382 Influence of Mines upon Land and Livestock 



Removal of Natural Soil. 



In many areas a much greater alteration of composition has been 

 produced than would result from mere contamination of the natural 

 soil. The partial, or in some cases even complete destruction of the 

 herbage, enabled the heavy rains on the hill slopes, and the river floods 

 in the valleys, to wash away a good deal of the fine soil. Consequently 

 the soil has become much more stony. For instance, on the slope above 

 Frongoch mine, where wind blown material from the heaps has proved 

 very destructive to vegetation, it was found that the soil contains 

 85 per cent, (approx.) of stones, whereas in the case of adjoining land 

 where the herbage had been but slightly affected the soil contained 

 only .58 per cent, of stones. See Photograph "0." In the case of the 

 river valleys the effect has been even greater. As a result of the destruc- 

 tion, by the poisoned water, of the vegetation which binds the soil on 

 the grassy borders of a river, the containing banks are weakened and 

 the course of the river is often diverted. The flow of the river may be 

 changed also by the accumulation of mine debris in the river bed. In 

 addition, the floods have washed away all the natural soil of adjoining 

 land. Consequently, in these situations at present we have a soil con- 

 sisting almost entirely of mine slime and sand, resting upon shingle beds 

 or river gravel. In both the Ystwyth and Rheidol valleys there are large 

 tracts of land of this type. 



Formation of New Surface Soil. 



In some situations the floods have deposited the mine refuse on the 

 surface of the original soil, thus forming an artificial soil with the natural 

 soil acting as subsoil. This is well exemplified by the following analytical 

 results obtained with samples taken near Capel Bangor in the Rheidol 

 valley. It will be noted that the mechanical composition of the subsoil 

 of affected land is very similar to that of the soil of unaffected land. 



