Dr Rutty was the foremost observer of the Irish climate in the eighteenth–century. Modern medicine was in its infancy, and eighteenth–century physicians relied on observation in their efforts to explain the causes of disease. In 1770 Dr Rutty published his meteorological observations in A Chronological History of the Weather and the Seasons, and the Prevailing Diseases in Dublin.Rutty believed that there was a connection between climatic conditions and outbreaks of certain types of disease, for example 'ague', which he felt was directly related to damp climates. Certainly there is ample evidence that the chilling damp of the Irish climate encouraged a widespread tendency to respiratory and rheumatic diseases. Many physicians shared Dr Rutty's interest, but his careful observations cover a long and particularly important period of the century. He kept seasonal records from 1716 to 1765 in which he noted the nature of the season and the direction and frequency of the wind, but not its duration. His records are descriptive rather than quantitative and it is difficult to draw other than general conclusions from them. Even so, it is almost certain that Ireland was generally cooler in the eighteenth than in the twentieth century.
Dr Rutty made his observations for medical purposes. Medical science was another enduring concern of the MPs, and it was reflected in the number of Dublin hospitals with eighteenth–century origins. The Charitable Infirmary – the first public hospital in the British Isles – was opened in Dublin in 1718. Other hospitals followed, almost entirely supported by private donation, occasional lotteries or the proceeds of public entertainments; for instance, the first performance of Handel's Messiah was given in aid of the Hospital for Incurables, which was sponsored by the Charitable Musical Society. In 1744/5 Ireland had the first maternity hospital in the British Isles, locally known as the Rotunda, taking its name from the Assembly Rooms, whose entertainments supported it. Where Dublin led, the rest of the country followed. As with the Dublin hospitals, those throughout the country were largely the result of private enterprise and public subscription. Occasionally parliament voted a small grant to a specific hospital.
Then, in an Act of 1765 (0646) amended in 1767 (0662), parliament attempted to provide a framework for the development of county infirmaries and, although the facilities and accommodation were totally inadequate to the need, by the end of the century almost every county had its infirmary. Many of the hospitals established under these acts are still extant today. The 1765 legislation acknowledged the inadequacy of the funding for the existing public infirmaries at Dublin, namely the Charitable Infirmary, Mercer's and the Hospital for Incurables, as well as the two public infirmaries at Cork, the North and South Infirmaries, and made provision for £50 p.a. to be paid out of the Treasury to supplement their budgets. The statutes made the clergy of the Church of Ireland a perpetual corporation for the erection of infirmaries, and qualifications were laid down for additional governors by subscription. Parliament allocated £100 for the surgeon's salary and the Grand Jury was to supplement this with a grant towards the hospital's expenses. It was hoped that private charity would provide the remainder, and in some cases it did. For example, by the end of the century Belfast had in addition to a general infirmary a Fever Hospital, both largely dependent on public support. Nevertheless, no hospital system was successful before the development of antiseptics and the improvement of medical and nursing training in the nineteenth century. The dispensary system, which offered an outpatient medical service, emerged in the closing decades of the eighteenth–century. It probably gave more effective medical service to greater numbers.