ME.  HOENEE  ON  THE  ALLUVIAL  LAND  OF  EGYPT. 
67 
the  surface  on  which  the  sediment  has  been  deposited,  in  insulated  patches  of  the  uneven 
ground,  the  fellah,  wading  in  mud,  begins  to  throw  seed  upon  them,  in  contour  lines, 
his  light  boat  bringing  to  him  his  seed  com.  As  the  retreating  waters  expose  more 
land,  so  soon  as  it  is  sufficiently  drained,  another  zone  of  ground  is  sown,  and  so  on 
until  the  lowest  parts  have  received  the  seed,  which  must  be  cast  before  the  surface 
begins  to  crack ; and  after  it  has  been  cast,  it  is  beaten  down  into  the  mud  with  a flat 
piece  of  wood  at  the  end  of  a pole.  During  the  dry  season,  when  vegetation  withers, 
and  the  underground  water  has  subsided,  the  ground  cracks  into  numerous  and  deep 
fissures,  forming  the  usual  polygonal  fissures  we  see  in  dry  mud  or  clay,  aflbrding 
receptacles  for  the  flying  sand.  For  three  or  four  months  in  every  year  the  surface  of 
the  valley,  stript  of  vegetation,  in  the  state  of  a dry  powder,  is  swept  by  violent  winds, 
raising  storms  of  dust.  By  these  combined  causes,  therefore,  every  trace  of  the  depo- 
sited layer  must  be  effaced*.  Instances  of  lamination  and  alternations  of  clay  and  sand, 
such  as  those  mentioned  by  Captain  Newbold,  are  not  unfrequently  met  with  in  the 
banks  of  the  river,  and  at  the  entrances  of  canals ; but  they  are  local  occurrences  caused 
by  eddies  and  cm’rents.  I have  in  my  possession  specimens  of  such  laminated  sediment 
firom  the  right  bank  of  the  river  near  Helwan,  a few  miles  above  Cairo. 
8thly.  That  there  are  occasional  accumulations  of  soil,  the  materials  of  which  are 
only  remotely  derived  from  the  inundation  water  and  the  storms  of  desert  sand.  In  the 
neighbourhood  of  old  buildings,  and  on  the  sites  of  former  buildings,  where  these  have 
been  constructed  of  crude  bricks,  the  soil,  to  a considerable  depth,  may  have  been 
derived  from  the  disintegration  of  these  bricks.  The  soil,  thus  derived,  would  have 
nearly  the  same  aspect  as  the  natural  deposit  of  Nile  mud.  In  the  Heliopolis  exca- 
vation B (Memoir’,  Part  I.  p.  132),  crude  bricks  were  seen  to  have  been  the  origin  of 
the  soil  there  by  visible  rectangular  lines  chequering  the  sides  of  the  pit.  This  last 
appearance,  however,  must  be  a rare  occurrence,  for  the  action  of  the  inundation  water 
softens  the  bricks  and  causes  them  to  melt,  as  it  were,  into  a homogeneous  mass. 
9thly.  That,  in  nearly  every  part  of  the  ground  penetrated,  artificial  substances  have 
* I have  stated  in  Part  I.,  p.  108,  that,  “ with  an  inclination  so  slight  as  that  of  the  land  over  which  the 
inundation  spreads,  the  solid  insoluble  matter  must  in  great  part  remain  where  it  is  deposited.”  I did  not 
then  take  into  account  the  violent  winds  which  swept  over  the  parched  land,  and  transport  the  soil  in  vast 
clouds  of  dust.  Neither  did  I take  into  account  the  great  absorption  of  the  constituents  of  the  soil  by  the 
grain  crops  which  succeed  the  inundation.  In  Johnston’s  ‘Elements  of  Agricultural  Chemistry,’  p.  71, 
we  find  the  following  statement : — “ 1000  lbs.  of  the  ash  of  the  straw  of  wheat,  barley,  oats,  rye,  and  Indian 
corn  have  been  found  to  contain  respectively, — 
Wheat. 
Barley. 
Oats. 
Rye. 
Indian  Corn. 
Silica 
654  lbs. 
676  lbs. 
484  lbs. 
645  lbs. 
270  lbs. 
Lime  
67 
85 
81 
90 
83 
Magnesia  
39 
50 
38 
24 
66 
Oxide  of  iron  
13 
10 
18 
14 
8 
773 
821 
621 
773 
427” 
