HEADQUARTERS DEPARTMENT OF THE GULF,
Brownsville, Tex., November 6, 1863- 10 p. m.

GENERAL: The Ninety- fourth Illinois Volunteers, the advance of my command, reached the neighborhood of Brownsville last evening, and entered the town this morning at 10 o'clock.

A battery of the First Missouri Light Artillery, and the Thirteenth Maine Volunteers, entered the town at 3 p. m. I arrived with my staff at 12 o'clock, making my headquarters at Brownsville. The enemy evacuated the town at our approach, burning the United States barracks, and destroying large quantities of property which they could not remove.

The conflagration extended to one or two squares of the town in the neighborhood of the barracks, which were also destroyed. The troops of General Bee's command gave themselves up to plunder and violence, which excited the citizens to a considerable degree of resistance. General Jose Maria Cobos, who has been a resident of this town since March last, having been banished from Mexico at the time of the evacuation of the Spanish and English authorities, excited by the violence of the rebel troops and the conflagration, received permission from the authorities of Brownsville to organize the people for the purpose of resisting the depredations of the rebels and the suppression of the conflagration. This occurred on the 4th of November. On the evening of the 5th, after the arrival of our troops, Cobos crossed the river with the men under his command, and, took possession of Matamoras, imprisoning the Military Governor of Tamaulipas, Senior Don Manuel Ruiz, and all his associate officers. To- day, at 10 o'clock, he issued a proclamation to the army, and another to the people of Matamoras, copies of which are herewith inclosed.

Cobos is a Spaniard by birth, forty- five years of age, and emigrated to this country from Spain at thirteen or fourteen. He has been twenty years in the Mexican army, always supporting the Mexican Government, but a partisan of the Church party. He has held commission as general of division for five years, is well educated, has much influence with the army, particularly with that portion in the interior of Mexico, and is in all respects an able man. He has never resided much in this part of the country. Since March he has been a resident of Brownsville. He is represented by his friends to be adverse to the French interests. They say his purpose is, if the French attack Matamoras, to resist them in the attempt, and to withdraw into the interior with his forces, and to continue the contest as guerrillas against their Government.

He was in Mexico and here the companion and friend of Miramon, and is supposed to favor the same general policy.

The friends of Cobos represent Miramon as being devoted to the interest of Mexico against those of France, but, from considerations of policy, to be affiliating with the French authorities at the same time for the purpose of gaining time and strength. This is the representation of the friends of Cobos.

My impression, from all that I can gain, and notwithstanding what is herein stated, is that the tendency of Cobos' movement is to the benefit of France. He is a desperate men, and seized Matamoras at this particular moment for the purpose of putting himself and friends in possession of power or property to treat with any party that can best subserve his and their interests. I am unable to see how it can end otherwise than in a coalition with France. Still, his friends declare that he is adverse to the French interests, and seeks only an improved theory,