part 1] ANNIVERSARY ADDRESS OF THE PRESIDENT. lxix 



invaded the land from the sea-hasins ; and it becomes questionable 

 how much of this drift was transported from the present sea-floors 

 as a fresh contribution to the land-mass, and how much was simply 

 picked up and redeposited within the present bounds of tbe land. 

 Some proportion certainly falls under the latter category, as 

 witness the boulders of Lake-District and Cheviot rocks in our 

 East-Coast drifts, and the boulders from Scotland and the Lake 

 District so plentiful in the lowlands of Lancashire, Cheshire, and 

 the North-Western Midlands ; but it is my impression that this 

 proportion is not great, and that a large part of the matrix of the 

 lowland boulder-clays and of the ingredients of the Glacial sands 

 and gravels have been scooped up and carried forward from the 

 sea-basins. In this matter we can glean little information from 

 existing glaciers and ice-sheets, as they are mostly underlain by 

 hard rocks, barring some quite minor tracts in Spitsbergen and the 

 smaller Arctic islands, and in East Greenland and South Victoria 

 Land. What happens when a wide massive ice-sheet rests upon 

 an extensive low-lying area of soft formations can only be deduced 

 from geological evidence. We can generally recognize what 

 formations have gone to the making of our boulder-cla}^ pastes : 

 in the North -Western Midlands, Cheshire and the coastal lowland 1 

 on the north — mainly Keuper Marl, with additions from Carboni- 

 ferous strata ; in North and East Yorkshire and Lincolnshire — 

 mainly Keuper Marl and Lias, with additions from other Jurassic 

 clays and a little Carboniferous ; in the Eastern Counties and the 

 eastern part of the Midlands — the Kimmeridge and Oxford Clays, 

 Chalk and Lias, with local additions from the Keuper. It is true 

 that all these formations occur on land, and often in proximity to 

 the corresponding sheets of drift ; but we must not forget that 

 they certainly extend also under the present seas in the path 

 which we know to have been taken by the invading ice, and that 

 their submarine outcrops must in many cases be more extensive 

 than their outcrops on land. Moreover, the thicker drift-masses 

 of the lowlands very frequently have stratified material, or bands 

 of local rubble and subaerial land-wash, at their base, and it is 

 certain that there can have been no glacial planing-down of the 

 solid floor in such places. Often, too, the derived fossils and other 

 debris in the boulder-clays are different from those of the known 

 outcrops : for instance, the Chalk belemnites, and black and red 

 Hints, and some of the Liassic ammonites in the Holderness 



