De Ulloas[169] and some friends in 1735 made an ascent of the river Chagres on their journey from Cruces to Panama. This voyage is interesting as being one of the first that is recorded over the river that has since played so prominent a part in the history of the canalisation of the isthmus. They found the banks of the Chagres impassable, for the most part, from the density of the vegetation and the velocity of the current. The vessels that were then more or less accustomed to navigate the Chagres were described by De Ulloas as _chatas_ and _bongos_—the first carrying 600 or 700 quintals, and the latter 400 or 500. The river was found to be so full of shallows that even vessels of this small size had to be lightened every now and again until they had passed over them. No one has taken a greater interest in the subject of a ship canal than Humboldt, who regarded Kelley’s Atrato route with approval, and who, replying to the objections brought against the proposal in his time, declared that “there is nothing more likely to obstruct the extension of commerce and the freedom of international relations than to create a distaste for farther investigation by discouraging, as some are too positive in doing, all hope of an oceanic channel.”[170] A survey was made of the isthmus in 1827 by Captain Lloyd and Captain Falmark, the former an officer of engineers in the Colombian service, and the latter a Swedish gentleman acting in that capacity for the time being. Beginning at Panama, they followed the old line of road from that city to Porto Bello, a distance of 22¾ miles, where they found the surface of the water in the river to be 152½ feet above high-water mark at Panama. At Cruces they found a fall in the river of 114½ feet, leaving only about 38 feet as the height above the Pacific. It was found that at Panama there was a rise and fall of the tide in the Pacific of 27·4 feet, being 13·5 feet above the high-water mark of the Atlantic at Chagres. These and other observations led them to conclude[171] that “in every twelve hours, commencing with high tides, the level of the Pacific is first several feet higher than that of the Atlantic; it becomes then of the same height, and at low tide it is several feet lower; again, as the tide rises, the two seas are of one height, and, finally, at high tide the Pacific is again the same number of feet above the Atlantic as at first.”[172]