362 0)1 British Drifts and the Intvrgiacial Problem. 



conditions very different from the waxing stages. It appears 

 from the evidence that the great ice-plateaus still lingered in 

 their basins even after the amelioration of the climate had 

 progressed so far that no permanent snow could remain on hills 

 that rose considerably above their level. Deprived of reinforce- 

 ment, and wasting ever more rapidly as their surfaces were 

 brought lower, the lobes must in all their embavments have 

 passed into that condition of ' dead ice ' with which the explorers 

 of Polar regions have made us familiar. The ' englacial ' load 

 of detritus which the ice was powerless farther to transport was 

 gradually dropped to the ground, and often modified and spread 

 by gravitational movement in the saturated mass. * The 

 peculiar features of the upper part of the lowland drifts were 

 thus explained many years ago by the late J. G. Goodchild in 

 his luminous description of the glacial deposits in the \'ale 

 of Eden,t and his conclusions have been supported by the 

 researches of Dr. N. O. Hoist in Southern Greenland, where 

 there was found to be the same difference between the un- 

 oxidised grovmd-moraine and the overlying oxidised material of 

 ' englacial ' origin as between the lower and upper boulder-clays 

 in areas of ancient glaciation. \ In adopting this explanation 

 we must recognise that the uppermost boulder-clay of an 

 extensive area was not formed at exactly the same time in 

 every part, but was accumulated progressively as a marginal 

 residue during the emergence of the land from its icy cloak. 



Liite Glacial and Post-Glacial Deposits. — Of the glacial and 

 interglacial epochs of Professor Geikie's scheme later than the 

 * Polandian ' it is admitted that no indication has been found in 

 Yorkshire. There seems, on the contrary, to be evidence of 

 steady amelioration in the climate, as the glacial deposits 

 opposite the mouths of the Wold valleys are overlain, first by 

 great deltas of chalky gravel, denoting torrential floods, 

 probably from the seasonal melting of heavy snows ; and then, 

 in the hollows of these gravels, or of the boulder-clay itself, we 



* Tlic flow of lot>sc' malcrial at tin- .surface wlicn satm-alccl b\- water has 

 been recently studied by J- O. Anderson (Upsala), who cites inanv remark- 

 able illustrations of the phenomenon, and proposes to apply to it the term 

 ' solifluction.' Jotirn. Geol., vol. xiv. (1906), pp. 91-112. 



t ' Ice Work In Edenside.' Trans. Cumberland .\ssoc.. No. 12 (1SS6-7), 

 ])p. 1 1 1-167. 



X 'Dr. N. O. Hoist's Stutlies in Glacial Geoloijy,' by Dr. j. Lindahl, 

 American Xalunilist, .Auif. 1888, pp. 705-71J. It should be noted, iiowever, 

 that Professor R. I). Salisbury did not find this ililVeri-nce apparent in the 

 moraines of North Greenland Glaciers. Svv Jouni. (n'o/., vol. iv. (iSqt*), 

 pp. 806-7. 



Naturalist, 



