36o 



ON BRITISH DRIFTS AND THE INTERGLACIAL 

 PROBLEM. 



(kxtracts from the aoi^kliss to the geological section, 

 British Association, York.) 



G. W. LAMPLUGH, F.R.S., 

 President of the Section. 



((\)u tinned from page J/ 7.) 



Local Shrinkage in the Ice-sheets. — There are many indica- 

 tions, especially in the Midland Counties and alons^ the southern 

 margin of the gflaciated reg'ion, that the several lobes and 

 tong^ues of ice of the Glacial Period in Britain did not all attain 

 their maximum development at the same time, but that while 

 some were creeping- forward, others were shrinking back. To 

 a certain extent this result may have been brought about simply 

 by changes in the currents as the ice-sheets overwhelmed their 

 erstwhile confining rims of bare land and opened up fresh 

 avenues of discharge. 



It appears to me, however, that the prime factor lay in the 

 displacement of the areas of greatest precipitation during the 

 course of the Glacial Period.* As the plateaus of ice rose 

 higher in the path of the moisture-laden air-currents they must 

 have gained increased effectiveness as condensers, thereby not 

 only augmenting the snowfall in one quarter, but also diminish- 

 ing the precipitation in the region to leeward. Hence I 

 imagine that there would be a persistent tendency for the great 

 ice-sheets of Western Europe to thicken and spread more rapidly 

 tow^ard the west than toward the east, until finally the eastern 

 portions were shrunken for want of sustenance, while the 

 westerly lobes were still waxing thicker and stronger. The 

 recent researches of Mr. F. W. Harmer into the probable 

 meteorological conditions of the Glacial Period t are full of 

 suggestion in their bearing iipon the changes which must have 

 been brought about by the expansion of the ice-sheets. The 

 subject is one of peculiar difficulty, but I believe that the 

 solution of many of the problems connected with the Glacial 

 Period are to be found along the lines of Mr. Harmer's investi- 

 gations. 



• Glcicialisis Miiif., vol. i. No. i i (iSi)4), p. -\^i ; aiul Mem. (if//. Simrv, 

 ' Isle of Man ' (1903), p. 395. 



I ' The Influence of Winds upon diin.ite diiring^ tin- Pleisloccne Epocli.' 

 Oiiii/-/. Journ. Gcol. Soc, vol. ivii. (1901), pp. 405-476. 



Naturalist, 



