88 
Mr. Waddy.— I do not for a moment mean to say that we are to suppose 
the rate of deposit in the Nile can be judged by the rules of deposit 
as applied to the Trent. To compare the two, you must discover whether 
the consistency of the deposit is the same in the two streams ; and if even 
you have discovered and settled that point, it does not follow that you have 
got a law of deposits that will carry you through centuries. There is not the 
slightest reason for believing that the rate of deposit now is the same that it 
was a hundred years ago. Your deposit now may be at the rate of a single 
inch per year, but it does not follow that it was the same 20 or 2,000 
years ago. I am told by those who are well able to judge that nothing is 
more clearly proved than this in warping, that the earlier deposits are 
a great deal thicker than the later ones, because of the greater depth of water 
and the greater quantity of mud that would be brought down the stream in 
its earlier flowings. When the channel is new there is more mud washed 
down than when it is old ; and where there is less water there is less deposit. 
Supposing the date of the statue to be quite fixed, and the borings to be 
relied upon, you are no nearer the truth, because, as I have just said, you 
have not and cannot have a knowledge of the variable rate of the deposit. 
There is another fact to be borne in mind. The deposit only takes place 
after the river begins to rise, and then it is not in the channel, but in the calm 
beyond the banks. Within twenty-four hours after the occurrence of the 
dam-accident near Sheffield I saw the scene of the catastrophe, and I did not 
see such a deposit in the bed of the torrent, whereas up the sides of 
the valley it was six or seven inches thick. The best authority that I can 
find on this matter tells me that it is utterly impossible to form any notion 
whatever, or any average, of the deposit of alluvial matter, there are so many 
contributing and conflicting causes, — the speed of the stream, the depth, and 
the quantity of mud carried in it. If the stream is higher than usual, 
it washes away the deposit of former years. I quite coincide with all that 
has been said of the value of this paper, but I don’t quite think Mr. Mitchell 
should say that Professor Huxley stated dogmatically that the rate of deposit 
was one foot per century; he believes five inches, but for the sake of 
argument he says one foot. 
Mr. Mitchell. — Yes ; I confess that is so, but I thought it was obvious 
that I started from the same ground that Professor Huxley adopted. 
Mr. Warington. — I should like to make a few remarks on two points, 
the Nile deposits and chalk. As to the Nile deposits, I would throw out a 
suggestion by which this question of the average rate of deposit might be 
settled, independently of borings or measurings. If samples of the water 
brought down the stream before any deposit takes place were bottled, and 
other samples were taken during and after the deposit had begun, and these 
observations were made from year to year, you might get a fair average 
of the quantity of sediment ; the bulk of water and the area over which it 
flowed might also be discoverable, and you might then get some clue as to 
how long the Nile deposit has been accumulating. Then as to the chalk. 
Here I must join issue with Mr. Mitchell entirely, for he has overlooked one 
