230 DRIFT DEPOSITS OP MANCHESTER 



The eflFects of large rivers carrying with them 

 the debris of the land flowing into estuaries, clearly 

 indicate the origin of sand banks ; and the power 

 of mountain streams to move vast masses of rock, 

 when once put in motion, is now well known ; but 

 all these agencies are insufficient to account for 

 the phenomena which are observed in the Till ; 

 for where do we see a current of water that, at the 

 same time and place, will deposit beds of fine lami- 

 nated silt, and homogeneous clay, with immense 

 masses of rock, blocks of the same kind of stone, 

 some of which are perfectly rounded, others 

 smoothed only on one side, having the rest of 

 their sides quite rugged, others perfectly angular, 

 and others again grooved or marked with strice ? 

 Such different effects cannot rationally be attri- 

 buted to one cause. Latierly the action of glaciers 

 and icebergs has been called in to assist us in our 

 enquiries ; and it is probably to the conjoint action 

 of these powerful agents and currents of water, 

 that we must look to for the origin of the deposit 

 of Till in the neighbourhood of Manchester. 



In my former paper on Drift,* it was shown that 



* Published in the Report of the Manchester Geological 

 Society, for 1843. 



