The next event in the history of the Observatory was the issue of Letters Patent (32 Geo. III., A.D. 1792), in which it is recited that “We grant and ordain that there shall be for ever hereafter a Professor of Astronomy, on the foundation of Dr. Andrews, to be called and known by the name of the Royal Astronomer of Ireland.” The letters prescribe the various duties of the Astronomer, and the mode of his election. They lay down regulations as to the conduct of the astronomical work, and as to the choice of an assistant. They direct that the Provost and Senior Fellows shall make a thorough inspection of the Observatory once every year, in June or July; and this duty was first undertaken on the 5th of July, 1792. It will thus be noted that the date fixed for the celebration of the Tercentenary of the University happens to be the centenary of the first Visitation of the Observatory. The Visitors on the first occasion were--A. Murray, Matthew Young, George Hall, and John Barrett. They record that they find the buildings, books, and instruments in good condition; but the chief feature in this report, as well as in many which followed it, related to a circumstance to which we have not yet referred. In the original equipment of the Observatory, Ussher, with the natural ambition of a founder, desired to place in it a telescope of more magnificent proportions than could be found anywhere else. The Board gave a spirited support to this enterprise, and negotiations were entered into with the most eminent instrument-maker of those days. This was Jesse Ramsden (1735-1800), famous as the improver of the sextant, as the constructor of the great Theodolite used by General Roy in the English Survey, and as the inventor of the Dividing Engine for graduating astronomical instruments. Ramsden had built for Sir George Schuckburgh the largest and most perfect Equatorial ever attempted. He had constructed mural quadrants for Padua and Verona, which elicited the wonder of astronomers, when Dr. Maskelyne declared he could detect no error in their graduation as large as two seconds and a-half. But Ramsden maintained that even better results would be obtained by superseding the entire quadrant by the circle. He obtained the means of testing this prediction when he completed a superb circle for Palermo of five feet diameter. Finding his anticipations were realised, he desired to apply the same principles on a still grander scale. Ramsden was in this mood when he met with Dr. Ussher. The enthusiasm of the Astronomer and the instrument-maker communicated itself to the Board, and a tremendous circle, to be ten feet in diameter, was forthwith projected.