But our enemies argue that slavery must be an obstacle to national growth and strength; for this is evinced by the very fact that they are nearly nineteen millions, and we only twelve and a quarter; when, at the beginning, the two sections were nearly equal in strength. Let us, therefore, look into this question. The increase of population is usually a sure test of the physical well-being of a people. Hardship and destitution repress population, by obstructing marriages, by breeding diseases, and by increasing the mortality of infants. If the population of the South be found to have a rapid natural increase, it will prove, therefore, the general prosperity of the people; and if the black race be found to multiply rapidly, it will be an evidence that their physical condition is happy, or in other words, that the institution of slavery is a humane one for them. Sufficient access being denied us to the statistics collected in 1860, our remarks must be based in part on the returns of 1850, and previous periods. These returns show that between 1840 and 1850, the whites of the free States increased thirty-nine and a half _per cent._, (39.42,) and the whites of the slave States increased thirty-four and a fourth _per cent._, (34.26.) The climate, the occupations, and the African labour of the South, repel almost the whole of that teeming immigration from Europe which has been rushing to our shores; so that making allowance for this source of population, it will be seen that the natural increase of Southern whites is as rapid as that of Northern. In 1860, the whites in the free States had increased to about eighteen and a half millions; and in the slave States, to about eight and a quarter millions. The increase for the free States was, therefore, forty-two (42) _per cent._, and for the slave States thirty-three _per cent._, (33.) The census showed that in the decade between 1840 and 1850, four-fifths of the foreign immigration, for the reasons mentioned, went into the free States. If we suppose the same ratio to have prevailed in the last decade, then the fact that the North has received four-fifths of the immense rush of Europeans who resorted to our shores in the last ten years, will abundantly account for this difference of increase. The South has grown as fast in white population, as the North would have done, left to itself.