POST-OFFICE, San Francisco, Cal., October 22, 1861.

Honorable WILLIAM H. SEWARD, Washington.

DEAR SIR: I have to inform you that William M. Gwin, formerly U. S. Senator, and Calhoun Benham, formerly U. S. district attorney for this district, both rank traitors, left this city for New York by way of Panama yesterday. They will arrive in New York on or about the 10th or 12th of November. Their destination is South.

Yours,

S. H. PARKER,

Postmasster.

Per W. H. STEVENS,

Assistant Postmater.

AT SEA, November 4, 1861.

Messrs. Gwin, Benham and Brent, all leading, active and influential men of the partyu in rebellion against the Government, are placed in arrest, and they will be taken to New York by Colonel Merchant as prisoners of state and placed on Governor's Island to await the orders of the Government.

E. V. SUMNER,

Brigadier-General, U. S. Army.

I, A. C. Hormenz, head ssteward of the Pacific Ssteamship Company's steamer Orizaba, do swear that on the morning of the 4th of November, 1861, between 11 a. m. and 12 m., I saw Calhoun Benham come out of his own state-room, Numbers 20, into the dining saloon with a roll of passed along I requested George Jansen, one of the stewards, to proceed immediately on deck and watch if they were thrown overboard. A few minutes afterward he came down and told me that the roll or papers referred to above together with the package and some books were thrown overboard from the port window of the room Numbers 13 occupied by Mr. J. S. Stockwell and Mr. Joseph L. Brent. As he passed along I resquested George Jansen, one of the stewards, to proceed immediately on deck and watch if they were thrown overboard. A few minutes afterward he came down and told me that the roll of papers referred to above together with the package and some books ver thrown overboard from the port window of the room Numbers 13 occupied by the ssaid J. S. Stockwell and Jowph L. Brent.

A. C. HORMENZ.

Sworn and subscribed to before me this 4th day of November, 1861, there being no civil officer present competent to administer oaths.

CHAS. S. MERCHANT,

Lieutenant-Colonel Third Artillery.

I, Frederick Seiden, ship's barber of the steamer Orizaba, do swear that on the morning of the 4th of November, 1861, somewhere between the hours of 9 a. m. and 12 m., I saw several articles thrown from one of the after ports of the ship on the port side. At the distance I was from the port I could not recognize them distinctly but they appeared to be papers of some kind. The only article I regocnized distinctly was a large book with a black cover. I could not see the port from which they were thrown as the quarter-boar was in the way.

FRED. SEIDEN.

Sworn and subscribed bofore me this 4th day of November, 1861, there being no civil officer present competent to administer oaths.

CHA. S. MERCHANT,

Lieutenant-Colonel Third Artillery.