III. Magnetic observations at Kerguelen
The Government expedition to Kerguelen Island for the observation of the Transit of Venus on December 8th, 1874, presented a very favourable opportunity for the accurate determination of the magnetic elements of an important station in the South-Indian Ocean, and one which will at most be visited only at distant intervals for the purpose of scientific investigations. When, therefore, I heard of my appointment to that station, I at once brought the question of terrestrial magnetism under the notice of the Astronomer Royal, and he readily agreed to my proposal of taking a complete set of magnetic instruments to Kerguelen, and of making any observations that would not interfere with the main object of our expedition. Being in charge of the whole Kerguelen party of observers, I could not expect to be able to devote much time personally to the magnetic work; but the Rev. W. Sidgreaves, whom long experience, both at the Stony-hurst Observatory and during our magnetic survey of Prance in 1868 and 1869, had made perfectly conversant with all the details both of instruments and observations connected with terrestrial magnetism, had already been placed on the staff of astronomical observers for Kerguelen. The assistance of a very efficient observer being thus secured, the next step was to procure the necessary instruments. Fortunately I experienced no difficulty in this matter, as the authorities at Kew immediately placed at my disposal a Jones unifilar and a Barrow dip-circle. There was no question of the want of a good chronometer, as the astronomers were to be supplied with nine of these, besides the eight reserved exclusively for longitude connexions, which remained always undisturbed in their quiet berth on shipboard.
