918 MEASUREMENT OF SEDIMENTARY DISCHARGE OF RIVERS. 
ON THE MEASUREMENT OF THE SEDIMENTARY 
DISCHARGE OF RIVERS. 
BY THE REV. J. D. LA TOUCHE. 
I propose in this paper to give a short account of some experiments 
which were made a few years ago with the object of estimating the quan- 
tity of sedimentary matter carried down annually by the waters of the 
Onny, a small stream in Shropshire. Unfortunately, at the very time 
when the arrangements for making these observations were matured and 
about to bear fruit, it was found impracticable to carry them further, 
since just then an extensive scheme of irrigation was started by an 
enterprising landlord, which involved the withdrawal at occasional 
intervals of large volumes of water from the stream, and thus my plans 
and methods of measurement were utterly disconcerted. Possibly 
others may be more favourably circumstanced; and I now record 
the results of my experiences in the hope that they may thereby be 
helped to pursue an investigation which requires but the simplest 
apparatus to carry it on, and which can hardly fail to lead to very 
interesting and important results. That such was the opinion of Sir 
Charles Lyell was shown by the energy with which he supported and 
encouraged my attempt, and advocated and succeeded in obtaining 
from the British Association a grant of money in two successive years to 
defray the expenses incurred in its prosecution. 
Every one must be struck by the condition of a river in full flood. 
The water, at other times quite clear, is then loaded with sediment; this 
sediment is an exact measure of the work done by atmospheric influences 
carried on over the whole area drained by that river. Starting from the 
rocky ridges which generally crown the water sheds and higher lands, all 
along the slopes of hills and through the undulations of the surface, down 
to the valleys at the bottom of which flows the stream that carries off 
the water which falls on the whole area, a slow, but ceaseless, and mighty 
atmospheric action is for ever grinding up the hardest materials and 
reducing the rocks, through the successive stages of greater and lesser 
fragments, stones, pebbles, gravel, sand, and lastly, soil, to an impalpable 
powder, which floats readily in the water of the river for a sufficient time 
to permit its transportation over many miles on its way to the sea. 
Here, as everywhere else in creation, the law of eternal change is 
maintained. Continents and all that is erected on them are swept away 
and give place to other continents to be built up out of their materials. 
What, however, we are now concerned in, is the fact that the measure- 
ment of this mud furnishes a proximate means of calculating the rate of 
geologic change ; and, if we could eliminate the errors which attend the 
computation, would help us to correct those vague and unsatisfactory 
statements in which the words ‘“ millions and billions of years” figure so 
freely, exciting, I fear, the not altogether unmerited incredulity of the 
unscientific. It is evident that if we could form any reliable estimate of 
the number of cubic yards of solid rock which in the form of mud are 
