The basic wealth of the country was and remained agricultural. Agricultural produce or labour paid the rent, so that a major, if unpredictable, consideration for the MPs was climate. Local, regional or national famines were a recurring feature of pre–industrial society. The severity of their impact was related to the ability of one area to compensate for scarcity in another, although areas of plenty were not always anxious or able to do this, as was shown in 1729.
In the early part of the century, communications were rudimentary and a surplus in one place could not easily be transferred to another. Even when it was possible, internal redistribution posed problems. For instance, in March 1728/9 Primate Boulter in his capacity as Lord Justice wrote to the Duke of Newcastle to explain the failure of the measures he had taken to alleviate the famine in the north. Money raised from an appeal for famine relief in Dublin had been used to buy corn in Munster, 'where it has been very cheap to send it to the North in order to keep the markets down'. But, this scheme had proved impossible, firstly because the wind, which normally blew from the south–west, had blown from the east (i.e. into the Atlantic) for three weeks, preventing the coastal shipping from transporting the corn; and secondly because of:
“the insurrection of the mob in those parts ... there have been tumults in Limerick, Cork and Waterford, Clonmel and other places, to prevent the corn we have bought from going north. Those at Limerick and Cork have been the worst, where they have broken open warehouses and cellars and get what price they pleased on provisions ... there is no doubt but that the buying corn there has raised their markets but still we are assured there is great plenty in the country, and provisions are in some places as cheap again as in the north, but, where dearest at least one third part cheaper.”
The Primate added that he had sent for 2,400 quarters of rye from Copenhagen but this was not expected until mid–May.
Famine was a spur to emigration, particularly among the northern Presbyterians. Boulter continued that 'the rumour of going to America still continues ... there are now seven ships at Belfast that are carrying about one thousand passengers thither. And if we knew how to stop them, as most of them can get neither victuals nor work at home, it would be cruel to do so.' The Ulster emigration of Presbyterians was a result of resentment at being deprived of their civil and religious rights, spurred on by hunger. They often migrated in congregations accompanied by their minister so that they arrived in America as an established community.
The worst famine of the century was that of 1740–41. Irish population figures are notoriously inaccurate, but it has been estimated that this famine claimed between 200,000 and 400,000 out of an estimated population of about 2,500,000. A debilitated population had little resistance, and famine was inevitably the forerunner of epidemics of endemic diseases. A contemporary observer wrote that 'want and misery are on every face, the rich unable to relieve the poor, the roads spread with dead and dying bodies, mankind the colour of the docks and nettles it feeds upon.' It was disaster on the same scale as that of a century later.
The seventeenth century had seen the culmination of the coldest weather cycle in a thousand years, and it has been calculated that for the decade 1690–99 the annual mean temperature in central England fell to just above 8°C. There is considerable evidence, albeit impressionistic, that weather patterns were very erratic in the first half of the eighteenth–century, although a tendency towards warmer weather became apparent as the century progressed. From the information on the Dublin area amassed by the Dublin Quaker physician, Dr John Rutty, it is possible to construct the following tentative picture of the decades preceding the widespread famine of 1740–41.
From 1717 to 1722 the weather showed an overall improvement, but the vitally important springs and autumns of these years were classed as 'variable' and there is ample evidence of poor harvests and consequent social and political unrest, which expressed itself in the northern migration to the American colonies and the political agitation surrounding Wood's Halfpence. In a predominantly agrarian country the success or failure of harvests has immediate effects on all levels of social and economic activity. However, 1723 was a consistently good year with an 'excessively hot and dry' spring, and an 'unusually hot and dry' summer and autumn were followed by a 'pretty open' winter. Thus in the middle of the decade there was a degree of stability, but the harvests of 1726, 1727 and 1728 were poor, particularly in the north, and the winter of 1728–9 was one of the coldest in the century. Poor harvests tended to come in successive years: weather was often cyclical, and in times of famine it was difficult to preserve seed for the next season.
Then, in the 1730s, the annual temperature rose fairly sharply. There was a series of hot summers, warm autumns and, with the exception of 1730–31, a decade of exceptionally mild winters. The winter of 1734 was the warmest for a hundred years, and 1732 and 1736 were probably the two best years of the century overall. Suddenly, in the autumn of 1738, the weather started to degenerate. There followed 28 disastrous months in which three successive and widespread bad harvests brought the worst famine of the century.
The 1741 and 1845 famines were classic examples of the demographic disasters to which a subsistence agrarian society is peculiarly vulnerable. In 1741 the catastrophe was aggravated by a combination of circumstances. Harvests failed not only all over Ireland, but also in England and parts of western Europe. In addition it coincided with the economic dislocation created by the outbreak of a major European war, the War of Austrian Succession. For these reasons, the impact of the 1740–41 harvest failure was magnified by the concurrent impossibility of any amelioration. The significance of this became very clear when the poor harvests of the early 1740s culminated in the harvest failure of 1744–5. In Co. Roscommon, Charles O'Conor of Belanagare considered that the autumn and winter of 1744–5 were at least as severe as those of 1739–40, but food could be redistributed and the human catastrophe was averted.
Recoveries were often as rapid as disasters, and after the 1740s disasters the population rose rapidly, with slight checks such as the poor harvests of the early 1780s, until it was just under nine million at the time of the next major demographic catastrophe, the great famine of the mid– to late 1840s. It is thought that the population rose from about two million to five and a quarter million between 1700 and 1800, increasing slowly in the first half of the century but with ever–increasing momentum in the second half.
In 1785 the Royal Irish Academy was founded as a theoretical counterpart to the Royal Dublin Society, and in 1799 the second President of the Academy was Richard Kirwan FRS, an internationally distinguished, if eccentric, scholar with a scientific interest in meteorology and a practical one in weather forecasting. Under his influence, the early volumes of the Academy's Transactions published a considerable amount of information on Irish weather during the preceding century. These included not only Kirwan's findings but also information gathered by Maria Edgeworth's brother, Henry Edgeworth; the observations of three physicians, Dr Rutty of Dublin, Dr Crump of Limerick and Dr Patterson of Londonderry; and an important speculative paper by Rev. William Hamilton arguing that the Irish climate had undergone a considerable change in recent times and that it was now more equitable than it had been earlier in the century. In support of his thesis he claimed that it was 50 years since the Foyle had completely frozen over at Londonderry. Possibly this freezing, which was unknown in the twentieth century, occurred during the winter of 1756–7. This was a particularly bad year and the distress was reflected in bank closures and other economic problems. It began with a cold, backward spring, followed by a very wet summer and an indifferent autumn; the harvest failed and the ensuing winter was bitterly cold. The economy slumped, partly because of the poor harvest and partly because it coincided with the opening of the Seven Years' War.
Hamilton's speculations were endorsed by John Williams, who in 1806 published A Treatise on the Climate of Great Britain, and have been substantiated by the twentieth–century researches of Dr H. H. Lamb in The Changing Climate. Lamb's figures also show a correlation with the seasonal comments given by Dr Rutty for the years 1716–65, endorsing Kirwan's (who attempted to turn them into scientific terms) belief in their validity. Although there were winters with cold snaps, as illustrated in Robert Healy's grisaille 'Skating at Castletown in 1768', the weather does appear to have become milder as the century progressed.