﻿358 
  PROCEEDING^ 
  OF 
  THE 
  CALIFORNIA 
  

  

  grains, 
  communicating 
  with 
  the 
  surface 
  by 
  a 
  small 
  opening. 
  A 
  few 
  foramiu- 
  

   eferjE 
  were 
  also 
  met 
  with, 
  and 
  two 
  or 
  three 
  specimens 
  of 
  what 
  appeared 
  to 
  be 
  a 
  

   minute 
  bivalve 
  shell. 
  Besides 
  these 
  elements, 
  evidently 
  derived 
  from 
  living 
  

   beiiigs, 
  the 
  sand 
  contained 
  small 
  black 
  particles, 
  which 
  the 
  microscope 
  showed 
  

   to 
  be 
  formed 
  principally 
  of 
  crystals 
  of 
  augite, 
  nepheline, 
  and 
  magnetic 
  oxide 
  of 
  

   iron, 
  imbedded 
  in 
  a 
  glassy 
  matrix. 
  These 
  were 
  undoubtedly 
  volcanic 
  sands. 
  

  

  I 
  have 
  shown 
  some 
  of 
  the 
  principal 
  forms, 
  as 
  seen 
  under 
  the 
  microscope, 
  but 
  

   such 
  is 
  the 
  beauty 
  and 
  delicacy 
  of 
  their 
  structure 
  that 
  it 
  would 
  be 
  impossible 
  to 
  

   give 
  anything 
  more 
  than 
  a 
  general 
  idea 
  of 
  it, 
  except 
  with 
  far 
  more 
  elaborate 
  

   drawing 
  than 
  I 
  am 
  artist 
  enough 
  to 
  make. 
  The 
  structure 
  of 
  these 
  grains 
  fully, 
  

   I 
  think, 
  explains 
  the 
  reason 
  why 
  sound 
  is 
  emitted 
  when 
  they 
  are 
  set 
  in 
  motion. 
  

   The 
  friction 
  against 
  each 
  other 
  causes 
  vibrations 
  in 
  their 
  substance, 
  and, 
  con- 
  

   sequently, 
  in 
  the 
  sides 
  of 
  the 
  cavities 
  they 
  contain, 
  and 
  these 
  vibrations 
  being 
  

   communicated 
  to 
  the 
  air 
  in 
  the 
  cavities, 
  under 
  the 
  most 
  favorable 
  conditions 
  

   for 
  producing 
  sound, 
  the 
  result 
  is 
  the 
  loud 
  noise 
  which 
  is 
  caused 
  when 
  any 
  large 
  

   mass 
  of 
  sand 
  is 
  set 
  in 
  motion. 
  We 
  have, 
  in 
  fact, 
  millions 
  upon 
  millions 
  of 
  

   resonant 
  cavities, 
  each 
  giving 
  out 
  sound 
  which 
  may 
  well 
  swell 
  up 
  to 
  resemble 
  a 
  

   peal 
  of 
  thunder, 
  with 
  which 
  it 
  has 
  been 
  compared 
  ; 
  and 
  the 
  comparison 
  — 
  I 
  

   know 
  from 
  others 
  who 
  have 
  heard 
  it 
  — 
  is 
  not 
  exaggerated. 
  The 
  effect 
  of 
  rain 
  

   in 
  preventing 
  the 
  sound 
  is 
  owing 
  to 
  the 
  cavities 
  in 
  the 
  sand 
  becoming 
  filled 
  

   ■with 
  water, 
  and 
  thus 
  rendered 
  incapable 
  of 
  originating 
  vibrations. 
  The 
  

   chemical 
  compositions 
  of 
  the 
  sand, 
  with 
  the 
  exception 
  of 
  the 
  volcanic 
  grains, 
  

   is 
  calcareous, 
  being 
  completely 
  dissolved 
  by 
  chlorhydric 
  acid, 
  although 
  I 
  think 
  

   it 
  probable 
  that 
  some 
  of 
  the 
  specular 
  in 
  the 
  sponges 
  are 
  silicious. 
  

  

  Canals 
  depending 
  on 
  Tide 
  Water 
  for 
  a 
  Supply, 
  or 
  the 
  Supply 
  

   of 
  Tidal 
  Water 
  to 
  Canals. 
  

  

  BY 
  THOMAS 
  GUERIN, 
  CIVIL 
  ENGINEER. 
  

  

  My 
  attention 
  was 
  first 
  drawn 
  to 
  this 
  question 
  by 
  a 
  survey 
  I 
  have 
  made 
  of 
  a 
  

   proposed 
  canal 
  which 
  was 
  intended 
  to 
  connect 
  the 
  waters 
  of 
  the 
  Bay 
  of 
  Fundy 
  

   with 
  those 
  of 
  the 
  Gulf 
  of 
  St. 
  Lawrence. 
  On 
  studying 
  the 
  rnap 
  of 
  North 
  

   America, 
  you 
  will 
  perceive 
  that 
  the 
  province 
  of 
  Nova 
  Scotia 
  is 
  connected 
  

   with 
  the 
  main 
  land 
  by 
  a 
  narrow 
  isthmus 
  called 
  the 
  Isthmus 
  of 
  Chignecto, 
  

   some 
  eighteen 
  miles 
  across. 
  

  

  Vessels 
  bound 
  from 
  Canada 
  to 
  the 
  United 
  States 
  have 
  to 
  sail 
  round 
  Nova 
  

   Scotia, 
  thus 
  increasing 
  the 
  sailing 
  distance 
  about 
  800 
  miles, 
  which 
  would 
  be 
  

   obviated 
  if 
  a 
  canal 
  were 
  constructed 
  across 
  the 
  isthmus. 
  

  

  I 
  found 
  during 
  the 
  progress 
  of 
  the 
  survey 
  that 
  there 
  was 
  little 
  or 
  no 
  water 
  

   •on 
  the 
  isthmus 
  which 
  could 
  be 
  made 
  available 
  for 
  feeding 
  the 
  canal, 
  so 
  that 
  the 
  

   tides 
  of 
  the 
  Bay 
  of 
  Fundy 
  had 
  to 
  be 
  relied 
  upon 
  for 
  the 
  necessary 
  supply. 
  

  

  In 
  questions 
  of 
  this 
  kind 
  it 
  is 
  necessary 
  that 
  the 
  high 
  and 
  low 
  water 
  sur- 
  

   faces 
  of 
  the 
  canal, 
  as 
  well 
  as 
  the 
  level 
  of 
  its 
  bottom, 
  must 
  be 
  at 
  such 
  elevations 
  

   and 
  its 
  dimensions 
  must 
  be 
  of 
  such 
  magnitude 
  as 
  to 
  enable 
  the 
  tide 
  to 
  fill 
  it 
  to 
  

   the 
  required 
  level 
  within 
  a 
  reasonable 
  time. 
  It 
  will 
  be 
  necessary 
  to 
  empty 
  the 
  

   canal 
  occasionally 
  for 
  the 
  purposes 
  of 
  cleaning 
  and 
  repairing 
  ; 
  and 
  there 
  must 
  

  

  