Narrative of the surveying voyages of his majesty's ships Adventure and Beagle (vol.2): between the years 1826 and 1836 : describing their examination of the southern shores of South America, and the Beagles's circumnavigation of the globe

PLAN OF VOYAGE. 25 « With this view, the run to Rio de Janeiro may be con- veniently divided into four parts : " 1st. Touching at Madeira, the exact position of which has been admitted by all parties. Having obtained a four days' rate there, or, if the weather and the exposed anchorage will not permit, at TenerifFe, the Beagle should, 2diy, proceed with the least possible delay to Port Praya, in the Cape de Verde Islands, not only to establish a fresh four days' rate ; but that point being the pivot on which all Captain Owen's longitudes turn, no pains should be spared in verifying the position he has assumed for it. From thence, 3dly, she should make the best of her way across the Line to Fernando Noronha. This island, indeed, lies somewhat to the westward of her track, and may retard her progress a little ; yet a series of chronometric observations there is essential to the object in view, because it forms the third nearly equal division of the whole run, and because it was the point of junction of Commander Foster's double line of longitudes. If two or three days' delay at either of these two last stations will enable him to obtain satisfactory occultations, and moon culminating observations, which are likely to be seen in this country, the increased certainty of the results will well atone for that loss of time. The Commander will, of course, be careful to adopt, in all those stations, the precise spot of the former observations, with which his are to be compared. The Governor of Fernando Noronha was pecu- liarly obhging to Commander Foster, and gave up part of his own house for the pendulum experiments. There will be no occasion now for trespassing so heavily on his kindness ; but the difference of longitude between that station and Comman- der Fitz-Roy's must be well measured. " However desirable it may be that the Beagle should reach Rio de Janeiro as soon as possible, yet the great importance of knowing the true position of the Abrolhos Banks, and the certainty that they extend much further out than the limits assigned to them by Baron Roussin, will warrant the sacrifice of a few days, if other circumstances should enable her to beat down about the meridian of 36° AV. from the latitude of