Over this country, Thompson made a series of rapid excursions by horse and canoe, in order that he might fix the location of the various trading houses of the North West Company. In the course of five weeks, he had crossed to the basins of the Red Deer and the Assiniboine rivers, and surveyed each of these streams to its source. He then descended the Assiniboine to its confluence with the Souris, near where the city of Brandon now stands. Here toward the end of November he put up at Assiniboine House, which was at that time kept by a trader called John McDonnell. McDonnell's house was the natural point of departure for the journey across to the Mandan Villages on the upper Missouri. The trail lay in a south-westerly direction along the south bank of the Souris river as far as the great bend, and from thence across the open plains to the heights of the Missouri. As the country was generally treeless, the custom of travellers was to move from point to point where patches of wood growing in the river bottom or at the higher levels afforded firewood and shelter for the night. Winter had come, and three inches of snow lay upon the ground, making travel both disagreeable and dangerous. Worse still, the road passed through the hunting grounds of the Sioux Indians, those wild riders of the plains who lived by pursuit of the bison. The Sioux had lately suffered the loss of several men at the hands of the Mandan Indians; and these losses they blamed on the whites who had supplied the Mandans with guns and ammunition. They were therefore in a very menacing temper, and had determined to waylay, scalp, and plunder the next party of traders who ventured the journey to the villages. Thompson, however, was not to be deterred; and he made his preparations for the dash across the plains. As guide and interpreter, he engaged a man who had resided for eight years among the Mandans, by name René Jussomme. He also picked up a light-hearted Irishman, Hugh McCrachan, who had often been to the villages for months at a time. The rest of the party was made up of French Canadians, gay and gluttonous vagabonds, who could nevertheless work as hard as they boasted, and hunt as much as they ate. All these men enlisted for the expedition as free traders; that is to say, each of them borrowed from McDonnell goods and trinkets to the value of fifty beaver skins, which he undertook to repay on his return. Thompson himself was supplied with two horses, and ammunition and tobacco for trade. Jussomme had one horse; while the men each bought two half-savage dogs from the Assiniboines. These were to haul their sled-loads of goods across the plains.