﻿Galloway 
  — 
  Rounding 
  of 
  Sand 
  by 
  Solution. 
  277 
  

  

  on 
  rounded 
  sand 
  grains. 
  Such 
  surfaces 
  can 
  be 
  produced 
  

   either 
  by 
  polishing 
  in 
  a 
  liquid, 
  as 
  glass 
  is 
  polished, 
  or 
  by 
  

   solution, 
  but 
  solution 
  seems 
  clearly 
  to 
  be 
  the 
  main 
  factor 
  

   in 
  this 
  case. 
  

  

  The 
  sand 
  seems 
  to 
  be 
  of 
  glacial 
  origin, 
  which 
  shows 
  that 
  

   it 
  is 
  geologically 
  young. 
  The 
  time 
  it 
  was 
  acted 
  upon 
  by 
  

  

  Fig. 
  5. 
  

  

  €£*>* 
  

  

  Fig. 
  5. 
  Sand 
  from 
  a 
  bubbliug 
  spring, 
  Dayton, 
  Me. 
  All 
  the 
  grains 
  are 
  

   somewhat 
  rounded, 
  the 
  largest 
  ones 
  the 
  least. 
  The 
  surfaces 
  of 
  the 
  quartz 
  

   and 
  feldspar 
  grains 
  are 
  perfectly 
  polished. 
  Transmitted 
  light. 
  X 
  50. 
  

  

  the 
  waters 
  of 
  the 
  spring 
  are 
  to 
  be 
  measured 
  in 
  a 
  few 
  

   thousands 
  of 
  years 
  at 
  most, 
  probably 
  a 
  much 
  shorter 
  

   time, 
  which 
  would 
  indicate 
  that 
  noticeable 
  effects 
  of 
  the 
  

   solvent 
  action 
  of 
  water 
  upon 
  quartz 
  can 
  be 
  accomplished 
  

   in 
  a 
  short 
  time 
  geologically, 
  especially 
  where 
  the 
  water 
  

   is 
  changed 
  continually 
  and 
  the 
  grains 
  are 
  in 
  motion. 
  

  

  Original 
  shape 
  of 
  grains. 
  — 
  The 
  more 
  angular 
  and 
  

   irregular 
  the 
  shape 
  of 
  grains 
  the 
  more 
  rapid 
  the 
  solution, 
  

   but 
  the 
  more 
  regular 
  the 
  shape 
  the 
  more 
  nearly 
  spherical 
  

   the 
  grains 
  become. 
  Thus 
  cubical 
  and 
  rectangular 
  grains 
  

   of 
  common 
  salt 
  rapidly 
  assume 
  rounded 
  forms, 
  while 
  

   grains 
  of 
  ammonium 
  chloride, 
  consisting 
  of 
  aggregates 
  

  

  