At an early day after the close of the last session of Congress an offer was formally communicated from His Imperial Majesty the Emperor of Russia of his mediation, as the common friend of the United States and Great Britain, for the purpose of facilitating a peace between them. The high character of the Emperor Alexander being a satisfactory pledge for the sincerity and impartiality of his offer, it was immediately accepted, and as a further proof of the disposition on the part of the United States, to meet their adversary in honorable experiments for terminating the war it was determined to avoid intermediate delays incident to the distance of the parties by a definitive provision for the contemplated negotiation. Three of our eminent citizens were accordingly commissioned with the requisite powers to conclude a treaty of peace with persons clothed with like powers on the part of Great Britain. They are authorized also to enter into such conventional regulations of the commerce between the two countries as may be mutually advantageous. The two envoys who, were in the United States at the time of their appointment have proceeded to join their colleague already at St. Petersburg. The envoys have received another commission authorizing them to conclude with Russia a treaty of commerce with a view to strengthen the amicable relations and improve the beneficial intercourse between the two countries. The issue of this friendly interposition of the Russian Emperor and this pacific manifestation on the part of the United States time only can decide. That the sentiments of Great Britain toward that Sovereign will have produced an acceptance of his offered mediation must be presumed. That no adequate motives exist to prefer a continuance of war with the United States to the terms on which they are willing to close it is certain. The British cabinet also must be sensible that, with respect to the important question of impressment, on which the war so essentially turns, a search for or seizure of British persons or property on board neutral vessels on the high seas is not a belligerent right derived from the law of nations, and it is obvious that no visit or search or use of force for any purpose on board the vessels of one independent power on the high seas can in war or peace be sanctioned by the laws or authority of another power. It is equally obvious that, for the purpose of preserving to each State its seafaring members, by excluding them from the vessels of the other, the mode heretofore proposed by the United States and now enacted by them as an article of municipal policy, can not for a moment be compared with the mode practiced by Great Britain without a conviction of its title to preference, inasmuch as the latter leaves the discrimination between the mariners of the two nations to officers exposed by unavoidable bias as well as by a defect of evidence to a wrong decision, under circumstances precluding for the most part