Narrative of the surveying voyages of his majesty's ships Adventure and Beagle (vol.1): between the years 1826 and 1836 : describing their examination of the southern shores of South America, and the Beagles's circumnavigation of the globe

Feb. 1827. BAROMETRICAL OBSERVATIONS, 41 their exposure to the prevailing winds, rose no higher than twelve or fourteen inches from the ground, with widely-spread- ing branches, so closely interwoven, as to form a platform that bore our weight in walking. We next traversed an extent of table-land,* much intersected by ponds of water. Mr. Tarn shot two plovers of a new species {Charadrius rubecola, Zool. Jour. vol. iv. p. 96), and a snipe. We then ascended three or four hundred feet, and crossed a deep ravine. The bottom of the ravine was clay-slate in a decomposing state, but the sur- face of the ground was strewed with pebbles of granite. Another plain, with many ponds, succeeded ; the intervening spaces being covered with tufts of chamitis, and studded here and there with small clusters of dwarf beech ; but the ground was so hard, and firm, that we proceeded rapidly, without fatigue, until we attained the height of 1,800 feet, when the ascent became very steep. Near the summit lay a large mass of snow, rapidly melting away. We reached the highest pin- nacle of the mount at seven o'clock (having left our resting- place at four), and immediately set up the instruments. I was obliged to avail myself of Mr. Tarn's assistance to hold the barometer, whilst two of my boat's crew held the legs of the theodolite-stand, for the wind was blowing very strongly, and the edge of a precipice was close to us, perpendicular for many hundred feet, and thence downwards so steep, that any body going over would fall at least a thousand feet. The theodolite-stand was unavoidably placed within a very few inches of the edge, and I took a round of angles, suffer- ing, however, intense pain from the piercing coldness of the wind, which, heated as we were by the ascent, was much felt, though the temperature was not lower than 39°. I was lightly clothed, and should have fared badly, had not one of the party lent me his Flushing jacket, while he descended under the lee of the mountain-top to make a fire. The barometer stood at 26, 618, the temperature of the air being 40°, and of • On this table-land the barometer stood at 27,767. Temperature of the air 46°,5, and of the mercury 47°,5, which gave the elevation 1 ,327 feet.