﻿84 
  PROCEEDINGS 
  OE 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  factor 
  in 
  mountain-making, 
  and 
  he 
  is 
  disposed 
  to 
  supplement 
  it 
  in 
  

   the 
  way 
  to 
  which 
  allusion 
  has 
  already 
  been 
  made 
  by 
  Mr, 
  Wynne 
  in 
  

   a 
  recent 
  Presidential 
  Address, 
  viz. 
  by 
  considering 
  the 
  effects 
  of 
  the 
  

   attenuation 
  of 
  strata 
  under 
  superincumbent 
  pressure 
  from 
  deposition 
  

   in 
  subsiding 
  areas, 
  which 
  involves 
  the 
  thickening, 
  puckering, 
  re- 
  

   duplication, 
  and 
  piling 
  up 
  of 
  strata 
  in 
  regions 
  where 
  pressure 
  has 
  

   been 
  lessened. 
  It 
  should 
  be 
  noted 
  that, 
  until 
  disturbance 
  of 
  " 
  cos- 
  

   mical 
  equilibrium 
  " 
  takes 
  place, 
  mere 
  pressure 
  does 
  not 
  produce 
  

   metamorphism. 
  The 
  extent 
  of 
  these 
  lateral 
  movements 
  is 
  described, 
  

   and 
  it 
  is 
  asserted 
  that 
  the 
  theories 
  hitherto 
  adopted 
  to 
  account 
  for 
  

   plication, 
  &c. 
  are 
  inadequate. 
  

  

  The 
  origin 
  of 
  the 
  horizontal 
  movements 
  is 
  further 
  discussed 
  on 
  

   the 
  hypothesis 
  that 
  solids 
  can 
  flow 
  after 
  the 
  manner 
  of 
  liquids, 
  

   when 
  they 
  are 
  subjected 
  to 
  sufficient 
  pressure. 
  He 
  considers 
  that 
  

   the 
  displacement 
  in 
  IST.W. 
  Scotland 
  may 
  have 
  been 
  initiated 
  by 
  the 
  

   force 
  due 
  to 
  contraction, 
  and 
  accumulating 
  in 
  the 
  crust 
  throughout 
  

   the 
  periods 
  marked 
  by 
  the 
  deposition 
  of 
  Torridon 
  Sandstone 
  and 
  

   Silurian 
  strata, 
  the 
  elements 
  of 
  movement 
  finding 
  an 
  exit 
  at 
  the 
  

   ancient 
  Silurian 
  surface. 
  In 
  this 
  case 
  the 
  pile 
  of 
  Silurian 
  strata 
  

   formerly 
  covering 
  the 
  region 
  now 
  occupied 
  by 
  the 
  North 
  Sea 
  and 
  

   part 
  of 
  the 
  Atlantic 
  forced 
  the 
  lowest 
  strata 
  to 
  move 
  laterally, 
  the 
  

   protuberances 
  of 
  the 
  underlying 
  pre- 
  Silurian 
  rocks 
  being 
  also 
  

   involved 
  in 
  the 
  shearing 
  process. 
  Similar 
  results 
  in 
  other 
  mountain 
  

   areas. 
  The 
  strata 
  compressed 
  have 
  been 
  greatly 
  attenuated 
  and 
  

   extended 
  in 
  proportion 
  ; 
  in 
  this 
  way 
  we 
  may 
  account 
  for 
  the 
  piling 
  

   up 
  of 
  strata 
  by 
  contortion 
  in 
  certain 
  regions. 
  The 
  connexion 
  of 
  

   this 
  interpretation 
  with 
  Mallet's 
  theory 
  of 
  volcanoes 
  is 
  also 
  indicated, 
  

   and 
  the 
  Author 
  concludes 
  by 
  applying 
  these 
  views 
  to 
  other 
  branches 
  

   of 
  terrestrial 
  physics. 
  

  

  Discussion. 
  

  

  The 
  President 
  observed 
  that 
  Mr. 
  Wynne, 
  in 
  his 
  recent 
  address, 
  

   had 
  acknowledged 
  his 
  indebtedness 
  to 
  Mr. 
  Kilroe. 
  He 
  himself 
  re- 
  

   garded 
  the 
  subject 
  as 
  well 
  worthy 
  of 
  consideration, 
  for 
  he 
  had 
  long 
  

   felt 
  convinced 
  that 
  the 
  theory 
  of 
  contraction 
  alone 
  was 
  insufficient 
  

   to 
  account 
  for 
  all 
  the 
  phenomena 
  of 
  movement 
  in 
  the 
  earth's 
  crust. 
  

  

  The 
  following 
  specimens 
  were 
  exhibited 
  : 
  — 
  

  

  Rocks 
  and 
  microscopic 
  sections, 
  exhibited 
  by 
  Major-Gen. 
  C. 
  A. 
  

   McMahon, 
  E.G.S., 
  in 
  illustration 
  of 
  his 
  paper. 
  

  

  Specimens 
  of 
  Jurassic 
  fossils 
  exhibited 
  by 
  Thomas 
  Eoberts, 
  Esq., 
  

   F.G.S., 
  in 
  illustration 
  of 
  his 
  paper. 
  

  

  Specimens 
  of 
  Hornblende 
  Schist 
  and 
  Gneiss 
  from 
  Sark, 
  exhibited 
  

   by 
  Prof. 
  T. 
  G. 
  Bonney, 
  F.R.S., 
  F.G.S. 
  

  

  Specimens 
  illustrating 
  the 
  effect 
  of 
  deforming 
  heterogeneous 
  

   masses 
  of 
  Clay, 
  exhibited 
  by 
  J. 
  J. 
  H. 
  Teall, 
  Esq., 
  E.G.S. 
  

  

  Specimen 
  of 
  Banded 
  Serpentine 
  from 
  the 
  Lizard, 
  exhibited 
  by 
  

   Sir 
  Warington 
  W. 
  Smyth, 
  F.R.S., 
  E.G.S. 
  

  

  Specimens 
  and 
  photographs 
  of 
  Fossil 
  Siliceous 
  Sponges 
  from 
  the 
  

   Quebec 
  Group 
  (Ordovician) 
  of 
  Little 
  Metis, 
  Lower 
  St. 
  Lawrence, 
  

   exhibited 
  by 
  Dr. 
  George 
  J. 
  Hinde, 
  F.G.S., 
  on 
  behalf 
  of 
  Sir 
  J. 
  W. 
  

  

  