The able author of the "_Note to Blackstone's Commentaries_," is entitled to be heard, even on a subject of such peculiar delicacy--a subject upon which it is natural that the best heads and purest hearts should essentially differ. Whilst we entirely concur with him that slavery as a political or social institution is a matter exclusively of our own concern--as much so as the laws which govern the distribution of property,--we must be permitted to dissent from the opinion that it is either a moral or political benefit. We regard it on the contrary as a great evil, which society will sooner or later find it not only its interest to remove or mitigate, but will seek its gradual abolition or amelioration, under the influence of those high obligations imposed by an enlightened christian morality. These are our honest sentiments, which we do not espouse however in derogation of the equally honest convictions of other minds. The "_Letters from a Sister_," the three first of which appear in the present number, and which shall be regularly continued, will be read with interest, notwithstanding the numerous diaries and epistles which treat upon the same subjects. We entertained some doubt about the admission of "_The Doom_" into our columns, not because of any inferiority in the style and composition, but because of the revolting character of the story. The writer, with apparent sincerity, states it to be founded upon actual occurrences; but we confess that it seems to us a wild and incredible fiction. True or false however, we derive from it this sound and wholesome moral,--that sooner or later wickedness will find its just reward,--and that of all the passions which ravage the heart and destroy the peace of society, there is none more detestable than revenge. The hero of the tale, who is described by his friend the writer, as "a light hearted and joyous fellow," was in truth a remorseless fiend; compared with whom Iago and Zanga were personifications of virtue; nor does the idle phantasy of a supernatural vision, or the pretended influence of fatalism, palliate the deep enormity of his crime. If the writer, who assumes the signature of "Benedict," really had such a friend, he should have drawn the mantle of oblivion over his dark frailties, and never have recorded them with seeming approbation. He should have avoided too, certain profane and unchaste allusions in his manuscript, which we have been obliged to suppress; for we scarcely deem it necessary to repeat that the "Messenger" shall not be the vehicle of sentiments at war with the interests of virtue and sound morals--the only true and solid foundation of human happiness. We invite attention to the third letter from New England, by a Virginian,--whose talents, learning, and acute observation of men and things, and whose easy style of composition, qualify him in a high degree for the task of a tourist.