Thompson, nevertheless, was not to be deterred from his enterprise. He proceeded at once to Fairford House, the trading post kept by Malcolm Ross on the Churchill near the mouth of the Reindeer river, where he hoped to get some assistance. To his great disappointment, he found that not a man could be spared from the trade in furs. There were, however, a few Chepawyan Indians lingering about the fort and from among these he managed to engage two young men. Kozdaw and "Paddy" had hunted for two winters in the country he was about to explore, although neither of them had ever been on the rivers and lakes in summer. Their only practice in canoes had been to lie offshore in the lakes on a calm day, watching for the deer to take refuge from the flies, and this gave them no experience of the currents and rapids of rivers; yet, such as they were, Thompson had no choice but to take them.

The first task was to construct a canoe. Having searched the forest for a supply of birch bark, they made a boat seventeen feet in length. Into this they packed their meagre outfit, a fowling piece with forty balls, five pounds of shot, three flints and five pounds of powder, a fishing net, a hatchet and a small tent of grey cotton. These articles, together with a few handfuls of beads, rings, and awls for trading, made up their terribly inadequate equipment.

In the grey dawn of a June morning, 1796, Thompson launched his canoe on the turbid waters of the Missinippi. The party advanced rapidly, making a survey as they went. For supplies they relied on their solitary net and gun. Turning into the Reindeer river, they worked their way north against a moderate current to Reindeer lake. A hundred miles up the west coast of this lake brought them to a point clothed with tolerably good pines. This point Thompson noted as a suitable site for building a trading post on his return.

The whole distance through which they had come had a barren, rocky appearance, relieved only by patches of stunted birch, aspen, and spruce. Since there was little or no soil, the trees stood with their roots interlaced like the trees on the frozen lands of Hudson Bay; and, like them, they were kept moist in summer by the wet moss with which their roots were covered. Through wide stretches the forest fires had passed, leaving the country unsightly and ghostlike, and destroying the wild animals of the forest. Thompson was now in fact approaching the northern limit of trees, beyond which stretch the barren lands, the home of the musk ox and caribou.

In order to avoid the wide circuit of the Cochrane river, which flows to Reindeer lake from Lake Wollaston, the guides directed Thompson up a stream that emptied from the west a few miles north of his point of pines. From the head of this stream there was a passage by a series of ponds and brooks to the south end of Wollaston lake. But the water was low, and they were forced to carry their packs for the better part of fifty miles, stumbling over the rocks and wading through the marshes, while clouds of mosquitoes buzzed about their defenceless heads. It was a welcome relief when they launched out on the clear and deep waters of Lake Wollaston, which they crossed without trouble to the Black river. Here they made camp on the evening of June 23, and rested while Thompson took observations and made up the notes of his survey.

Two days later they were once more under way. Lake Wollaston, as Thompson discovered, was situated on the height of land between the basins of Hudson Bay and the Mackenzie river. Part of its waters discharged eastward and south into Reindeer lake, while part flowed westward through the Black river into Lake Athabaska. From this curious circumstance, the lake was known to the Indians as "Lake Manito," and was considered to be of supernatural character. Entering the Black river, the party passed at first through the quiet reaches of the upper river, in a wretched country of solitude, where the wild laugh of the loon alone woke the echoes of the barren hills. Presently the banks closed in, and as the current stiffened, they had to paddle vigorously to avoid the projecting rocks. Finally an expansion of the stream brought them to Black lake. It was during this stretch that they came upon the only human beings they had so far encountered—five tents of Chepawyans, hunting and fishing in an otherwise deserted land.

They could afford but one day to enjoy the hospitality of the Indians. From Black lake, the river tumbles in two wild cascades to the level of Lake Athabaska. A series of rapids, cutting through a high hill, warned them that they were approaching the first of the falls. For half a mile they shot the rapids to a point where the river is compressed within a channel only twelve yards in width. At the end of this channel, the current rushed against a projecting ledge of rock with such force that the whole river seemed to be turned up from its bottom. The dashing of the water against the rocks, the deep roar of the torrent, the hollow sound of the fall, in the midst of the dark, high, and frowning hills, made a sight so grand and terrible that Kozdaw and Paddy were awe-struck, and offered their simple tributes to the manito of the fall—the one a bit of tobacco, the other a ring. Past this fall the travellers descended by a well-beaten native trail. A second series of rapids and a second fall brought them to the last lap of their journey, and they paddled quietly for six miles into the east end of Lake Athabaska. Here they passed the night, resting from their dangers, toils, and sufferings under a pine tree which had been lopped and marked by Philip Turnor in his survey of 1791.

Thompson's heart was thrilled by the thought that he had finally accomplished the journey on which for the last five years his heart had been set, and that in so doing he had blazed a trail through the wilderness over ground which the feet of white men had never trod before. He was sobered, however, by the prospect of the long and difficult journey home. His net and gun afforded but a scanty supply of food, and should these fail him, there was but slight hope of succour. But gloomy as were his forebodings, it was well that he did not know what lay before him.

Half way up the Black river, he encountered one of the rapids which was broken about the middle by a twelve-foot fall. Portaging past the fall, he attempted to "track" the canoe up the rest of the rapid. The two Indians were ashore tugging at the tow-line, while Thompson in the canoe tried to steer and at the same time direct their movements. Near the head of the rapid there was at the water's edge a tree which blocked their progress, and as the Indians stood hesitating which side of it they should pass, the canoe sheered off across the current. An upset was inevitable, had not Thompson waved to the Indians to let go the line and leave him to his fate. Springing to the bow, he cut the rope off short with the clasp knife which he kept in his waistcoat pocket, and got the head of the canoe around into the stream just in time to take the plunge over the cataract. For an instant, Thompson was buried beneath the boiling water at the foot of the fall. Striking his feet against the bottom, he pushed himself to the surface close to the upturned canoe. This he seized and dragged through shallow water to the beach. The Indians came rushing to his assistance, and, while he lay on the rocks, bruised, bleeding, and exhausted by his exertions, they searched the shore below the rapids for what could be recovered of their precious kit.

The gun, the axe, and the tent had remained fastened in the canoe. In half an hour's time, the Indians brought back the cork-lined box containing Thompson's instruments and the maps of his survey, together with their three paddles and a pewter basin. Not one moment was to be lost. Thompson's body was naked except for his shirt and a thin linen vest, and his companions were in like condition. The small tent they tore into three pieces with which to wrap themselves as a defence against flies by day and chill by night. Worse still, Thompson found as he painfully raised himself from the rocks that the flesh of his foot had been torn away by the impact of the jagged stones of the river bed, and a part of his share of the tent had to be taken to bind the wound.