The annual _increment_ from 1840 to 1850, was 50,000 per annum, or about six per cent. The annual increment from 1850 to 1857, was 172,000, or about twelve per cent. The _ratio_ of increase is, therefore, increasing, and we may assume it will not be less than _ten_ per cent, per annum till 1860. This will give 3,380,000 for 1860, or _fourfold the population_ of 1840! At a diminishing ratio the territory round Mackinaw will contain 5,400,000 in 1870, and (8,000,000) _eight millions_ in 1880. The principal city of the district (wherever it may be) must then contain about _one hundred thousand inhabitants_. Of the cities and towns we have above enumerated, the greatest and most rapid in its development is Chicago, whose first warehouse lot was sold in 1834, and which, in 1857, is said to contain near one hundred thousand inhabitants. Let us, for a moment, compare the _material advantages and resources_ of that place, with those of Mackinaw city. Dean Swift said, that a large city must combine the resources of agriculture, commerce and manufactures. Cities have risen, however, to large size almost exclusively on commerce. Witness Tyre and Palmyra. But commerce, we concede, when left to itself, is so fluctuating, that the cities it builds, like Tyre and Palmyra, may, in the decay of commerce, be left to ruin and desolation. Cities may, likewise, be built up almost exclusively on manufactures, such as Birmingham and Sheffield; and it is quite remarkable that the oldest and most stable cities have depended largely on manufactures. Damascus, the oldest historical city--which has resisted all the destructive influences of time and revolution--has always been a manufacturing town. Paris, Lyons, Lisle, the great interior towns of France, depend very largely on the manufacture of fine and fashionable articles, distributed throughout Europe and America. Of the great elements of civic success, we consider manufactures the most important; but, to make a city of the first magnitude, it is obviously necessary to have all the resources of food, industry and commerce. Chicago is remarkable chiefly as a grain city--like Odessa, on the Baltic. But, whence is the grain derived? By the construction of railroads, at that point, from Indiana, Illinois, Missouri, Wisconsin and Iowa, the whole mass of surplus grain in that region--amounting to more than twenty millions of bushels per annum--has been exported from Chicago. But, this is the drainage of three hundred thousand square miles, two-thirds of which will not export through Chicago when railroads extend directly east to Milwaukee, Superior and Mackinaw, from Wisconsin and Iowa, and connect, from the south, at Cairo, with Missouri and Illinois. Reduced to its own proper limits, the agricultural resources of Chicago must be confined to half the surface of Illinois, Missouri and Iowa, or about one hundred thousand square miles. This is but little over one-third the surface drained of