156 
SEDIMENT IN RIVERS. 
tained in a certain amount of river water, by taking 
a portion from different parts of the stream, and, 
after evaporating the fluid part, weigh the sediment. 
In this manner it has been computed that the Rhine, 
when most flooded, contains one part in a hundred 
of mud in volume, and that the Yellow River in 
China contains one part to two hundred; and Sir 
George Staunton calculated from a number of ex- 
periments, that it brought down, in a single hour, 
two million cubic feet of earth, or forty-eight mill- 
ion daily : so that, if the Yellow Sea be taken to 
be 120 feet deep, it would require but 70 days to 
convert a square mile into firm land. Manfredi, the 
celebrated Italian philosopher, conceived the aver- 
age proportion of sediment in all the running water 
on the globe to be one part to 175 of water, and 
that it would take 1000 years for the sediment car- 
ried down to raise the general level of the sea onej 
foot. Major Rennell,* of the British army, states! 
that a glass of water taken from the Ganges when! 
at its height, yields about one part in four of mud. 
Later observations by the Rev. Mr. Everest, show 
that this calculation was erroneous, or, more proba- 
bly^ a typographical error, and that the average 
quantity of solid matter was only l-428th part by 
weight and l-856th part in bulk, and that the total 
annual discharge is 6,368,077,440 cubic feet. 
" In order," says Mr. Lyell, " to give some idea 
of the magnitude of this result, we will assume that 
the specific gravity of the dried mud is only one 
half that of granite (it would, however, be more) ; in 
that case, the earthy matter discharged in a year 
would be equal to 3,184,038,720 cubic feet of gran- 
ite. Now about 12 1-2 cubic feet of granite weigh 
one ton ; and it is computed that the great Pyramid 
But as these conditions vary at different seasons of the year, we 
must make observations at different periods, and then take the 
mean of them all. 
* Phil. Transact., 1781. 
