On the 27th of March he began his his journey eastward up the Clearwater river into Minnesota, picking up a guide from some Chippewas whom he found on the way. As the day wore on, the rays of the sun increased in power, and walking became difficult in the thawing snow. The night was mild, and the following morning the guide took care to break his snow-shoes that he might have an excuse for returning to camp. The day was wasted, while Thompson waited impatiently for another guide to be sent to take the place of the first. At sundown a storm came on with thunder, lightning, and rain, which continued the night through and far into the next day. The snow was now so heavy that progress was impossible. The continuous rains had soaked the clothes and the baggage of the party through and through. The fourth day opened with gusts of hail and sleet. The country before them was like a lake, and Thompson was compelled to admit himself beaten. Splashing and stumbling through the bush and along the treacherous ice of the river, the party struggled to make their way back to the protecting shelter of Cadotte's roof. But their baggage was too much for them, and they had to give in. Finally Thompson with one man, travelling light, pressed forward to the post for help; and by the afternoon of the second day the weary travellers were brought safely into camp. When the rivers were finally clear of ice, Thompson, with his three Canadians and a native woman, made a fresh start, this time by canoe and with dried provisions to last for twelve days. They had first to battle their way against the current of Clearwater river, to the portage which brought them to Red lake. The country was everywhere soaked with water, so that at night they were forced to cut down trees and sleep on the branches. Red lake, they found, was still covered with patches of broken ice. Hauling and paddling their canoe in turn they crossed the lake, and entered an immense area of pond and marsh to the south. Everywhere stretched beds of wild rice, the haunt of innumerable geese, duck, and loon. With infinite toil they made their way from lake to lake and brook to brook, until after five days in the marsh they arrived at Turtle lake. This lake Thompson took to be the true source of the Mississippi. Twenty years later American surveyors reached the conclusion that, of all the ponds whose waters join to form the Mississippi, Lake Itaska most deserved the name. Lake Itaska lies a few miles to the south and west of Turtle lake. Yet this fact hardly suffices to rob David Thompson of the glory of being the first man to fix the point from which the Father of Waters takes its rise.