7 hundred and sixty-five or two hundred and seven- ty dollars to the hand. And in the old slave States, South of the Po- tomac, the average is about 130 dollars to the hand. This, according to our calculation, is rather above the average for East Virginia, but below that for West Virginia. The average for all Virginia is about 138 dollars. Thus it appears by the best evidence which the case admits of, that the farmers of the mid- dle States, with their free labor, produce more than twice as great a value to the hand, as the farmers and planters of theoldslave States; and that even the New Euglanders, on their poor soils and under their wintry sky, make nearly forty per cent more to the hand, than the old South- erners make in the sunny South,' with the ad- vantage of their valuable staples, cotton and tobacco. In Maryland, the result is intermediate be- tween the average of the North and that of the South; and this agrees strikingly with her condi- tion as a half-slave State; for lower Maryland is cultivated by negroes, and has a languishing agriculture, as well as a stationary population: but upper Maryland is cultivated by free labor, and has a thriving agriculture with a growing population. These results, founded on the best evidence, and confirmed by general observation, are for substance indubitably correct, and cannot be overthrown. Now it is admitted on all hands, that slave labor is better adapted to agriculture, than to any other branch of industry; and that, if not good for agriculture, it is really good for Poth- ing Therefore, since in agriculture, slave labor is proved to be far less productive than free labor- slavery is demonstrated io be not only unprofita- ble, but deeply injurious to the public prosperity. We do not mean that slave labor can never earn any thing for him that employs it. The question is between free labor and slave labor. He that chooses to employ a sort of labor, that yields only half as much to the hand as another sort would yield, makes a choice that is not only unprofitable, but deeply injurious to his inter- est. If we now compare Virginia with New York, the disadvantages of slavery will appear in a still more striking point of view. One of the citizens of our State, Thomas F. Marshall, in a pamphlet published in 1840, daaws the follow- ing comparison between Virginia and New York: "In 1790, Virginia, with 70,000 square miles of Territory, contained a population of 749,308, New York, upon a surface of 45,658 square miles contained a population of 344,120. This statement exhibits in favor of Virginia a differ- ence of 405,188 inhabitants, which Is double that of New York and 68,000 more. In 1830, after a race of 40 years, Virginia Is found to contain 1,211,405 souls, and New York 1,918,. 608, which exhibits a difference in favor of New York of 707,203. The increase on the part of Virginia will be perceived to be 453.187, starting from a basis more than double that of New York. The increase ofNew York upon a basis of 310,120 has been 1,578,301 human beings.- Virginia has increased in a ratio of 61 percent., and New York in that of 566 per cent. The total amount of property in Virginia, u nder the assessmentof 1838, was 211,930,508. The ag- gregate value of Real and Personal property in New York, in 1839, was 654,000,000, exhibit- an excess in New York over Virginia of 442,. 066,492. Statesmen may differ about policy, or the means to be employed in the promotion of the public good, but surely they ought to agree as to what prosperity means. I think there can be no dispute that New York is a grea- ter, richer, more prosperous and powerful State than Virginia. What has occasioned tho difference There is but one explanation of the fact I have shown. The clog that has staidthe march of herpeople, the incubus that has weighed down her enter- prise, strangled her commerce, kept sealed her exhaustless fountains of mineral wealth, and paralysed her arts, manufactures and improve- ment, is Negro Slavery." We thus perceive that slavery produces the same melancholy result in Virginia as we have pointed out as existing in Maryland. But bad as the condition of Virginia is, a still more gloomy state of things is before her. She now gains her support principally by selling slaves to other States. This trade, in the present state of things,is to her of the most vital importance, but it places her at the mercy of the States with which she carries on the traffic. These States have drained off the dark waters which would have overwhelmed her. But now some ofthem show an inclination to shut out the stream from themselves, Itmust then roll back and spread desolation over the face of that ancient Commonwealth. She will be reduced to a con- dition worse than any which herworstememies could wish for her. Sooner or later this state of things must come. Too many of her citizens seem to think that they can keep off this dark cloud by shutting their eyes. If they continue to do so, its thunders will burst upon their ears when it is too late for them to avoid the storm. Look upon the gloomy picture of the ultimate effect of slavery on all classes, drawn by Gov McDowell, of Va. in the speech which he recent- ly delivered in Congress. He says: "Not only is the increase of the black race greater under all circumstances than that of the white, because of the absence, in their case, of all prudential restraint, but when no emigration is allowed to keep down that excessive growth, will follow, of course, that that race will nb.