﻿Macklin. 
  — 
  Protection 
  of 
  River 
  Banks, 
  145 
  

  

  river 
  tlireatens 
  to 
  form 
  a 
  new 
  cliaunel, 
  leading 
  directly 
  through 
  the 
  town, 
  as 
  

   the 
  lowest 
  portion 
  of 
  the 
  plain. 
  The 
  construction 
  called 
  a 
  "dam" 
  was 
  

   erected 
  some 
  two 
  years 
  ago, 
  at 
  the 
  point 
  Z, 
  (plan 
  No. 
  1) 
  and 
  has 
  not 
  only 
  

   diverted 
  the 
  stream 
  into 
  the 
  " 
  new" 
  channel, 
  but 
  raised 
  the 
  bank 
  of 
  shingle 
  

   behind 
  and 
  below 
  it. 
  The 
  old 
  bed 
  is 
  gradually 
  silting 
  up. 
  Had 
  solid 
  

   planking 
  been 
  put 
  in 
  to 
  divert 
  the 
  current, 
  it 
  would 
  have 
  got 
  undermined 
  

   almost 
  immediately, 
  and 
  the 
  shingle 
  been 
  carried 
  on 
  and 
  deposited 
  where 
  

   it 
  would 
  do 
  harm. 
  

  

  The 
  theorem 
  is 
  as 
  follows 
  : 
  — 
  If 
  a 
  current 
  will 
  carry 
  shingle, 
  when 
  

   travelling 
  at 
  the 
  rate 
  of 
  six 
  or 
  seven 
  miles 
  -per 
  hour, 
  but 
  will 
  not, 
  if 
  the 
  

   velocity 
  is 
  decreased 
  to 
  say 
  four, 
  then, 
  anything 
  so 
  decreasing 
  it, 
  will 
  force 
  

   it 
  to 
  drop 
  the 
  shingle 
  ; 
  and, 
  what 
  is 
  of 
  more 
  importance, 
  at 
  the 
  point 
  where 
  

   it 
  is 
  so 
  decreased. 
  The 
  invention 
  I 
  have 
  to 
  describe 
  was 
  suggested 
  to 
  Mr. 
  

   Drushn, 
  by 
  observing 
  and 
  experimenting 
  on 
  the 
  action 
  of 
  one 
  log 
  floating 
  

   and 
  moored 
  diagonally 
  across 
  a 
  current, 
  by 
  which 
  it 
  was 
  seen 
  that 
  the 
  

   surface 
  current 
  was 
  deflected. 
  It 
  then 
  became 
  clear 
  that 
  a 
  series 
  of 
  logs 
  

   moored 
  at 
  certain 
  distances 
  from 
  the 
  bottom 
  above 
  one 
  another, 
  and 
  so 
  fixed 
  

   to 
  upright 
  posts 
  that 
  they 
  would 
  float 
  or 
  rise 
  with 
  the 
  flood, 
  would 
  not 
  

   only 
  divert 
  the 
  current 
  by 
  producing 
  a 
  resultant 
  between 
  the 
  downward 
  

   velocity 
  and 
  the 
  resistance, 
  but 
  by 
  forming 
  eddies 
  below 
  the 
  logs, 
  and 
  

   decreasing 
  the 
  velocity, 
  cause 
  the 
  deposit 
  of 
  all 
  the 
  shingle. 
  The 
  water 
  

   here 
  in 
  flood 
  time 
  is 
  about 
  twelve 
  feet 
  deep, 
  and 
  there 
  is 
  a 
  series 
  of 
  frame- 
  

   works 
  of 
  five 
  logs 
  each, 
  averaging 
  twenty-eight 
  inches 
  in 
  diameter, 
  placed 
  

   diagonally 
  across 
  the 
  stream, 
  sloping 
  from 
  the 
  bank 
  at 
  an 
  angle 
  of 
  135 
  

   degrees 
  down 
  stream. 
  It 
  will 
  be 
  seen 
  that 
  these 
  logs, 
  fixed 
  in 
  the 
  following 
  

   manner, 
  check 
  about 
  half 
  the 
  volume 
  of 
  current 
  and 
  divert 
  the 
  remainder. 
  

  

  Piles 
  of 
  very 
  heavy 
  timber 
  are 
  driven 
  into 
  the 
  bed 
  of 
  the 
  river 
  ; 
  the 
  first 
  

   horizontal 
  log 
  lies 
  on 
  the 
  bottom, 
  the 
  next 
  about 
  a 
  foot 
  above 
  it, 
  and 
  so 
  on 
  

   to 
  the 
  surface 
  ; 
  the 
  whole 
  series 
  is 
  so 
  arranged 
  that 
  the 
  top 
  log 
  always 
  floats 
  | 
  

   in 
  fact 
  the 
  structure 
  is 
  so 
  buoyed 
  that 
  it 
  rises 
  on 
  the 
  piers 
  with 
  the 
  flood. 
  

   The 
  accompanying 
  plans 
  will 
  show 
  the 
  construction. 
  Eeference 
  to 
  plan 
  No. 
  

   3 
  will 
  show 
  how 
  the 
  stones 
  and 
  sand 
  get 
  piled 
  up 
  during 
  a 
  flood, 
  so 
  high 
  as 
  

   to 
  reach 
  within 
  a 
  short 
  distance 
  of 
  the 
  surface, 
  while 
  in 
  front 
  of 
  the 
  logs 
  

   there 
  is 
  a 
  raging 
  torrent. 
  There 
  is 
  one 
  defect 
  about 
  this 
  invention, 
  which 
  

   led 
  many 
  people 
  to 
  condemn 
  it 
  at 
  first. 
  During 
  flood-time 
  a 
  bank 
  of 
  shingle 
  

   is 
  raised, 
  averaging 
  eight 
  feet 
  (see 
  along 
  the 
  line 
  m 
  n 
  on 
  plan 
  No. 
  1), 
  but 
  

   during 
  its 
  subsidence, 
  and 
  until 
  the 
  next 
  flood 
  occurs, 
  the 
  river 
  is 
  acting 
  on 
  

   it, 
  and 
  cutting 
  it 
  away. 
  But 
  plans 
  are 
  now 
  devised 
  for 
  placing 
  a 
  wing-wall 
  

   of 
  planks, 
  perpendicularly 
  to 
  the 
  horizon, 
  in 
  a 
  frame 
  in 
  such 
  a 
  manner 
  

   that 
  they 
  will 
  drop 
  into 
  any 
  holes 
  made 
  beneath 
  them 
  by 
  the 
  water, 
  

   thus 
  keeping 
  the 
  bank 
  of 
  shingle 
  intact. 
  There 
  is 
  no 
  doubt 
  in 
  my 
  mind 
  

  

  