304 
THE GEOLOGIST. 
qiiaiilily — 0-55 por cent. From an analysis of nine samples made in the 
Museum of Praetical Geology, the average quantity of metallic irou was found 
to be about 39 per cent. 
The outcrop of the rock may be traced along ihe valley of the Cherwell, at 
Fawler, on the property of the Duke of Marlborougli, where it is now being 
quarried for transport to Soutli Staffordshire ; and it is expected that u[)on the 
completion of the Worcester and Hereford Railway large quantities will be 
sent into the ii-on-districts of South Wales. 
Thickness of the Formations below tiie Great Oolite, at Stones- 
field. — For the purpose of ascertaining the depth of the iron-bed below the 
Stonesfield Slate, the Duke of Marlborough directed one of the slate pits to 
be continued downwards till the ore was reached. This has not been accom- 
plished, for on reaching, at a depth of one htuidred and twenty feet, the Upper 
Lias Clay, the water flowed m so plentifully that the sinking had to be 
abandoned. With the assistance of a very interesting section at the west side 
of the railway opposite Fawler, we can easily complete the scries of strata 
down to the Lower Lias. 
If we compare the development of these formations in this part of Oxford- 
shire with that which tliey attain in Gloucestershire, we shall lind that there is 
a great diminution in volume when traced from their north-western outcrop 
towards the south-east of England. On former occasions I have endeavoured 
to show that aU the Lower Secoudary Formations undergo a similar degree of 
attenuation from the north-west towards the south-east, in which direction they 
ultimately disappear. This will be illustrated by the following table of com- 
parative thicknesses in Oxon and Gloucestershire : — 
Section in Slate Fit at Slone.ijield. 
Thickness. 
10 feet 
80 feet 
30 feet 
6 feet 
10 to 15 feet 
15 to 30 feet 
Comparatice Thickness of Formations. 
Gloucestershire. 
Oxfordshire. 
Thickness in feet. 
Thickness in feet. 
30 
Absent. 
Marlstoue 
Inferior oolite. 
201 
Sauds 20—50 
Shale 380 
250 
6 
25 
Total 
911 
CI 
