The same traveler adds: “When you ask the natives how the hieroglyphic characters carved on the mountains of Urbana and Encaramada could have been traced, they reply that this was done in the age of the great waters, at the time when their fathers were able to reach the heights in their canoes.” If these legends and these petroglyphs are proof of an extinct civilization, it is astonishing that their authors should have left no other traces of their culture. To come to the point, is it admissible that they were replaced by savage tribes without leaving a trace of what they had been, and can we understand this retrograde march of civilization when progress everywhere follows an ascending course? These destructions of American tribes in place are very convenient to prop up theories, but they are contrary to ethnologic laws. The remarkable height of some petroglyphs has misled authors of good repute as well as savages. Petroglyphs frequently appear on the face of rocks at heights and under conditions which seemed to render their production impossible without the appliances of advanced civilization, a large outlay, and the exercise of unusual skill. An instance among many of the same general character is in the petroglyphs at Lake Chelan, Washington, where they are about 30 feet above the present water level, on a perpendicular cliff, the base of which is in the lake. On simple examination the execution of the pictographic work would seem to involve details of wharfing, staging, and ladders if operated from the base, and no less elaborate machinery if approached from the summit. Strahlenberg suggests that such elevated drawings were made by the ingenious use of stone wedges driven into the rock, thus affording support for ascent or descent, and reports that he actually saw such stone wedges in position on the Yenesei river. A very rough geological theory has been presented by others to account for the phenomena by the rise of the rocks to a height far above the adjacent surface at a time later than their carving.