But some man might ask me here again, from whence cometh this quality, this diversity, I mean, of waters? I must answer, it comes of two causes. First, from the very breaking or bursting of it out, and passage along through rough, rich, rank and fat countries; for rivers participating of the nature of the grounds that make them their beds and banks, become thereby themselves also fat and slimy, and of quality much like to oil. The next cause proceedeth from the swiftness and the shortness of the course; forasmuch as the length of a voyage and the rage of the rivers maketh thin and subtleth the substance, and breaks and cuts in sunder the sliminess of the water: which happeneth in Nile. For running in a manner as it doth two thousand miles by a direct line (for by an oblique and crooked line it would be a good deal more) and falling from places exceeding steep and headlong where, through the vehemency and violent force of the course, and by the inestimable rage of the fall it breaketh and dissolveth all into a very small and fine rain, as it were, it waxeth so fine and subtle, and so tireth his waters that they lose all their slimy properties, which resteth all at the rivers of Almaine and of France. For they grow and walk through most rich and pleasant countries, and they be not ordinary swift nor violent. Now that this is the true reason thereof the water of Seine shall make a true proof of, for if you wash your hands with it, it scoureth like soap and cleanseth you of all manner of spots.
But let us now pass to the wideness; and that is necessary to begin withal in rivers and in channels of which we speak of, that they should be wide and large, that ships may commodiously wind and turn here and there at their will and pleasure, and give way each to other. But the wideness of a river without depth serves not for our purpose, for it dissipateth and disperseth the water in such sort that it maketh it unfit for navigation, which happeneth to the river of Plate, which through overmuch wideness is for the most part low and of uneven bottom, and full of rocks and little islands. And for the selfsame cause the rivers of Spain are not greatly navigable; for they have large bellies but they spread wide, and uneven they are, and uncertain. And thus much sufficeth to have said of rivers.
Now forasmuch as the commodities and profits are such and so great which the water bringeth to advance the greatness of a city, of consequent those cities must be the fairest and richest that have the most store of navigable rivers. And even such are those cities that are seated upon good havens of the seas, rivers or lakes, that are commodious, apt and fit for sundry navigations.
It may seem to some that with the easiness of conduct the foundation is now found out, and full complement and perfection of the greatness of a city. But it is not so, for it behoves besides that that there be some matter of profit that may draw the people and cause them to repair to one place more than to another. For where there is no commodity of conduct the multitude of people cannot be great, which the hills and mountains teacheth us, on which we may well see many castles and little towns, but no store of people that we might thereby call them great. And the reason is, because of the cragginess and steepness of their sites such things as are necessary and commodious for a civil life cannot be brought unto them without an infinite toil and labour.