ri. III. Oli POISONED BY VEGETABLE GROWTH? 171 



tlie complexion of the river to see tins. And the river 

 deposits the mud in the pond, which it would otlierwise 

 have carried down to the sea. I will instance the 

 ponds at Ahxsford and at Warnford. 



This universal portage of soil by rain, the eternal 

 effect of eternal causes, Wiiich in huge spaces of time 

 results in such vast geological changes, would to some 

 be incredible were it invisible. But this I think may 

 be made visible, oculis fidelibus. It may be seen wlier- 

 ever a fence runs horizontally along the side of a hill. 

 A natural terrace is then formed, for aqueous denuda- 

 tion goes on below the fence, and in chalk countries the 

 ground becomes white : and not only does aqueous 

 denudation cease above the fence, but aqueous deposit 

 takes place, and the good soil which was on its way to 

 the valley is arrested. Even a slight dead w^attle, if 

 kept up, will produce this effect, and, though the hedge 

 is dead, the ground on which it is placed will grow ; 

 and a gateway wrongly placed will often let consider- 

 able quantities of this collection of the best soil escape, 

 which might otherwise have accumulated for what man 

 might call for ever. So an injudicious, downhill wag- 

 gon-way, across fields, Avill sometimes act as a channel, 

 and, catching soil laterally, convey it away from its 

 proper owner. If your neighbour's land lies below you 

 on a steep hill-side, unless you wish to make him a 

 present of your soil, pound it back on to your own 

 land by a fence, and, when it accumulates against your 

 own fence, cart it up the hill again. 



