A general rumor was brought down on the Central train Thursday, of renewed heavy skirmishing on our lines. From what we can learn, however, there bas been no movement of consequence, outside of the usual brushes between the pickets.

Reconnoisances of the banks of the Potomac show that the enemy have perfected a line of works from the Chain Bridge to four miles south of Alexandria, having accomplished, for a distance of about fifteen miles, a line of well-constructed earthworks.