. Ere this 

 could have taken place, the powerful currents indicated by the gravel 

 must have been arrested, and as this could only be effected by a great 

 lowering of the inclination of the bed of the river, we may infer the 

 check arose from the entire subsidence of the range of hills above 

 alluded to. The extent to which this took place it is impossible for 

 us to estimate, but the deposits which the river continued to make 

 would repose upon the depressed masses, and were boring operations 

 to be carried on successfully in such localities they would ultimately 

 expose these again to our observation. Supposing then, as without 

 impropriety we may do, that the rocks of which these hills were 

 composed stretched away beneath the conglomerate bed formed by 

 the large gravel borne along by the torrent issuing from them, we 

 are led to believe that had the Fort William boring operations been 

 successfully carried through the entire depth of the conglomerate, 

 the auger would then have impinged on the solid rock, and if so, 

 would the experiment have terminated favourably ? 



" When we remember," observes Lieut. Smith, " that the con- 

 glomerate was almost entirely composed of debris from primary rocks, 

 admitting of the inference that the chain of hills itself was formed of 

 members of this series, there can be but little hesitation in replying 

 in the negative." 



" On Pipes or Sandgalls in Chalk." By Joshua Trimmer, Esq., 

 F.G.S. 



In a former paper (Proceedings, vol. iii. p. 185) the author de- 

 scribed two detrital deposits in Norfolk, which appear to have been 

 produced by powerful currents of water. The lowest of these is 

 marked on the surface with numerous furrows and penetrated by 

 cylindrical and funnel-shaped cavities like those of the chalk, though 

 in general of smaller dimensions. If these have been caused by the 

 mechanical action of water, they indicate a pause between the two 

 deposits of sufficient duration to allow of the consolidation of the 

 lower bed before the other was thrown down upon it. Therefore, 

 to learn the true history of the beds, we must discover the cause of 

 the pipes ; the action is so similar in the chalk and the detrital de- 

 posits that the one will explain the other. 



From recent study of the pipes or sandgalls in the chalk of a part 

 of Kent, Mr. Trimmer has arrived at the conclusion that they are 

 due to the mechanical, not to the chemical action of water ; and that 

 this action was the breaking of the sea on a low shore antecedent to 

 the formation of the eocene strata. This opinion he bases on the 

 following grounds. 



