New York, April 26. The Hcrald's corresponderse Williamsburg, Virginia, April 28d, says: Contrabuds ;iro igain coming IVom the swamps of the uhiokahominy, uithin the Union lines at Williamsburg. Por gome titilo there have been but few arrivjils of this deseription The appearanee of this advanoe guard f colored refugees a an almost an infalüblo ndioation of in'ireratint on the part of tha enemy. From üll reporta so taras re ceived, tho rol'elti are eviduntly raussin troopa in all strong positions, tti rosis an expooted advance up the Ponin-uli The Riohmond uuthoritieo are evirlently oompletely puzzled as to the designs of Giant, and inforniation is being con stantly received of the marching and coiiiitermarching of troops General Fiizhucrh Leo made his appearance in the oeighborhood of Charles Uity Court Houso nilh a cavalry forue variously esimated at íroni Ihreu tbousahd fivetiundred to six thousaod. The greater part of ibis forcé 8 composeij of re-enliwted veterans vvho have ktely returned from recruiting furlouglis. Col. Robbins also coinniiimlf a torce in thia immediate naighborhood. Charles City Court House is garrisoued by Pickett's oíd infiiiitry división, under command "I General Elsey, and a regimeut of heavy artillery. Thy forcé is compo.-ed prinoipalíy of heavy irtillery stationed at Bromley'g station, York liiver, where they ara reponed engaged in throwing up earthworks. Troops are also conaentrating on all interinediate pointe between the York and James Rivera. Contrabatida etate that great exeitement prevails atnong the scatterod inhabitants of this región, and a Yankee advance is momentarily expected.