While the advance of Massachusetts, with her limited area and sterile soil, especially in view of the thousands of her native sons who have emigrated to other States, is one of the wonders of the world, yet the relative increase of the population of New Jersey from 1790 to 1860, compared with that of Maryland, is still greater than that of Massachusetts. The law is inflexible wherever slavery disappears. Population of New Jersey in 1790, 184,139, in 1860, 672,035, being an increase of 264 per cent. (264.96) for New Jersey, of 225 per cent. (225.06) for Massachusetts, and for Maryland 114 percent. (114.88). The ratio of increase per square mile from 1790 to 1860 was: Massachusetts, 48.55 in 1790, and 157.82 in 1860; Maryland, 28.74 in 1790, and 61.76 in 1860; and New Jersey, 22.01 in 1790, and 80.70 in 1860. Thus, while Maryland from 1790 to 1860, little more than doubled her ratio of increase per square mile (28.74 to 61.76), and Massachusetts little more than tripled her ratio (48.55 to 157.82), New Jersey very nearly _quadrupled_ hers (22.01 to 80.70). It must be conceded, however, that the natural advantages of New Jersey are far greater than those of Massachusetts, whose material and intellectual progress, in defiance of such serious obstacles, now is, and most probably forever will be, _without a parallel_. Now the area of New Jersey is but 8,320 square miles; the soil of Maryland is far more fertile, the hydraulic power much greater, the shoreline much more than double, viz.: 531 for New Jersey, to 1,336 for Maryland; while New Jersey, with rich iron mines, has no coal, and one third of her area is south of the celebrated Mason and Dixon's line, the northern boundary of Maryland. While the Free States have accomplished these miracles of progress, they have peopled eleven vast Territories (soon by subdivision to become many more States), immigration to which has been almost exclusively from the North as compared with the South. The Slave State which has increased _most_ rapidly to the square mile of all of them from 1790 to 1860, has had a smaller augmentation per square mile than that Free State which has increased most _slowly_ per square mile during the same time of all the Free States, and the result is the same as to wealth and education also. Under the _best_ circumstances for the Slave States, and the _worst_ for the Free States, this result proves the uniformity of the rule (like the great law of gravitation), knowing no exception to the effect of slavery in depressing the progress of States in population, wealth, and education. The isothermals of the great Humboldt (differing so widely from parallels), which trace the lines of temperature on the earth's surface, prove, as to heat, the climate of the South (running a line from Charleston to Vicksburg) to be substantially the same as that of Greece and Italy-each, in its turn, the mistress of the world.