﻿120 
  GEOKGE 
  MAW 
  S 
  NOTES 
  ON 
  A 
  JOUEN'EY 
  

  

  in 
  the 
  open 
  Sahara 
  plain 
  to 
  a 
  height 
  of 
  a 
  little 
  over 
  2000 
  feet, 
  where 
  

   it 
  is 
  overlain 
  hy 
  sand! 
  1 
  ills. 
  

  

  The 
  raised 
  beaches 
  along 
  the 
  coast, 
  ranging 
  in 
  height 
  from 
  the 
  

   sea-level 
  to 
  600 
  feet, 
  and 
  similar 
  beaches 
  inland 
  south 
  of 
  the 
  Tell 
  

   Plateau, 
  occurring 
  at 
  an 
  elevation 
  of 
  2000 
  feet, 
  may 
  be 
  contempo- 
  

   raneous 
  in 
  age 
  with 
  the 
  Sahara 
  loam. 
  

  

  In 
  addition 
  to 
  these 
  deposits, 
  which 
  are 
  evidently 
  marine, 
  the 
  allu- 
  

   vium 
  of 
  the 
  valley 
  of 
  the 
  Cheliff, 
  near 
  Boukhari, 
  containing 
  bones 
  

   of 
  the 
  Hippopotamus, 
  and 
  the 
  superficial 
  calcareous 
  crust, 
  coating 
  

   both 
  the 
  Sahara 
  loam 
  and 
  the 
  older 
  beds, 
  may 
  be 
  enumerated 
  as 
  the 
  

   most 
  recent 
  formations 
  in 
  Algeria. 
  

  

  Succession 
  of 
  Events, 
  and 
  Changes 
  of 
  Level. 
  — 
  (1) 
  The 
  oldest 
  land 
  

   on 
  the 
  the 
  line 
  of 
  section 
  is 
  the 
  anticlinal 
  of 
  mica-schist 
  near 
  Algiers. 
  

   As 
  the 
  north 
  and 
  south 
  strike 
  is 
  nearly 
  at 
  right 
  angles 
  to 
  the 
  strike 
  

   of 
  the 
  neighbouring 
  Atlas 
  and 
  of 
  the 
  Mesozoic 
  beds 
  of 
  the 
  Tell 
  and 
  

   Hauts 
  Plateaux, 
  which 
  do 
  not 
  seem 
  to 
  have 
  been 
  affected 
  by 
  the 
  

   mica-schist 
  upheaval, 
  these 
  beds 
  must 
  have 
  been 
  more 
  recently 
  de- 
  

   posited. 
  

  

  (2) 
  The 
  upheaval 
  of 
  the 
  Mesozoic 
  rocks 
  may 
  have 
  been 
  contem- 
  

   poraneous 
  with 
  the 
  first 
  upheaval 
  of 
  the 
  chain 
  of 
  the 
  Lesser 
  Atlas, 
  

   striking 
  N.E. 
  by 
  E. 
  and 
  S.W. 
  by 
  W., 
  with 
  which 
  the 
  strike 
  of 
  the 
  

   Mesozoic 
  beds 
  corresponds. 
  

  

  (2) 
  A 
  long 
  period 
  of 
  denudation 
  followed, 
  which 
  removed 
  at 
  least 
  

   a 
  thousand 
  feet 
  of 
  Mesozoic 
  strata 
  from 
  the 
  area 
  of 
  the 
  north 
  Sahara 
  

   plain, 
  and 
  commenced 
  moulding 
  the 
  rocks 
  of 
  the 
  Lesser 
  Atlas 
  into 
  

   hill- 
  and 
  valley-contour 
  ; 
  but 
  there 
  is 
  no 
  clear 
  evidence 
  as 
  to 
  the 
  

   amount 
  of 
  this 
  denudation, 
  which 
  was 
  Pre- 
  and 
  Posttertiary. 
  

  

  (4) 
  A 
  subsidence 
  of 
  at 
  least 
  3000 
  feet 
  during 
  the 
  Tertiary 
  period, 
  

   in 
  whieh 
  were 
  deposited 
  the 
  Miocene 
  beds 
  capping 
  the 
  Tell 
  and 
  

   similar 
  beds 
  at 
  Algiers, 
  fragments 
  of 
  which 
  are 
  seen 
  skirting 
  the 
  

   denuded 
  ravines 
  of 
  the 
  Atlas. 
  

  

  (5) 
  An 
  elevation 
  of 
  at 
  least 
  4000 
  feet 
  of 
  the 
  Tell 
  Plateau, 
  and 
  a 
  

   lesser 
  elevation 
  of 
  at 
  least 
  a 
  thousand 
  feet 
  of 
  the 
  district 
  north 
  of 
  the 
  

   Lesser 
  Atlas 
  chain, 
  including 
  what 
  is 
  now 
  the 
  plain 
  of 
  the 
  Mitidja. 
  

   1 
  am 
  inclined 
  to 
  think 
  that 
  the 
  north 
  face 
  of 
  the 
  Lesser 
  Atlas 
  was 
  a 
  

   Posttertiary 
  line 
  of 
  fault 
  of 
  at 
  least 
  3000 
  feet 
  ; 
  otherwise 
  it 
  is 
  difficult 
  

   to 
  account 
  for 
  the 
  great 
  altitude 
  of 
  the 
  Tertiary 
  beds 
  on 
  the 
  Tell 
  

   compared 
  with 
  the 
  height 
  of 
  those 
  surrounding 
  Algiers. 
  

  

  (6) 
  A 
  long 
  period 
  of 
  denudation 
  followed, 
  during 
  which 
  the 
  Ter- 
  

   tiary 
  beds 
  were 
  removed 
  from 
  the 
  plain 
  of 
  the 
  Mitidja, 
  and 
  a 
  further 
  

   denudation 
  took 
  place 
  of 
  the 
  Mesozoic 
  beds 
  from 
  the 
  north 
  Sahara 
  

   plain. 
  

  

  (7) 
  This 
  was 
  followed 
  by 
  a 
  Posttertiary 
  depression, 
  which 
  I 
  shall 
  

   term 
  the 
  Sahara 
  submergence, 
  during 
  which 
  the 
  formation 
  took 
  place 
  

   of 
  the 
  concrete 
  shell-beds 
  along 
  the 
  Mediterranean 
  coast 
  to 
  a 
  height 
  

   of 
  600 
  feet, 
  and 
  similar 
  beds 
  on 
  the 
  south 
  or 
  inland 
  side 
  of 
  the 
  Tell 
  

   Plateau 
  at 
  a 
  height 
  of 
  at 
  least 
  2000 
  feet. 
  The 
  deposition 
  of 
  shingle 
  

   and 
  loam 
  in 
  the 
  plain 
  of 
  the 
  Mitidja 
  at 
  a 
  height 
  of 
  from 
  100 
  to 
  300feet, 
  

   was 
  probably 
  contemporaneous; 
  and 
  to 
  the 
  same 
  period 
  of 
  submer- 
  

   gence 
  must 
  be 
  ascribed 
  the 
  formation 
  of 
  loam-beds 
  and 
  sand-hills 
  on 
  

  

  