Lord Lyons to Mr. Seward.

Sir: I have received a letter from a Mr. J. Hardcastle, stating that he has been incarcerated in the old capitol prison since the 17th instant. He represents that the military authorities have been very courteous and kind to him hitherto, but that he is not aware that any charges have been preferred against him.

I have the honor to request that you will be good enough to acquaint me with the cause of his arrest and imprisonment.

I have the honor to be, with the highest consideration, sir, your most obedient, humble servant,

LYONS.

Hon. W. H. Seward, Secretary of State, &c., &c.