There are two water systems presented in North America. North of about the forty-first degree of latitude probably the southern limit of the once glacial region--a _reservoir system_ prevails toward the headwaters of all the streams. It includes New England, New York, Michigan, Wisconsin, Minnesota, Dakota, and to the Rocky Mountains divide, and all of the British Provinces to the Arctic Circle. It also somewhat occurs on the western slope of the Rockies. This region is notable for the great lake system, and the immense number of smaller lakes and ponds--natural inland reservoirs, supposed to be largely of glacial formation to hold back considerable portions of the cumulative waters upon any given water-shed, and serving to restrain the outflow, even after they are filled. These basins exercise a happy and protective influence in many ways. South of the forty-first parallel, the rivers have no _reservoirs_ to hold any part of the flow from their water-shed. Within this vast area few lakes or ponds exist. The superabundance of water has no restraint, but at once takes to the bottom lands. To this southern system the Ohio River notably belongs, with all its tributaries. Within its two hundred thousand square miles of area, scarcely a natural reservoir is to be found. No other part of the country is so devoid of basins. Its feeders drain the western slopes of the Alleghany and Cumberland Mountains--Western Pennsylvania and West Virginia, representing sixty thousand square miles, the southern portions of Ohio, Indiana, and Illinois, and most of Kentucky and Tennessee. These States are without lakes or ponds. Nothing intervenes to hold back any portion of the vast flow from these coincidents of nature before spoken of, and therefore the excessive floods of last year and this. Such results must continue to follow. During the summer droughts the other extreme prevails. For lack of a reservoir system to withhold and control the flow of water, the river falls from flood-tide--seventy-one feet--to points so low as to seriously impede or prevent navigation. Sometimes even the smallest steamers and barges fail to pass between Pittsburgh and Cincinnati, and coal famines have not been unfrequent, resulting from difficult navigation. An equable flow of this stream is impossible. It will always be subject to these extremes. Nothing but an extensive method of filling or diking is likely to prevent the inundation of cities and villages that are not seventy feet above low-water mark, with attending suffering and destruction of life and property. All Southern rivers are liable to like extremes.