The number of English forges rapidly dwindled, and the amount of the home production became insignificant in comparison with what was imported from abroad.

Yarranton, writing in 1676, speaks of "the many iron-works laid down in Kent, Sussex, Surrey, and in the north of England, because the iron of Sweadland, Flanders, and Spain, coming in so cheap, it cannot be made to profit here." There were many persons, indeed, who held that it was better we should be supplied with iron from Spain than make it at home, in consequence of the great waste of wood involved by the manufacture; but against this view Yarranton strongly contended, and held, what is as true now as it was then, that the manufacture of iron was the keystone of England's industrial prosperity.

He also apprehended great danger to the country from want of iron in event of the contingency of a foreign war.

"When the greatest part of the iron-works are asleep," said he, "if there should be occasion for great quantities of guns and bullets, and other sorts of iron commodities, for a present unexpected war, and the Sound happen to be locked up, and so prevent iron coming to us, truly we should then be in a fine case!" Notwithstanding these apprehended national perils arising from the want of iron, no steps seem to have been taken to supply the deficiency, either by planting woods on a large scale, as recommended by Yarranton, or by other methods; and the produce of English iron continued steadily to decline.

In 1720-30 there were found only ten furnaces remaining in blast in the whole Forest of Dean, where the iron-smelters were satisfied with working up merely the cinders left by the Romans.