ON THE MANUFACTURE OF IRON. 731 
contain bands and nodules of ironstone in sufficient quantity to supply im- 
mense works, established in these localities, for smelting iron. The coal- 
field of the North of England, on the contrary, extensive and productive in 
mineral fuel as are its strata, is singularly deficient in those ores of iron 
which distinguish many other carboniferous districts, An explanation, then, 
of the prominent position occupied, as a seat of the iron-trade, by the loca- 
lity under consideration, must be looked for in another direction, and a very 
brief mental survey of the geology of the adjoining country will furnish 
the necessary information. Starting from the.coal-field itself, which, as con- 
taining the fuel required for smelting, may be considered as the keystone to 
the whole, we arrive within no great distance at strata which abundantly 
compensate for that poverty in ironstone already spoken of as inherent to our 
coal-measures themselves. 
The district known as the Newcastle and Durham coal-field contains an 
area of something like 700 square miles, and in shape may be roughly con- 
sidered as an isosceles triangle, having its apex coincident with the coast- 
line at Warkworth. As the sea principally forms its eastern barrier, our 
observations are necessarily almost exclusively confined to those formations 
bounding it on.the west and south. In the former direction, 7. ¢. towards 
the west, a narrow strip, having a width of four or five miles, of the mill- 
stone grit, rising up from under the coal-formation, separates this latter from 
an extensive tract of country, of which the mountain limestone is the pre- 
vailing rock, From the south-west corner of our coal-field, and separated 
from it by a great expansion of the millstone grit accompanied by mountain 
limestone, we pass over a thin wedge of the old red sandstone and enter 
upon the new red, to the west of which the carboniferous limestone again 
appears as a long, narrow, curve-shaped district, extending ‘from Pen- 
rith to Whitehaven, and of importance in describing our subject. On the south, 
and skirting the coal-field on the south-east, we have the magnesian lime- 
stone some half-dozen miles in width. Beyond it, forming for some distance 
the valley of the Tees, is the new red sandstone, separating, by an interval 
of twenty miles, our collieries form those hills of lias in Yorkshire, the ore of 
which will form the greater portion of the subject of this paper. 
We will now briefly allude to the position of the minerals which consti- 
tuted the sources whence our furnaces in former times were supplied, adding 
a few remarks on their practical application, and then consider those means 
which at the present day furnish our greatly extended ironworks with that 
immense quantity of raw materials which their increased capacity demands. 
We may pass over without further notice at the present moment both 
the immense beds of coal, of the purest kind, in this northern coal-field; and 
the inexhaustible supplies of lime furnished by the extensive tracts of moun- 
tain and magnesian limestone previously alluded to. We shall, therefore, at 
once proceed to name the different combinations in which ironstone is found 
in the various strata of the measures already referred to, reserving any fur- 
ther remarks when we come to speak of the composition and nature of the 
minerals generally. 
Ironstone of the Coal-measures.—Many of the numerous beds of shale as- 
sociated with the coal-formation in this neighbourhood contain, interspersed 
in their thickness, nodules of ironstone, but these have rarely been sufficiently 
abundant to lead to their being worked for smelting purposes. 
Above the seam of coal known on the Wear as the High Main, and sepa- 
rated from it by a distance of 18 inches, is a continuous band of this ore. 
It is 43 inches thick, and was formerly wrought on Waldridge Fell for the 
