After a long and somewhat stormy series of negotiations, Texas, first visited by La Salle in his vain quest for the mouth of the Mississippi, and afterward colonized by the Spanish from Mexico, was ceded to the all-powerful American republic, and, being rapidly settled by enterprising emigrants from the East, it soon in its turn formed the starting-point for new expeditions westward. First California, and then Arizona and New Mexico, became the property of the United States, while the intervening districts between the first state on the Pacific seaboard to become the property of the American republic and the Mississippi were gradually filled up by an ever-increasing tide of emigration from the East and from the South, from the North and from the West. Step by step, little by little, the red men receded before the march of the whites, making every now and then a deeply pathetic, but ever futile attempt to stem the advance of their insidious destroyers. What was originally a vast population of some millions of aborigines――ranking among them, to quote the words of their great historian, Hubert Howe Bancroft, “every phase of primitive humanity, from the reptile-eating cave-dweller of the Great Basin to the Aztec and Maya-Quiché civilization of the southern table-land ... vanished at the touch of European civilization, and their unwritten history, reaching back for thousands of ages, ended.... Their strange destinies fulfilled, in an instant they disappeared, and all we have of them besides their material relics is the glance caught in their hasty flight, which gives us a few customs and traditions, and a little mythological history.” Simultaneously with the advance of the Americans westward, the districts now collectively known as British America were being rapidly opened up by enterprising explorers of various nationalities; but, to avoid any further break in the continuity of our narrative, we will reserve our account of the Hudson’s Bay and other companies who took part in the great work in the North for a future chapter. We will follow first the fortunes of the earliest heroes sent forth by the United States Government to survey the regions west of the Mississippi, which, when purchased, were as little known as the heart of Africa before the journeys of Livingstone, Butler, Speke, Grant, Baker, Stanley, and others. Illustration: THE UPPER MISSOURI. CHAPTER X. PIKE’S VOYAGE UP THE MISSISSIPPI, AND DISCOVERY OF THE SOURCE OF THE ARKANSAS; THE DISCOVERY OF THE SOURCES OF THE MISSOURI BY LEWIS AND CLARKE, AND THEIR VOYAGE DOWN THE COLUMBIA TO THE PACIFIC.