488 EIVER EMBANKMEISTTS. 



unless future generations shall discover new modes of controlling 

 those forces, or new remedies against their action, he must at last 

 succumb in the struggle. When the marine estuaries and other 

 basins of reception shall be filled up with the sedimentary debris 

 of the mountains, or when the lower com'se of the rivers shall be 

 raised or prolonged, by their own deposits, until they have no 

 longer such a descent that gravitation and the momentum of the 

 current can overcome the frictional resistance of the bed and 

 banks, the water will, in spite of all obstacles, diffuse itseK later- 

 ally and for a time raise the level of the champaign land upon 

 its borders, and at last convert it into morasses. It is for this 

 reason that Lombardini advises that a considerable space along 

 the lower course of rivers be left undiked, and the water allowed 

 to spread itself over its banks and gradually raise them by its 

 deposits.* This would, indeed, be a palliative, but only a palK- 

 ative. Tor the present, however, we have nothing better, and 

 here, as often in pohtical economy, we must content ourselves 

 with " apres nous le deluge," allowing posterity to suffer the pen- 

 alty of our improvidence and our ignorance, or to devise means 

 for itself to ward off the consequences of them. 



The deposit of shme by rivers upon the flats along their banks 

 not only contributes greatly to the fertihty of the soil thus 

 flowed, but it subserves a still more important purpose in the 

 general economy of nature. All running streams begin with 

 excavating channels for themselves, or deepening the natural de- 

 pressions in which they flow ; f but in proportion as their outlets 



* This method has beeu adopted on the lower course of the Lamone, and a 

 considerable extent of low ground adjacent to that river has been raised by 

 spontaneous deposit to a sufficient height to admit of profitable cultivation. 



f I do not mean to say that all rivers excavate their own valleys, for I have 

 no doubt that in the majority of cases such depressions of the surface origi' 

 nate in higher geological causes, such as the fissures and other irregularities 

 of surface that could not faU to accompany upheaval, and hence the valley 

 makes the river, not the river the valley. But even if we suppose a basin of 

 the hardest rock to be elevated at once, completely formed, from the submarine 

 abyss where it was fashioned, the first shower of rain that falls upon it, after 

 it rises to the air, will discharge its waters along the lowest lines of the sur- 

 face, and cut those lines deeper, and so on with every successive rain. The 

 disintegrated rock from the upper part of the basin forms the lower by allu- 

 vial deposit, which is constantly transported farther and farther until the 

 resistance of gravitation and cohesion balances the mechanical force of the 



