the mules usually arrived so late in the afternoon or evening that I could not depend upon being able to write at that time.  Of course, if we made a very early start I could not write at all.  At night there were no mosquitoes.  In the daytime gnats and sand-flies and horse-flies sometimes bothered us a little, but not much.  Small stingless bees lit on us in numbers and crawled over the skin, making a slight tickling; but we did not mind them until they became very numerous.  There was a good deal of rain, but not enough to cause any serious annoyance.

Colonel Rondon and Lieutenant Lyra held many discussions as to whither the Rio da Duvida flowed, and where its mouth might be.  Its provisional name—­“River of Doubt”—­was given it precisely because of this ignorance concerning it; an ignorance which it was one of the purposes of our trip to dispel.  It might go into the Gy-Parana, in which case its course must be very short; it might flow into the Madeira low down, in which case its course would be very long; or, which was unlikely, it might flow into the Tapajos.  There was another river, of which Colonel Rondon had come across the head-waters, whose course was equally doubtful, although in its case there was rather more probability of its flowing into the Juruena, by which name the Tapajos is known for its upper half.  To this unknown river Colonel Rondon had given the name Ananas, because when he came across it he found a deserted Indian field with pineapples, which the hungry explorers ate greedily.  Among the things the colonel and I hoped to accomplish on the trip was to do a little work in clearing up one or the other of these two doubtful geographical points, and thereby to push a little forward the knowledge of this region.  Originally, as described in the first chapter, my trip was undertaken primarily in the interest of the American Museum of Natural History of New York, to add to our knowledge of the birds and mammals of the far interior of the western Brazilian wilderness; and the labels of our baggage and scientific equipment, printed by the museum, were entitled “Colonel Roosevelt’s South American Expedition for the American Museum of Natural History.”  But, as I have already mentioned, at Rio the Brazilian Government, through the secretary of foreign affairs, Doctor Lauro Muller, suggested that I should combine the expedition with one by Colonel Rondon, which they contemplated making, and thereby make both expeditions of broader scientific interest.  I accepted the proposal with much pleasure; and we found, when we joined Colonel Rondon and his associates, that their baggage and equipment had been labelled by the Brazilian Government “Expedicao Scientifica Roosevelt-Rondon.”  This thenceforth became the proper and official title of the expedition.  Cherrie and Miller did the chief zoological work.  The geological work was done by a Brazilian member of the expedition, Euzebio Oliveira.  The astronomical work necessary for