The great length of the Mississippi and Missouri present the gravest difficulties. The sources of each lie in regions where heavy snows fall during a considerable part of the winter: and all the melting snows of the central portion of the country--from western Pennsylvania to Colorado, Montana and central Dakota--must find their way to the sea by way of the single stream. By reason of the difference in latitude and altitude, the melted snows of the head-waters usually swell the lower river in May and early in June, after the spring rains are over. But it quite often happens that after unusually heavy winter snows the warm weather sets in in the mountains very early: so that the great floods of the upper valleys reach the lower river just when extremely heavy rains are prevalent in the central and southern regions. This forms a combination that is terrible to combat, and is the cause of all the trouble. The present system is effective in ordinary cases; but for the occasional great exceptions it has hitherto proved insufficient. We do not seem to be any nearer a practical solution of the problem than when it first presented itself. Yet, the government of the United States spends millions of dollars every year in attempts which have, so far at least, proved totally futile to confine the great river within its banks, and so avoid the perils which every spring threaten an area larger than all New England and the Middle States. The wonderful and often terrible changes that come with the changes of season, and which produce such effects as the illustrations show, are simply inconceivable to one who has not seen them. That a stream so quiet and comparatively small as the Mississippi is at low water, should become a raging torrent of twenty miles average width, and ten feet average depth from shore to shore, throughout the eleven hundred miles from Cairo to the sea, is simply incredible until one has seen it. This river, however, did that in 1882, when the great general overflow occurred. Unnumbered lives were lost that year, and the damage to property was never even estimated. Details were hard to get when communication was so nearly cut off as it then was; and after the floods were over, no effort was made to reckon the extent of the disaster. Since that spring the reports have not indicated any flood equal to the present one; and the only reason why this year has not proved as disastrous as 1882, is that the levees have been strengthened since then. The fact, however, that the levee system has, as a whole, successfully withstood the pressure of the highest water known for many years, is by no means as reassuring as it seems on first consideration; for there is grave reason to believe that the levees themselves serve to increase the very danger against which they are a guard. The planters of the earlier days made efforts to protect themselves by means of “levees:” a name given by the [Illustration: TROPICAL FLOOD.]