(4) It was his special duty to determine the exact position of the posts of the North-West Company visited by him, and all agents and employés were instructed to render him every assistance in his work.
Astronomer Thompson only waited the departure of one of the Great Northern brigades to enter upon the duties of his new office. These departures were the events of the year, having in the eyes of the fur-traders something of the nature of a caravan for Mecca about them. Often a brigade consisted of eight canoes laden with goods and well-manned. The brigade which Thompson accompanied was made up of four canoes under trader McGillies, and was ready to start on August 9th, 1796. He had taken the observation for Grand Portage and found it to be 48 deg. (nearly) N. latitude and 89 deg. 3´ 4´´ (nearly) W. longitude.
He was now ready with his instruments—a sextant of ten inches radius, with quicksilver and parallel glasses, an excellent achromatic telescope, one of the smaller kind, drawing instruments, and a thermometer, and all of these of the best make. The portage was wearily trudged, and in a few days, after a dozen shorter portages, the height of land was reached in 48 deg. N. latitude, and here begins the flow of water to Hudson Bay. It was accordingly the claim of the Hudson's Bay Company that their territory extended from this point to the Bay. At the outlet of Rainy Lake still stood a trading post, where Verendrye had founded his fort, and the position of this was determined, 48 deg. 1´ 2´´ N. latitude. In this locality was also a post of the Hudson's Bay Company.
No post seems at this time to have been in use on Rainy River or Lake of the Woods by any of the trading companies, though it will be seen that the X Y Company was at this date beginning its operations. At the mouth of the Winnipeg River, however, there were two establishments, the one known as Lake Winnipeg House, or Bas de la Rivière, an important distributing point, now found to be in 50 deg. 1´ 2´´ N. latitude. There was also near by it the Hudson's Bay Company post, founded in the previous year.
Thompson, being in company with his brigade, which was going to the west of Lake Manitoba, coasted along Lake Winnipeg, finding it dangerous to cross directly, and after taking this roundabout, in place of the 127 miles in a straight line, reached what is now known as the Little Saskatchewan River on the west side of Lake Winnipeg.
Going by the little Saskatchewan River through its windings and across the meadow portage, he came to Lake Winni pegoosis and, northward along its western coast, reached Swan River, the trappers' paradise. Swan River post was twelve miles up the river from its mouth, and was found to be in 52 deg 24´ N. latitude. Crossing over to the Assiniboine (Stone Indian) River, he visited several posts, the most considerable being Fort Tremblant (Poplar Fort), which some think had its name changed to Fort Alexandria in honour of Sir Alexander Mackenzie.
John McDonnell, North-West trader of this period, says:—"Fort Tremblant and the temporary posts established above it furnished most of the beaver and otter in the Red River returns, but the trade has been almost ruined since the Hudson's Bay Company entered the Assiniboine River by the way of Swan River, carrying their merchandise from one river to the other on horseback—three days' journey—who by that means, and the short distance between Swan River and their factory at York Fort, from whence they are equipped, can arrive at the coude de l'homme (a river bend or angle) in the Assiniboine River, a month sooner than we can return from Grand Portage, secure the fall trade, give credits to the Indians, and send them to hunt before our arrival; so that we see but few in that quarter upon our arrival."
The chief trader of this locality was Cuthbert Grant, who, as before mentioned, was a man of great influence in the fur trade.
The astronomer next went to the Fort between the Swan and Assiniboine Rivers, near the spot where the famous Fort Pelly of the present day is situated. Taking horses, a rapid land journey was made to Belleau's Fort, lying in 53 deg. N. latitude (nearly).
The whole district is a succession of beaver meadows, and had at this time several Hudson's Bay Company posts, as already mentioned. Thompson decided to winter in this beaver country, and when the following summer had fairly set in with good roads and blossoming prairies, he came, after journeying more than 200 miles southward, to the Qu'Appelle River post, which was at that time under a trader named Thorburn. Thompson was now fairly on the Assiniboine River, and saw it everywhere run through an agreeable country with a good soil and adapted to agriculture.