The accounts from the seat of war in the States of the Rio Grande, are becoming every day more serious; perhaps, I should say, alarming. It is now placed beyond all doubt, that Santa Anna, instead of throwing himself between the city of Mexico and the expected march of General Scott, has suddenly advanced on General Taylor at Saltillo. We now see the effect of weakening the army of the Rio Grande, under the supposition, that the Mexican Commander could make no other military movement than that of covering the national capital. The American General, by extraordinary exertion, has collected all his disposable force at the point where he can most advantageously arrest the march of Santa Anna; but his division does not exceed five thousand men, not more than half of them regulars, while the Mexican army is not short of twenty thousand, and by far the most formidable ever yet embodied in that country. We have every confidence in General Taylor and his gallant officers and soldiers; he is one of those, whose resources of mind have always been brought out by emergencies, and always found equal to them; but it must be confessed, the odds, at present, are fearfully against him. It is said, that General Taylor has received orders (perhaps discretionary) both from the war department, and the commander in chief, to retreat to Monterey. This, I am confident, he will never do. He must meet Santa Anna on the edge of the desert of three hundred miles, which he is compelled to cross, and he will make his stand at the admirably chosen battle field of Buena Vista, which, according to the description of Captain Hughes, is a defile just suited for an army like that of General Taylor to defend, and to withstand the shock of an attacking force, four times its numbers. Here is exactly one of those cases, where every thing must be put to “the hazzard of the dye,” or every thing must be lost.