Trunk Drainage. 
•deltas have caused them to be opened, embanked, and watch- 
fully preserved. Thus, around our coast — not including Scotland, 
with its great outfall works on the Clyde and Tay — we find that 
below Chester the river Dee has been straightened, and a large tract 
of its white sands reclaimed ; in Somersetshire tlie flat land lias 
been embanked from the sea, and the mouth of the Parret and its 
connected rivers confined from spreading into shallow w ater ; 
several harbours and estuaries along the south coast have skil- 
fully contended with the battling waves and shifting shingle of 
the Channel. In East Norfolk not only the mouths of the 
streams have been guarded, but the very existence of the seaport 
of Yarmouth secured by artificial ramparts of sand and beach. 
The great works which have procured an unimpeded outflow for 
the Ouse, Nene, Welland, and Witham rivers, through the muddy 
shoals of the Wash, are justly celebrated as triumphs of engineer- 
ing ; and similar improvements of the Trent, \ orkshire Ouse, 
and associated streams, have facilitated their confluence with the 
Humber. As a set-ofF against these artificially preserved 
estuaries we have several yet waiting for our interference : of 
which we may mention the Ribble, in Lancashire, where exten- 
sive flats of land have almost in vain constructed flood-gates and 
tunnels against the .shoaling of the broad estuary sands ; and 
the Severn, where a peculiar difficulty in the outfall has led 
not only to the conversion of the river into an artificial navi- 
gation by the erection of locks and weirs, but has compelled the 
formation of a canal for shipping below Gloucester, running in 
an entirely separate course for about twenty miles alongside that 
■estuary.* 
However, as regards farming, it is not generally the river mouths, 
but their inland courses, that are so defective. Our drainage 
arteries, large and small, might possibly have fulfilled their office 
had they been left to follow their native levels, or, at any rate, if 
their current had been assisted by prudent art. But a glance at 
the map will tell how they have been used for other purposes, 
dammed into reservoirs, intercepted for canals, especially in the 
central, northern, and western counties ; and the number of 
brooks and streamlets thus held back as feeders for deep-water 
navigations, or lifted to gain a water-power for myriads of mills, 
often appropriating the whole descent of the stream, it is im- 
possible for us to compute. Neither can we conjecture, except 
in the widest manner, the relative extent of the ground injured 
by the consequent floodings, in comparison with the magnitude 
* In the lengthy Parliamentary Reports upon " Tidal Harbours " the reader 
may gather full information as to the nature, improvements, and capabilities of 
all the main outfalls in Great Britain ; but this being a subject that -would fill 
volumes, we only make this reference. 
B 2 
