"V Ol. 69.] ANNIVERSARY ADDRESS OF THE PRESIDENT. lxxi 



Upon the map thus revised (PI. A, facing p. lxxviii) all noteworthy 

 borings are shewn, so far as regards Central and Southern England. 

 Upwards of forty of them, made in search either of coal or water, 

 have been carried down to the Palaeozoic platform, and against each 

 is placed the depth in feet below sea-level at which the platform 

 was met. Against the others, which failed to reach the platform, 

 the depth attained is indicated, but is distinguished by a difference 

 in type and by being placed in parentheses with the symbol 4- . 



Though the borings are scattered with some abundance over parts 

 of the area illustrated, the platform remains unknown in two 

 regions. You will notice that it has not been reached anywhere 

 south of a line drawn through Brabourne, Slough, and Burford, 

 though some of the borings have attained a depth of nearly 2000 feet. 

 Further, it may be pointed out that no attempt has been made to 

 reach it in a broad tract extending from the estuary of the Thames 

 north-westwards between "Ware and Weeley. 



Contour-lines drawn at intervals of 500 feet upon the surface 

 of the platform have been inserted, wherever there is sufficient 

 evidence of their position. Thus a contour-line at 1000 feet below 

 sea-level (indicated on PI. A as —1000) can be drawn with fair 

 precision through Kent and to the south and east of London, 

 though its position in the intervening area is not known. This 

 same contour-line also separates Weele}% Harwich, and Lowestoft 

 on the one hand, from Stutton and Culford on the other. A 

 second contour-line drawn at 500 feet below sea-level can be 

 located on the sides of a valley in the platform northwards from 

 liugby, and can be followed thence along a meandering course 

 with a general south-easterly trend between Calvert and Wytham, 

 where it turns north-eastwards past Ware, The evidence does 

 not suffice for the insertion of auy lines between "Ware and 

 Culford ; but the fact that at Saffron Walden between these two 

 places Oolitic rocks exist, although they are absent on either 

 side, proves that the area has been one of depression in Oolitic 

 times, and is not unlikely to be one of low elevation now. Lastly, 

 a contour-line could be drawn with considerable precision at 

 sea-level ; but it suffices for my purpose to show the areas in 

 which the Palaeozoic rocks emerge from beneath the Secondary rocks 

 into the open air. On these areas contour-lines at 500 and 

 1000 feet above sea-level could easily be added, though they would 

 indicate, not the original features of the platform, but those which 

 it has acquired through denudation since it was exposed to the 

 air, which is not part of my present subject. 



