FELLOW LABORERS.--In reviewing the labors of the several Anti-Slavery Societies in the United States, there is much to cheer and gratify us. In looking over the different sections of our extended country, we find the cause of truth and humanity has slowly, but regularly advanced, in the minds of our fellow citizens generally. And we think nothing remains but perseverance in presenting the subject of slavery in its native deformity and its hideous aspect, to convince its advocates of their error, and to overcome all the opposition which can be arrayed against us. We are satisfied that to the perseverance of its advocates alone, we are indebted in a considerable degree for the change of opinion in the Northern, Middle, and some of the Western States: and we sincerely hope that a similar change will be ultimately made in the southern sections of our county. Let us never relax in our exertions to promote the emancipation, and meliorate the condition of slaves, till every human being in these United States shall equally enjoy, all the blessings of our free Institutions. How can we feel apathy or indifference while we can almost see from the windows of the room in which we are now deliberating, a receptacle for slaves, in which they are thrust, manacled and bound, all ready to ship by their avaricious owner in the first vessel whose master or owners are as hard hearted and unprincipled as himself! Yes! A dungeon, the horrors of which has called forth deep emotions of regret from all who are permitted to see the misery and wretchedness of its inmates, and particularly the tears and great agitation of a benevolent aged stranger, who, in visiting this country, which has always professed "That all men are by nature, and of right ought to be free," was surprised and shocked to find in the precincts of one of the most professedly enlightened and patriotic cities in the Union, a storehouse of human flesh! Slavery in whatever point of light considered, is a revolting subject, repugnant to the best feelings of our nature, as inconsistent with the rights and happiness of man. We therefore, urge the respective Societies to renewed exertions, in behalf of our colored population, and to petition Congress to abolish Slavery in the District of Columbia, and also to prevent its further extension in the territories of the United States.