Before 1828 the iron trade of Scotland was of little importance and was failing to keep abreast of the metallurgical industries of England and Wales. High costs of production effectively prevented Scottish ironmasters from competing with others, a barrier which was overcome only by the application of hot instead of cold air in the blast at the furnaces. In turn this made possible the use of the local deposits of black-band ironstone and, without coking, the splint coal of Lanarkshire. The trade which was built on these foundations specialised in the production of pig iron for sale. Because of its cheapness Scotch pig iron was used extensively not only in Britain but throughout the world. In the middle of the nineteenth century the chief foreign consumers were the United States and Germany, though by the seventies Germany was dominant. The exceptionally favourable conditions on which the trade was based could not last indefinitely. The technical innovation which brought the new Scottish trade into being was available for all to adopt, though in most cases outside Scotland its adoption was not attended with such startling reductions in cost. Unlike the technical benefits, others did not possess the inimitable geological advantages of the Scots. However, as the blackband ironstone and the better coal deposits were used, these geological advantages were of necessity gradually lost. In addition other factors also operated against Scottish producers. Since Scotch pig iron was a phosophoric iron it was unsuitable for the early processes of the modern steelmaking industry. More important, however, was the appearance of strong competition from the north east of England. After 1850, through using the rich local deposits of ironstone, the trade of that district rose rapidly in importance. Unfortunately, the effects of these adverse forces beyond the control of the Scots were intensified by the imperviousness of many Scottish ironmasters to technical change after their initial introduction of the hot blast. Not until immediately after the period covered by the present study, when the economic prospects of the trade were less favourable, were further general advances made along these lines. In many ways, therefore, it is possible to regard the period from 1828 to 1873 as one phase of technological development. During the period 1828 to 1873 the Scottish pig iron trade went through five main cycles of economic activity. The course of the first, from about 1828 to 1843, was completely determined by the introduction of the hot blast, which ralsed the trade into a prosperous condition, when other sectors of the economy remained depressed. New producers appeared and there was extensive capital investment, mainly in Lanarkshire, lasting well after the peak of the cycle. In the second and third cycles in the new pig iron trade, from 1844 to 1851 and from 1852 to 1862, the level of capital investment diminished. In the boom of the forties investment still remained considerable. Much, however, was no longer in Lanarkshire, where minerals were less easily obtained, but in Ayrshire and on the east coast. After the peak of that cycle, however, there was a decided drop in investment, which, though it reappeared once more in the boom of the fifties, was less buoyant. After the national financial crisis of 1857 investment was undertaken usually because of the super-session of existing, equipment or through the need to move to new sources of supply of minerals. These second and third cycles are also noteworthy because, first, during them the vital nature of the dependence of the Scottish pig iron trade on foreign demand was clearly demonstrated, and, secondly, because during the forties the peculiar system of storing pig iron in Glasgow and the selling of storekeepers' warrants on the Glasgow Pig Iron Market evolved. Because of the extensive speculation in warrants which grew up, this system played a particulerly important part in moulding the later growth of the Scottish pig iron trade. In the fourth and fifth cycles, from 1863 to 1868 and from 1869 to 1873, the character of the trade was changed, because then the extent of competition from the north east of England, which was first experienced in the depression years after 1857, became the chief determinant of the Scottish ironmasters' prosperity. Only for a time in the exceptionally prosperous times of the early seventies were the Scots freed from this adverse influence. Nevertheless it was beneficial in bringing home to the ironmasters the need for further technical improvements, which were undertaken in the main only after 1873.