Doubtless the weary gaze of the tired voyageurs turned longingly westward.  Where was the Western Sea?  Did it lie just beyond the horizon where skyline and prairie met, or did the trail of their quest run on—­on—­on—­endlessly?  The Assiniboine flows into the Red, the Red into Lake Winnipeg, the Lake into Hudson Bay.  Plainly, Assiniboine Valley was not the way to the Western Sea.  But what lay just beyond this Assiniboine Valley?  An old Cree chief warned the boatmen that the Assiniboine River was very low and would wreck the canoes; but he also told vague yarns of “great waters beyond the mountains of the setting sun,” where white men dwelt, and the waves came in a tide, and the waters were salt.  The Western Sea where the Spaniards dwelt had long been known.  It was a Western Sea to the north, that would connect Louisiana and Canada, that De la Verendrye sought.  The Indian fables, without doubt, referred to a sea beyond the Assiniboine River, and thither would De la Verendrye go at any cost.  Some sort of barracks or shelter was knocked up on the south side of the Assiniboine opposite the flats.  It was subsequently known as Fort Rouge, after the color of the adjacent river, and was the foundation of Winnipeg.  Leaving men to trade at Fort Rouge, De la Verendrye set out on September 26, 1738, for the height of land that must lie beyond the sources of the Assiniboine.  De la Verendrye was now like a man hounded by his own Frankenstein.  A thousand leagues—­every one marked by disaster and failure and sinking hopes—­lay behind him.  A thousand leagues of wilderness lay before him.  He had only a handful of men.  The Assiniboine Indians were of dubious friendliness.  The white men were scarce of food.  In a few weeks they would be exposed to the terrible rigors of Northern winter.  Yet they set their faces toward the west, types of the pioneers who have carved empire out of wilderness.

[Illustration:  The Ragged Sky-line of the Mountains.]

The Assiniboine was winding and low, with many sand bars.  On the wooded banks deer and buffalo grazed in such countless multitudes that the boatmen took them for great herds of cattle.  Flocks of wild geese darkened the sky overhead.  As the boats wound up the shallows of the river, ducks rose in myriad flocks.  Prairie wolves skulked away from the river bank, and the sand-hill cranes were so unused to human presence that they scarcely rose as the voyageurs poled past.  While the boatmen poled, the soldiers marched in military order across country, so avoiding the bends of the river.  Daily, Crees and Assiniboines of the plains joined the white men.  A week after leaving the Forks or Fort Rouge, De la Verendrye came to the Portage of the Prairie, leading north to Lake Manitoba and from the lake to Hudson Bay.  Clearly, northward was not the way to the Western Sea; but the Assiniboines told of a people to the southwest—­the Mandans—­who knew a people who lived on the Western Sea.  As soon as his baggage came up, De la Verendrye ordered the construction of a fort—­called De la Reine—­on the banks of the Assiniboine.  This was to be the forwarding post for the Western Sea.  To the Mandans living on the Missouri, who knew a people living on salt water, De la Verendrye now directed his course.