sent many citizens of the early Trans-Allegheny commonwealths to the Spanish side of the Mississippi,[411] while the Natchez District on the east bank of the river contained a sprinkling of French who had become dissatisfied with Spanish rule in Louisiana and changed their domicile. These are some of the movements of individuals and groups which contribute to the blending of races along every frontier, and make of the boundary a variable zone, as opposed to the rigid artificial line in terms of which we speak. NOTES TO CHAPTER VII [326] A.W. Greely, Report of the Lady Franklin Bay Expedition, Vol. I, pp. 28-33, 236. Misc. Doc. No. 393. Washington, 1888. [327] A.P. Engelhardt, A Russian Province of the North, pp. 123-130. Translated from the Russian. London, 1899. [328] Nordenskiold, Voyage of the Vega, pp. 60-62. New York, 1882. [329] _Ibid._, pp. 146, 161. [330] Col. F.E. Younghusband, The Heart of a Continent, pp. 194-199. London, 1904. [331] A.R. Wallace, Geographical Distribution of Animals, Vol. I, pp. 387-389, 426-431, 436-438. London, 1876. [332] _Ibid._, 409, 424. [333] A. Heilprin, Geographical Distribution of Animals, pp. 105-108. London, 1894. [334] A.R. Wallace, Geographical Distribution of Animals, Vol. I, pp. 313, 321-322. London, 1876. [335] Anatole Leroy-Beaulieu, The Empire of the Tsars, Vol. I, ethnographical map. New York, 1893. [336] Eleventh Census of the United States, _Population_, Part I., maps on pp. xviii-xxiii. [337] L. March Phillipps, In the Desert, pp. 64-68, 77. London, 1905. [338] Fully treated in E.C. Semple, American History and Its Geographic Conditions, pp. 22-31. Boston, 1903. [339] Sir S.W. Baker, The Nile Tributaries of Abyssinia, pp. 88, 128-129, 135. Hartford, 1868. [340] Norway, Official Publication for the Paris Exhibition, pp. 3-4 and map. Christiania, 1900. [341] J. Partsch, Central Europe, p. 297. London, 1903. [342] Caesar, _Bello Gallico_, Book IV, chap. 3 and Book VI, chap. 23. [343] _Ibid._, Book VI, chap. 10. [344] T. Hodgkin, Italy and Her Invaders, Vol. II, p. 56, Note I. Oxford, 1892. [345] Helmolt, History of the World, Vol. IV, p. 510. New York, 1902-1906. [346] Grote, History of Greece, Vol. IX, chap. 70, pp. 99, 115. New York, 1859. [347] Dr. Wilhelm Junker, Travels in Africa, pp. 18, 45, 79, 87, 115, 117, 138, 191, 192, 200, 308, 312, 325, 332. Translated from the German. London, 1892. [348] H. Barth, Human Society in North Central Africa, _Journal Royal Geographical Society_, Vol. XXX, pp. 123-124. London, 1860. [349] Boyd Alexander, From the Niger to the Nile, Vol. II, pp. 163-164. London, 1907. [350] John H. Speke, Discovery of the Sources of the Nile, pp. 74, 89, 91, 94, 95, 173, 176-177, 197. New York, 1868. [351] Theodore Roosevelt, The Winning of the West, Vol. I, pp. 50, 70, 135. New York, 1895. [352] C. C. Royce, The Cherokee Nations of Indians, p. 140. _Fifth Annual Report of the Bureau of Ethnology_. Washington, 1884.