(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 Winnipegoosis 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.