Towards the spring of 1799 Thompson had been on the North Saskatchewan and had moved round the region of Lesser Slave Lake. That year, at Grand Portage, at the annual meeting of the traders of the North-West Company, he was ordered to begin a thorough exploration of the mountains; and the spring of 1800 saw him at Rocky Mountain House[1] on the upper reaches of the North Saskatchewan above the junction of the Clearwater. Hitherto the Nor'westers had crossed the {102} mountains by way of the Peace river. But Thompson was to explore a dozen new trails across the Great Divide. While four of his men crossed over to the Red Deer river and rafted or canoed down the South Saskatchewan, Thompson himself, with five French Canadians and two Indian guides, crossed the mountains to the Kootenay country. The Kootenay Indians were encamped on the Kootenay plains preparatory to their winter's hunt, and Thompson persuaded some of them to accompany him back over the mountains to Rocky Mountain House on the North Saskatchewan. This was the beginning of the trade between the Kootenays and white men. Probably from these Indians Thompson learned of the entrance to the Rockies by the beautiful clear mountain-stream now named the Bow; and Duncan M'Gillivray, a leading partner, accompanied him south from Rocky Mountain House to the spot on the Bow where to-day the city of Calgary stands. It was on this trip that Nor'westers first met the Piegan Indians. From these horsemen of the plains the explorers learned that it was only a ten-day journey overland to the Missouri. Snow was falling when the traders entered the Rockies at what is now the Gap, on the {103} Canadian Pacific Railway. Inside the gateway to the rugged defile of forest and mountain the traders revelled in the sublime scenery of the Banff valley. At Banff, eastward of Cascade mountain, on the sheltered plain where Kootenays and Stonies used to camp, one can still find the circular mounds that mark a trading-station of this era. Whether the white men discovered the beautiful blue tarn now known as Devil's Lake, or saw the Bow river falls, where tourists to-day fish away long summer afternoons, or dipped in the famous hot springs on the slope of Sulphur mountain, we do not know. They could hardly have met and conversed with the Kootenays and Stonies without hearing about these attractions, which yearly drew Indian families to camp in the encircling mountains, while the men ranged afield to hunt. Thompson and M'Gillivray were back at Rocky Mountain House on the Saskatchewan for Christmas. Some time during 1800 their French-Canadian voyageurs are known to have crossed Howse Pass, the source of the North Saskatchewan, which was discovered by Duncan M'Gillivray and named after Joseph Howse of the North-West Company.