On the afternoon of the 2d of August we commenced our journey, having, in addition to our three canoes, a smaller one to convey the women; we were all in high spirits, being heartily glad that the time had at length arrived when our course was to be directed towards the Copper-Mine River, and through a line of country which had not been previously visited by any European. We proceeded to the northward, along the eastern side of a deep bay of the lake, passing through various channels, formed by an assemblage of rocky islands; and, at sunset, encamped on a projecting point of the north main shore, eight miles from Fort Providence. To the westward of this arm, or bay, of the lake, there is another deep bay, that receives the waters of a river, which communicates with Great Marten Lake, where the North-West Company had once a post established. The eastern shores of the Great Slave Lake are very imperfectly known: none of the traders have visited them, and the Indians give such loose and unsatisfactory accounts, that no estimation can be formed of its extent in that direction. These men say there is a communication from its eastern extremity by a chain of lakes, with a shallow river, which discharges its waters into the sea. This stream they call the Thlouee-tessy{ 54}, and report it to be navigable for Indian canoes only. The forms of the south and western shores are better known from the survey of Sir Alexander Mackenzie, and in consequence of the canoes having to pass and repass along these borders annually, between Moose-Deer Island and Mackenzie's River. Our observations made the breadth of the lake, between Stony Island, and the north main shore, sixty miles less than it is laid down in Arrowsmith's map; and there is also a considerable difference in the longitude of the eastern side of the bay, which we entered.
This lake, owing to its great depth, is seldom completely frozen over before the last week in November, and the ice, which is generally seven feet thick, breaks up about the middle of June, three weeks later than that of the Slave River. The only known outlet to this vast body of water, which receives so many streams on its north and south shores, is the Mackenzie's River.