504 RIVER EMBANKMENTS. 
when his ramparts have been, by his toil, raised to a certain 
height and widened to a certain thickness, she, by her laws of 
gravitation and cohesion, consolidates their material until it be- 
comes almost as hard, as indissoluble, and as impervious as the 
rock. 
But, though man may press the forces of nature into his 
service, there is a limit to the extent of his dominion over 
them, and 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 débris of the mountains, or when the 
lower course 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 itself laterally 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 Lombar- 
dini 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 palliative. For 
the present, however, we have nothing better, and here, as 
often in political economy, we must content ourselves with 
“aprés nous le déluge,” allowing posterity to suffer the penalty 
of our improvidence and our ignorance, or to devise means for 
itself to ward off the consequences of them. 
The deposit of slime by rivers upon the flats along their 
banks not only contributes greatly to the fertility 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 
* This method has been 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, 
