204 THE RIVER VALLEYS OF 



Lewis and Brighton, we traced numerous breaks, not 

 only forming features on the escarpment, but also 

 across the Downs, to which are due the irregularities 

 in the boundary of the chalk. Furthermore, Messrs 

 Foster and Topley's suggestion would corroborate 

 the idea that these ravines and hollows are connected 

 with breaks, although these breaks are not marked 

 on the map ; for they state, " These valleys are pro- 

 bably due to the dissolving away of the chalk along 

 lines of underground drainage." Mr Whitaker also 

 has suggested the same, in relation to the ravines in 

 the chalk of other places. There are also the ponds 

 on the Downs, which must be connected with subter- 

 ranean streams (similar to the turloughs in the lime- 

 stone districts of Ireland), and become filled during 

 wet weather (the underground passages being too 

 small to carry off all the water), but are dry at other 

 times. 



The authors of this paper on the "Weald seem to 

 believe that in landlocked bays sea action is neces- 

 sarily feeble. This, however, does not appear to be 

 borne out by observed facts, as after the high tides 

 of 1870 we found on the west coast of Ireland, that 

 on the open seaboard little work was done even on 

 such frail materials as those forming the sand-dunes, 

 while in the bays and other landlocked places, cliffs, 

 piers, embankment roads, and everything the tides 

 could reach, were more or less injured or carried 



