﻿14 
  GEOLOGICAL 
  MEMOIRS. 
  

  

  elevated 
  from 
  below, 
  but 
  they 
  will 
  also 
  raise 
  themselves 
  should 
  

   their 
  increase, 
  through 
  combination 
  with 
  water, 
  be 
  greater 
  than 
  the 
  

   decrease 
  of 
  bulk 
  caused 
  by 
  substances 
  carried 
  downwards. 
  

  

  As 
  a 
  geological 
  proof 
  of 
  the 
  action, 
  in 
  the 
  elevation 
  of 
  rock-masses, 
  

   of 
  the 
  cause 
  here 
  explained, 
  Professor 
  Bischof 
  cites 
  the 
  slow 
  rising 
  

   of 
  portions 
  of 
  the 
  Scandinavian 
  area, 
  remarking 
  that 
  the 
  eleva- 
  

   tion 
  takes 
  place 
  where 
  crystalline 
  rocks 
  (containing 
  silicates) 
  occur, 
  

   and 
  that 
  where 
  they 
  are 
  absent, 
  as 
  in 
  the 
  south 
  of 
  Sweden, 
  there 
  is 
  

   no 
  upheaval. 
  Again, 
  where 
  a 
  hydrated 
  silicate 
  becomes 
  altered, 
  and 
  

   a 
  consequent 
  decrease 
  of 
  volume 
  ensues, 
  a 
  depression 
  of 
  the 
  land 
  is 
  

   the 
  result, 
  as 
  is 
  now 
  taking 
  place 
  on 
  the 
  coast 
  of 
  Greenland. 
  

  

  Professor 
  Bischof 
  also 
  brings 
  forward 
  many 
  facts, 
  drawn 
  from 
  

   various 
  sources, 
  to 
  show 
  how 
  causes 
  apparently 
  slight, 
  resulting 
  in 
  a 
  

   small 
  increase 
  of 
  the 
  volume 
  of 
  the 
  body 
  acted 
  upon, 
  may 
  produce 
  

   an 
  important 
  effect 
  througn 
  the 
  magnitude 
  of 
  the 
  mechanical 
  force 
  

   thus 
  called 
  into 
  action. 
  

  

  According 
  to 
  Yon 
  Dechen, 
  oak 
  props, 
  as 
  much 
  as 
  1 
  foot 
  in 
  dia- 
  

   meter, 
  used 
  in 
  driving 
  levels 
  through 
  clay-layers 
  in 
  coal-mines 
  

   at 
  Saarbriicken, 
  are 
  crushed 
  by 
  the 
  expansion 
  of 
  clay 
  in 
  com- 
  

   bining 
  with 
  water. 
  This 
  extraordinary 
  force 
  is 
  not 
  even 
  a 
  conse- 
  

   quence 
  of 
  chemical 
  affinity, 
  but 
  merely 
  a 
  mechanical 
  action 
  caused 
  

   by 
  expansion 
  of 
  the 
  individual 
  particles 
  of 
  clay. 
  

   k 
  The 
  roots 
  of 
  trees 
  and 
  shrubs 
  growing 
  downwards 
  also 
  cause 
  an 
  

   elevation 
  of 
  the 
  soil, 
  as 
  they 
  find 
  least 
  resistance 
  towards 
  the 
  surface, 
  

   but 
  more 
  downwards 
  and 
  at 
  the 
  sides. 
  This 
  elevation, 
  after 
  long 
  

   geological 
  periods, 
  Dr. 
  Bischof 
  considers 
  would 
  become 
  a 
  considerable 
  

   item 
  in 
  primaeval 
  forests, 
  where 
  most 
  of 
  the 
  products 
  of 
  vegetation 
  are 
  

   never 
  removed, 
  and 
  where 
  new 
  roots 
  replace 
  old 
  decayed 
  ones, 
  the 
  

   latter 
  forming 
  bituminous 
  coal. 
  

  

  Bulbous 
  plants 
  prove 
  what 
  vegetation 
  may 
  accomplish 
  even 
  in 
  a 
  

   few 
  months. 
  A 
  potato 
  weighing 
  five 
  pounds 
  was 
  found 
  in 
  the 
  

   neighbourhood 
  of 
  Bonn, 
  in 
  1863; 
  its 
  specific 
  gravity 
  was=l-l; 
  it 
  

   measured 
  119 
  Prussian 
  cubic 
  inches, 
  or 
  was 
  very 
  nearly 
  equal 
  to 
  a 
  

   cube 
  5 
  inches 
  in 
  length. 
  Thus 
  it 
  must 
  have 
  displaced 
  an 
  equal 
  bulk 
  

   of 
  soil. 
  Just 
  as 
  carbon 
  and 
  water 
  are 
  assimilated 
  by 
  plants, 
  so 
  are 
  

   they 
  fixed 
  when 
  decomposition 
  of 
  silicates 
  by 
  means 
  of 
  inorganic 
  

   processes 
  takes 
  place, 
  carbonic 
  acid, 
  however, 
  being 
  assimilated 
  

   without 
  decomposition. 
  

  

  The 
  author 
  also 
  lays 
  down 
  general 
  formulas 
  of 
  the 
  increase 
  of 
  

   volume 
  through 
  decomposition 
  by 
  means 
  of 
  chemical 
  affinity, 
  and 
  

   applies 
  them 
  to 
  several 
  minerals 
  and 
  rocks. 
  Suppose 
  the 
  volume 
  of 
  

   the 
  undecomposed 
  substance 
  equal 
  to 
  1, 
  he 
  finds 
  the 
  following 
  figures 
  

   to 
  represent 
  the 
  average 
  volume 
  of 
  the 
  decomposed 
  substances 
  : 
  — 
  

  

  Felspar 
  =1-70 
  

  

  Augite 
  = 
  1-79 
  

  

  Granite 
  and 
  Gneios 
  =1-24 
  

  

  Basalt 
  =1-88 
  

  

  Lava 
  = 
  1-94 
  

  

  Clay-slate 
  =1-349 
  

  

  