714 
SIE  CHAELES  LTELL  ON  THE  STEHCTTEE  OP  LATAS 
yards  westwards  from  F towards  G (fig.  3),  gradually  rising  100  feet  or  more  from  the 
Bastione  to  near  the  top  of  the  platform  of  Aci  Eeale.  The  crust  of  scoriae  is  sometimes 
Pig.  3. — Section  in 'part  ideal  of  the  lavas  and  of  the  ancient  cmd  modern  cliff  at  A.ci  JReale. 
A,  B,  C.  Portion  of  the  lavas  and  tuffs  supposed  to  have  been  removed  hy  the  sea. 
B,  C,  E,  G.  Lava-current  of  the  Bastione,  of  which  a portion,  B,  D,  P,  C,  was  afterwards  removed  by  the  sea. 
E,  P.  Existing  cliff  at  the  Scalazza. 
0,  i.  East  and  west,  or  longitudinal  section  seen  at  the  Bastione. 
The  interrupted  lines  — indicate  the  brick-red  tuffs  and  soils  torrified  by  the  overlying  lavas. 
(as  may  be  seen  at  the  road-side  on  the  Scalazza  close  to  the  Bastione),  separated  mto 
irregular  alternate  layers  of  solid  dolerite  and  beds  of  loose  scoriae.  From  the  point 
where  the  natural  section  (fig.  2,  p.  713,  and  o,  ^,  fig.  3)  presents  itself,  this  upper  crust 
unites  without  any  break  with  the  mass  which  we  can  follow,  through  gardens,  and  also 
in  another  line  up  a steep  lane,  to  a point  where  the  dip  is  gradually  reduced  to  15°. 
Still  higher  up  the  hill  we  arrive  at  the  church  of  Santa  Maria,  where  in  the  subiu'bs  of 
Aci  Beale,  a lava,  which  I believe  to  be  the  same,  has  a dip  of  only  9°. 
If  the  red  stratum,  indicated  in  fig.  3 by  the  interrupted  line  above  o,  i,  on  which  the 
inclined  dolerite  of  the  Bastione  rests,  had  consisted  simply  of  a burnt  soil  derived  fr-om 
the  decomposition  of  an  older  and  subjacent  lava,  we  might  have  supposed  the  rmrrsually 
steep  dip  of  23°  and  29°  to  have  arisen  from  the  accident  of  the  newer  crnreirt  harirrg  at 
this  point  overflowed  the  terminal  slope  of  a preexisting  lava ; for  when  lavas  come  to 
a halt  (as  is  well  exemplified  by  the  rrewest  of  all  the  Etnean  currerrts,  that  of  1852  in 
the  suburbs  of  Zafarana),  they  commonly  end  in  a steep  wall,  20  and  30  feet  or  often 
more  in  height,  and  sloping  at  angles  of  from  20°  to  35°,  as  represented  at  H,  fig.  3. 
But  this  hypothesis  is  rendered  untenable  by  the  fact  that  the  stratum  of  tufif  and  lapilh 
burnt  red,  is  not  the  disintegrated  surface  of  an  underlying  lava,  brrt  the  upper  pari  of 
a series  of  strata  of  tuff  and  loose  black  sand  containing  borrlders,  deposits  such  as  we 
find  in  the  wide  channels  of  torrents  on  the  flanks  and  near  the  base  of  Etna. 
To  explain,  therefore,  the  steep  inclination  which  the  sur-face  of  the  stratum  (B,  fig.  2, 
p.  713,  and  i,  fig.  3)  had  acquired  before  the  lava  G,  F,  C,  B reached  the  preserrt  site  of  the 
Bastione,  I think  it  necessary  to  suppose  that  a sea-cliff  (D,  d,  o,  i)  already  existed,  the 
top  of  the  cliff  consisting  of  beds  of  brown  tuff  and  loose  black  sand,  forming  the  mass  ^ as 
above  described,  which  as  a whole  was  too  iircoherent  to  produce  a precipice,  but  which 
