TRANSVERSE VALLEYS.

360

[Ch. xix.

projecting masses of chalk to be the headlands of a coast whichseparated the different bays from each other.

Occasionally in the North Downs sand-pipes are intersected in theslope of the escarpment, and have been regarded by some geologistsas more modern than the slope; in which case they might afford anargument against the theory of these slopes having originated as sea-cliffs or river-cliffs. But, when we observe the great depth of manysand-pipes, those near Sevenoaks, for example, we perceive that the

lower termination of such pipesmust sometimes appear at thesurface far from the summit ofan escarpment, whenever por-tions of the chalk are cut away.

In regard to the transversevalleys before mentioned, as in-tersecting the chalk hills, someidea of them may be derivedfrom the subjoined sketch (fig.360.) of the gorge of the RiverAdur, taken from the summit ofthe chalk-downs, at a point inthe bridle-way leading from thetowns of Bramber and Steyning to Shoreham . If the reader willrefer again to the view givenin a former woodcut (fig. 353.p. 358.), he will there see theexact point where the gorge ofwhich I am now speaking in-terrupts the chalk escarpment.A projecting hill, at the point a,hides the town of Steyning , nearwhich the valley commenceswhere the Adur passes directlyto the sea at Old Shoreham. Theriver flows through a nearlylevel plain, as do most of theothers which intersect the hillsof Surrey, Kent, and Sussex;and it is evident that these open-ings could not have been pro-duced by rivers, except underconditions of physical geographyentirely different from those nowprevailing. Indeed, many of theexisting rivers, like the Ousenear Lewes, have filled up armsof the sea, instead of deepeningthe hollows which they traverse.