716 
SIE  CHAELES  LTELL  ON  THE  STEHCTTJEE  OE  LAVAS 
below y*,  and  not  far  from  the  Grotto  delle  Palombe,  we  see  a longitudinal  section  for 
the  space  of  100  feet,  the  scoriaceous  crust  being  removed  by  denudation.  Here  a 
central  stony  but  not  compact  layer  is  laid  open  to  view,  2 or  3 feet  thick,  with  a dip 
of  25°.  On  the  margin  of  the  sea,  we  find  below  the  scoriaceous  crust,  a stony  mass, 
more  than  20  feet  thick,  exposed  in  a vertical  clilf,  at  the  foot  of  which  the  waves  have 
excavated  a cavern  14  feet  high,  called  the  Grotto  delle  Palombe  (D,  fig.  1,  p.  712),  only 
approachable  in  a boat.  Here  the  rock  is  compact  and  columnar,  the  erect  and  often 
weU-shaped  pillars  being  composed  of  a dark  dolerite.  Over  the  cave,  in  a bed  of  lava 
in  which  many  fragments  of  scorise  are  involved,  oblique  and  irregular  prisms  appear. 
Still  higher  up,  a nearly  horizontal  stratum,  4 feet  thick,  with  a vertically  prismatic 
structure,  is  observable.  As  this  coast  has  undergone,  as  before  stated,  p.  710,  an  up- 
ward movement  in  very  modern  times,  it  is  possible  that  the  lava  of  Indirizzo  and  of 
the  Grotto  delle  Palombe  may  be  ancient  enough  to  have  participated  in  the  upheaval, 
in  which  case  the  columnar  mass  may  have  been  at  first  submarine,  and  may  have  cooled 
on  a gently  sloping  ledge  of  rock.  We  cannot,  however,  infer  its  original  submergence 
from  the  prismatic  structure  alone,  because  we  have  innumerable  examples  in  Auvergne 
and  the  Vivarrais  of  subaerial  lavas,  in  which  there  are  fine  ranges  of  basaltic  columns 
as  perfect  as  any  in  the  Giant’s  Causeway  or  Fingal’s  Cave. 
About  a mile  north  of  Santa  Tecla,  and  nearly  three  miles  north  of  Aci  Eeale,  another 
much  more  modern  lava,  namely,  that  of  1329,  is  seen  descending  from  the  interior  or 
region  of  lateral  cones,  and  entering  the  sea  at  a place  where  the  coast  is  much  less  lofry- 
than  at  Aci,  with  a breadth,  as  will  be  seen  by  S.  Vais’  Waltekshausest’s  map,  of  about 
a mile.  If  we  refiect  on  its  position,  as  well  as  on  that  of  many  other  lavas  of  different 
ages  which  have  thus  poured  down  one  after  the  other  over  these  sea-cliffs  whde  the 
waves  are  always  eating  away  the  sea  margin,  the  hypothesis  above  suggested  in  expla- 
nation of  the  steep  slope  of  the  tuff  underneath  the  lava  of  the  Bastione  of  Aci  will  not 
seem  far-fetched  or  improbable.  But  in  whatever  manner  we  may  account  for  that 
slope,  it  is  undeniable  that  a mass  of  compact  dolerite,  20  feet  thick,  exposed  to  Hew  at 
the  Bastione,  has  consolidated  into  compact  rock,  with  a dip  of  23°,  26°,  and  29°;  and 
had  the  sea  removed  as  much  of  the  current  of  the  Grotto  delle  Palombe  (or  C,  fig.  1) 
as  I assume  it  to  have  done  in  the  case  of  Aci  at  B,  E,  F,  C (fig.  3,  p.  714),  a similar 
exhibition  of  stony  beds  dipping  at  angles  as  great  or  greater  would  I beheve  have  been 
made.  But  this  the  reader  will  be  more  ready  to  admit  when  he  has  fully  considered 
the  section  next  to  be  described. 
Highly  inclined  lava  of  Cava  Gi'ande. 
From  the  Scalazza  of  Aci  Eeale,  we  journeyed  (Signor  G.  G.  Gemmellaeo  and  I. 
October  1857)  by  Giarre  and  La  Macchia,  and  thence  through  part  of  the  woody  region 
to  the  great  chestnut,  called  the  “ Castagno  dei  Cento  Cavalli,”  which  stands  on  a 
tufaceous  deposit  at  a height  of  more  than  2000  feet  above  the  sea.  We  then  went 
direct  to  Milo,  and  in  our  way  fell  in  with  a second  fine  example  of  a sheet  of  modern 
