﻿542 
  Geological 
  Society. 
  

  

  The 
  advance 
  and 
  retreat 
  of 
  the 
  Spitsbergen 
  glaciers 
  is 
  very 
  irregular, 
  

   and 
  apparently 
  due 
  to 
  local 
  changes. 
  The 
  observations 
  of 
  the 
  

   authors 
  support 
  the 
  views 
  of 
  those 
  who 
  ascribe 
  a 
  limited 
  erosive 
  

   power 
  to 
  glaciers. 
  Lastly, 
  the 
  theory 
  that 
  glacial 
  periods 
  occurred 
  

   as 
  a 
  consequence 
  of 
  epeirogenic 
  uplifts 
  receives 
  no 
  support 
  from 
  

   Spitsbergen. 
  

  

  2. 
  ' 
  On 
  a 
  Quartz-rock 
  in 
  the 
  Carboniferous 
  Limestone 
  of 
  Derby- 
  

   shire.' 
  By 
  H. 
  H. 
  Arnold-Bemrose, 
  Esq., 
  M.A., 
  F.G.S. 
  

  

  The 
  paper 
  describes 
  the 
  occurrence 
  in 
  the 
  field 
  and 
  the 
  micro- 
  

   scopic 
  structure 
  of 
  a 
  rock 
  consisting 
  essentially 
  of 
  quartz, 
  which 
  is 
  

   found 
  in 
  the 
  Mountain 
  Limestone 
  in 
  several 
  localities. 
  It 
  occurs 
  

   in 
  irregularly-shaped 
  bosses 
  and 
  veins, 
  and 
  shows 
  no 
  signs 
  of 
  

   stratification. 
  

  

  Its 
  closo 
  association 
  with 
  a 
  quartzose 
  limestone, 
  which 
  in 
  turn 
  

   passes 
  into 
  an 
  ordinary 
  limestone 
  with 
  few 
  it' 
  any 
  quartz-crystals, 
  

   leads 
  to 
  the 
  inference 
  that 
  it 
  is 
  a 
  silicified 
  limestone. 
  

  

  The 
  microscopical 
  structure 
  of 
  a 
  number 
  of 
  thin 
  slices 
  of 
  these 
  

   rocks 
  is 
  described. 
  The 
  quartz 
  -rock 
  is 
  seen 
  to 
  be 
  made 
  up 
  of 
  

   quartz-grains 
  which 
  generally 
  interlock 
  closely, 
  but 
  sometimes 
  

   possess 
  a 
  crystalline 
  outline 
  and 
  contain 
  zones 
  of 
  calcite. 
  Fluor 
  

   is 
  occasionally 
  present. 
  

  

  The 
  quartzose 
  limestone 
  is 
  usually 
  a 
  foraminifcral 
  limestone 
  

   containing 
  a 
  large 
  percentage 
  of 
  quartz, 
  which 
  occurs 
  as 
  separate 
  

   crystals 
  and 
  as 
  aggregates 
  of 
  crystals. 
  The 
  latter 
  and 
  the 
  small 
  

   quartz-veins 
  have 
  a 
  structure 
  similar 
  to 
  that 
  of 
  the 
  quartz-rock. 
  

   The 
  former 
  often 
  contain 
  zones 
  of 
  calcite 
  and 
  penetrate 
  organisms. 
  

   The 
  residue 
  consists 
  of 
  quartz-crystals. 
  

  

  The 
  author 
  considers 
  that 
  the 
  quartz-rock 
  is 
  not 
  a 
  gritty 
  lime- 
  

   stone, 
  altered 
  by 
  the 
  growth 
  of 
  crystalline 
  quartz 
  around 
  the 
  detrital 
  

   grains, 
  but 
  that 
  it 
  is 
  a 
  limestone 
  replaced 
  by 
  quartz. 
  The 
  gradual 
  

   passage 
  from 
  the 
  quartz-rock 
  through 
  a 
  quartzose 
  limestone 
  to 
  an 
  

   ordinary 
  limestone, 
  the 
  presence 
  of 
  chert, 
  of 
  part 
  of 
  a 
  foraminifer, 
  

   and 
  of 
  pieces 
  of 
  quartzose 
  limestone 
  in 
  it, 
  support 
  the 
  opinion 
  that 
  

   it 
  is 
  an 
  altered 
  limestone. 
  

  

  February 
  23rd.— 
  W. 
  Whitaker, 
  B.A., 
  F.H.S., 
  President, 
  

   in 
  the 
  Chair. 
  

  

  The 
  following 
  communications 
  were 
  read 
  : 
  — 
  

  

  1. 
  ' 
  On 
  some 
  Submerged 
  Hock- 
  Valleys 
  in 
  South 
  Wales, 
  Devon, 
  

   and 
  Cornwall.' 
  By 
  T. 
  Codrington, 
  Esq.^ 
  M.Inst.C.E., 
  F.G.S. 
  

  

  The 
  author 
  describes 
  various 
  valleys 
  in 
  which 
  the 
  solid 
  rock 
  

   is 
  reached 
  at 
  a 
  considerable 
  depth 
  below 
  sea-level, 
  on 
  the 
  sides 
  of 
  

   Milford 
  Haven 
  and 
  in 
  the 
  Haven 
  itself; 
  beneath 
  the 
  Tivy, 
  Tawe, 
  

   and 
  ]S 
  T 
  eath, 
  the 
  Wye, 
  the 
  Severn, 
  the 
  Bristol 
  Avon, 
  the 
  Dart, 
  the 
  

   Laira, 
  the 
  Tavy, 
  the 
  Tamar, 
  and 
  other 
  rivers. 
  In 
  the 
  case 
  of 
  the 
  Dart 
  

   the 
  rock-bottom 
  has 
  been 
  found 
  at 
  one 
  place 
  at 
  a 
  depth 
  of 
  110 
  feet 
  

   below 
  low-water 
  level, 
  and 
  in 
  the 
  case 
  of 
  other 
  rivers 
  at 
  varying 
  

   depths 
  less 
  than 
  this. 
  The 
  deposits 
  show 
  that 
  some 
  of 
  the 
  infilling 
  

   took 
  place 
  after 
  the 
  period 
  of 
  submerged 
  forests, 
  and 
  much 
  before 
  

  

  