3i6 SCIENCE PROGRESS 



The width of the wedge may vary within very wide limits on either hypothesis, 

 but of the two, planation gives the greater latitude. With such a high dip as that 

 of the Hog's Back, it might reduce the width to a few hundred yards, and only a i 

 part of that would be covered with flints (Upper Chalk). If, on the other hand, 

 the submerged bank be credited with such gradients as are ordinarily found round 

 our coasts where the strata are soft, the wedge would be inconveniently wide 

 (20 miles or more), and flints, in any case, would extend over its whole surface. 

 It is only by assuming an exceptional slope such as that of the Continental Edge 

 off the west of Ireland (1 in 25) that we can reduce the width to the three or 



Fig. 2. — Section showing the original limits of the Chalk according to Major Marriott. 



The thin line indicates the original surface, and the black one the present surface, u.c, Upper Chalk ; 

 L.c, Middle and Lower Chalk; s., Upper Greensand and Gault (Selbornian) ; l.g., Lower Greensand; 

 w., Weald Clay. 



Fig. 3. — Section showing the subjects of marine planation on inclined strata. 



p., Plain of marine denudation. 



four miles to which the flints commonly extend, and it is doubtful whether even 

 this is small enough to accord with the distribution in all cases. 



(2) "The non-existence of any residual flint deposits on the plateaus and 

 summits such as would undoubtedly result from the removal of the soft parts of 

 the Upper Chalk." This is obviously only another aspect of the previous question. 

 Against planation it has no weight at all, for the sea which removed the Chalk, etc., 

 may well have removed the flints also. Nor is it really in the least fatal to the 

 Chalk Dome theory ; for ex hypothesi thousands of feet of strata must have been 

 denuded from the " plateaus and summits " ; the materials being dragged down 

 to lower and lower levels, but always with a tendency to work outwards (as the 



