Claim: At the Khone Falls, the men realized that the river was not at all navigable for any merchandise transport vessel and the steamboats had to be left behind; still, the mission spent a week studying the falls; which will ultimately end in April upon arrival in  Luang Prabang.
Evidence: At the Khone Falls, the men realized that the river was not at all navigable for any merchandise transport vessel and the steamboats had to be left behind. Still, the mission spent a week studying the falls, hoping to find a point where an average-sized river boat might be able to pass the cataracts or otherwise, whether the establishment of a lateral channel would be feasible. In April, the mission arrived in Luang Prabang, where the exhausted men rested for four weeks and obtained their passports for China. After much debate over the further route, the expedition left on 25 May 1867.