1st. In the case of the white man cohabiting with the negress, or “married” to a negro female, there will be a more limited progeny than if she were married to one of her own race. 2d. The mulatto offspring of this connection intermarrying with other hybrids, will exhibit still less virility. 3d. The offspring of the former again intermarrying with hybrids equally removed from the original parentage, shows a yet greater diminution of virile power. 4th. By still intermarrying with hybrids, and of a corresponding remove, virility is correspondingly decreased. 5th. Finally, the fourth generation of mulattoism is as absolutely sterile as muleism, and though there may be, at rare intervals, a possible exception, yet, in every practical sense, and for all the purposes of philosophic inquiry, it may be assumed as the natural and impassable barrier of this abnormal and exceptional form of being. Of the essential correctness of these laws, or their data, almost every one living in the South, or perhaps in the larger cities of the Middle States, will be able to satisfy himself, if he will take the trouble to investigate the matter. He need not pursue the subject to its ultimate end, or to an extent necessary to arrive at all the results here presented, but he may, with comparatively trifling attention to it, satisfy himself of the _tendencies involved, and that there is somewhere at least approximating to these laws a fixed and absolute barrier beyond which mulattoism can not exist_. All the dealers in “slaves” and many “slave owners” know this from observation and individual experience, and while entirely ignorant of any thing like the scientific formulæ here presented, not a few among the former have actually stated it to the author in total unconsciousness that either he or any one else had ever thus formalized the essential character of mulattoism. But there is a very important feature of this matter, which, not understood or overlooked, may lead astray those who undertake its investigation. As has been said, hybridity is a phenomenon to be tested and determined by the nature of the beings involved, and as it must be wholly different in the human creatures from that manifested in animals, and life is limited to four generations in the case of mulattoes, while the mule is confined to a single generation, so, too, must the mere quality or capacity of offspring be taken into consideration. The mule is remarkable for its powers of endurance—the mulatto for its fragility and incapacity to endure hardships. A northern climate is fatal to the negro, but the same climate is still more fatal to the hybrid, for his approximation to the Caucasian, and therefore capacity for a northern clime, is more than balanced by his constitutional tendencies to fragility and decay. Thus, of the ten thousand free negroes in Massachusetts, whom, “freedom” and climate together, were there no more external additions, must finally