[Illustration: MEXICO'S ARTIFICIAL HARBOURS: THE NEW PORT WORKS AT VERA CRUZ, A SOLID AND COSTLY ENTERPRISE.] No fact is more strongly borne upon the traveller in Andine and Cordillera-formed countries than that latitude forms but an unreliable guide to climate and temperature. Nearness to the Equator, with its accompanying torridity, is often counterbalanced by high elevations above sea-level, with consequent rarefied air and low temperature--a combination which embodies considerable advantages, as well as some drawbacks. These conditions are very marked in Mexico. Entering the country from Vera Cruz, we rise rapidly from sea-level to 7,410 feet at the City of Mexico; entering from the United States, we rise imperceptibly from 4,000 feet to the same elevation. As to its geographical position, the country extends over 18 degrees of latitude, from 32-1/2 degrees north to 14-1/2 degrees north, and it lies between the 86th and 118th meridian west of Greenwich. Topographically the country offers a very varied surface, the main features of which are the Great Plateau, the extensive, lofty tableland known as the _mesa central_; and the Pacific and Atlantic slopes, formed by the flanks of the Sierra Madres mountains towards these oceans respectively. At the base of these ranges are the lowlands of the coasts; whilst the eastern extremity of the country is formed by the singular plains of the peninsula of Yucatan. A large part of the country's area is taken up by this great plateau of Anahuac, as it is sometimes termed. The tableland is bounded both on the east and the west by ranges of mountains, known as the Eastern Sierra Madre and the Western Sierra Madre respectively. These mountains close in towards the south, enclosing the tableland in a tapering form, and the Valley of Mexico which forms its extremity. On the north the _mesa central_ is intersected by the Rio Grande, which forms the boundary of Mexico with the United States; and the plateau continues thence into the territory of that country. The length of this plateau, from north-west to south-east, or, roughly, upon its longitudinal axis, is approximately 800 miles, and its greatest width between the summits of the enclosing mountains about 500 miles. The tableland is, however, intersected by various lesser ranges of hills, and is not by any means a flat, unbroken expanse. Nevertheless, its formation is such that a vehicle might be driven from the City of Mexico for vast distances without having resort to roads. It may be looked upon physically as a great plane, inclined or tipped from south to north, or from the City of Mexico to the United States border. The general elevation above sea-level of the inclined plane at its southern end is 8,000 feet, and that at its northern 4,000 feet--a slope of 4,000 feet in a direction away from the Equator; and a fact which greatly influences its climate. The Mexican plateau is the result of after-formation from the mountain system of the country.