84 HAUPT — THE MISSISSIPPI RIVER PROBLEM. [Feb. 19, 



tion of bed is reflected in that of the surface as recorded by the 

 gauges. That the bed may rise and yet the gauge readings dimin- 

 ish, will be apparent when it is remembered that the width may be 

 increased by caving and the area of the cross-section be increased 

 even, with a resulting lower record on the gauges, as has happened 

 in the Mississippi. Moreover, it is admitted that even in a state of 

 nature or without levees the bed will gradually rise. It is, there- 

 fore, only a question of degree as to whether the rate of elevation 

 is augmented or not by the levees. 



To determine this mooted point as to the elevation of the Po, an 

 American scientist made a personal inspection and reported his 

 observations in 1896.^ In his description he says, inter alia : '' Sir 

 Charles Lyell has been frequently quoted as stating, ' At Ferrara the 

 surface of the water has become more elevated than the roofs of the 

 houses.' .... My visit showed this danger to be less imminent 

 than might be supposed. Its population has dwindled away from 

 100,000 to less than 30,000, while great stretches of land within 

 its walls are now quite deserted. It is in a great plain only six and 

 a half feet above the sea level. The roads across the plain are raised 

 considerably above the general level, thus keeping them dry. 



"In 1847, Lombardini showed by actual measurement that the 

 mean height of the Po only here and there rose above the general 

 level of the plain and was generally considerably below it, and that 

 even during the great flood of 1830 the pavement in front of the 

 Palace was scarcely ten feet below the level of the surface of the 

 water in the river. Since that time, however, these conditions have 

 altered in a marked manner, the more recent investigation of ZoUi- 

 kofer having shown that in the normal condition of the river the 

 surface of the water in the neighborhood of Ferrara is somewhat 

 over eight feet above the surrounding plains, while in flood the 

 water in some places rises from sixteen ro nearly twenty feet above 

 the plain on either side. 



'' The dikes are estimated to be twenty-six feet high, and the crest 

 is cut down somewhat to permit the road to pass through with easier 

 grades, but the cut is closed with a brick wall arranged fur stop- 

 planks to exclude the higher floods. Though the danger is not so 

 great as indicated by Lyell, yet the river in flood time hangs sus- 

 pended, so to speak, over the surrounding plains, and the city of 



1 See Science of May 22, 1S96. 



