472 On the Agricultural Geology of England and Wales. 



of marine glacial action during the period of submergence, to 

 which we attribute the boulder clay. 



Even in districts like Norfolk, which have been wholly sub- 

 merged, foreign detritus is most abundant in the lower erratics, 

 near the mouths of valleys, or in valleys like the Waveney, open 

 at both ends. The fragmentary matter of the upper part of 

 closed valleys is chiefly that of the bounding rocks. 



In the district between the Snowdonian chain and the Menai 

 Straits there are extensive accumulations of gravel, loam, and 

 boulders, destitute of marine remains, and borne outwards from 

 the chain ; granitic fragments and shells, which indicate transport 

 inwards, being only found at one or two spots, and there heneatk 

 this local gravel. Near the mouth also of the great valley v/hich 

 descends from Snowdon to the head of Cardigan Bay, marine 

 deposits with fragments of shells, and blocks transported from a 

 distance, are replaced, between Criccieth and Harlech, by accu- 

 mulations of local fragments derived from the interior of the 

 chain. 



On the whole, it is impossible to have traversed the interior of 

 Wales without seeing that, beyond the influence of existing streams, 

 there are great accumulations of detritus, more or less local, which 

 we must attribute chiefly to the operations of this period, and 

 which, though the materials have been derived from the neigh- 

 bouring rocks, exhibit sufficient indication of transport by water 

 to negative the doctrine of the dependence of the composition of 

 soils on that of the rock beneath, except on steep acclivities and 

 at great elevations. Without more extended observations, how- 

 ever, than have yet been made, it is impossible to form even an 

 approximate conjecture respecting the marine or terrestrial origin 

 of such accumulations, or to point out the districts in which the 

 influence of the superficial deposits, or that of the subjacent rock^ 

 prevails in the soil. We have seen enough, however, to be certain 

 that there, as elsewhere, the distribution of soils is dependent on 

 contours ; and that but for such accumulations these mountains 

 would have been more barren than they are. One fact, which 

 we have observed in Wales, is, that the thinner and poorer soils 

 on the sides of hills are generally preferred, because naturally 

 dry, to the deeper and better soils in lower situations, which 

 require to be drained, and are therefore abandoned to their native 

 rushes. A Welch farmer, who was asked Why do you not 

 drain, or ask your landlord to drain this land ?" replied, " If 

 God had intended it to be dry, it would have been made dry by 

 nature.'' Another, speaking of the new agent, who had drained 

 a large extent of fine, but wet alluvial land, said, Upon my 



word, Mr. will spoil all our farms ; we shall have no rushes 



to ' thatch with.' " 



