Calcutta Delta. 555 



rests ;)* while the upper loose portion would indicate that the volume 

 of the river had increased by the arrival of the monsoon or heavy rains, 

 which enabled it to dispose its silts " intermixed with fragments of 

 quartz, felspar, and granite, twenty five-feet deep," which it is truly 

 remarked, " indicate a more rapid current entering the basin." 



After this it would appear " that a season of repose" occurred, in 

 which was deposited " a thick stratum of fine ferruginous sand intermix- 

 ed with clay," and subsequently, " the currents again became disturb- 

 ed and so continued, while a coarse quartzose conglomerate, ten feet in 

 depth, took place ;" this too, " is followed by a bed of fine calcareous 

 clay, five feet in thickness, and corresponding in its characters with the 

 lower calcareous clay which is supposed to have been a lacustrine 

 deposit." 



These three deposits in my opinion indicate nothing more than the 

 simple fact, that a lapse of time followed the monsoon, during which, 

 from the usual decreased force of the river, the sea again returned to 

 deposit the fine ferruginous sand mixed with the clays more properly 

 the produce of the river, with which its waves were commingling, un- 

 til the return of another monsoon or a violent inland storm caused the 

 river to depositf " the coarse quartzose conglomerate," followed again 

 by the calcareous lacustrine clays as its force abated, and the sea re- 

 sumed its former chemical action. If to these causes we add the pro- 

 bability, that during the deposition of the earlier strata, some mountain 

 lakes had burst through their barriers and escaped, we shall derive an 

 additional agent in producing the coarser materials of the deposits. 



I do not attempt to point out, more particularly how the strata be- 

 neath Fort William have been accumulated, because I have had no 

 opportunities of inspecting them ; nor do I think it necessary to do so, 

 since if the causes I have assigned are thought sufficient or probable, 



* It is suggested that the superior sandy stratum has been cemented by calcareous matter 

 derived from the underlying stratum of calcareous clay ; this however would appear to be 

 founded in error, for had the calcareous bed rested upon the sandstone stratum, it might have 

 been reasonably argued that the calcareous matter with which the latter is cemented, was 

 derived from the former by infiltration, but as it lies below the sand, the cementing of the 

 latter must be due to other causes, as the solution of lime would not have ascended. 



Note by the Editor. — We have had numerous opportunities of seeing sand consolidated in 

 this manner by the infiltration of water containing oxide of iron till it reaches a subjacent 

 impervious bed, from thence it consolidates the superineumbeut sands from below upwards. 

 Captain Hutton here seems to have misunderstood us. 



t We confess we do not clearly comprehend this, for the rivers alluded to by Captain 

 Hutton, must either have been running at a depth of 300 feet below the sea, or the sea 

 must since have risen to that height above its former level. We rather suggest a sinking 

 of the surface at different periods in this situation. — Ed. 



