Down the river sped the canoe, the paddlers with long swinging strokes easily keeping abreast of the stream. Most of the rapids they were able to shoot; and before nightfall they had completed the ninety miles to the village of which they had heard above. Tents were pitched and Thompson summoned the chiefs to smoke with him.

In a short while the chief arrived, followed by his men in single file. All sat down in a circle about the tent, and the chief made a brief speech, welcoming the strangers and offering them presents of dried salmon and native herbs. Pipes were then lighted and solemnly passed round. Following this the chief delivered a long harangue, in which he expressed the hope that the white men would provide his people with guns, ammunition, axes, knives, awls, not to mention steels and flints and many other articles of which they stood sadly in need. They were, he said, able and willing to hunt, and would pay for everything they got. At present, however, they had only their hands with which to procure food and clothing.

Thompson explained that his object was to explore the course of the river to the sea. If it proved navigable, very large canoes would come from over the ocean with goods of all kinds, and industrious hunters would be supplied with everything they required.

The colloquy finished, permission was given for the women of the tribe to approach. A dance of welcome followed, at the end of which the weary travellers were left to their repose. In this way Thompson made friends with the natives wherever he found them along the river.

As he advanced, Thompson passed out of the forest country, and entered the arid plain that lies about the confluence of the Snake river with the Columbia. Occasional willows and cottonwoods were to be seen, growing in the neighbourhood of streams; but over the greater part of this region, the only shrub capable of finding a lodging was the hardy sage. The natives he now encountered were of the unhappy Snake family, who had been driven for refuge to this barren country by the relentless pressure of their foes. Some of them fled in terror at his approach. Others, less timid, gazed with admiring eyes upon the guns, kettles, axes, and other paraphernalia of his camp. Their eagerness to obtain such wonders was in proportion to their need; for they did not appear to possess even bows and arrows or the stone axes and knives that were common among the Eskimos of the far north.

The river now turned to the west; and far ahead on his left Thompson discerned the snow-capped cone of Mount Hood, which marked the line of the Cascade Mountains near the coast. Fifty miles short of this, he came to a village at which, as usual, he put ashore. Here the natives warned him of the treacherous Dalles or rapids just ahead, where the river for a distance of two miles glides noiselessly through a cañon never more than two hundred yards wide, and the ledges of basalt, projecting into the stream, create whirlpools and eddies in which the traveller is sucked to his death. At the same time, the natives informed him that at the mouth of the river, a party of white men who had come in a great canoe from the ocean, were busy erecting a house. Thus he learned that the Astorian party had anticipated him in reaching the mouth of the Columbia.

A guide from the village carried him safely through the Dalles, was paid, and returned to the village. Fifty miles further down stream, Thompson approached "the Cascades," where the river cuts through the deep lava beds of the Cascade mountains and makes a descent of about three hundred feet. Here the cañon was no less than six miles long, and nearly a mile in depth. Trying in vain to secure a guide, Thompson entered the rapids alone. For three miles he "ran" the rapids; a portage of one mile followed, taking him past the worst stretch of the river; he then re-embarked, and emerged in safety to the quiet water below.

There was still one hundred and fifty miles to the mouth of the river; but the magnificent forests of Douglas fir, cedar, and hemlock which now clothed the country told them that they had come within the beneficient influence of the sea. Two days' paddle brought them to Tongue point, beyond which they had a full view of the ocean. To the left, not more than a couple of miles distant, they beheld four low log huts, constructed of timbers newly cut—in the words of Thompson, "the famous Fort Astoria of John Jacob Astor and the United States".

At Fort Astoria, Thompson was welcomed by Duncan McDougall and David Stuart, old colleagues in the service of the North West Company. As their guest, he spent a week at the post taking observations for its position and preparing for the return voyage. Toward the mouth of the river, the natives had been demoralized by their association with wandering traders from the sea; and remembering their surly behaviour and menacing looks, Thompson saw to it that his men had their arms in readiness. On the 22nd of July, he embarked. At the Cascades, he was forced to appeal to the natives for assistance in climbing the rapids. The scoundrels were importunate in their demands. With knives in their hands and poisoned arrows in their bows, they were ready to kill and plunder the travellers. But the courage and resolution of Thompson warded off the crisis; and once above the Cascades he was again among the poor but friendly savages of the interior. Thompson was anxious to avoid the ninety miles of rapids below Kettle Falls. When he came to the mouth of the Snake river, he turned up this stream and ascended it as far as the present Lyon's Ferry. From thence, having borrowed horses of the natives, he journeyed overland across the sterile, sandy plain as far as Spokane House; and from Spokane House, with the assistance of Jaco Finlay, he once more reached the Columbia above Kettle Falls. There, building a fresh canoe, he re-embarked and made his way through the Arrow lakes to the Boat Encampment, thus completing his survey of the Columbia from its source to its mouth.

The following winter Thompson spent inspecting his various posts, and distributing among them additional supplies of goods which he had received from beyond the mountains. From Salish House, he rode east along Clark's Fork to a hill top within the limits of the present city of Missoula; and from thence he was able to trace the route of Lewis and Clark through the Bitter Root Mountains to the banks of Snake river.