Note 10 — Chapter I
Reading edition
“Swinging for the compass” is thus performed. The vessel is moored in the bight at Greenhithe, and by means of warps to certain Government buoys she is placed with her head towards the various points of the compass. The bearing by the compass on board (influenced by the attraction of the iron she carries) is taken accurately by one observer in the vessel, and the true bearing is signalled to him by another observer on shore, who has a compass out of reach of the “local attraction” of the vessel. The error in each position due to the local attraction is thus ascertained, and the corrections for these errors are written on a card in a tabulated form, thus:—