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

34)2 TllACKING — MEASUREMENT. April Strength of the stream ; so landing all our party, except two in each boat, we made the boats fast to one another, at a few yards apart, in a line a-head : and then taking the end of a coil of whale-line ashore, half our party fixed themselves to it by laniards of broad canvas straps, which passed across their breasts and over one shoulder, and walked together steadily along the river's bank. The bight of the line was passed round a stout mast, stepped in the headmost boat and attended by the two men, who veered away or shortened in the line as the varying width of the stream, or frequent impe- diments rendered necessary. In this manner, one-half of our party relieving the other about once an hour, every one wil- lingly taking his turn at the track rope,* we made steady progress against the stream of the river, which rather increased m rapidity as we ascended, until its usual velocity was be- tween six and seven knots an hour. While among the islands which I mentioned tracking was difficult and tedious, many were the thorny bushes through which one half of the party on the rope dragged their companions. Once in motion no mercy was shewn : if the leading man could pass, all the rest were bound to follow. Many were the duckings, and not trifling the wear and tear of clothes, shoes, and skin. At intervals stoppages were made for refreshment and obser- vations. Three chronometers were carried in the boats, with other necessary instruments: among them two mountain barome- ters, with which Mr. Darwin and myself wished to measure the height of the river above the level of the sea, and the heights of the neighbouring ranges of hills above the level of the river. This afternoon we picked up a boat-hook upon the south bank of the river, which was immediately recognized to be one which had been left by accident sticking in a mud- bank, by the party who accompanied Captain Stokes in his excursion up this river in the year 1827. It was very cold at our bivouac this night, being a sharp * Mr. Stokes alone being- excepted, as his duty required continual attention.