﻿380 
  REV. 
  E. 
  HILL 
  ON 
  THE 
  ROCKS 
  OF 
  

  

  24. 
  The 
  Eocxs 
  of 
  Allerxey 
  and 
  the 
  Casquets. 
  By 
  Eev. 
  E. 
  Hill, 
  

   M.A., 
  F.G.S., 
  Eellow 
  and 
  Tutor 
  of 
  St. 
  John's 
  College, 
  Cam- 
  

   bridge. 
  (Eead 
  May 
  8, 
  1889.) 
  

  

  1. 
  General 
  Description. 
  

  

  2. 
  Principal 
  Igneous 
  Masses. 
  

  

  3. 
  Minor 
  Igneous 
  Rocks. 
  

  

  4. 
  The 
  Grits. 
  

  

  5. 
  Age 
  of 
  the 
  Grits. 
  

  

  6. 
  Comparisons 
  and 
  Conclusions. 
  

  

  1. 
  General 
  Description. 
  

  

  Alderney 
  is 
  seldom 
  visited 
  and 
  has 
  been 
  seldom 
  described. 
  It 
  

   deserves 
  both 
  description 
  and 
  visit. 
  Macculloch 
  gives 
  an 
  account 
  of 
  

   it 
  in 
  the 
  first 
  paper 
  of 
  the 
  first 
  volume 
  of 
  our 
  ' 
  Transactions.' 
  Ansted, 
  

   in 
  his 
  ' 
  Channel 
  Islands,' 
  notices 
  many 
  features 
  with 
  accuracy, 
  and 
  

   seems 
  to 
  have 
  taken 
  a 
  special 
  interest 
  in 
  the 
  place. 
  Since 
  his 
  time 
  

   I 
  am 
  not 
  aware 
  of 
  a 
  single 
  addition 
  to 
  our 
  knowledge 
  until 
  the 
  

   admirable 
  map 
  of 
  Erance 
  by 
  MM. 
  Yasseur 
  and 
  Carez, 
  sheet 
  No. 
  IV. 
  

   IST.E. 
  of 
  which 
  assigns 
  colours 
  and 
  letters 
  to 
  the 
  island. 
  After 
  the 
  

   first 
  draft 
  of 
  this 
  paper 
  had 
  been 
  Avritten, 
  a 
  paper 
  by 
  M. 
  Bigot* 
  came 
  

   into 
  my 
  hands, 
  containing, 
  besides 
  notes 
  on 
  Jersey 
  and 
  Guernsey, 
  

   a 
  brief 
  but 
  excellent 
  description 
  of 
  Alderney, 
  which 
  includes 
  several 
  

   of 
  the 
  facts 
  that 
  I 
  have 
  independently 
  discovered. 
  

  

  I 
  have 
  to 
  thank 
  Professor 
  Bonney 
  for 
  invaluable 
  notes 
  on 
  the 
  

   rock-sections, 
  which 
  he 
  has 
  allowed 
  me 
  to 
  incorporate 
  in 
  this 
  paper. 
  

  

  Alderney 
  is 
  an 
  oval 
  island 
  (see 
  Map, 
  p. 
  381f), 
  about 
  3J 
  miles 
  long 
  

   by 
  1 
  mile 
  broad, 
  lying 
  E.K.E. 
  to 
  W.S.W. 
  The 
  western 
  portion 
  is 
  a 
  

   tableland 
  just 
  over 
  300 
  feet 
  in 
  height, 
  which, 
  along 
  the 
  west 
  and 
  

   south, 
  falls 
  in 
  grand 
  cliffs 
  to 
  the 
  sea, 
  but 
  slopes 
  to 
  the 
  shore 
  along 
  

   the 
  north-western 
  side. 
  The 
  eastern 
  extremity 
  is 
  separated 
  from 
  

   this 
  by 
  lower 
  ground 
  and 
  the 
  deep 
  indentation 
  of 
  Longy 
  Bay, 
  but 
  

   above 
  the 
  Mannez 
  Quarry 
  and 
  at 
  Eort 
  Albert 
  there 
  are 
  elevations 
  of 
  

   140 
  feet 
  and 
  180 
  feet 
  respectively. 
  Distant 
  about 
  a 
  mile 
  and 
  a 
  half 
  

   to 
  the 
  W.N.W., 
  across 
  a 
  channel 
  called 
  The 
  Swinge, 
  lies 
  Burhou, 
  an 
  

   uninhabited 
  island, 
  with 
  nearly 
  a 
  mile 
  of 
  rock 
  available 
  for 
  exami- 
  

   nation 
  when 
  low 
  tide 
  lays 
  bare 
  the 
  reefs 
  to 
  the 
  west. 
  Around 
  it 
  is 
  

   an 
  archipelago 
  of 
  rocks, 
  the 
  Yerte 
  Tete, 
  the 
  Nannels, 
  Les 
  Mac- 
  

   quereaux, 
  exposed, 
  awash, 
  or 
  sunken, 
  to 
  ships 
  dangers 
  of 
  every 
  

   kind 
  and 
  degree, 
  to 
  the 
  fishermen 
  and 
  pilots 
  sea-marks 
  and 
  fishing- 
  

   grounds. 
  A 
  sunken 
  ridge 
  runs 
  west 
  for 
  some 
  three 
  miles, 
  bearing 
  

   these 
  and 
  other 
  rocks 
  and 
  reefs, 
  its 
  end 
  marked 
  far 
  over 
  the 
  sea 
  by 
  

  

  * 
  Bull. 
  Soc. 
  Geol. 
  de 
  France, 
  1888, 
  p. 
  412. 
  

  

  t 
  This 
  map 
  is 
  drawn 
  on 
  a 
  reduced 
  scale 
  from 
  the 
  English 
  Admiralty 
  chart 
  of 
  

   " 
  Alderney 
  and 
  Casquets," 
  which 
  visitors 
  should 
  obtain 
  and 
  use. 
  The 
  

   dotted 
  lines 
  round 
  the 
  shores 
  are 
  intended 
  to 
  indicate 
  areas 
  exposed 
  at 
  low 
  

   water. 
  The 
  broken 
  line 
  marks 
  the 
  railway-track 
  ; 
  some 
  of 
  the 
  roads 
  are 
  shown 
  

   by 
  continuous 
  lines. 
  Cap 
  La 
  Hague, 
  the 
  nearest 
  point 
  of 
  the 
  mainland, 
  is 
  dis- 
  

   tant 
  a 
  little 
  less 
  than 
  10 
  miles, 
  due 
  east 
  across 
  the 
  Eace 
  of 
  Alderney. 
  

  

  