The coast of Tamaulipas is more than three hundred and fifty miles in length, and is fringed with lagunes, varying from four to eighteen miles in width, which are divided from the gulf by barriers and banks of sand. The shallowness of the shores along the whole of this coast, and the dangerous bars which choke the mouths of the rivers, render the navigation difficult and dangerous for vessels of almost all classes. In the northern part of the State, in the neighborhood of the Rio Grande, the country is comparatively level. South of these high plains, however, and some distance in the interior, the land is varied by a succession of mountains, hills and vallies, which gradually slope eastwardly until they are lost in the flats and sands of the sea coast. The Cerro de Martinez, the Cerro de Xeres, the Cerro del Coronel, and the mountain ridges, or sierras, de la Palma and del Carico, are the most remarkable elevations. The land is well watered. Fine vallies extend along the Rio del Norte or Rio Grande, the Tigre, Borbon, Panuco and Dolores. On the coast are found the lagunes of La Madre, Morales and Tampico. The climate of the interior of Tamaulipas is mild and healthy; but on the coast an intense heat prevails during the greater part of the year, and, combined with the rank vegetation and moisture, produces diseases similar to those which scourge the adjacent shores of Vera Cruz. As soon as the northers begin to blow, all nature--animal and vegetable--is refreshed by the grateful change; but the hot season generally recommences in March, and soon spreads miasma and death throughout the whole of the low lands. The population of Tamaulipas,--consisting chiefly of Meztizos and Indians,--was estimated by the Mexican Calendar of 1833, at 166,824, who were divided among three departments and eleven districts or cantons. In 1842 the population, as stated in the estimate for a congress, was 100,068; and if to this we add ten per cent. for the estimated increase in seven years, we shall have 110,074 in 1850. The chief productions and the indigenous plants are similar to those found in the State of Vera Cruz; and considerable trade is carried on with the interior--especially with the States of San Luis Potosi, Zacatecas, and Queretaro,--in mules, oxen, horses, honey and wax. The coasting and foreign commerce is conducted principally in the ports of Tampico de Tamaulipas and Matamoros. From these places, large quantities of European and North American manufactures, enter the middle and northern States of the republic. Queretaro, San Luis, Nuevo Leon, Coahuila, Zacatecas, Jalisco, Durango, Chihuahua and Sonora are all benefitted by this trade in a greater or less degree; and the Panuco, Rio Grande and other streams are all availed of partially for this interior trade as far as they are navigable. At Soto la Marina an important smuggling business was long and vigorously carried on.