Advices from Texas, March 12, announce the invasiÃ³n of that country by a tvell organized and well appointed Mexican array under the command of General Arista, llis advance has been rapid, and thus far without opposition. On the fifth he entered San Antonio, and on the 7ih took possession of the town of Victoria. All accounts agree that the Mexican force is 14,000 strong. Scarcely any prepara tions have been made on the part of the Texans. But they had begun to concÃ©ntrate at Austin, to the number of about 4000. A writer at Galveston, attached lo one of the companies, says : "Our motto is victory or death. For our part we expeci noquarters from the Mexicans, therefore, we gioe none. We, one and all, go into a war of extermination. Deuth is far preforable to a Spanish prison. That the enemy has got n foot hold in our country s not lo be doubted now, and tliere is to be some lall fighting done before they will retreat, and it is the opiniÃ³n of all that we will have a long, tedious and bloody war. The News leaves here to-day for New Orleans, and a coinmittee goes for the urpose of procuriag aid from the StatesiVe have been promi?ed aid and assistance from there, and it s from such a source hat we can depend on, at least 2000 men, n ten days from this time, all equipped and ready for march.We are now under mariial law. Com mittees are busy pressing arms, arnmuniion and horses, for those who intend to oin ihe main army. The cilizens of this sland alone have conlributed, in provisons and cash $10,000; yet we will have o cali on the citizens of the Siates to asUt uf, aa it will be impossible for us to prosccute the war to any extent wih our own limited means."' Orders have been issued at Washingqn for the 6ih regiment oi infantry, and live companies 2d dragoons to repair forlhwith to the Sabine River, to prevent any nterference on the part of the American itizens with the affairs of Texas. A new company called ihe "Patriots," onsisting ofabout 200 young men, are bout leaving Philadelphia to jin the 'exan?.