Mode  of  repairing  the  Banks  of  Tidal  Rivers.  179 
would  have  a similar  effect,  and,  after  trying  different  expedients, 
1 at  last  adopted  the  plan  of  trenching  in  stout  hedges  of  dead 
thorns  from  high-water  mark  to  low-water  mark,  burying  their 
lower  ends  2 feet  in  the  mud,  and  allowing  their  heads  to  stand 
up  at  least  5 feet  above  it,  the  higher  the  better.  These  hedges 
being  at  right  angles  with  the  stream,  necessarily  created  a con- 
siderable obstruction  to  the  tide,  and  caused  a rapid  deposit  of 
mud ; but,  wherever  the  bank  was  steep,  I found  it  necessary  to 
trench  in  another  hedge  parallel  with  the  stream  and  at  low-water 
mark,  connecting  together  the  hedges  that  stood  at  right  angles 
with  the  stream,  in  order  to  prevent  the  mud  that  was  being 
deposited  from  dropping  again  into  the  course  of  the  tide.  The 
accompanying  sketch  will  explain,  perhaps  better  than  words,  the 
plan  which  I have  followed : — 
It  is  essential  to  the  success  of  this  plan  that  the  thorns  should 
be  at  least  7 feet  in  length,  and  that  any  hedge  that  is  made 
parallel  with  the  stream  should  be  as  low  down  the  bank  as 
possible,  for,  if  placed  on  the  steep  side  of  the  bank,  it  will 
frequently  be  unable  to  support  the  weight  of  mud  which  will 
accumulate  upon  it.  I have  now  tried  this  system  long  enough 
to  satisfy  myself  that  it  collects  the  mud  more  rapidly,  and  is  infi- 
nitely cheaper,  than  any  other  system  which  has  been  tried  on 
this  river.  The  apparent  slightness  of  the  material,  and  its 
perishable  nature,  may  at  first  sight  be  considered  objections,  but 
they  are  not  so.  I have  never  known  these  hedges  washed  away ; 
the  rapid  collection  of  mud  effectually  secures  them,  and  the  only 
injury  they  are  likely  to  receive  is  from  a ship  occasionally  making 
a gap  in  them  in  passing  up  or  down  the  river.  This,  however, 
is  easily  repaired.  The  material  also  will  not  decay  before  it 
has  effected  its  purpose.  If  the  hedges  are  put  in  at  the  right 
places,  in  the  right  way,  and  of  sufficient  height,  a few  months, 
and  frequently  a few  weeks,  will  cover  them  with  mud,  and  a 
hole  in  the  bank,  large  enough  for  a schooner  to  lie  in,  will  be 
entirely  filled  up. 
Thorns  are  delivered  on  the  bank  of  the  river  at  10s.  per 
waggon-load,  which  contains  sixty  bundles.  The  labour  of 
trenching  them  in  costs  2s.  6 d.  a waggon-load  more.  It  takes 
about  a waggon-load  of  thorns  on  an  average  to  make  one  hedge 
N 2 
