...Mouth of the Rio Grande Blockaded."The annexed extract from a Brownsville letter is published in the Austin Gazette, of the 24th ult., The harbor at Brazos is blockaded, and the big gate of the Confederate States closed up. An 1800 ton two-masted propeller, war vessel, stars and stripes flying, is at anchor there watching for prey. No attempt at landing has, as yet, been made, though to-day it has been too ...