﻿410 
  A. 
  W. 
  Duff 
  — 
  Seiches 
  on 
  the 
  Bay 
  of 
  Fundy. 
  

  

  question 
  seems 
  of 
  importance. 
  (1) 
  A 
  determination 
  of 
  seiche 
  

   period 
  will 
  afford 
  an 
  estimate 
  of 
  mean 
  depth 
  and 
  may 
  assist 
  in 
  

   checking 
  soundings 
  or 
  even 
  discovering 
  areas 
  of 
  depression, 
  

   such 
  as 
  Forel 
  found 
  in 
  Lake 
  Wallenstadt. 
  (2) 
  Many, 
  at 
  

   least, 
  of 
  the 
  often 
  noted 
  but 
  (except 
  for 
  Airy's 
  apparently 
  half- 
  

   forgotten 
  remark") 
  unexplained 
  " 
  secondary 
  undulations 
  " 
  may 
  

   be 
  merely 
  seiches 
  on 
  salt 
  water. 
  The 
  Bay 
  of 
  Fundy 
  offers 
  

   special 
  advantages 
  for 
  testing 
  this 
  latter 
  point. 
  The 
  care 
  with 
  

   which 
  it 
  has 
  been 
  sounded 
  and 
  its 
  great 
  tidal 
  range 
  (at 
  St. 
  John 
  

   27 
  feet 
  at 
  springs), 
  should 
  enable 
  us 
  to 
  apply 
  the 
  three 
  follow- 
  

   ing 
  tests 
  : 
  (1) 
  Calculation 
  should 
  give 
  a 
  vibration 
  period 
  agree- 
  

   ing 
  with 
  the 
  period 
  of 
  the 
  " 
  secondary 
  undulations." 
  (2) 
  This 
  

   period 
  should 
  be 
  greater 
  at 
  low 
  water, 
  owing 
  to 
  the 
  less 
  depth, 
  

   than 
  at 
  high 
  water. 
  (3) 
  Opposite 
  sides 
  should 
  move 
  in 
  the 
  

   same 
  or 
  in 
  opposite 
  phase, 
  according 
  as 
  the 
  vibrations 
  have 
  an 
  

   odd 
  or 
  an 
  even 
  number 
  of 
  nodes. 
  

  

  Let 
  us 
  first 
  make 
  a 
  calculation 
  for 
  the 
  small 
  bay 
  at 
  Indian 
  - 
  

   town. 
  From 
  the 
  chart 
  of 
  the 
  river 
  we 
  have, 
  for 
  the 
  width 
  at 
  

   the 
  point 
  of 
  observation 
  (Marble 
  Point), 
  2,030 
  feet. 
  This 
  is 
  

   also 
  about 
  the 
  width 
  for 
  some 
  distance 
  farther 
  up 
  ; 
  imme- 
  

   diately 
  below, 
  there 
  is 
  a 
  great 
  increase 
  of 
  width, 
  due 
  to 
  a 
  small 
  

   cove 
  ; 
  but 
  as 
  this 
  cove 
  is 
  very 
  shallow 
  while 
  the 
  main 
  basin 
  is 
  

   unusually 
  deep, 
  it 
  will 
  have 
  no 
  practical 
  effect 
  on 
  the 
  period 
  of 
  

   vibration. 
  For 
  the 
  mean 
  depth 
  we 
  have 
  the 
  following 
  sound- 
  

   ings 
  (in 
  feet), 
  along 
  the 
  shortest 
  line 
  to 
  the 
  opposite 
  bank, 
  56, 
  

   60, 
  78, 
  94, 
  108, 
  136, 
  124, 
  108 
  the 
  mean 
  of 
  which 
  is 
  95 
  feet. 
  

   Immediately 
  above 
  and 
  below, 
  the 
  depth 
  is 
  slightly 
  greater, 
  in 
  

   one 
  place, 
  196 
  feet. 
  Remembering 
  that 
  the 
  formula 
  for 
  calcu- 
  

   lation 
  is 
  only 
  approximate, 
  it 
  will 
  suffice 
  if 
  100 
  feet 
  be 
  taken 
  

   as 
  mean 
  depth. 
  Substituting 
  these 
  figures 
  in 
  the 
  first 
  formula, 
  

   we 
  get 
  for 
  binodal 
  vibrations 
  a 
  period 
  of 
  72 
  seconds 
  and 
  for 
  

   trinodal 
  37*5 
  seconds. 
  This 
  seems 
  to 
  point 
  to 
  the 
  35-second 
  

   pulsations 
  being 
  trinodal 
  vibrations. 
  (The 
  less 
  accurate 
  for- 
  

   mula 
  would 
  have 
  given 
  a 
  period 
  of 
  35 
  '8 
  seconds.) 
  As 
  the 
  

   tidal 
  range 
  is 
  less 
  than 
  two 
  feet 
  this 
  period 
  should 
  not 
  appre- 
  

   ciably 
  vary 
  with 
  the 
  tide. 
  

  

  In 
  the 
  case 
  of 
  the 
  " 
  secondary 
  undulations 
  " 
  in 
  the 
  harbor, 
  

   we 
  have, 
  for 
  the 
  width 
  of 
  the 
  bay 
  along 
  a 
  line 
  from 
  the 
  tide- 
  

   gauge 
  station 
  at 
  St. 
  John 
  to 
  the 
  nearest 
  point 
  of 
  the 
  Nova 
  

   Scotia 
  coast, 
  39*8 
  miles. 
  There 
  will 
  be 
  a 
  slight 
  error 
  in 
  taking 
  

   this 
  as 
  the 
  width 
  of 
  the 
  basin, 
  for, 
  while 
  the 
  Nova 
  Scotia 
  

   coast 
  is 
  nearly 
  straight 
  and 
  unbroken, 
  St. 
  John 
  harbor 
  forms 
  

   an 
  indentation 
  on 
  the 
  New 
  Brunswick 
  side. 
  As 
  it 
  is 
  uncertain 
  

   how 
  much 
  deduction 
  should 
  be 
  made 
  on 
  this 
  account 
  (perhaps 
  

   about 
  two 
  miles), 
  the 
  above 
  figure 
  will 
  be 
  used 
  as 
  it 
  stands. 
  

   From 
  the 
  chart 
  we 
  obtain 
  the 
  following 
  (low 
  water) 
  soundings 
  

   between 
  St. 
  John 
  and 
  the 
  opposite 
  coast 
  : 
  10, 
  4, 
  5, 
  9, 
  21, 
  27, 
  

  

  