Fig. 1. — Vertical section of the 

 Eastern Boring. 



[The arrows indicate non-sequences.] 

 Soil-4' 



Ornatum Zone 

 9B'3' 



Forest Marble 



38'9" 



Great Oolite 



59'6" 



Chipping Nprt on L _ 



Algoviadum Zone 



Capricornus Zone? 



Striatum Zone 



and they have been noted 

 in the shafts at Dover and in 

 the cores of the Brabourne 

 borehole. 1 



A critical comparison of 

 the Forest Marble passed 

 through at Calvert, with the 

 sections exposed in the new 

 railway-cuttings near Bices- 

 ter, shows some interesting 

 points both of resemblance 

 and of difference. The forma- 

 tion in the Calvert borehole 

 is considerably thicker than 

 any of the sections where the 

 whole of the beds have been 

 cut through in the Bicester 

 cuttings, xit Blackthorn Hill 

 the Forest Marble is only 

 21 feet 9 inches thick 2 ; in 

 the cuttings between Buck- 

 nell and Ardley Wood the 

 details show the formation 

 to be slightly thinner. 3 At 

 Calvert the beds reach the 

 total of 38 feet 9 inches, and 

 are thus very nearly twice 

 as thick. 



In the borehole, however, 

 the thickening appears to 

 have taken place in the clays. 

 In the section at Blackthorn 

 Hill 4 there is a bright bluish- 

 green clay to which Mr. Bar- 

 row drew special attention, 

 and he remarked that its 

 presence could scarcely be 

 missed even in a hand-boring. 

 A clay indistinguishable from 

 the Blackthorn-Hill bed was 

 passed through at Calvert. 

 It thus appears to mark a 



i G. W. Lamplugh & F. L. 

 Kitchin, ' On the Mesozoic Rocks- 

 in some of the Coal-Expl orations 

 in Kent ' Mem. Geol. Siu-y. 1911, 

 pp. 28 & 48. 



2 G. Barrow, ' The New Great 

 Western Railway from Ashendon 

 to Aynho, near Banbury ' Sum- 

 mary of Progress for 1907, Mem. 

 GeoL Sury. 1908, p. 145. 



3 Ibid. p. 149. 4 Ibid. p. 145. 



