﻿THE 
  STOBY 
  OF 
  A 
  PEARL. 
  49 
  

  

  as 
  is 
  known, 
  no 
  one 
  ever 
  saw 
  a 
  pearl 
  in 
  the 
  liquid 
  condition 
  here 
  

   described. 
  

  

  The 
  imcertaint}' 
  concerning 
  the 
  origin 
  of 
  pearls 
  is 
  probably 
  

   responsible 
  for 
  some 
  of 
  the 
  statements 
  as 
  to 
  their 
  position 
  in 
  the 
  

   animal. 
  Thus 
  some 
  record 
  their 
  occurrence 
  in 
  the 
  organ 
  of 
  

   Bojanus 
  (De 
  Filippi) 
  ; 
  others, 
  as 
  Bouchon-Brandely 
  (Secretary 
  

   of 
  the 
  College 
  of 
  France), 
  locate 
  them 
  in 
  the 
  reproductive 
  gland, 
  

   in 
  the 
  adductor 
  muscle,* 
  in 
  the 
  transverse 
  muscle, 
  as 
  well 
  as 
  in 
  

   the 
  mantle. 
  Some 
  pearls 
  are 
  found 
  free 
  in 
  the 
  cavity 
  of 
  the 
  

   shell-fishes, 
  both 
  marine 
  and 
  freshwater 
  — 
  and, 
  indeed, 
  the 
  native 
  

   divers 
  in 
  Ceylon 
  were 
  sufficiently 
  acquainted 
  with 
  this 
  fact. 
  In 
  

   this 
  connection 
  it 
  was 
  formerly 
  the 
  custom 
  of 
  residents 
  on 
  the 
  

   banks 
  of 
  rivers 
  in 
  which 
  Unios 
  abounded 
  to 
  drag 
  the 
  bottom 
  for 
  

   free 
  pearls. 
  t 
  

  

  It 
  can 
  easily 
  be 
  understood 
  also 
  how, 
  when 
  the 
  surface 
  of 
  the 
  

   pearl 
  projects 
  from 
  its 
  sac, 
  it 
  becomes 
  fixed 
  by 
  the 
  exposed 
  part 
  

   to 
  the 
  inner 
  surface 
  of 
  the 
  valve. 
  Moreover, 
  it 
  sometimes 
  hap- 
  

   pens 
  that 
  the 
  pearl 
  becomes 
  embedded 
  in 
  the 
  calcareous 
  mass 
  of 
  

   the 
  valve 
  during 
  growth, 
  so 
  that 
  all 
  trace 
  of 
  it 
  disappears, 
  only 
  

   to 
  be 
  again 
  brought 
  into 
  view 
  when 
  the 
  valves 
  are 
  being 
  cut 
  by 
  

   machinery 
  into 
  discs 
  for 
  buttons. 
  Valuable 
  pearls 
  have 
  thus 
  

   been 
  procured. 
  

  

  Chemical 
  Composition. 
  — 
  Whilst 
  the 
  nacreous 
  layer 
  of 
  the 
  

   Common 
  Oyster, 
  according 
  to 
  Schlossberger, 
  contains 
  94 
  to 
  98 
  

   per 
  cent, 
  of 
  carbonate 
  of 
  lime, 
  and 
  only 
  0*8 
  to 
  2 
  per 
  cent, 
  of 
  

   nitrogenous 
  organic 
  matter, 
  the 
  true 
  Pearl- 
  Oyster 
  has 
  in 
  the 
  

   same 
  layer 
  only 
  87 
  per 
  cent, 
  of 
  carbonate 
  of 
  lime, 
  whilst 
  the 
  

   organic 
  matter 
  reaches 
  11 
  per 
  cent. 
  The 
  hardness 
  of 
  the 
  pearl, 
  

   which 
  exceeds 
  that 
  of 
  crystals 
  of 
  carbonate 
  of 
  lime, 
  is 
  due 
  to 
  the 
  

   large 
  proportion 
  of 
  organic 
  matter. 
  This 
  hardness 
  is 
  illustrated, 
  

   for 
  instance, 
  by 
  the 
  methods 
  of 
  the 
  native 
  dealers 
  in 
  Ceylon, 
  

  

  ■* 
  Vide, 
  in 
  this 
  connection, 
  Victor 
  Audouin's 
  ' 
  Observat. 
  pour 
  servir 
  a 
  

   l'histoire 
  de 
  la 
  Formation 
  des 
  Perles.' 
  Extr. 
  des 
  Mem. 
  du 
  Mus. 
  d'Hist. 
  Nat. 
  

   Paris, 
  1828. 
  

  

  f 
  Vide 
  " 
  Pearls 
  and 
  Pearl-Fisheries," 
  M. 
  Weber, 
  'Bullet. 
  U.S. 
  Fish. 
  Com.' 
  

   vol. 
  vi. 
  p. 
  321, 
  1886 
  ; 
  C. 
  T. 
  Simpson, 
  "The 
  Pearly 
  Freshwater 
  Mussels 
  of 
  the 
  

   United 
  States," 
  ' 
  Bullet. 
  U.S. 
  Fish. 
  Com.' 
  vol. 
  xviii. 
  pp. 
  279-288. 
  Also 
  

   H. 
  M. 
  Smith, 
  " 
  The 
  Mussel 
  Fishery 
  and 
  Pearl 
  Button 
  Industry 
  of 
  the 
  

   Mississippi 
  River," 
  ibid. 
  pp. 
  289-314, 
  1899. 
  See 
  also 
  J. 
  Lawrence-Hamilton, 
  

   M.E.C.S., 
  ' 
  Pearl 
  and 
  Mother-of-Pearl 
  Industries.' 
  Brighton, 
  1902. 
  

  

  