The various offices attached to the house are conveniently disposed in the wings, the height of the ground story. The rooms at the back of the mansion look out upon a large lawn and pleasure-ground, beyond which are the Fellows’ Garden and the College Park. From the windows of the house to the Cricket Pavilion at the further end of the Park is nearly a quarter of a mile of green sward, a noble expanse in the heart of a great city. The only intervening structure is a small building of Portland stone, of pseudo Greek or classical design--the Magnetical Observatory. This little temple of modern science was built in the year 1837 at the instigation of the celebrated mathematician, Dr. Humphrey Lloyd, afterwards (1867) Provost of Trinity College; and at the time of its completion in 1838 it was the only observatory specifically devoted to magnetic research--with the exception of that at Greenwich, under the direction of the Astronomer-Royal--in the United Kingdom. And it was here that Dr. Lloyd conducted those numerous and most interesting experiments, of which the results were communicated to many successive meetings of the British Association. The building itself, in the Doric order of architecture, was erected under the superintendence and from the design of Mr. Frederic Darley, of Dublin. The front elevation is not ungraceful, being partly copied from an Athenian model. But the architectural beauty of the rest of the building has been sacrificed to the scientific necessities of the interior, and the result is very far from satisfactory as a work of art. It stands in latitude 53° 21′ N. and longitude 16° 6′ W. It is forty feet in length by thirty feet in width, constructed of Portland stone, the interior being of the calpe, or argillaceous limestone of the valley of Dublin. Several specimens of each of these stones were submitted to severe tests, and found to be entirely devoid of any magnetic influence. To preserve a uniform temperature, and also as a protection from damp, the walls are studded internally. The nails employed in the wood-work are all of copper, and all locks and metal work of every kind throughout the building of brass or gun metal. No iron, of course, was used in any part of the work. The interior is divided into one principal room and two smaller rooms, lighted by a dome at the top, and by one window at either end of the building. A complete account of this Observatory within and without, and of the numerous and most interesting instruments which it contains, will be found in _An Account of the Magnetical Observatory of Dublin, and of the Instruments and Methods of Observation employed there_, by the Rev. Humphrey Lloyd, D.D., University Press, 1842. WEST FRONT.