238 Corres2)0)idence — Professor Prestwich. 



clay and rock strata, to the depth of 632 feet. Unfortunately the 

 record was drawn up by coal-miners, who have employed the terms 

 in common use in the coal-fields, and no specimens have been pre- 

 served which would have enabled us to correct the deficiencies of 

 description ; nevertheless there is sufficient evidence, on independent 

 grounds, to show that the strata, so far from belonging all to tha 

 Oxford clay, include probably the whole of the Oolitic series, and 

 part of the Lias. 



"My reasons for believing the assignment wrong are these : in the 

 Oxford clay, whether seen in sections at St. Clement's, Oxford, Sum- 

 mertown, or elsewhere, no beds of rock are met with, — nothing but 

 a few seams of septaria, nor have any been found in the outcrop or 

 pits of the lower division of this formation at Kirtlington or North 

 Leigh, or in any well-sections. The 10 ft. of Kelloway rock which 

 lies at the base of the Oxford clay in Wiltshire, has not been recog- 

 nized in Oxfordshire. The alternation of thick beds of rock, some of 

 them 30 ft. thick, and of a light colour, such as described in the 

 Wytham boring, is entirely unknown in the Oxford clay of any part 

 of England. I should therefore exclude these rock strata, and restrict 

 the Oxford clay at Wytham to the strata numbered 1 to 24 inclusive, 

 the total thickness of which is 273 ft. No. 25, ' a strong blue rock,' 

 lOJ ft. thick, I should refer to the Cornbrash ; No. 26 to 32, alter- 

 nating clays and rock 33 ft. thick, to the Forest Marble ; No. 33 to 

 50, consisting of grey and light coloured rocks, two of them 30 ft. 

 thick, with seams of clay, altogether 131-| ft. thick, to the Great 

 Oolite ; No. 51 and 55, together 14J ft., to the rubblylDferior Oolite 

 of Fowler ; while the thin seam of ironstone and the clays with iron- 

 stone, No. 53 to 59, which were penetrated to the depth of 170 ft., 

 may represent the Marlstone and Lower Lias ; the Upper Lias, which 

 at Fowler is reduced to a thickness of 5 ft., has here apparently 

 thinned out, 



" If we compare the section grouped in this manner with the dimen- 

 sions and characters of the several Ooliticformations immediately north- 

 of Oxford, as described by Prof. Phillips,' Prof. Hull,^ and Mr. Green,*- 

 they will be found to agree very closely. 



Average Thickness of Strata at Charlbury, 

 Woodstock, and Enslow Bridge, 

 ft. 



Thickness of the Strata at the 



Wytham boring. 



Beds. ft, in. 



Cornbrash 9"] 



No. 25 



... 10 6^ 



Forest Marble 25 | 



„ 26—32 ... 



... 33 



Great OoHte— Upper 60^179 



„ „ Lower 70 | 



Inferior Oolite 15 j 



„ 33—50 1 ... 

 ,, 51, 55 



... 131 6^19^^ 

 ... 14 6, 



Upper Lias 8 



Marlstone and Lower Lias 400 



„ 56, 59 



wanting ? 

 ... 170 6* 



"■ A few years later, another boring was made at St. Clement's in 

 search of water. No particulars are preserved. It was 420 ft. deep,, 

 and is merely stated to have been through 265 ft. of clay, and 135 ft. 



1 Geology of Oxford, pp. 139, 297, and 495. 



2 Mem. Geol. Survey, Geol. of Sheet No. 45 S.W., pp. 14, 26, and 30. 

 ^ Ibid., Geol. of Sheet No. 45, p. 9 et seq. 



^ Described as a uniform bed of clunch (clay) with ironstone. 



