66 



Point, Haltou and Beeston Castles. These, indeed, are the 

 escarpments of the uplifted strata on the line of fault, -which 

 must he somewhere between 200 and 300 feet. This forms 

 the last boundary of the area. 



Within the limits of the area thus defined there is a 

 superficies of from 70 to 80 square miles ; but, notwithstand- 

 ing the physical constitution of the strata, — their confor- 

 mation and genera] arrangement being highly favourable for 

 collecting and retaining the atmospheric water which falls 

 over this extensive area, — there exist over its surface several 

 impediments which affect materially the passage of the 

 water into their mass. The first I shall notice is, what I 

 before alluded to in the change that had taken place in the 

 relation of sea and land, viz., the deposit of a bed of dilu- 

 vial clay, which is spread over, at least, nine-tenths of the 

 surface, and which, in the valleys and lower parts of the 

 district, occasionally attains a great thickness. This clay is 

 of a stiff retentive quality, and suffers water to pass through it 

 very slowly ; the length of time that water is retained in the 

 shallow pits that are dug in it is a proof of its impervious 

 nature. The second are, the improved and improving modes 

 of cultivation, which by rendering the soil more friable, and 

 thereby more favourable for absorption and evaporation, 

 together with the extensive system of drainage carried on 

 for agricultural purposes, allow of little of the water, of even 

 continuous days' rain, to pass down into the strata, but, on 

 the other hand, almost immediately carry it off and discharge 

 it from the surface. I may also notice the rapidly-extending 

 covering of the surface of the district with houses. The 

 formation of macadamized roads, paved streets, and other 

 impervious media through which no water can penetrate into 

 the strata, but is immediately carried off by sewers and 

 other artificial channels into the sea, must of course diminish, 

 in a corresponding ratio, the quantity of w r ater that would 

 otherwise sink down into their mass. 



