From what regions of the continent the future wealth is to be derived we cannot predict. The uncertainty is, perhaps, the consideration in the problem of development that leaves vast areas with undefined boundaries, though nominally within the sphere of influence of a specified power. There are fully 2,000,000 square miles yet to be explored before we may know the general geographic features of the continent, and a much larger area that must be examined and studied by experts before any reasonable estimate of its value and adaptability to the schemes of civilized man can be approached. The great strides that have been made in recent years in seizing upon the unclaimed territories doubtless received the larger impetus from the revelations in Mr. Stanley's explorations. The Kongo is recognized to be a natural highway leading to a region believed to be susceptible of remunerative development. Preparations have been made to construct a railroad around the falls in the lower river to overcome the greatest practical obstacle to its fullest utilization. We may reasonably expect commercial enterprises on extensive scales to speedily follow the completion of this road and hasten the acquisition of a more perfect knowledge of the Kongo basin, not within the boundaries of the Kongo Free State alone, but also the region drained by the great tributaries from the north and the sections naturally dependent upon this great river system. The Kongo is but one line on which the general advance is being made upon the interior of the continent. The French seem determined upon extending their influence on the northern and western coasts, and the Portuguese, English, Germans, and Italians are pronounced in their efforts on the eastern coast, while the English are careful, too, of their interests from the south, and seem to have almost unlimited scope north of Victoria Nyanza. The progress of the advancing colonization will necessarily be accelerated or retarded by the geographic conditions encountered in the different regions. In some, it may be the difficulty of maintaining communication with older settlements; in others, that the land is unproductive or the probable gains not sufficiently attractive; and lastly, the great density of the native population in certain districts is likely to prove a hindrance that it may require many years to overcome. On the lower Niger, in {35} the British west African colony, in Egypt, in Natal, on the shores of Lake Victoria Nyanza, and in parts of the Kongo basin, it is estimated that the native population is nearly as dense as in India; but the climatic conditions are so unfavorable that it is not probable that any attempt will be made to advance in these regions for a more serious purpose than to maintain a foothold for the future. The more attractive districts for the white man are thought to be much less populous, and are not scourged with such an unhealthy climate.