It is unfortunate that, notwithstanding the rich mineralogical and agricultural character of Mexico, no thoroughly accurate survey or geological examination has ever been made of the whole country. There is no complete map of the territory which may be confidently relied on. The enterprise of developing Mexico, since the foundation of the colonial government by Spain has been almost entirely abandoned to private enterprise, and, consequently the valuable information, collected by individuals, either perished in their hands after it had been used for their own benefit, or, if imparted to the government, has never been united and collated with other accounts and reconnoissances which were in the hands of national authorities. A great deal was done by Baron Alexander Humboldt, during his visit to New Spain early in this century, towards gathering the geographical, geological and statistical information which was then in existence, though scattered, far and wide, over the viceroyalty, in a thousand different hands. His voluminous work is an enduring monument to his industry and talent; but there is necessarily a great deal of it that was altogether transitory in its character both on account of the political and social revolution which has since occurred, and in consequence of the opening, by the republic, of Mexican ports to the commerce of the world. Nevertheless, at the period of Humboldt's visit, the main bold geographical and geological features of Mexico were sufficiently well known for practical purposes, and as his descriptions have, in most cases, stood the test of criticism during near half a century, we may still safely appeal to him, and to his industrious countryman, Muhlenpfordt,[1] as the most reliable authorities upon these topics. * * * * * According to Humboldt, Mexico presented a surface of one hundred and eighteen thousand four hundred and seventy-eight square _leagues_, of twenty-five to the degree, yet this calculation did not include the space between the northern extremity of New Mexico and Sonora, and the American boundary of 1819. Thirty-six thousand five hundred square leagues, comprising the States of Zacatecas, Guadalajara, Guanajuato, Michoacan, Mexico, Puebla, Vera Cruz, Oajaca, Tabasco, Yucatan, Chiapas, were within the torrid zone; while New Mexico, Durango, New and Old California, Sonora and a great part of the old Intendancy of San Luis Potosi, containing in all eighty-six thousand square leagues, were under the temperate zone.[2] A more recent, and, generally, an accurate writer,[3] has estimated the boundaries of Mexico, prior to the treaty of 1848, at Guadalupe, between the United States and Mexico, to have embraced an area of one million six hundred and fifty thousand square miles, including Texas. By the treaty just mentioned we acquired an undisputed title to Texas, and a territorial cession of New Mexico and Upper California.