298 



H. A. Baker — The Pre-Thanetian Erosion 



showing the present contours in the sub-Eocene Chalk surface.' 

 The first map indicates the amount of correction to be applied to the 

 base of the Chalk at any point in order to bring it to horizontality at 

 present sea-level, and the superimposed map is corrected corre- 

 spondingly. For example, the points at which the O.D. contour 

 of the superimposed map intersects the —600 contour of the base of 



^ In this investigation the writer has used the map of the Pre-Tertiary Chalk 

 surface prepared by Mr. L. J. Wills [Records of London Wells, Mem. Geol. 

 Surv., 1913) and also that by Professor P. G. H. Boswell (Q.J.G.S., 

 -vol. Ixxi, pi. l). 



