1882.] 39 [Davis. 



The frequent recurrence of glacial till on stratified gravel 

 shows how weak a destructive force the ice-sheet generally had. 

 in this marginal region. 



B. 8. Great Britain. The glacial centres of Great Britain, in 

 which no extended preglacial gravels remain, occupy all the 

 mountainous areas of Scotland, North-western England, and 

 Wales ; in these districts, especially on their greater elevations, 

 much glaciated rock and comparatively little drift is found ; what 

 remains there is probably connected with the retreat of the ice 

 rather than with its advance. The lowlands and shores of Scot- 

 land, with the eastern and central parts of England, are about all 

 of the marginal area now above sea-level ; it is in these regions 

 that we find examples of preglacial soils, striated pavements and 

 drumlins. 



A. Geikie described a number of stratified beds under the drift at Clack- 

 mannan, near Sterling, Aberdeen and Edinburgh and in the Clyde 

 basin; as well as several striated pavements near Edinburgh, on the Firth 

 of Forth between Leith and Fisherrow, and farther east by Dunbar, at 

 Gareloch and on the Solway by Carsethorn. (On the Glacial Drift of Scot- 

 land, Glasgow Geol. Soc. Trans., I, 1862, 2°, 59, 66.) 



J. Geikie devotes several chapters to the pre- and interglacial beds of 

 Scotland and elsewhere, and remarks on their common occurrence in the 

 marginal areas of the Lowlands and near the coasts. (Great Ice Age, 1877; 

 Geol. Mag., v, 1878, 73-79; Prehistoric Europe, 1881. The latter volume 

 gives the best resume of the history and present condition of glacial re- 

 search in Europe that has yet appeared.) 



Lyell described the Forest-bed of Cromer, on the Norfolk coast of Eng- 

 land, as overlaid by pebbly sands and clays with lignite, and above these, 

 twenty to eighty feet of boulder clay, containing erratics, some of which 

 have been identified as Scandinavian. (Antiquity of Man, 1873, 254.) 



T. M. Reade contends that floating ice, not land ice, has been at work 

 here. (On the Chalk Masses or Boulders included in the Contorted Drift 

 of Cromer. Geol. Soc. Journ. xxxviii, 1882, 222-238. j 



S. V. Wood, Jr., finds a series of boulder clays and sands interbedded in 

 the same region. (Geol. Mag., vn, 1870, 18, 19.) 



Hull, Harkness, Mackintosh, Ranee and others, have written of the sub- 

 glacial and interglacial beds of England and Ireland; I do not pursue the 

 subject here because it is complicated with possibil'ties of iceberg as well 

 as of land-ice action; so far as the results show true glacial action, they 

 bear out the small erosive power of the marginal parts of the ice. 



B. 9. North-eastern America. The Atlantic Border of North 

 America shows few examples of preglacial or interglacial gravels* 



