DOWLING, D. B. _General Index to the Reports of Progress_ [of the Geological Survey of Canada], _1863-1884_. Published by the Canadian Geological Survey, Ottawa, Canada, 1900. WARMAN, P. C. _Catalogue and Index of the Publications of the United States Geological Survey, 1880 to 1901._ Published as Bulletin No. 177 of the United States Geological Survey, Washington, D. C., 1901. WEEKS, F. B. _Bibliography of North American Geology, Paleontology, Petrology, and Mineralogy for the Years 1892-1900, Inclusive._ United States Geological Survey, Bulletins No. 188 and 189, Washington, D. C., 1902. Of the numerous general treatises on the geology, the following will be found especially helpful to the student: DANA, J. D. _Manual of Geology._ Fourth edition. American Book Company, New York, 1895. KEMP, J. F. _The Ore Deposits of the United States and Canada._ Scientific Publishing Company, New York, 1900. LE CONTE, J. _Elements of Geology._ Fifth edition, revised and partly rewritten by Prof. H. L. Fairchild. D. Appleton and Company, New York, 1903. MERRILL, G. P. _A Treatise on Rocks, Rock-Weathering, and Soils._ The Macmillan Company, New York, 1897. SHALER, N. S. _Outlines of the Earth's History._ D. Appleton and Company, New York, 1898. CHAPTER VII THE ABORIGINES At the time the Western Hemisphere became known to Europeans, as has been shown by subsequent explorations, it was inhabited by native tribes from the Atlantic to the Pacific and from the extreme north to Patagonia. The aborigines were distributed principally along the coast, about the borders of lakes, and on the margins of streams, but much of the interior was also inhabited or roamed over by hunting and war parties, or crossed by various tribes during their migrations. Large areas, it is true, more especially among the rugged mountains, in the great subarctic forest, and on the trackless tundras, had no permanent residents, but in general terms the entire land was inhabited. In spite of the reports as to the density of the aboriginal population made by several early explorers, who for the most part followed the waterways, visited the most thickly inhabited regions, and saw the natives when brought together by motives of curiosity or defence, it is now known that North America, considering its vast extent, was but sparsely peopled. As to the number of the inhabitants, there is no even approximately accurate knowledge. The greatest density of population, so far as can be judged, was in the tropical region, and decreased northward in a general way in conformity with change in latitude, but varied also in a conspicuous manner in accord with local climatic and topographic influences.