﻿AND 
  BANDED 
  CRYSTALLINE 
  ROCKS 
  OF 
  THE 
  LIZARD. 
  529 
  

  

  capillary 
  attraction 
  into 
  the 
  space 
  (e-f). 
  Similarly 
  the 
  water 
  that 
  

   had 
  been 
  flowing 
  along 
  (c-d) 
  would 
  find 
  its 
  way 
  into 
  the 
  spaco 
  

   below 
  it. 
  As 
  a 
  result 
  of 
  this 
  slow 
  percolation 
  chemical 
  action 
  

   would 
  be 
  set 
  up 
  in 
  the 
  body 
  of 
  the 
  rock 
  between 
  the 
  planes 
  of 
  

   lamination. 
  Now 
  suppose 
  the 
  flow 
  along 
  the 
  planes 
  (a-b) 
  and 
  (c-d) 
  

  

  Fig. 
  5. 
  

  

  / 
  

  

  were 
  to 
  be 
  reestablished, 
  the 
  liquid 
  in 
  the 
  rock 
  above 
  (a-b) 
  would 
  

   be 
  drained 
  off 
  by 
  (a-b) 
  and 
  the 
  water 
  in 
  the 
  space 
  (e-f) 
  would 
  be 
  

   drained 
  by 
  (c-d) 
  : 
  for 
  the 
  flow 
  along 
  (a-b) 
  and 
  (c-d) 
  being 
  more 
  easy 
  

   than 
  in 
  a 
  transverse 
  direction, 
  the 
  supply 
  from 
  (a-b) 
  into 
  (e-f), 
  and 
  

   from 
  (c-d) 
  into 
  the 
  space 
  below, 
  would 
  decline, 
  and 
  the 
  force 
  of 
  

   gravity 
  would 
  carry 
  the 
  water 
  in 
  (e-f) 
  downwards 
  into 
  (c-d). 
  

  

  That 
  such 
  periodical 
  currents 
  would 
  be 
  established 
  in 
  water- 
  

   bearing 
  strata 
  adjoining 
  the 
  roots 
  of 
  active 
  volcanoes 
  I 
  think 
  highly 
  

   probable. 
  Considering 
  the 
  amount 
  of 
  water 
  in 
  the 
  form 
  of 
  steam 
  

   given 
  off 
  by 
  active 
  volcanoes, 
  and 
  considering 
  the 
  tremendously 
  

   explosive 
  character 
  of 
  the 
  periodic 
  discharges 
  from 
  some 
  craters, 
  

   powerful 
  suction 
  must, 
  I 
  think, 
  follow 
  each 
  explosive 
  discharge, 
  

   which 
  must 
  affect 
  the 
  water-bearing 
  strata 
  in 
  which 
  the 
  roots 
  of 
  

   volcanoes 
  are 
  planted. 
  This 
  powerful 
  suction* 
  and 
  pumping 
  action 
  

   is 
  sufficient, 
  it 
  seems 
  to 
  me, 
  to 
  account 
  for 
  a 
  periodic 
  capillary 
  flow 
  

   of 
  water 
  in 
  strata 
  within 
  the 
  range 
  of 
  a 
  volcano's 
  influence 
  com- 
  

   parable, 
  as 
  regards 
  the 
  character 
  of 
  the 
  flow, 
  with 
  the 
  circulation 
  of 
  

   fluids 
  in 
  the 
  tissues 
  of 
  animal 
  and 
  vegetable 
  bodies. 
  

  

  That 
  our 
  ancient 
  volcanoes 
  did, 
  as 
  a 
  matter 
  of 
  fact, 
  exhibit 
  ex- 
  

   plosive 
  action 
  of 
  the 
  most 
  powerful 
  kind 
  and 
  on 
  the 
  most 
  extensive 
  

   scale, 
  no 
  one 
  can 
  doubt 
  who 
  has 
  examined 
  the 
  extensive 
  deposits 
  

   of 
  the 
  Charnwood 
  Forest, 
  which 
  range 
  from 
  the 
  finest 
  ash 
  to 
  coarse 
  

   agglomerates 
  in 
  which 
  the 
  blocks 
  are 
  several 
  feet 
  in 
  diameter. 
  Prof. 
  

   Bonney 
  and 
  others 
  tell 
  us 
  that 
  the 
  Charn 
  wood-Forest 
  deposits 
  be- 
  

   long 
  to 
  the 
  Archaean 
  series 
  ; 
  and 
  at 
  all 
  events 
  no 
  one 
  will 
  deny 
  that 
  

   they 
  belong 
  to 
  a 
  pre-Carboniferous 
  age. 
  

  

  In 
  these 
  Charnwood-Forest 
  rocks 
  ash 
  predominates 
  and 
  lava-beds 
  

   are 
  very 
  subordinate. 
  Ash-beds, 
  moreover, 
  according 
  to 
  the 
  Geo- 
  

   logical 
  Survey 
  Keport 
  already 
  quoted, 
  are 
  to 
  be 
  found 
  in 
  abundance 
  

   in 
  Cornwall 
  itself, 
  and 
  the 
  beds 
  that 
  contain 
  them 
  are 
  as 
  old, 
  according 
  

   to 
  present 
  received 
  opinion, 
  as 
  the 
  Ordovician 
  age. 
  

  

  That 
  water 
  has 
  flowed, 
  or 
  percolated, 
  through 
  the 
  Lizard 
  born- 
  

   blende-schists 
  in 
  the 
  direction 
  of 
  the 
  banding 
  is 
  not 
  altogether 
  a 
  

   matter 
  of 
  inference 
  or 
  theory. 
  In 
  the 
  following 
  illustration 
  (fig. 
  6) 
  

   I 
  give 
  a 
  sketch 
  taken 
  from 
  one 
  of 
  those 
  banded 
  hornblende-schists. 
  

  

  * 
  The 
  vigour 
  of 
  the 
  response 
  to 
  this 
  suction 
  would, 
  of 
  course, 
  depend 
  on 
  the 
  

   porosity 
  of 
  the 
  rock 
  and 
  the 
  " 
  head" 
  of 
  the 
  water 
  permeating 
  it. 
  

  

  Q.J.G. 
  S. 
  No. 
  179. 
  2p 
  

  

  