Chap. 12. GEOLOGY, BOTANY, &c. 257 



QUATEENABY DEPOSITS. 



Perhaps the most remarkable of our local deposits is that found, 

 almost invariably, covering the older solid rocks. The surface soil 

 rests upon drift sands or gravel, or upon a duU, red clay, which is 

 sometimes of great depth, and contains numerous rounded stones, often 

 polished and striated in a characteristic manner. This tells us of a 

 time when by some remarkable distribution of land and sea, or a 

 stiU more extraordinary cosmical cliange, our country, together with 

 the whole of Northern Europe, endured a climate as arctic as that of 

 Greenland to-day. Probably the whole of England north of the 

 Thames was covered by a huge ice-sheet. The British Alps were 

 occupied by extensive snow-fields, from which radiated numerous 

 glaciers. These latter traversed the valleys and lowlands, scoring 

 and abrading the solid rocks and forming a fine impalpable mud, 

 which was deposited wherever the conditions were favourable. 



This rigorous climate continued sufficiently long to allow a deposit 

 in some areas of 200 feet of this Lower Boulder Clay. Then followed 

 a more genial period. The land was partially submerged, the ice 

 melted, and the drift-deposits were spread on the surface of the clay. 

 These consist of sands and gravels, with a maximum depth of 50 feet, 

 containing marine shells, the majority of which are identical with the 

 shells of species of moUusca still existing on the Lancashire coast. 



The drift-deposits are found from the sea-level in some localities, up 

 to 1,400 feet altitude in others. Therefore the land must have been 

 submerged until only the summits of our highest hiUs were above water. 

 Subsequently the land partly emerged and a second glacial period 

 began, though less severe than the former. Again our hills were 

 covered with snow and our valleys filled with glaciers. Some of these 

 glaciers reached the sea, and discharged their streams of muddy water 

 over the submerged areas and the Upper Boulder Clay was formed. 

 Icebergs and ice-rafts floated about, travelling for great distances 

 laden with cargoes of rocky debris torn from the higher lands. When 

 the bergs and rafts melted, this cargo was precipitated upon the 

 muddy bottom many miles from its parent rock. We thus find erratic 



