Several factors combined to break the wilderness to the uses of the Americans into whose possession it eventually fell. One of these, and it was one of the most important in its effect on primary exploration, was the presence there in vast numbers of a comparatively small and singularly intelligent animal called the beaver, belonging to the order _Rodentia_. While not of great size it was, nevertheless, with one exception, the largest of its kind, weighing thirty or forty pounds and being about three and one-half feet long. In colour it was chestnut brown and was endowed with a rich, thick fur, one-half to three-quarters inch long, with coarse hair scattered through it about one inch longer. It so happened that this particular quality of fur was in great commercial demand in Europe for the making of hats. For some time it had constituted an article of profitable export from the eastern part of the continent, as the similar animal in Europe had been exterminated. Finally the supply from America also diminished as the trappers pursued their merciless task. Then followed the discovery that the great wild region west of the Mississippi contained beaver in immense numbers, and beaver trapping immediately became the principal quest of many bold natures eager to stake their lives in a tilt with Fortune, just as others later played a different game with the golden gravels of California. [Illustration: The Mountain Part of the Wilderness. Relief map by E. E. Howell.] [Illustration: No Place for Beaver. Photograph by J. K. Hillers, U. S. Geol. Survey.]