The chief's name was, I found, Aguskogaut.  The tribe into whose hands I had fallen were Sioux, who live entirely on the prairies, and subsist by hunting the buffalo.  They had come further east than they generally venture, in order that their warriors might make predatory excursions against the more pacific and civilised Indians living near the white men.  They seemed to have no fear of being attacked by the latter, as, being well supplied with horses, they could beat a rapid retreat to the westward; and I discovered that they had scouts out in all directions to give notice of the approach of a foe.