Though he had objected strongly on his first coming to the Observatory to the excessive time devoted to the merely commercial side of the care of chronometers, yet the perfecting of these instruments was one that he had much at heart, and many recent appliances are either of his own invention or are due to suggestions which he threw out. Much work lying outside the Observatory, and yet intimately connected with it, was carried out either by him or in accordance with his directions. The transit of Venus expeditions of 1874, the delimitation of the boundary line between Canada and the United States, and, later, that of the Oregon boundary; the determination of the longitudes of Valencia, Cambridge, Edinburgh, Brussels, and Paris; assistance in the determination of the longitude of Altona--all came under Airy's direction. Nor did he neglect expeditions in connection with what we would now call the physical side of astronomy. On three occasions, 1842, 1851, and 1860, he himself personally took part in successful eclipse expeditions. The determination of the increase of gravity observable in the descent of a deep mine was also the subject of another expedition, to the Harton Colliery, near South Shields. But with all these, and many other inquiries--for he was the confidential adviser of the Government in a vast number of subjects: lighthouses, railways, standard weights and measures, drainage, bridges--he yet always kept the original objects of the Observatory in the very first place. It was in order to get more frequent observations of the moon that he had the altazimuth erected, which was completed in May, 1847. This was followed, in 1851, by the transit circle, as he had long felt the need for more powerful light grasp in the fundamental instrument of the Observatory. The transit circle took the place both of the old transit instrument and of the mural circle. Above all, he arranged for the observations of moon and stars to be carried out with practical continuity. The observations were made and reduced at once, and published in such a way that any one wishing to discuss them afresh could for himself go over every step of the reduction from the commencement, and could see precisely what had been done. The greatest addition made to the equipment of the Observatory in Airy's day was the erection of the 12-3/4-inch Merz equatorial, which proved of great service when spectroscopy became a department of the Observatory. [Illustration: THE SOUTH-EAST TOWER. (_From a photograph by Mr. Lacey._)]