From Southwestern Virginia.
Lynchburg, Oct. 18.
--Reliable information says that the enemy who advanced this side of Bristol, retreated to East Tennessee yesterday.
They destroyed five bridges on the Virginia and Tennessee road between Bristol and Abingdon, threw one engine from the track at Bristol, tore up half a mile of track, burnt the cross-ties and bent the iron, and burnt two engines and five cars belonging to the Virginia and Tennessee road, loaded with salt.
Our cavalry now occupy Bristol.
The Yankees reported before leaving Bristol, that Gen. Buckner's force occupied Knoxville, which is believed to have been the cause of their falling back.