Nw York, April 7. A special dispatch to tlio Phihdelphia Inquircr, (Juted Tliorofaro Gap, Va.. April 2J, 1862, ma Baltimore, April 6, says : " A rcbtl foroe of scven rogiments of infantry, two reglweuts of cuv alry, and threo batteries, were tlirown across the liappahanuoek to cut off Colonel Geary'a oomjö'snd at White Pluiijs. By a forced maroh they reathed Salem, within five miles of the Union band last eveniug, with the intention of attacking Coloiioi Goary in two columua, cuttimolT liis rütroat, and then seizing this tong idulile gap to intercept the progresa of recunstructing the Mauassas Gap Eailroad. Tho attack was to bu made at daybreak thia morning, Their müveinenta were made seoretly with the iutention of makiuja dash and cuttiug the Uuioo commaud to piucea. Colonül Geary bccame appri3ed of thcir pressrice aad designs, and moved Lia wholo commaiid off quietly during the night and bat (led with the mountain roack, WadÍDg .troaum, and rivers of mud for fiva inik'3 and by duylight occupied this gap, where ho pvcparcd for a resoluto and determined stand in the mountain dcfiles. The movemeut was most important, frustrating a design to acoompli.-!i a victory, and, by the destruction of a niuch dreaded command, to revive the drooping feelica of the rebels in Virginia. The calis were beaten in the evening and the camp Cres kopt burning as usual after the command marched. Although in suoh superior force, the rebel had not the tcmerity to follow and attempt an entranoe into the rasrged defiles hero. It 3 snpposed they" returucd to their original poaition, gouth of tho liappahannoek. Ono of the Union scouts was killed and three of the rebels taken prisoners. Thorofare Gap is west of Manassas. It ia a gap iu the I3ull Run Mountain.