166 Geological Society:-— 



The other conclusions arrived at, after mature consideration of all 

 the evidence hitherto obtained, are : — that a gradual passage will be 

 found to exist from the base of the Crag up to and through the drift- 

 deposits to those of recent date ; that in East Anglia we have evi- 

 dence of but one, and that a gradual, period of glacial submergence, 

 succeeded by a corresponding movement of reelevation ; and that 

 there are no " middle glacial " deposits whatever within the area of 

 the Cambridge valley. 



2. " Denuding Agencies and Geological Deposition under the 

 Flow of Ice and Water, with the Laws which regulate these actions, 

 and the special bearing on River- action of observations on the 

 Mississippi and other great rivers, and their present and past Mete- 

 orological conditions, and similar remarks on Marine Deposits, illus- 

 trated by the Irish Sea and the Chesil Beach." By A. Tylor, Esq., 

 F.G.S. 



The writer adduced evidence by measured sections and drawings 

 to show that the Quaternary gravels were deposited rather in a wet 

 or pluvial than in a snowy or glacial period. He thought the de- 

 nuding action of springs and the alternate action of rain and frost 

 had been neglected. He considered Agassiz and other writers had 

 overlooked the previous writings of Playfair, to whom he referred. 



The rainfall of "Westmoreland, Switzerland, and the Mississippi 

 valley were compared in summer and winter, to prove that floods 

 were not necessarily greater from land covered with snow than 

 from land covered with trees and vegetation when height above the 

 sea and local circumstances were taken into consideration. Mr. 

 Dana's " Great Glacier,*' whose melting was to supply a Quaternary 

 river Mississippi 50 miles wide, would require a supply equal to 

 625 times the present rainfall to fill it. 



The melting of snow was assumed to be of such proportions by 

 modern writers as to equal the debacles of older geologists. 



The high Swiss mountains pointed to a greater diminution of snow 

 on high ground in the Glacial period ; and he believed the clouds 

 then discharged near the sea-level, so that the mass of snow and ice 

 was at low levels. 



It appears that in Greenland in the 80th parallel, according to 

 Nordenskiold, near the sea in summer there is no snow on the 

 ground 1000 or 1500 feet above the sea. Open water at the poles 

 must depend upon the abstraction of the vapour from the atmosphere 

 at lower latitudes ; and probably in the Glacial period the ice-cap 

 was thickest at the 70th parallel of latitude. 



Mr. Tylor thought the theories of former depressions of the land, 

 as in the Mississippi valley, should be tested by examination for 

 flexures. He had found (in 1868) that flexures, and not fractures, 

 had very much affected the course of the "Wealden denudation in 

 the Quaternary period. 



The laws of river-motion are very simple and precise ; and as 

 depressions and upheavals are always unequal, any great movements 

 in the Quaternary period would affect the courses of rivers, and be 

 traceable in their deposits. 



