522 COAST OF THE NETHEELANDS- 



of the earth, which has been arrested by those works and em- 

 ployed to raise the bed and reverse the dechvity of the valley, 

 would have been carried down to the Tiber and thence into the 

 sea. The deposit thus created would, of course, have contributed 

 to increase the advance of the shore at the mouth of that river, 

 which has long been going on at the rate of three metres and 

 nine-tenths (twelve feet and nine inches) per annum.* It is 

 evident that a quantity of earth, sufficient to effect the immense 

 changes I have described in a wide valley more than thirty miles 

 long, if deposited at the outlet of the Tiber, would have very 

 considerably modified the outhne of the coast, and have exerted 

 no unimportant influence on the flow of that river, by raising its 

 point of discharge and lengthening its channel. 



The Coast of the Netlierlcmds. 



It has been shown in a former section that the dikes of the 

 ISTetherlands and the adjacent states have protected a consider- 

 able extent of coast from the encroachments of the sea, and have 

 won a large tract of cultivable land from the dominion of the 

 ocean waters. The immense results obtained from the operations 

 of the Tuscan engineers in the Val di Chiana and the Maremma 

 have suggested the question, whether a different method of ac- 

 complishing these objects might not have been adopted with 

 advantage. It has been argued, as in the case of the Po, that a 

 system of transverse inland dikes and canals, upon the principle 

 of those which have been so successfully employed in the Yal di 

 Chiana and in Egypt, might have elevated the low grounds above 

 the ocean tides, by spreading over them the sediment brought 

 down by the Rhine, the Maes and the Schelde. If this process 

 had been introduced in the Middle Ages, and constantly pursued 

 to our times, the superficial and coast geography, as well as the 

 hydrography of the countries in question, would undoubtedly 

 have presented an aspect very different from their present con- 

 dition ; and by combining the process with a system of maritime 

 dikes, which would have been necessary, both to resist the advance 

 of the sea and to retain the slime deposited by river overflows, it 



* See the careful estimates of Rozkt, Moyens de forcer les Torrents, etc., 

 pp. 42, 44. 



