It was thus only a few years before Sir W. R. Hamilton’s death that Dunsink Observatory possessed a really fine objective; but it was only an objective, it was not a telescope. The engrossing labours of Sir W. R. Hamilton’s mathematical work, his advancing years, and his declining health, did not permit him to undertake the arduous labour of its erection. Sir James South found in this a sad grievance. I have heard him denounce this inaction with that vigorous language which he was accustomed to use. He had even offered to contribute liberally to the expenses of mounting, if the College authorities would put it in hands. It was not, however, until Sir W. R. Hamilton’s successor was appointed (1865) that the work was done. South lived just long enough to know that the great instrument was at last being erected. A view of the instrument, named the South Equatorial, after the donor, is shown in the adjoining illustration. The successor of Sir William Rowan Hamilton as Andrews Professor of Astronomy was Dr. Francis Brünnow. He was a German by birth, who had distinguished himself by various astronomical researches, and by an excellent work on Practical Astronomy. He had previously occupied the Chair of Astronomy at the University of Michigan. When Brünnow came to Dunsink, his first care was the mounting of the great South Equatorial. A building was erected on the lawn, surmounted by a dome, and fitted with revolving machinery by Messrs. Grubb, who also constructed the tube and stand. A micrometer, from the Berlin firm of Messrs. Pistor & Martin, was added, and thus the South object-glass, forty years after it was made, came into actual use. Dr. Brünnow devoted himself chiefly to the investigation of the Parallax of Stars. In this he was, indeed, following the traditions of the Observatory as laid down by Brinkley. Brünnow published two parts of his researches on this difficult subject. These papers are now regarded as a classical authority in this branch of astronomy. The pains which he took to eliminate error, and the consummate manner in which he has discussed his results, show him to have been both a skilful observer and an ingenious computer.