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Then we should bear in mind (as suited to special circumstances) the vise of 
chemical means, in the application of manures and fertilisers and in the accumula- 
tion of organic matter, which change the texture of the soil and make it more 
porous and more absorbent of water, so that there is less to run off over the surface. 
IV. Falling in of Banks. 
These friable, rich soil banks of the Hunter and some of its tributaries fall 
to some extent, wet or dry. In dry weather they cvack and tumble into the bed of 
the stream because of their lack of cohesion. It wet weather the rain soaks them, 
expansion takes place, cohesion again fails, and the result is the same. These banks 
are, in fact, in a condition of unstable equilibrium. 
V. Floods and Weeds. 
Another aspect of floods often lost sight of is the havoc committed in the 
lower lands by the transmission of weed-seeds and plants to lower levels, e.g., Nut Grass 
(Cyperus rotundus), Yellow or Prickly Poppy (Argemone mexleana), Yellow Indigo 
(Cassia spp.}, Bathurst Burr (Xanthium spinosum], Yellow Thistle (Kentrophylhim 
lanalum), Chinese Thistle (Centaurea calcitrapa], and other thistles and pests of 
various kinds, The undisturbed propagation of weeds in the bed of an upper creek 
thus means loss to any rich lands on a lower level. Therefore, althovjgh for 
engineering purposes the consensus of opinion is to work from Newcastle, my view 
as regards weeds prevention is to begin as high up the Hunter and its tributaries as 
possible. They not only float the seeds down, but nice rich silt to give the weed- 
plants a fair start in life. 
VI. Some Miscellaneous Factors in Erosion. 
(a) Boulders. The small stones and boulders in the bed of a stream are set 
in motion by floods, and forming eddies, &c., grind down the banks. Good rich 
basaltic land is very fine-grained, and washes away readily. The stones which are 
always found in it more or less help to break it away. Sometimes they form masses 
of considerable weight. The black soil everywhere rests on a bed of gravel. The 
water gets underneath and through the black soil, these gravel-stones facilitating the 
circulation of the. water and the disintegration of the superimposed soil. 
(b) Dead trees. The dead trees and branches felled for stock, unless they are 
dry enough for burning before the floods .come, do much damage. So many river 
oaks (and other trees) are cut down during a drought that if a flood comes soon, 
enormous damage is done through these dead trees tearing down the creeks and 
rivers. Dead timber, of course, threatens the bridges, and also churns up the banks 
and works destruction. The courses of creeks are so irregular, and the water comes 
down so suddenly, that a stream may become a succession of grinding whirlpools. 
There are evidences that in former times the beds of nearly all our rivers, especially the larger ones, 
occupied from time to time the lowlands adjoining their present course. These ancient depressions or beds 
may now be readily traced the original courses suddenly changed by the blocking up of the river by trees 
