JNew ïork, July 7. A letter to the Post confirma the report of a skirmish on Thursday and tho capture of six guns and some prisoners. Gen. McGlellan bad removed his headquarters, and the anny had advanced ome five miles towards Richmond. The correspondent of the Philadel)hia Inquirer statcs tliat the liichmnnd apers of the 5th acknowledgo the loss of 30,000 men, th'ough they claim the victory. The correspondent of the Philadelphia Press of the same date, reports that McDlellan is pusliiiig rajiidly forwurd, drivng the enemy at all pointe. The gunsoats accompanied his advanee, sheliing ,he woods and Rcattoring the enemy, his main forco following in support.