﻿380 
  Geological 
  Society. 
  

  

  The 
  form 
  of 
  the 
  rivers 
  and 
  valleys 
  suggests 
  that 
  some 
  amount 
  of 
  

   capture 
  may 
  have 
  taken 
  place 
  before 
  the 
  deposition 
  of 
  the 
  Upper 
  

   Boulder 
  Clay 
  ; 
  and 
  that 
  the 
  present 
  river-system 
  is 
  recovering 
  from 
  

   a 
  state 
  of 
  arrested 
  development, 
  due 
  to 
  the 
  ' 
  overloading 
  ' 
  of 
  the 
  

   valleys 
  with 
  Drift 
  deposits 
  and 
  torrential 
  debris 
  during 
  the 
  last 
  

   glaciation 
  of 
  the 
  area, 
  and 
  to 
  the 
  subsidence 
  (some 
  60 
  to 
  80 
  feet) 
  

   which 
  followed 
  it. 
  

  

  2. 
  ' 
  The 
  Internal 
  Structure 
  of 
  Upper 
  Silurian 
  Rugose 
  Corals 
  from 
  

   the 
  Grindrod 
  Collection, 
  Oxford 
  Museum.' 
  By 
  Donald 
  Esme 
  Innes, 
  

   B.A. 
  

  

  June 
  11th. 
  — 
  Dr. 
  Aubrey 
  Strahan, 
  F.R.S., 
  President 
  ; 
  and 
  

   afterwards 
  W. 
  Whitaker, 
  B.A., 
  F.R.S., 
  in 
  the 
  Chair. 
  

   The 
  following 
  communications 
  were 
  read 
  : 
  — 
  

  

  1. 
  ' 
  Certain 
  Upper 
  Jurassic 
  Strata 
  of 
  England.' 
  By 
  Dr. 
  Hans 
  

   Salfeld, 
  University 
  of 
  Gottingen. 
  

  

  2. 
  'The 
  Volcanic 
  Rocks 
  of 
  the 
  Forfarshire 
  Coast 
  and 
  their 
  

   Associated 
  Sediments.' 
  By 
  Albert 
  Jowett, 
  M.Sc, 
  F.G.S. 
  

  

  The 
  peculiar 
  intermingling 
  of 
  fine 
  sediments 
  with 
  the 
  Lower 
  

   Old 
  Red 
  Sandstone 
  lavas 
  of 
  Scotland 
  is 
  well 
  known 
  from 
  the 
  

   writings 
  of 
  Sir 
  Archibald 
  Geikie. 
  The 
  author 
  has 
  found 
  that 
  in 
  

   Forfarshire 
  these 
  sediments 
  are 
  frequently 
  amygdaloidal, 
  the 
  pro- 
  

   duction 
  of 
  the 
  cavities 
  having 
  been 
  accompanied 
  by 
  the 
  buckling 
  and 
  

   fracturing 
  of 
  the 
  layers 
  of 
  sediment. 
  It 
  is 
  suggested 
  that 
  such 
  

   effects 
  may 
  result 
  from 
  the 
  pouring 
  of 
  molten 
  rock 
  over 
  wet 
  

   unconsolidated 
  sediment: 
  steam 
  being 
  produced 
  within 
  the 
  sedi- 
  

   ment, 
  but 
  unable 
  to 
  escape 
  owing 
  to 
  the 
  presence 
  of 
  the 
  overlying 
  

   rock. 
  The 
  surface 
  of 
  the 
  sediment 
  was 
  apparently 
  ploughed 
  up 
  

   by 
  the 
  lava, 
  the 
  lower 
  portion 
  of 
  which 
  occasionally 
  contains 
  

   rounded 
  nodules 
  of 
  hard 
  amygdaloidal 
  sediment. 
  The 
  sediment 
  is 
  

   sometimes 
  slightly 
  altered 
  where 
  in 
  contact 
  with 
  the 
  volcanic 
  rock. 
  

   Further 
  evidence 
  of 
  the 
  pouring 
  of 
  molten 
  rock 
  into 
  water 
  is 
  

   furnished 
  by 
  the 
  occurrence 
  of 
  a 
  rude 
  pillow-structure 
  in 
  some 
  of 
  

   the 
  lavas. 
  

  

  Several 
  lenticular 
  conglomerates 
  are 
  interbedded 
  with 
  the 
  volcanic 
  

   rocks, 
  resting 
  upon 
  eroded 
  surfaces 
  of 
  the 
  latter. 
  The 
  conglomerates 
  

   consist 
  of 
  large 
  rounded 
  blocks 
  of 
  volcanic 
  rock, 
  enclosed 
  in 
  a 
  matrix 
  

   composed 
  almost 
  entirely 
  of 
  volcanic 
  debris. 
  

  

  Most 
  of 
  the 
  volcanic 
  rocks 
  are 
  olivine-basalts, 
  rhombic 
  pyroxene 
  

   as 
  well 
  as 
  olivine 
  sometimes 
  being 
  present. 
  Some 
  contain 
  rhombic 
  

   pyroxene 
  to 
  the 
  exclusion 
  of 
  olivine. 
  A 
  few 
  porphyrite-dykes 
  of 
  

   Lower 
  Old 
  Red 
  Sandstone 
  age 
  are 
  intruded 
  in 
  the 
  lavas. 
  

  

  The 
  fine 
  sediments 
  consist 
  of 
  a 
  variable 
  proportion 
  of 
  quartz 
  and 
  

   mica 
  and 
  a 
  little 
  felspar, 
  together 
  with 
  chlorite, 
  iron 
  oxides, 
  and 
  

   occasional 
  minute 
  fragments 
  of 
  volcanic 
  rock. 
  

  

  Calcite, 
  quartz, 
  chalcedony, 
  and 
  chlorite 
  are 
  the 
  commonest 
  

   minerals 
  in 
  the 
  amygdales, 
  in 
  both 
  lavas 
  and 
  sediments. 
  

  

  In 
  the 
  south-west 
  of 
  Lunan 
  Bay, 
  a 
  mass 
  of 
  Upper 
  Old 
  Red 
  

   Sandstone 
  with 
  a 
  basal 
  conglomerate 
  has 
  been 
  found 
  resting 
  

   unconformable 
  7 
  upon 
  the 
  Lower 
  Old 
  Red 
  Sandstone 
  volcanic 
  rocks. 
  

  

  