Lord John Roxton has chartered a large steam launch, the Esmeralda , which was to carry us up the river. So far as climate goes, it was immaterial what time we chose for our expedition, as the temperature ranges from seventy-five to ninety degrees both summer and winter, with no appreciable difference in heat. In moisture, however, it is otherwise; from December to May is the period of the rains, and during this time the river slowly rises until it attains a height of nearly forty feet above its low-water mark. It floods the banks, extends in great lagoons over a monstrous waste of country, and forms a huge district, called locally the Gapo, which is for the most part too marshy for foot-travel and too shallow for boating. About June the waters begin to fall, and are at their lowest at October or November. Thus our expedition was at the time of the dry season, when the great river and its tributaries were more or less in a normal condition.