Ch. XIX.] 



TKANSVEESE VALLEYS. 



275 



sand, and sometimes, also, tlie gault, crop out. This steep declivity, 

 is the great escarpment of the chalk before mentioned, which overhangs 

 a valley excavated chiefly out of the argillaceous or marly bed, termed 

 Gault (No. 3). The escarpment is continuous along the southern ter- 

 mination of the North DoAvns, and may be traced from the sea, at 

 Folkestone, westward to Guildford and the neighborhood of Petersfield, 

 and from thence to the termination of the South Downs at Beachy 

 Head. In this precipice or steep slope the strata are cut off abruptly, 

 and it is evident that they must originally have extended farther. In 

 the wood-cut (fig. 323, p. 274), part of the escarpment of the South 

 Downs is faithfully represented, Avhere the denudation at the base of 

 the declivity has been somewhat more extensive than usual, in conse- 

 quence of the upper and lower greensand being formed of very inco- 

 herent materials, the former, indeed, being extremely thin and almost, 

 wanting. 



The geologist cannot fail to recognize in this view the exact likeness 

 of a sea-cliff; and if he turns and looks in an opposite direction, or 

 eastward, towards Beachy Head (see fig. 324), he will see the same line 



Fig;. 324. 



Chalk escarpment, as seen from the hill above Steynincr, Sussex. The castle and village 

 of Bramber in the foreground. 



of heights prolonged. Even those who are not accustomed to specu- 

 late on the former changes which the surface has undergone may fancy 

 the broad and level plain to resemble the flat sands which were laid dry 

 by the receding tide, and the different projecting masses of chalk to be 

 the headlands of a coast which separated the different bays from each 

 other. 



Occasionally in the North Downs sand-pipes are intersected in the 

 slope of the escarpment, and have been regarded by some geologists 

 as more modern than the slope ; in which case they might afford an 

 argument against the theory of these slopes having originated as sea- 

 clifi"s or river-cliffs. But when we observe the great depth of many 

 sand pipes, those near Sevenoaks, for example, we perceive that the 

 lower termination of such pipes must sometimes appear at the sur- 

 face far from the summit of an escarpment, whenever portions of the 

 chalk are cut away. 



In regard to the transverse valleys before mentioned, as intersecting 

 the chalk hills, some idea of them may be derived from the subjoined 



