St. Louis, April 13. The correspondent of the Missouri Democrat, Rock IIouso deck, Mo., April 6th, says: "Tho advance guard of our army, under Geu. Ousterhaus, looamped at this point last evening, íaving marchad twonly miles from their old camp at Cross .Timbors. The eaple in this vicinity are mostly Union, .hero being but threo seeessiouists on ,his rood fi-om Cassville to Flat Creek. '. stopped vith a good Uoion man last üght and found several of his ueighjors present, all anxious to be informed whether our army was gonig to loavo hem to the tender mercies of the secessionists. They aaid no money could lire thom to enduro tho constant anloyance eubmitted to last surnmer. - They were obJigod to leavo their famiies and cropa sufiuring, and shelter humselves for da}-8 and weeks in the )ush to get out of the reach of the ■obels, Banda of oatlawe frequently carne down frora Cassville and would rob Union men ol cvcrytluiig in the louse, blankeU, bread, bacon, &e., ind if they Cftugbt the owner h would iü taken to Caeeville uruler astrong ruará. In consequence of the unceraintios of tho i'uturs and the uuquiet tato of the country, but a fevv aro Daking any preparatioos to put.itxjrops. aro hticl waste and fenees burned ip along tho rnain road and UniOD men u-e diecuuraged, " The sece8sionists have inostly gonc outh witli their negroos. Sorne LJnion jeoplo have not only abandoned tho idea of niíiking orope, but aro getting their wagDne out intendipg to forsake all, and emigrate to a place of safety. ' Tho wounded are doing well at CassvilJe. Tho court-houso and all prominent stores aro boing used as hospitals, it b'eing a forttinalo circuuistanco for thcm that the owners of the principa] buildings had stam peded írom the tovvn. "Ontho30th an oxpedition, consisting ol oavalry and two mountod hovvit7.ers was reconnoitering the country about Jluntsville. At the Jatter place it was found that a forcc of rebel Oavalry, whora we intendod to bag, had made good their rotreat. " The ilag plantod by Gen. Curtís at Keitsville was ruthlessly torn down, but was recently brought in, and when last seen was ttoating over the Provost Marshal'a office at Cassville." E The Confedérate battle flag is described as very handsome, being a largo square standard, with blue ground, red bars running diagonally across, and gilt stars on tho bars equal to tho Confedérate States. ïbis standard ie eaid to be carriod in evory aetioö.