492 EIVEE EMBANKMENTS. 



eartliy matter it holds in suspension, and chokes up harbors with 

 a deposit which it would otherwise have spread over a wider sur- 

 face; they interfere with roads and the convenience of river 

 navigation, and no amount of cost or care can secure them from 

 occasional ruptm-e, in case of which the rush of the waters 

 through the breach is more destructive than the natural flow of 

 the highest inundation.* 



* To secure the city of Sacramento, in California, from the inundations to 

 which it is subject, a dike or levee was built upon the bank of the river and 

 raised to an elevation above that of the highest known floods, and it was con- 

 nected, below the town, with grounds lying considerably above the river. 

 On one occasion a breach in the dike occurred above the town at a very high 

 stage of the flood. The water poured in behind it, and overflowed the lower 

 part of the city, which remained submerged for some time after the river had 

 retired to its ordinary level, because the dike, which had been built to keep 

 the water out, now kept it in. 



According to Arthur Young, on the lower Po, where the surface of the 

 river at high water has been elevated considerably above the level of the adja- 

 cent fields by diking, the peasants in his time frequently endeavored to secure 

 their grounds against threatened devastation through the bursting of the 

 dikes, by crossing the river, when the danger became imminent, and opening 

 a cut in the opposite bank, thus saving their own property by flooding their 

 neighbors'. He adds, that at high water the navigation of the river was abso- 

 lutely interdicted except to mail and passenger boats, and that the guards 

 fired upon all others ; the object of the prohibition being to prevent the peas 

 ants from resorting to this measure of self-defence. — Travels in Italy and Spain, 

 Nov. 7, 1789. 



In a flood of the Po in 1839, a breach of the embankment took place at 

 Bonizzo. The water poured through, and inundated 116,000 acres, or 181 

 square miles, of the plain to the depth of from twenty to twenty-three feet 

 in the lower parts. In the inundation of May, 1872, a great breach occurred 

 in the dike near Ferrara, 170,000 acres of cultivated land were overflowed, 

 and a population of 30,000 souls driven from their homes. In the flood of 

 October in the same year, in consequence of a breach of the dike at Revere, 

 250,000 acres of cultivated soil were overflowed, and 60,000 persons were 

 made homeless. The dikes were seriously injured at more than forty points. 

 See page 271, ante. In the flood of 1856, the Loire made seventy-three 

 breaches in its dikes, and thus, instead of a comparatively gradual rise and 

 gentle expansion of its waters, it created seventy-three impetuous torrents, 

 which inflicted infinitely greater mischief than a simply natural overflow 

 would have done. The dikes or levees of the Mississippi, being of more recent 

 construction than those of the Po, are not yet well consolidated and fortified, 

 and for this reason crevasses which occasion destructive inundations are of 

 very frequent occurrence. The great flood of 1881-2, in the valley of the 

 Mississippi, which surpassed all former experience, is said to have overflowed 



