It seems to me that such a war, independent of any other consequenes, would go far to prevent the restoration of the rebel States to the authority of the Costitution, a restoration so anxiously desired by every true citizen. My object in troubling you is to explain the motive of my telegraphic communication. I thought the suggestions were worth consideration, offering as they appeared to me to do an honorable means of terminating all difficulty with England as to the capture of Slidell and Mason.

Though I think it was justifiable upon grounds laid down and acted upon by England, yet I considered it a most useless and unfortunate affair-an affair which from its evident importance should never have been undertaken by Captain Wilkes without express orders from his Government, and his interference is the more inexcusable as he states in his report that in his search into the authorities upon the law of nations he could find no such case decided and was brought to consider the rebel commissioners as the "embodiment of dispatches"-I think is his phrase-in order to justify the arrest; a strage reason to be officially given for such a procedure. And what has amazed me more than anything else in this whle affair are the laudations bestowed upon Captain Wilkes for his courage in taking three or four unarmed men out of an unarmed vessel. No doubt the indignation justly felt against Slidell a Mason for their treasonable conduct has produced a decided effect upon the public mind in the views that have been expressed.

As to any unjury which these rebel agents could do us in Europe it is all nonsense. The auestion of recognition will be decided by the gevernments there on views of their own intersts and not from any representations which such men or any men indeed could make. They would have been perfectly harmless in Europe, but have been exalted into importance by this unlucky accidnet. So far as depends upon the political communication of the rebel States with Europe they can send just as many agents there as they please.

But the principle of capture is of very little political importance to us as is manifest on the slightest consideration.

Wishing you all success in the difficult circumstances in which the country is placed, I am, truly, yours,

LEWIS CASS.

OFFICE OF THE SUPT. METROPOLITAN POLICE,

New York, December 19, 1861. (Received 20th.)

Honorable WILLIAM H. SEWARD, Secretary of State.

SIR: I have just this moment received a letter from a friend residing at Halifax, Nova Scotia, dated 11th or 15th instant, and which was written in the warehouse at the dock while the steamer was lying there on her way to Boston. He says:

I happened to be within hearing of the commander-in-chief (here) when he received his dispatches telegraphed to him from London to Queenstown. He hold his officers that Lord Lyons was instructed to demand of President Lincoln the release of Mason and Slidell and to deliver the within six weeks on board a British ship in Boston Harbor in the presence of thitry British and thirty U. S. Navy officers.

If this is true you of course knew it before to-day, but I think it proper to communicate it even if the commander-in-chief alluded to was giving vent to his wishes instead of his instructions. My authority is entirely reliable.

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