42 Reports and Proceedings — Geological Society of London. 



to the beds wanting at Chatham of some 400 feet of Purbeclc and 

 Portlandian, of over 1100 feet of Kimmeridgian, and of nearly 500 ft. 

 of Corallian, etc. In a section of 32 miles, therefore (the distance 

 between the Subwealden and the Chatham borings), we have a 

 thinning of beds to the extent of over 3400 feet, or at the average 

 rate of about 100 feet in a mile. 



This northerly thinning agrees with the facts that have been 

 brought before us from other deep borings in and near London ; but 

 the Chatham boring is the first in the London Basin in which a 

 Middle Jurassic formation has been found. The teaching of the 

 deep borings, as a whole, is that north of the Thames older rocks 

 rise up beneath the Cretaceous beds, whilst on the south newer rocks 

 come in between the two. 



The question of the finding of the Coal-measures beneath parts of 

 the London Basin seems to admit of a hopeful answer, whilst the 

 lesson of the deep borings as regards water-supply is that there is 

 small chance of getting water from the Lower Greensand at great 

 depths underground. 



It would be well if underground exploration could be conducted 

 on a systematic plan, with proper regard to both topographical and 

 geological considerations, and not left any longer to the chance work 

 of people in search of water. 



2. " Note on some recent openings in the Liassic and Oolitic 

 Bocks of Fawler in Oxfordshire, and on the arrangement of those 

 rocks near Charlbury." By F. A. Bather, Esq. (Communicated by 

 Prof. J. Prestwich, M.A., F.R.S., F.G.S.) 



The river Evenlode rises in the Lower Lias of the Vale of Moreton, 

 traverses the range of Oolites, and joins the Isis opposite Wytham 

 Mill. Lias is exposed to about three-quarters of a mile below 

 Fawler, where Great Oolite is brought down by a fault ; and in the 

 Geological Survey map Lower Lias is brought down the valley to 

 within half a mile of Charlbury Railway Station. 



In this paper the author gives reasons for believing that the dis- 

 tribution of the different beds constituting the Lias in the Evenlode 

 Valley do not agree with the Geological Survey map, nor with Prof. 

 Hull's description, recent sections and borings made for clay, used in 

 brick- and pottery-making, having exposed Lower-Lias clay in a 

 brick-yard at Fawler, marlstone and Upper-Lias clay in a neigh- 

 bouring coombe, and in a long section 100 yards north of the 

 brick-yard Inferior Oolite comes in upon the Upper-Lias clay. On 

 examining the banks of the Evenlode north of Charlbury, it was 

 found that clays referred to in the Survey map to Lower Lias are 

 really Upper Liassic, being above the Marlstone, sections of which 

 are exposed near Culsham Bridge. 



It was shown how these corrections in the mapping of the ground 

 are explained by the section along the Hue of the Evenlode and by 

 the dips of the beds. 



