374 PLEASANT WA YS IN SCIENCE. 



in the course of time it will become unfit to drain the region 

 through which it flows. Its bottom must of necessity become 

 less inclined. Now although it will then be lower than at 

 present, and therefore be then even more than now the place 

 to which the water falling upon the region traversed by the 

 river will naturally tend, it will no longer carry off that water 

 with sufficient velocity. Three consequences will follow 

 from this state of things. In the first place there will be 

 great destruction in the surrounding region through floods 

 because of inadequate outflow ; in the second place, the 

 overflowing waters will in the course of time find new 

 channels, or in other words new rivers will be formed in 

 this region ; thirdly, owing to the constant presence of large 

 quantities of water in the depressed bed of the old river, the 

 banks on either side will suffer, great landslips occurring and 

 choking up its now useless channel. Several rivers are 

 undergoing these changes at the present time, and others, 

 which are manifestly unfit for the work of draining the region 

 through which they flow (a circumstance attested by the 

 occurrence of floods in every wet season), must before long 

 be modified in a similar way. 



We are thus led to the consideration of the second form 

 in which the destructive action of inland waters, or we may 

 truly say, the destructive action of rain, is manifested, 

 viz., in landslips. These, of course, are also caused not 

 unfrequently by vulcanian action, but equally of course land- 

 slips so caused do not belong to our present subject. Land- 

 slips caused directly or indirectly by rain, are often quite 

 as extensive as those occasioned by vulcanian energy, and 

 they are a great deal more common. We may cite as a 

 remarkable instance a landslip of nearly half a mile in 

 breadth, now in progress, in a district of the city of Bath 

 called Hedgmead, which forms a portion of the slope of 

 Beacon Hill. It is attributed to the action of a subterranean 

 stream on a bed of gravel, the continued washing away of 

 which causes the shifting; but the heavy rains of 1876-77 

 caused the landslip to become much more marked. 



