﻿366 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Duncan 
  Company, 
  who 
  has 
  used 
  the 
  Francis 
  formula 
  for 
  the 
  

  

  Merrimac 
  dam, 
  namely: 
  

  

  Q=3.012L 
  H 
  1 
  - 
  53 
  ; 
  (36) 
  

  

  in 
  which 
  — 
  

  

  L 
  = 
  length 
  of 
  dam 
  = 
  794 
  feet; 
  

  

  H 
  == 
  depth 
  on 
  crest 
  of 
  dam, 
  in 
  feet. 
  

  

  This 
  formula 
  has 
  been 
  used 
  in 
  all 
  cases, 
  whether 
  flashboards 
  

   are 
  on 
  or 
  off. 
  Mr 
  Bloss 
  states 
  that 
  his 
  reason 
  for 
  using 
  this 
  

   formula 
  is 
  that 
  there 
  was 
  a 
  litigation 
  at 
  Mechanicville 
  in 
  which 
  

   the 
  quantity 
  of 
  water 
  flowing 
  over 
  the 
  dam 
  became 
  an 
  important 
  

   element. 
  He 
  therefore 
  used 
  the 
  Francis 
  formula 
  for 
  the 
  Merri- 
  

   mac 
  dam 
  because 
  the 
  courts 
  were 
  familiar 
  with 
  this 
  formula, 
  

   whereas, 
  had 
  he 
  continued 
  to 
  use 
  the 
  East 
  Indian 
  engineers' 
  

   formula, 
  the 
  courts 
  would 
  not 
  be 
  familiar 
  with 
  it 
  and 
  might 
  not 
  

   accept 
  it. 
  The 
  difference 
  between 
  the 
  two 
  formulas 
  is 
  not 
  very 
  

   great. 
  At 
  4 
  feet 
  depth 
  it 
  is 
  about 
  one 
  cubic 
  foot 
  per 
  second 
  

   per 
  foot 
  of 
  crest, 
  which 
  would 
  make 
  at 
  that 
  depth 
  794 
  cubic 
  feet 
  

   per 
  second 
  for 
  the 
  entire 
  dam. 
  Probably 
  the 
  greatest 
  oversight 
  

   in 
  this 
  computation 
  is 
  the 
  use 
  of 
  the 
  formula 
  for 
  the 
  Merrimac 
  

   dam 
  when 
  the 
  flashboards 
  are 
  on. 
  At 
  4 
  feet 
  depth 
  the 
  variation 
  

   between 
  the 
  formula 
  for 
  the 
  Merrimac 
  dam 
  and 
  Francis 
  formula 
  

   for 
  a 
  sharp-crested 
  weir 
  is 
  about 
  13 
  cubic 
  feet 
  per 
  second 
  per 
  

   linear 
  foot 
  of 
  dam, 
  and 
  even 
  at 
  2 
  feet 
  depth 
  on 
  crest 
  the 
  varia- 
  

   tion 
  is 
  over 
  6 
  cubic 
  feet 
  per 
  second 
  per 
  foot 
  of 
  dam. 
  It 
  is 
  con- 
  

   cluded, 
  therefore,, 
  that 
  the 
  computations 
  from, 
  1899 
  to 
  date 
  are 
  

   somewhat 
  less 
  reliable 
  than 
  those 
  of 
  the 
  previous 
  years. 
  The 
  

   following 
  cut 
  shows 
  a 
  section 
  of 
  the 
  Mechanicville 
  dam. 
  

  

  Fig. 
  26 
  Section 
  of 
  Mechanicville 
  dam. 
  

  

  