These physical features, and consequent diversities of temperature, have caused the division of Mexico, as it rises from the two Oceans, into three regions, or superficial strata, which are called, the _tierras calientes_, or _hot lands_; the _tierras templadas_, or _temperate lands_; and the _tierras frias_ or _cold lands_. The _tierra caliente_ covers chiefly that portion of the territory which lies on the borders of the Atlantic and Pacific; yet it is not confined exclusively to the coast, inasmuch as all those parts of Mexico in which there is heat and moisture enough to produce the fruits and maladies of the tropics, are classed under this head. The _tierra fria_ comprises the mountainous districts rising above the level of the capital up to the limit of constant snow; while the _tierra templada_ embraces those milder middle regions not comprehended in the two other sections. Classing them by elevation _in feet_, we may suppose that the _tierras calientes_ extend to between 3,000 and 4,000 feet above the level of the sea; the _tierras templadas_ to between 4 and 8,000 feet; and that the _tierras frias_ embrace all the remaining portions up to the region of eternal ice. POLITICAL DIVISIONS AND BOUNDARIES OF MEXICO. It is, perhaps, more of historical or antiquarian interest, than of actual present value, to recur to the ancient divisions of the viceroyalty of New Spain. Nevertheless, there are readers who are naturally anxious to trace the territorial aggrandizement as well as the recent curtailment of Mexico, and we have, therefore, thought it proper to present a picture of the limits and apportionment of the country at several periods. The territorial limits of that region generally called NEW SPAIN, were comprised between the degrees of 15° 58´ and 42° of north latitude; and between 89° 4´ and 126° 48´ 45´´ west longitude from Paris,--calculating from the easternmost point of Cape Catoché, in Yucatan, to the extreme western limit of the land at Cape Mendocino, in California. The Gulf of Mexico and the Carribean Sea bounded this country on the east and south-east; the Pacific Ocean on the west; Guatemala on the south; and the United States, on the north. There was a multitude of islands comprehended under this territorial dominion. On the east coast of Yucatan were the isles of Holvas, Comboy, Mugeres, Cancun, Cozumel and Ubero;--in the Gulf of Mexico, the island of Bermejos and several smaller ones;--in the Pacific, the isles of Revilla-gigedo, of Maria, Cedros, San Clemente, Santa Catalina, San Nicolas, Santa Barbara, Santa Cruz, San Bernardo, San Miguel;--and in the Gulf of California, or Cortéz, the isles of Cerralvo, Espiritu Santo, San José, Santa Cruz, Carmen, Tortugas, Tiburon, Santa Iñez, and numerous insignificant islets or keys. * * * * *