Hence the numerous heaps of scoriae found in the neighbourhood of Leeds,--at Middleton, Whitkirk, and Horsforth--all within the borough.

At Horsforth, they are found in conglomerated masses from 30 to 40 yards long, and of considerable width and depth.
The remains of these cinder-beds in various positions, some of them near the summit of the hill, tend to show, that as the trees were consumed, a new wind furnace was erected in another situation, in order to lessen the labour of carrying the fuel.

There are also deposits of a similar kind at Kirkby Overblow, a village a few miles to the north-east of Leeds; and Thoresby states that the place was so called because it was the village of the "Ore blowers,"-- hence the corruption of "Overblow." A discovery has recently been made among the papers of the Wentworth family, of a contract for supplying wood and ore for iron "blomes" at Kirskill near Otley, in the fourteenth century;[3] though the manufacture near that place has long since ceased.
Although the making of iron was thus carried on in various parts of England in the Middle Ages, the quantity produced was altogether insufficient to meet the ordinary demand, as it appears from our early records to have long continued one of the principal articles imported from foreign countries.

English iron was not only dearer, but it was much inferior in quality to that manufactured abroad; and hence all the best arms and tools continued to be made of foreign iron.

Indeed the scarcity of this metal occasionally led to great inconvenience, and to prevent its rising in price Parliament enacted, in 1354, that no iron, either wrought or unwrought, should be exported, under heavy penalties.
For nearly two hundred years--that is, throughout the fourteenth and fifteenth centuries--the English market was principally supplied with iron and steel from Spain and Germany; the foreign merchants of the Steelyard doing a large and profitable trade in those commodities.
While the woollen and other branches of trade were making considerable progress, the manufacture of iron stood still.