The emigration of Ulster Scots to America on a large scale began early in the eighteenth century and increased in volume as the century advanced. There were certain periods when the tide was unusually strong; these were the years 1717-1718, 1727-1728, 1740-1741, and 1771-1773. The emigration in 1717-1718, when the first mass emigration of the Ulster Scots began, was caused by the destruction of the woolen industry, by the disabilities arising from the Test Act, and by the rack-renting of the landlords, the last of which was the most immediate and potent cause. Following this first wave of emigration, the tide ebbed somewhat until 1727-1728, when it reached an even greater height than before and was still going strong in the seventeen-thirties. The causes which had produced the earlier exodus were still potent now, but to these was added the immediate cause of a series of poor harvests, culminating in the famine of 1727-1728. Another great wave of emigration from Ulster began in 1740-1741. While the grievances previously described were still operating to produce discontent and to induce emigration, the immediate occasion of this particular exodus was the famine of 1740- 1741, which was quite as severe as that of 1727-1728, and probably even more devastating in its effects. It is estimated that within two years at least 400,000 people in Ireland perished from starvation. A large movement of population to America at once began, and continued for some years above the ordinary volume; in fact, for a decade or more. The immigrant tide slackened in the period of the French and Indian War and was not noticeably strong thereafter until 1771, when a new wave of emigration from Ulster, stronger than any that had preceded it, began to gather headway and reached its climax in 1772-1773. It constituted by far the largest immigration to America of any single racial group in the years immediately preceding the Revolution. This exodus, besides the usual causes of emigration, was motivated particularly by the decline of the linen trade centering in Ulster and by a new outburst of rack-renting. It is computed that during 177i-1773 twenty-five or thirty thousand emigrants sailed from Ulster alone to ports in the New World, especially to those on the Delaware.