But how remote the Mound-Builders were from the era of European settlement, whence they came; how, whither, and when they vanished,--these are questions before which science stands harassed, impotent to answer positively. There are those who, marking certain apparent resemblances between the implements, religious rites and customs, and cranial formations, of the Mound-Builders, and those of the Asiatic Mongols, conclude that the former were originally Asiatic hordes, who, crossing Behring Straits, when, perhaps, the two continents were united at that point, formed a new home and established a new empire here. Others, with more proof, connect them with that great Toltec race which occupied Central America and Mexico, before they were driven out by the ruder and more warlike Aztecs. [Sidenote: The Aztecs.] The Toltecs have left ample records of their existence and gorgeous civilization, in noble monuments and very numerous though till recently undecipherable inscriptions; and many similarities lend weight to the theory that the empire of the Mound-Builders, in the Ohio, Mississippi, and Missouri valleys, was the result of a great Toltec migration from Central America, which they left to Aztec dominion. Thus while we call our continent the "New World," it is not improbable that we may be living in a country which was alive with art, splendor, invention, and power, when Europe was a dreary waste, over which the now extinct monsters roamed unmolested by man. II. THE ERA OF DISCOVERY. [Sidenote: Historic Myths.] We live in times when the researches of scholars are minute, pitiless, and exhaustive, and when no hitherto received historical fact is permitted to escape the ordeal of the most critical scrutiny. Many are the cherished historical beliefs which have latterly been assailed with every resource of logical argument and formidably arrayed proofs, unearthed by tireless diligence and pursuit. Thus we are told that the story of William Tell is a romantic myth; that Lucretia Borgia, far from being a poisoner and murderess, was really a very estimable person; and that the siege of Troy was a very insignificant struggle, between armies counted, not by thousands, but by hundreds. In the same way the old familiar question, "Who discovered America?" which every school-boy was formerly as prompt to answer as to his age and name, has in recent years become a perplexing problem of historical disputation; and at least can no longer be accurately answered by the name of the gallant and courageous Genoese who set forth across the Atlantic in 1492. [Sidenote: Icelandic Discoverers.]