La Salle's people, hearing no mention of his ship all this while, began first to murmur, and then to leave him: six of them deserted in one night. In other respects events occurred ominous of evil for the termination of the enterprise. To occupy the attention of his companions, and prevent them from brooding on apprehended ills, as well as to guard them against a surprise by any hostile natives, he set them on erecting a fort upon an eminence, at a place four days' journey distant from Lake Peoria; which, when finished, he named Breakheart (_Crevecoeur_), in allusion to the mental sufferings he then endured. To put an end to an intolerable state of suspense, in his own case he resolved to set out on foot for Frontenac, four hundred or five hundred leagues distant--hoping there to obtain good news about the Griffin; also in order to obtain equipments for a new bark, then in course of construction at Crevecoeur, in which he meant to embark upon his return thither, intending to descend the Mississippi to its embouchure. He charged Pere Hennepin to trace the downward course of the Illinois to its junction with the Mississippi, then to ascend the former as high as possible and examine the territories through which its upper waters flow. After making Tonti captain of the fort in his absence, he set out, March 2, 1680, armed with a musket, and accompanied by three or four whites and one Indian.[1] [Footnote 1: Charlevoix, by following the relation attributed to Tonti, has fallen into some obvious errors respecting La Salle's expedition to the Illinois River. Hennepin, an ocular witness, is assuredly the best authority, corroborated, as his narration is, by the relation and letters of Pere Zenobe Mambre.] Pere Hennepin, who left two days before, descended the Illinois to the Mississippi, made several excursions in the region around their confluence; then ascended the latter to a point beyond the Sault St. Antony, where he was detained for some months by Sioux Indians, who only let him go on his promise to return to them next year. One of the chiefs traced on a scrap of paper the route he desired to follow; and this rude but correct chart, says Hennepin, "served us truly as a compass." By following the Wisconsin, which falls into the Mississippi, and Fox River, when running in the opposite direction, he reached Lake Michigan mission station, passing through, intermediately, vast and interesting countries. Such was the famous expedition of Hennepin; who, on his return, was not a little surprised to find a company of fur-traders near the Wisconsin River, led by one De Luth, who had probably preceded him in visiting that remote region.