304 



THE GEOLOGIST. 



quantity — 0-55 per cent. From an analysis of nine samples made in tlie 

 Museum of Practical Geology, the average quantity of metallic iron was found 

 to be about 32 per cent. 



T!ie outcrop of the rock may be traced along the valley of the Cherwell, at 

 Pawler, on the property of the Duke of Marlboroug^h, where it is now being 

 quarried for transport to South Staffordshire ; and it is expected that upon the 

 completion of the Worcester and Hereford Railway large quantities will be 

 sent into the iron-districts of South Wales. 



Thickness op the Tormations below the Great Oolite, at Stoxes- 

 FiELD. — Eor 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 hundred and twenty feet, the Upper 

 Lias Clay, the water flowed in 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 series of strata 

 down to the Lower Lias. 



Sectiofi in Slate Fit at Stonesfield, 



Thickness. 



fv I- ("Upper Zone. — White limestone resting on calcareous 10 feet 

 r>J^^ \ shales and marl with Ostrea Sowerhyi. 



^' (.Lower Zone, — Sandy flags, slates, and shelly oolite, 

 with a band of "Stonesfield Slate at 

 10 feet from the top. Trlgonia im- 



pressa, &g 80 feet 



Inferior f^PP®^ Hagstone or^ Coarse-grained rubbly oolite. 

 Oolite^ ■< zone of Aimnonites >WLtliCli/peus Plotli, Lima {/ilj- 



(,Parkinsonii (Wright) 3 l^osa, Trigonia cost at a, &c... 30 feet 



Upper Lias Clay, at Eawler 6 feet 



CI. — Iron-ore or rock-bed 10 to 15 feet 



Marlstone. < 2. — Sands with concretionary nodules of iron- 



(. ore 15 to 30 feet 



Lower Lias. — Thickness unknown ; but, judging from analogy 

 with the above formations, not very great. 



If we compare the development of these formations in this part of Oxford- 

 shire with that which they attain in Gloucestershire, we shall find 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 all the Lower Secondary Pormations undergo a similar degree of 

 aiiemuition from the north-west towards the south-east, in wlii-ch direction they 

 iilliinat-ely disa]ipcnr. This will be illustrated by the following table of com- 

 ])aralivc thicknesses in Oxon and Gloucestershire : — 



ComiKiratice Tluchiess of Forhiations. 



Gloucestershire. O.rfordsJiire. 

 Thickness in feet. Thickness in feet. 



Inferior oolite 261 30 



Sands 20—50 Absent. 



Shale 380 6 



Upper Lia 



Marlstone 250 25 



Total Oil Gl 



