These mythical water-courses, which had been eliminated from the domain of geography by Bonneville's map of 1837, proved indeed to be veritable waters of the desert, mere mirages that nearly led Frémont to an untimely fate. Frémont's frequent allusions in his field journal to these imaginary streams show his then belief in their existence, which appears extraordinary in view of existing publications. In Bonneville's maps are charted with general accuracy the great interior basins of the Great Salt, Mud, and Sevier Lakes, the Humboldt and Sevier Rivers. The general extent and direction of the Willamette, Sacramento, and San Joaquin Rivers are indicated, and the non-existence of the Buenaventura and other hypothetical streams was conclusively determined. The existence of these maps was generally known, and their absence from Frémont's topographic outfit is remarkable; a most unfortunate omission, as Benton in his "Thirty Years' View" describes Frémont's charts and geographic information as "disastrously erroneous." Struggling along in the snow through a forest of unknown extent, Frémont halted, on December 16th, on the verge of a rocky precipice, from which the party looked down more than one thousand feet upon a broad lake, the most westerly waters of the great interior basin, which, from its pleasing contrast to the wintry weather of the Sierra Nevada, they called Summer Lake. Attempting to travel in an easterly direction Frémont found himself beaten back by an impassable country, there being rocky, sterile mountains on either side which obliged him to keep to the south through a wild, barren, and uninhabited region. Frémont, describing the country, says: "On both sides the mountains showed often stupendous and curious-looking rocks, which at several places so narrowed the valley that scarcely a pass was left for the camp. It was a singular place to travel through--shut up in the earth, a sort of chasm, the little strip of grass under our feet, the rough walls of bare rock on either hand, and the narrow strip of sky above."