﻿Galloway 
  — 
  Rounding 
  of 
  Sand 
  by 
  Solution. 
  '273 
  

  

  duced 
  by 
  strong 
  abrasion. 
  The 
  solution 
  surfaces 
  of 
  min- 
  

   erals 
  containing 
  impurities 
  or 
  other 
  lack 
  of 
  homogeneity 
  

   are 
  pitted 
  or 
  develop 
  other 
  irregularities, 
  especially 
  if 
  

   the 
  rate 
  of 
  solution 
  is 
  slow. 
  

  

  Factors 
  in 
  Rounding 
  by 
  Solution 
  

  

  Several 
  factors 
  enter 
  into 
  the 
  rounding 
  of 
  grains 
  of 
  

   sand 
  by 
  solution, 
  the 
  most 
  important 
  of 
  which 
  are 
  : 
  

  

  Fig. 
  2. 
  

  

  Fig. 
  2. 
  Grains 
  sifted 
  from 
  beach 
  sand 
  from 
  Bockaway, 
  L. 
  I., 
  abont 
  half 
  

   of 
  which 
  may 
  be 
  considered 
  as 
  well 
  rounded. 
  These 
  grains 
  vary 
  in 
  size 
  

   from 
  -05 
  to 
  -1 
  mm. 
  Transmitted 
  light. 
  X 
  50. 
  

  

  (1) 
  rate 
  of 
  solution, 
  (2) 
  time, 
  (3) 
  size 
  of 
  grains, 
  (4) 
  orig- 
  

   inal 
  shape 
  of 
  grains, 
  (5) 
  motion 
  of 
  grains 
  and 
  solvent, 
  

   (6) 
  cleavage, 
  and 
  (7) 
  purity 
  of 
  the 
  mineral. 
  

  

  Rate 
  of 
  solution. 
  — 
  The 
  more 
  soluble 
  a 
  mineral 
  is 
  the 
  

   more 
  rapidly 
  grains 
  of 
  it 
  will 
  approach 
  roundness 
  until 
  

   the 
  saturation 
  point 
  of 
  the 
  solvent 
  is 
  reached. 
  A 
  balance 
  

   is 
  then 
  obtained 
  between 
  mineral 
  and 
  solvent, 
  and 
  the 
  

   grains 
  tend 
  to 
  assume 
  their 
  crystalline 
  outlines. 
  "When 
  

   the 
  solvent 
  becomes 
  supersaturated, 
  as 
  by 
  evaporation, 
  

   the 
  grains 
  are 
  built 
  up 
  into 
  more 
  or 
  less 
  perfect 
  crystals. 
  

  

  Am. 
  Jour. 
  Sci. 
  -Fourth 
  Sertes, 
  Vol. 
  XLVIT, 
  No. 
  280.— 
  April, 
  1919. 
  

   19 
  

  

  