80 
ME.  HOEJ^EE  ON  THE  ALLUVIAL  LAND  OE  EGYPT. 
Trachelomonas  granulata^  Tafel  xxxv.  A.  13. 
Eunotia  amphioxys,  Tafel  xiv.  31.  Taf.  xxxix.  29,  30. 
Phytolithaeia. 
lAthostylidium  rude,  Tafel  111.  iii.  21. 
Lithostylidium  quadratum,  Tafel  xxxiv.  vi.  6. 
lAthostylidium  spinulosum,  Tafel  xxxv.  A.  xiv.  6. 
lAthostylidium  Trabemla,  Tafel  xxxiv.  vi.  8. 
Ldthodontium  nasutum,  Tafel  xxxix.  61,  62. 
Lithodontium  rostratum,  Tafel  i.  iii.  25. 
Spongolithis  acicularis,  Tafel  I;  i.  16. 
Spongolithis,  Tafel  xxxiv.  v.  B.  16. 
Spongolithis,  Tafel  x.  22. 
Spongolithis,  Tafel  xiv.  109. 
Note  C,  page  72. 
M.  Gieard’s  estimate  of  the  Secular  Increase  of  the  alluvial  land. 
His  conclusions  were  founded  on  observations  made  at  the  ruined  Nilometer  on  the 
island  of  Elephantina,  near  Assouan,  and  afterwards  at  the  existing  Nilometer  on  the 
island  of  Rhoda  near  Cairo. 
He  visited  Elephantina  towards  the  end  of  July  1799,  and  formd  at  the  shore  a wall 
or  quay  160  metres  (525  feet)  in  length,  and  in  a part  of  it  a gallery  and  chamber,  and 
from  the  latter  a staircase  leading  down  to  the  river.  On  cleaning  the  walls  of  this 
staircase,  he  observed  upon  them  four  vertical  grooves  cut  into  the  stone  to  a depth  of  a 
centimetre  (about  -j^ths  of  an  inch)  with  horizontal  divisions,  which  proved  to  be  marks 
of  cubits,  some  of  them  having  numbers  annexed  to  them.  He  had  thus  no  doubt  that 
he  had  found  the  Nilometer.  “ The  last  cubit,”  says  M.  Girard,  “ of  this  Nilometer  is 
marked  in -Greek  characters  with  the  number  24;  that  was,  in  effect,  Egyptian  cubits, 
the  use  of  which  was  continued,  as  we  know,  under  the  Ptolemies,  indicating  the  height 
of  great  inundations,  as  measured  immediately  below  the  last  cataract.  At  the  time, 
therefore,  when  the  Nilometer  was  constructed,  the  inundations  did  not  rise  beyond 
that  mark To  compare  the  level  of  the  twenty-fourth  cubit  of  this  Nilometer  uith 
that  of  the  highest  recent  inundations,  it  was  necessary  to  know  the  height  to  which  the 
latter  rise  at  this  place,  and  fortunately  the  marks  they  leave  are  not  obliterated  from 
year  to  year,  and  we  observed  them  very  distinctly  on  the  face  of  the  wall  of  the  quay, 
behind  which  the  scale  of  the  Nilometer  is  traced.  The  result  of  the  levelings  I took, 
to  determine  the  space  between  the  twenty-fourth  cubit  of  the  Nilometer  and  the  level 
of  the  highest  inundations  of  the  present  time,  showed  a difference  of  2 HI  3 metres 
(7  feet  11  inches).  Thus,  the  bed  of  the  Nile  has  risen  by  that  amount,  at  least,  be- 
tween the  time  when  the  Nilometer  was  erected,  for  there  is  no  reason  to  think  that  the 
