The Potomac blockade.—William Howard Russell’s Diary.

December 12th.–The navy are writhing under the disgrace of the Potomac blockade, and deny it exists. The price of articles in Washington which used to come by the river affords disagreeable proof to the contrary. And yet there is not a true Yankee in Pennsylvania Avenue who does not believe, what he reads every day, that his glorious navy could sweep the fleets of France and England off the seas to-morrow, though the Potomac be closed, and the Confederate batteries throw their shot and shell into the Federal camps on the other side. I dined with General Butterfield, whose camp is pitched in Virginia, on a knoll and ridge from which a splendid view can be had over the wooded vales and hills extending from Alexandria towards Manassas, whitened with Federal tents and huts. General Fitz John Porter and General McDowell were among the officers present.