The prime mover in all this mischief, and the leading agent in the most atrocious scene of it, was a half-blooded Indian of little note before this time, and of no consequence in the councils of his tribe; for his name is not to be seen in the treaty either of Payne's Landing or Fort Gibson. We call him Powell; by his tribe he was called Osceola. He led the attack in the massacre of the agent, and of those who were killed with him, in the afternoon of the 28th of December. The disbursing agent, whose letter has been read, in his account of that massacre, applies the epithet _traitor_ to the name of this Powell. Well might he apply that epithet to that assassin; for he had just been fed and caressed by the very person whom he waylaid and murdered. He had come into the agency shortly before that time with seventy of his followers, professed his satisfaction with the treaty, his readiness to remove, and received subsistence and supplies for himself and all his party. The most friendly relations seemed to be established; and the doomed and deceived agent, in giving his account of it to the government, says: "The result was that we closed with the utmost good feeling; and I have never seen Powell and the other chiefs so cheerful and in so fine a humor, at the close of a discussion upon the subject of removal." This is Powell (Osceola), for whom all our sympathies are so pathetically invoked! a treacherous assassin, not only of our people, but of his own--for he it was who waylaid, and shot in the back, in the most cowardly manner, the brave chief Charley Emarthla, whom he dared not face, and whom he thus assassinated because he refused to join him and his runaway negroes in murdering the white people. The collector of Indian curiosities and portraits, Mr. Catlin, may be permitted to manufacture a hero out of this assassin, and to make a poetical scene of his imprisonment on Sullivan's island; but it will not do for an American senator to take the same liberties with historical truth and our national character. Powell ought to have been hung for the assassination of General Thompson; and the only fault of our officers is, that they did not hang him the moment they caught him. The fate of Arbuthnot and Ambrister was due to him a thousand times over.