Chapter 1 has shown that there was an energy crisis in the seventeenth century, between the 1630s and the 1680s, caused primarily by Oliver Cromwell’s unprecedented naval rearmament and aggressive imperial policy which placed a strain on the island’s timber and fuel resources. That crisis was easily solved within the ambit of the timber economy through a substantial permanent dependence on Baltic sources of energy; then, for about seventy years after the 1680s, Britain enjoyed an abundance of timber and charcoal iron, except when trade with Sweden was suspended in 1717-19. The decisive challenge came in the period 1750-90 when there was a resumption of dynamic shortage of timber and fuel, driven this time by a population explosion (Chapter 3). This crisis could not be solved, as the previous one had been, by drawing more energy from the Baltic. This would have meant almost total dependence on foreign sources of timber-based energy at increasing real cost; the price of imported Scandinavian bar iron nearly doubled between the 1740s and the 1790s (Table 3.2). Both economic and national defence considerations ruled this out. I shall argue that the type of technology which the seventeenth-century crisis evoked—the reverberatory furnace and the steam engine—proved to be a major part of the answer to the eighteenth-century crisis. The Cromwellian Revolution put Britain on the economic path which led to the Industrial Revolution. In this respect Britain’s experience was unique. This chapter pays particular attention to the contribution of Henry Cort.