NORTH STAFFORDSHIRE COAL-FIELD.
This is a comparatively small midland coal-field, containing from 40,000 to 50,000 acres of coal area, and is distinguished from other basins in the district as "the Potteries." We notice it particularly on account of its supply of iron ores and fire clays in connection with the coal-seams.
The basin is 2925 feet deep on the west side, and 5500 feet on the east side; it is covered by the new red sandstone in its central portions, which, however, has not been developed, and the area not included in the above estimate. The aggregate or maximum thickness of the coal is 168 feet, and its average thickness, if distributed over the entire area, 32 feet. The maximum thickness of iron-stone is feet, and aggregate 5 feet.
The coal is distributed in 45 seams from 2 to 10 feet thick, and 8 seams from 6 inches to 18 inches thick.
There are several seams bearing iron-stone as the roof, besides those illustrated above, though generally smaller. It will be noticed, by those who are familiar with such matters, that this com bination of coal and iron is eminently available for mining operations; and the consequent result is here practically manifest in the numerous successful furnaces which are in blast. The amount of iron-stone available in this district alone is enormous,—enough to supply the vast demand of the British manufac turers for 50 years.
The ore is peculiarly rich, producing double the yield of the Welsh ores.
The average yield of metal in the furnace is over 50 per cent., while the best calcined carbonaceous will yield from 60 to 70; it is much used by puddlers to line their furnaces, and is there known as "puddle-mine." There is also a small seam of calcareous ore in the Carboniferous lime stone, which is used in the furnace as a flux.
In 1853-4 there were 20 furnaces in blast and 5 in course of erection, &c. The production was 100,000 tons of pig-iron per annum. The coals on the east side of the basin are used raw in the furnaces, being free-burn ing and not liable to cake, while the coals of the west side are coked before used. The amount of coal consumed to the ton of pig-iron produced is 3 tons 14 cwt.
The primitive mode of mining was pursued to a late period, compara tively, in this district : the " post and stall," or " punch and thirl," was a favorite system with the old miners; but the cost of mining and the loss of coal in pillars forced improvements on them. By the old mode of mining, with coaves, water-buckets, &c., the cost of delivering coal on the bank was about 7s. 6d. per ton. By the recently adopted improvements and the general introduction of the " long wall" system of mining, the cost has been reduced to 3s. 4d. on the bank.
North Staffordshire is the great metropolis of the earthenware manu facturers, owing to the presence of immense beds of fire and potter's clay. Some of these beds are 45 feet thick, and of a fine-grained or impalpable texture. 50,000 tons of fire-clay are used annually for the " saggers" in which the ware is baked, and 800,000 tons of coal consumed in the opera tions at the potteries. The value of the goods produced is nearly $20,000,000 annually.
About 2,000,000 tons of coal is mined per annum in this district, mostly for home consumption, and 500,000 tons of iron-stone, of which about one-fourth is shipped to manufacturers outside of the district.