Communication cut off.
Washington, April 21st.
--The telegraphic wires between Washington and Baltimore are down — supposed to have been cut by the Baltimoreans, as the Administration at Washington have control of the office in that city.
The report about the Federal fortifications at Arlington Heights and Hoover's Hill, are by the most available reliable authority denied.
The bridges on the Washington and Baltimore Railroad are reported and believed to be destroyed --there is no communication between the two cities.
Joseph Segar, Esq., a member of the Virginia Legislature, has just arrived in Washington from Richmond.
He reports that the secession sentiment is unanimous and universal in the whole of Eastern Virginia. 