But when the river is to be ascended, known as _subida_ or _surcada_, several _bogas_ are necessary. The route must then be close to the bank, where the current is not so strong, but where such obstacles as logs, stumps, salient rocks, overhanging branches, troublesome insects, and other similar inconveniences are numerous. Here the paddles are useless, except when crossing the river[75] in search of an easier route on the opposite bank, and the _bogas_ must push the canoe along by main force, employing for this purpose long poles called _botadores_ or _tanganas_. In canoeing in the smaller rivers, especially in the dry season, bad places, caused by the shallowness of the water or the immobility of the huge logs that frequently form an impenetrable network on or near the surface of the water, are often met with; in such cases the _bogas_ either wade ashore and pull the canoe out of the bad place by means of a rope or else enter the water and shove and lift until it is free. If, however, the canoe is very heavy and these methods fail, they strip the bark from the _setico_-tree, which is always to be found on the banks of these rivers, and stretch it out on top of the obstacle. As this bark is very slippery and soapy, the canoe readily slides over it when they push. Materón informed us that, as a general rule, one day's descent is equivalent to three days' _surcada_; this, however, is subject to numerous circumstances and mishaps, such as the conduct of the boatmen, the condition of the river, the weight of the cargo, the cut of the canoe, the character of the travellers, the necessity of hunting and fishing for food, &c. What a pleasant sensation it was to sit calmly in the canoe, while the swift current bore us steadily onwards, and to watch the thick, tropical vegetation, which lined the banks of the stream, swiftly recede until hidden from view by a bend of the river! How different it was from the monotonous climbing and descending of the Andes that had caused us so much toil! Several times we passed through places that seemed to me perilous in the extreme, for the whirling current would dash us with frightful rapidity directly towards some huge stump or half-submerged log, while other obstacles of a similar nature appeared on every hand. We seemed to be almost upon it, when a deft turn of the _popero's_ paddle would bring us to one side by a margin of three or four inches. Again, we would shoot some small rapid; the canoe would give a jump, and the next instant we would dash the water out of our half-blinded eyes, and, looking around, would see the rapid far behind us.