Ht'ftdqunrters Army of tie Southwest,) In tlie Field, Furt Scuii, Kansus, Aug 2li.) The greatest activity prevnils bera in getting thia army roady for ari irainediate advaoee towards Arkansas. tíen Blunt, commauditig the furres here, has received iuforraatiou that all the troops ia the Department of Kansas, aud all those in Southwestern Missouri, includiug aíJ the recent levy of mihtia, 11 be conccntratcd nt such poiuts as lie sbatl desígnate. Tliis portion of the army is finely equippeJ and contaiiis four complete batturio of eirht guns oach. ïroops have beeu bügaded and diöcrent commariders ordered to move their commands to a suitable plate east and south of Fort Soott where a full supply of f'orage, grass, fuel and good healthy water can bo obtained. Informatiou bas just beeu received here confirming tbc report that the rebels are concentratuig in large numbers at Cross llollows, Arkansas, with thointcntion ot inarching nortli, proposing to taks Fort Scott, theii Fort LeavenwortU.- Pike had made a speech te bis men, mg he intenued to be quarlercd in Fort Leuven woi'tli "btfore snow feil. Thero is uo niistakiug that such is the idea held out to the rebel forcfi now concentrating at Cross Hollows, and the recent expedítion under Cockrell and Coffue, to Lodo Jack, was for the purpose of escovting the new leviea down to Arkansas, Hundreds of men followed thtMii, and the two pieces of tho Indiana battery which thej captured at Lone Jack, but they wero mostly without arms. Di'y before yesterday, Quantrell and Ilay's bauds catue upon six eompanies of tlie Second Ivansus aud threo couipanies of tlie Sixth Kuns.is, near LaDiar. Major Campbell and Capt Greuo, of tba Sixth, attaekcd tiiem with about sixty of tlieir men, and liad a severe tiglit, lasting two houis. Two men were killed and twenty one wounded. Lieut. Col, Bas6ett, eoniinanding the Second Knnsas, morched upon the opposite sido of tha stream out of danger. Tho wounded men sny the rebels had about 700. and if Bassett luid helpcd they would havi wliippid thein. Col. Cloud left Ti i3 forco the day before to report at tliis place. All say had l;e been diere Quantrell and Hayes would have been taken.