DAMAGE BY FLOODS IN RIVERS PREVENTION. 639 
out by the current to great depths. In the Mississippi and 
Hoangho the heavy deposits are approaching the mouth, and 
the river-bed is shallow, rising yearly. In some of the New 
Zealand rivers the heavy deposits have long ago reached the 
sea, and consequently the slope of the beds is at the rate 
of 30 to 60 feet per mile, and when heavy gravels begin to 
come down, the slope may be still steeper. In a state of 
nature the changes in bed and banks of rivers are very 
slow, but when the country is inhabited the changes which 
take place are sometimes alarmingly rapid, and in a few 
years I have seen the entire character of a river altered by 
changes brought about by cultivation and clearing of the 
country. 
But if embankments, or “levees,” as the Americans call 
them, are built to keep the adjacent lands from being 
flooded, the bed of the river continues to rise, but the land 
is prevented from doing so, and sooner or later serious 
consequences follow. In Holland, I saw much land which 
was a considerable depth below the ordinary level of the 
river, and seemed to be in a very risky position. Engineers 
of the Dutch Waaterstad told me that some of the embank- 
ments were as old as the time of the Romans, and it had 
been calculated that if they had not been erected the 
adjacent land would now be 15 feet higher than it is by 
reason of the yearly deposits which would have been left 
on it. The Americans have had great trouble with 
their levees on the banks of the Mississippi; the ex- 
perience of them in China has been terribly disastrous ; 
and the River Po in Italy, and some of the Japanese rivers, 
are cocked up high above the plains—-so much so, that in 
Japan some of the railways have to pass under the rivers. 
In these cases, if it had been possible to imitate Egypt, 
the land could have risen proportionately with the river- 
bed, and all would have been well. Even as it is, I have 
often thought that people are too eager to embank their 
lands and keep out the floods; they ignore the value of the 
manure with which the floods yearly enrich the soil, and 
before many years they find that they must provide manures 
at a great annual cost. The future effects of embanking 
the rivers naturally find no place in their thoughts. 
Embanking to keep out floods is rendered all the more 
risky, because the height of the floods is necessarily raised 
by the process, and all the alleviations found in natural 
conditions in the inundating of great flats and marshes 
are denied to the river confined by embankments. There 
is only one compensating advantage, which is that the 
