DAMAGE BY LNUNDATIOIT. 239 



or of mediaeval France is neither sufficiently extensive nor suffi- 

 ciently minute to permit us to say, with certainty, that the sources 

 of this or that particular river were more or less sheltered by 

 wood at any given time, ancient or mediaeval, than at present.* 

 I say the sources of the rivers, because the floods of great rivers 

 are occasioned more by heavy rains and snows which faU in the 

 more elevated regions around the primal springs, than by precipi- 

 tation in the main valleys or on the plains bordering on the lower 

 com-se. 



The destructive effects of inundations, considered simply as a 

 mechanical power by which life is endangered, crops destroyed, 

 and the artificial constructions of man overtlirown, are very ter- 

 rible. Thus far, however, the flood is a temporary and by no 

 means an irreparable evil, for if its ravages end here, the prolific 

 powers of nature and the industry of man soon restore what had 

 been lost, and the face of the earth no longer shows traces of the 

 deluge that had overwhelmed it. Inundations have even their 

 compensations. The structures they destroy are replaced by bet- 

 ter and more secure erections, and if they sweep off a crop of 

 com, they not unfrequently leave behind them, as they subside, 

 a fertilizing deposit which enriches the exhausted field for a suc- 

 cession of seasons.f If, then, the too rapid flow of the surface- 



* Alfred Maury has, nevertheless, collected, in his erudite and able work, 

 Les Forets de la Oaule et de Vancienne France, Paris, 1867, an immense 

 amount of statistical detail on the extent, the distribution, and the destruction 

 of the forests of France, but it stQ] remains true that we can very seldom pro- 

 nounce on the forestal condition of the upper valley of a particular river at the 

 time of a given inundation in the ancient or the mediaeval period. 



f The productiveness of Egypt has been attributed too exclusively to the fer- 

 tilizing effects of the slime deposited by the inundations of the Nile ; for in that 

 climate a liberal supply of water would produce good crops on almost any or- 

 dinary sand, whUe, without water, the richest soil would yield nothing. The 

 sediment deposited annually is but a very small fraction of an inch in thick- 

 ness. It is alleged that in quantity it would be hardly sufficient for a good 

 top-dressing, and that in quality it is not chemically distinguishable from the 

 soU inches or feet below the surface. But to deny, as some writers have done, 

 that the slime has any fertilizing properties at all, is as great an error as the 

 opposite one of ascribing all the agricultural wealth of Egypt to that single 

 cause of productiveness. Fine soils deposited by water are almost uniformly 

 rich in all climates ; those brought down by rivers, carried out into salt water, 

 and then returned again by the tide, seem to be more permanently fertile than 

 any others. The polders of the Netherland coast are of this character, and the 



