The travellers soon settled in a _rocinha_, or country-house, a mile and half from Pará, and close to the forest, which came down to their doors. Like other towns along the Amazons, Pará stands on ground cleared from the forest that stretches, a well-nigh pathless jungle of luxuriant primeval vegetation, two thousand miles inland. In that paradise of the naturalist, the collectors gathered consignments which met with ready sale in London, and thus spent a couple of years in pursuits moderately remunerative and wholly pleasurable, till, on reaching Barra, at the mouth of the Rio Negro, one thousand miles from Pará, in March, 1850, Bates and Wallace, who was accompanied by his younger brother, parted company, "finding it more convenient to explore separate districts and collect independently." Wallace took the northern parts and tributaries of the Amazons, and Bates kept to the main stream, which, from the direction it seems to take at the fork of the Rio Negro, is called the Upper Amazons or the Solimoens. Different in character and climatic conditions from the Lower Amazons, it flows through a "vast plain about a thousand miles in length, and five hundred or six hundred miles in breadth covered with one uniform, lofty, impervious, and humid forest." Bates stayed in the country till June, 1859, but Wallace left in 1852, and in the following year published an account of his journey under the title of Travels on the Amazon and Rio Negro. That book was written under the serious disadvantage of the destruction of the greater part of the notes and specimens by the burning of the ship in which Mr. Wallace took passage on his homeward voyage. That it remains one of the select company of works of travel for which demand is continuous is evidenced in a reprint which appeared in 1891. If it affords few hints of the author's bent of mind toward the question of the origin of species, it shows what interest was being aroused within him over the allied subject of the geographical distribution of plants and animals which Mr. Wallace was to make so markedly his own.