n 4 THE BOOK OF NATURE STUDY 



material, some ground fine by its own action, some coarse and 

 angular because transported on the surface of the ice. This was 

 eventually shot down either in single valley moraines (Fig. 83), or 

 in great sheets of detritus which have filled up valleys or spread 

 over plains to a thickness of hundreds of feet. This drift covers 

 hundreds of square miles of lowland in Eastern England and 

 elsewhere, masking the rocks below and giving rise to new 

 types of landscape and soil. Among other results the ice has 

 transported boulders often of considerable size and in great quan- 

 tities for hundreds of miles from their source, and dropped them 

 when the ice melted. These travelled blocks, or erratics as they 

 are called, have been carried from the southern uplands of Scot- 

 land, from Ailsa Craig, from the Lake District, and from Wales 

 to many parts of Midland and Western England ; while much of 

 the Eastern Counties is covered with drift broken from the Chalk 

 or from other rocks derived from England itself mingled with 

 others brought from so far as Scotland and Scandinavia. 



All denuded matter ultimately makes its way to the sea and 

 is there deposited. Where deposition is most rapid, on the 

 margins of the sea, the deposit is gradually brought up to the 

 level of the sea surface, and, being thus reclaimed, it is added to 

 the area of the land mass. This occurs in several parts of the 

 coast of Britain for instance, about Yarmouth and Lowestoft, 

 at Romney Marsh, on the Chesil Beach near Portland, and on the 

 Lancashire coast about Southport. The growth of land generally 

 begins with the deposit of shingle ; sand is then drifted in by the 

 wind, and eventually great heaps of sand known as dunes are 

 formed of drift sand, which increase in height and importance and 

 often gradually travel inland. 



This is one way by which the waste of the land is made good, 

 but it is evident that if rocks in the earth's crust have been 

 made out of sediments in this way something more is necessary. 

 The sediment must have been hardened, lifted higher, and in 

 many cases tilted and broken ; and we have not yet observed any 

 process by which this might be effected. To this attention will 

 be directed ; yet it may be well to ascertain, in the first instance, 

 how close a comparison can be instituted between rocks and 

 sediments to see if it is worth while to pursue the inquiry further. 



