IRON-ORES. 303 
Layers and globular concretions of ironstone were found by 
Mr. Gr. E. Gavey about the junction of the Lower and Middle Lias 
at Mickleton Tunnel, near Chipping Gampden ; and similar beds 
have been noticed to the north of Dumbleton Hill, and at Hev/lets 
Hill, Charlton Kings and Leckhampton, near Cheltenham. 
These layers cannot be considered to be of economic value. 
They occur at the base of the partially pervious loamy clays of the 
Middle Lias, and may be due to the waters that have percolated 
from the upper ferruginous beds of the Middle Lias. 
It is at the summit of the Middle Lias, in the Marlstone or 
Rock Bed, that we find the most valuable beds of iron-ore in 
certain localities, near Woodstock and Banbury, and between 
Market Harborough and Lincoln. 
Nowhere in Dorsetshire and Somersetshire does the Middle 
Lias yield any important layers of ironstone, though here and there 
a thin layer may be found to yield a good per-centage of iron-ore, 
and the stone as a rule is an iron-shot earthy limestone. 
Thus at Ilminster, the Marlstone was found on analysis to 
yield the following ingredients : 
Carbonate of iron - - - 36 ' 53 
Carbonate of lime (with traces of carbo- 
nates of magnesia, manganese, &c.) - 30' 14 
Sand and clay - - - - 33 33 
100 00 
The total quantity of iron present here amounts 'to 15 or 16 per cent. 
Another thin band of ironstone (1ft. Sins.) was noticed by 
Charles Moore in the Middle Lias at Upton Cheney near Bath. 
In this case analysis showed an average of 24 per cent, of metallic 
iron in the rock. 
Beneath the Marlstone near Stinchcombe., there are ferruginous 
beds. There, shafts have been sunk, but without a profitable 
result, the average yield of metallic iron being about 17 per cent* 
Where the Marlstone furnishes a valuable ironstone it is often 
interbedded with fossiliferous layers ("jacks ") crowded with 
Rhynchonella tetrahedra and with Terebratula punctata. In 
many cases the fossils are filled with calc-spar, but in other 
cases the shell has been dissolved away and only casts in ironstone 
remain. 
At Fawler, Adderbury, and (recently) at Hook Norton in 
Oxfordshire, and at King's Sutton in Northamptonshire, iron-ores 
have been obtained from the Middle Lias. 
The iron-stone at Fawler near Stonesfield was discovered in 
1859. It is usually spoken of as the Blenheim iron-ore, being 
situated not far distant from Blenheim Park, Woodstock. 
Prof. Hull remarks that " The appearance of the rock at the 
surface indicates its strongly ferruginous nature, but at some 
depth, where it has been protected from atmospheric influences, 
the ore is found to be of a deep green colour, and under the 
* Moore, Proc. Somerset Arch, and Nat. Hist. Soc., vol. xiii. pp. 125), 147, lb'2. 
