640. PROCEEDINGS OF SECTION H. 
river is made deeper and steeper by the embankments, 
which has the effect of scouring out its bed and so enlarging 
the water-way ; but this has little effect, considering the im- 
mense extent to which the water-way is curtailed by the em- 
‘bankments. Notwithstanding the risks and inconveniences 
attending this method, it will always be the most popular, 
and many thousand lives of men and cattle will continually 
be sacrificed to it. 
We may next consider a system of abating floods, which 
always finds heaps of advocates, who are almost invariably 
wrong as to their ideas of obtaining relief in this way. 
In numerous instances, I have known people strongly 
urging that diversions or by-washes should be cut to 
relieve the floods. Their contention usually is, that if only 
the ‘“‘ top few feet of the flood could be cut off, all would be 
well.”” Unless they are conversant with hydraulics, and 
such people never are, it is almost impossible to convince 
them that the “top of the flood” is at the bottom, not at 
the top; if it were possible to drain off the bottom, the top 
of the flood would give no trouble; just as in the sea, if 
you wish to kill a wave, you much obstruct the bottom of 
it—the top will then do no harm. Thus,a deputation wished 
to get relief from the floods of a river in Queensland. They 
urged that a by-wash should be made 200 feet wide and 
8 feet deep, which they said would take the top off the 
flood, and be all they wanted ; but they were surprised when 
it was shown that if the bye-wash were made the whole 
width of the river, viz., 500 feet, and 8 feet deep, it would 
only iowér the flood about 18 inches. 
Other projects of this nature are to make diversions to 
take away one-third or one-half of the flood-water, under 
the impression that the floods will then be greatly relieved. 
But in the long run no relief can usually be had in this 
way, for no benefit can be expected except on the assump- 
tion that the floods carry no sediment, which is seldom or 
never the case; and for this reason, if there is to be any 
diversion, or shortening, or straight-cuts, it must be of the 
whole river. 
On this subject, a friend of mine, a highly scientific and 
experienced engineer, in a lecture delivered at Shanghai 
in 1888, remarks :—‘‘ When the Chinese have been troubled 
with floods in their rivers, they have always been too ready 
to cut extra channels to carry off the surplus waters. This 
is, as a rule, the exact opposite of what should be done. The 
extra channel lowers the velocity, the river deposits more 
silt, the bed rises, and the level of floods becomes worse 
