296 
THE MIDDLE LIAS OF NORTHAMPTONSHIRE. 
sufficient for the ore to flux itself, and making it especially 
valuable for mixing with refractory ores. Wliat the parti¬ 
cular cause of failure at King’s Sutton was, I am not in a 
position to say, but only a little over a mile from this spot, 
at Adderbury in Oxfordshire, the stone is extensively worked. 
It seems at least improbable that within this short distance 
the stone can have so far altered in character as to render 
its working unprofitable. 
According to Mr. Thomas Beesley, F.C.S.,* the average 
percentage of iron in the King’s Sutton stone is higher than 
that in the Adderbury stone, for specimens of the former 
yielded from 18*7 to 84 per cent, of iron, whereas some of 
the best specimens of the latter only yielded from 18 to 24 
per cent. It appears, therefore, that the statement which 
occurs in Professor Phillips’ “ Geology of Oxford and the 
Valley of the Thames,” that the Adderbury stone yields one 
ton of iron to three tons of stone, and that 30,000 tons of 
iron to the acre might be reckoned upon, requires modifying. 
Mr. Beesley further states that the richer stone at King’s 
Sutton is sandy, but that the phosphatic concretions are 
sufficiently abundant to pay for picking out. 
I do not anticipate that the Marlstone of Northampton¬ 
shire will ever be much used as an ironstone. It is rather 
remarkable that here, as in Yorkshire, and, I believe, 
Leicestershire, the quantity of iron in the Bock-bed 
diminishes with a decrease in the thickness of the bed. 
Thus the average thickness for Northamptonshire is about 
six feet, but the instances in which it is less are numerous; 
whereas in the south-western parts of the county, where 
alone it has been used, the thickness is about twelve feet. 
It is unnecessary to enter largely into a consideration 
of the condition of the iron in the Middle Lias of 
Northamptonshire, considering that there is such a small 
prospect of its being used as a source of iron. Suffice it to 
say that the grey, green, or greenish blue colour of the 
unweathered portions of the Bock-bed, and parts of some 
of the other beds, is due to carbonate of iron chiefly, 
modified by the presence of phosphate or silicate of the 
protoxide of iron,! or both, the blue tint where present 
being particularly due to the former. 
* “A Sketch of the Geology of the neighbourhood of Banbury,” 
by Mr. Thomas Beesley, F.C.S. 
t The green colour is usually regarded as due to an earthy 
mineral, called glauconite, which consists essentially of the hydrous 
silicate of iron and potash, but often contains magnesia, or other 
things. 
