Page:Popular Science Monthly Volume 28.djvu/750

730 and Sierra Nevada Mountains, and which, commencing within the territory of the United States as far north certainly as Central Colorado, and perhaps beyond, extends as far south as the Isthmus of Tehuantepec; a north and south length, measuring from the southern frontier-line of the United States, of about two thousand miles. Entering the country by the Mexican Central Railway at El Paso, where the plateau has already an elevation of 3,717 feet, the traveler progressively and rapidly ascends, though so gradually that, except for a détour, made obligatory in the construction of the road to climb up into the city of Zacatecas, he is hardly conscious of it until, at a point known as Marquez, 1,148 miles from the starting-point and 76 miles from the city of Mexico, the railroad-track attains an elevation of 8,134 feet, or 1,849 feet higher than the summit of Mount Washington. From this point the line descends 834 feet into the valley of the city of Mexico, the bottom of which is about 7,300 feet above the sea-level. In fact, as Humboldt as far back as 1803 pointed out, so regular is the great plateau on the line followed by the Central road, and so gentle are its surface slopes where depressions occur, that the journey from the city of Mexico to Santa Fé, in New Mexico, might be performed in a four-wheeled vehicle.

Starting next from the city of Mexico, and going east toward the Atlantic, or west toward the Pacific, for a distance in either direction of about one hundred and sixty miles, and we come to the edge or terminus of this great plateau; so well defined and so abrupt that in places it seems as if a single vigorous jump would land the experimenter, or all that was left of him, at from two to three thousand feet lower level. Up the side of this almost precipice—tunneling through or winding round a succession of mountain promontories—the Vera Cruz and City of Mexico Railroad has been constructed; "rising" or "falling"—according to the direction traveled—over four thousand feet, in passing over a circuitous track of about twenty-five miles; and of which elevation or depression about twenty-five hundred perpendicular feet are comprised within the first thirteen miles, measured from the point where the descent from the edge of the plateau begins. To overcome this tremendous grade in ascending, a sort of double locomotive—comprising two sets of driving machinery, with the boilers in the center, and known as the "Farlie" engine—is employed; and even with this most powerful tractor it is necessary, with an ordinary train, to stop every eight or ten miles, in order to keep up a sufficient head of steam to overcome the resistance. In descending, on the other hand, only sufficient steam is necessary to work the brakes and counteract the tendency to a too rapid movement. As an achievement in engineering the road has probably no parallel, except it may be in some of the more recent and limited constructions among the passes of Colorado; and, as might be expected, the cost of transportation over the entire distance of 263 miles, from Vera Cruz to the city of