lxxvi PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May IC;00, 



division so far east. It also occurs at Loughton, in Essex, where 

 it is 30 feet thick, whence one may infer that from London a 

 northerly extension or bay of Upper Greensand juts out. 



North of the Thames eastward of the above-mentioned localities 

 there is but little information, and what there is comes from a long 

 way off. An old MS. description (in the Society's library) of a boring 

 made at Coombs, near Stowmarket, Suffolk, in 1855, says that Gault 

 and Greensand alternately, to the thickness of 21 feet, were found at 

 the bottom, while a printed account (of 1860) definitely mentions 

 10 feet of Upper Greensand between Chalk and Gault ; but this is 

 not enough to warrant one in making sure of the first, as it is not 

 uncommon for the glauconitic base of the Chalk Marl to be called 

 Upper Greensand, and no lithological description is given. 



At Harwich, again, occurs Gault mixed with Greensand, for 

 22 feet, which is no more satisfactory, and at Norwich we are still 

 left in doubt. On the other hand, there are three borings in 

 which no Upper Greensand was found, at Weeley (south-west 

 of Harwich), at Stutton (west of Harwich), and at Culford (north 

 of Bury St. Edmunds), and the clear evidence of these outweighs 

 the doubtful evidence of the borings at Coombs and Harwich. 



Nor is there in the northern part of Norfolk any Upper Greensand, 

 so far as is known ; thus, on the whole, it may be said that under 

 East Anglia, with the exception of the western margin of Essex, 

 there is probably none of it, or but a little here and there. That 

 so thin a division should extend as far as it does is perhaps more to 

 be wondered at, than that it should be absent over a large extent of 

 country. 



The Gault. 



The Gault is the only formation below the Chalk that has any 

 claim to the virtue of constancy in underground matters. In every 

 one of the deep borings has it been found, and except in the far 

 north-western part of the Norfolk Cretaceous tract, there is every 

 reason to expect that Gault will be found in any new boring that 

 goes deep enough. With constancy of occurrence, however, there 

 is considerable vacillation in the matter of thickness, though not 

 locally, only as regards places far apart. With the question of 

 thickness alone, therefore, are we concerned. 



The greatest thickness of Gault known (over 340 feet), in the 

 district under consideration, is in the deep boring at Caterham in 

 East Surrey, near the outcrop, which outcrop seems to have been. 



