president's address. 15 



of their greatest development, upon the adjacent lowlands. They are 

 generally believed to have advanced and retreated more than once, and 

 their movements have been correlated by Professor J. Geikie with 

 those already mentioned in the Alps. Into that very difficult question 

 I must not enter; for my present purpose it is enough to say that in 

 early Pleistocene times glaciers undoubtedly existed in the mountain 

 districts of Britain and even formed piedmont ice-sheets on the low- 

 lands. On the west side of England smoothed and striated rocks have 

 been observed near Liverpool, which can hardly be due to the move- 

 ments of shore-ice, and at Little Crosby a considerable surface has been 

 cleared from the overlying boulder clay by the exertions of the late 

 Mr. T. M. Eeade and his son,' Mr. A. Lyell Reade. But, so far as 

 I am aware, rocks thus affected have not yet been discovered in the 

 Wirral peninsula. On the eastern side of England similar markings 

 have been found down to the coast of Durham, but a more southern 

 extension of land ice cannot be taken for granted. In this direction, 

 however, so far as the tidal valley of the Thames, and in corresponding 

 parts of the central and western lowlands, certain deposits occur which, 

 though to a great extent of glacial origin, are in many respects different 

 from those left by land ice in the Alpine regions and in Northern 

 America. 



They present us with problems the nature of which may be inferred 

 from a brief statement of the facts. On the Norfolk coast we 

 find the glacial drifts resting, sometimes on the chalk, sometimes on 

 strata of very late Pliocene or early Pleistocene age. The latter 

 show that in their time the strand-line must have oscillated slightly 

 on either side of its present level. The earliest of the glacial 

 deposits, called the Cromer Till and Contorted Drift, presents its most 

 remarkable development in the cliffs on either side of that town. Here 

 it consists of boulder clays and alternating beds of sand and clay; 

 the first-named, two or three in number, somewhat limited in extent, 

 and rather lenticular in form, are slightly sandy clays, full of pieces 

 of chalk, flint, and other kinds of rock, some of the last having 

 travelled from long distances. Yet more remarkable are the huge 

 erratics of chalk, in the neighbourhood of which the sands and clays 

 exhibit extraordinary contortions. Like the beds of till, they have not 

 been found very far inland, for there the group appears as a whole to 

 be represented by a stony loam, resembling a mixture of the sandy and 

 clayey material, and this is restricted to a zone some twenty miles 

 wide bordering the coast of Norfolk and Suffolk; not extending 

 south of the latter county, but being probably represented to the north 

 of the Humber. Above these is a group of false-bedded sands and 

 gravels, variable in thickness and character — the Mid-glacial Sands of 

 Searles V. Wood and F. W. Harmer. They extend over a wider area, 



