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

APPENDIX. 203 place the methods adopted by the officers of the Beagle, in the exa- mination of a wild sea-coast — such, for example, as that of the south-western part of Tierra del Fuego. On that coast the weather was so continually bad, there was so much swell, and the water near the steep precipitous shores always so deep, that anchorage (except in harbours) was impracticable : boats were seldom able to assist (while under way), and the bearing compass, though particularly good, and well placed, was of very little use : it was therefore never trusted in important bearings. Another impediment, and not a slight one, was the current ; which set irre- gularly from one knot to three knots an hour, along the shore. But there are seldom evils, unbalanced by remedies. The stormy and desolate shores of Tierra del Fuego are broken into numerous islands, about which anchorages are abundant, and they are excel- lent, when once a vessel is in them. To find, and enter, or leave them in most instances, was troublesome, and often dangerous. But, with the help of those havens, and the distinct marks afforded by a high rocky shore ; and by tlie sharp peaks of more distant heights, a correct survey was effected. Beginning at the western extreme, near Cape Pillar (because the prevaihng winds are westerly, and the current sets to the eastward), our first object was to find a safe harbour in which to secure the ship. There we made observations for latitude, time, and true bear- ing ; on the tides, and magnetism. We also made a plan of the harbour and its environs ; and triangulations, including all the visible heights, and more remarkalile features of the coast, so far as it could be clearly distinguished from the summits of the highest hills near the harbour. Upon these summits a good theodolite was used, which was set, invariably, to a well-defined mark, near the observatoiy ; from which mark the true bearings of the stations on the summits of the hills were ascertained by observations of the sun made with a theodolite. Many leagues of exposed, and difficult coast, were looked down upon, in this manner ; and, at the least, their exact bearings from one fixed spot ascertained. But if more than one height afforded a round of angles with the theodolite, and the position of each of those heights was accurately known by triangulation depending upon a base measured at the harbour, then the positions of various other hills or marks were ascertained ; and so much easier became