726 
SIE  CHAELES  LYELL  OX  THE  STEUCTUEE  OF  LAVAS 
with  a moss,  named  for  me  by  Professor  Toexabeae,  Steelina  pilifera.  I also  found 
some  other  portions  of  the  current  whitened  by  a lichen  called  Stereocaulon,  the  same 
which  I had  seen  on  modern  lava,  both  in  the  Canary  Islands  and  on  Vesuvius.  The 
natural  growth  even  of  a cryptogamous  vegetation,  although  restricted  to  limited  areas, 
on  lava  of  such  recent  date,  is  worthy  of  notice,  and  seems  to  give  promise  of  an  early 
fertility  for  the  future.  More  than  four  centuries  and  a half  have  left  the  lava  of  1381,  at 
L’Ognina  north  of  Catania,  still  black  and  barren,  whereas  the  proprietors  have  akeady 
planted  certain  tracts  of  this  new  current  of  1862-53  with  broom,  which  is  growing 
most  freely. 
Between  Zafarana  and  the  lower  entrance  of  the  valley  of  Calanna,  called  the  Portella, 
we  had  occasion  to  pass  and  repass  daily  certain  portions  of  the  fresh  lava,  the  surface  of 
which  displays  a series  of  longitudinal  ridges  and  furrow's  of  extraordinary  height  and 
depth,  running  nearly  north  and  south  (N.N.W.  and  S.S.E.).  According  to  a rough 
estimate,  I found  that  the  crests  of  the  ridges  rose  from  30  to  70  feet  above  the  bottom 
of  the  intervening  and  parallel  depressions,  and  they  varied  in  number  from  three  to  five 
within  the  same  area,  when  crossed  from  east  to  west.  The  coui’se  of  the  ridges  is  similar 
Fig.  9. — Gigantic  'parallel  ridges  in  the  lava  q/’1852,  near  the  Portella  of  Calanna. 
A.  Older  inclined  lavas  and  tulfs  of  Sciuricosimo. 
Nos.  1 to  5.  Parallel  ridges  running  from  N.N.W.  to  S.S.E.,  and  here  supposed 
to  be  intersected  transversely. 
in  direction  to  that  of  the  lava-current.  The  letter  A,  fig.  9,  represents  the  escarpment 
of  ancient  rocks,  called  Sciuricosimo  (see  Map,  Plate  L.).  The  ridge  No.  1 has  a vertical 
height  of  25  feet  on  its  western  side,  where  it  slopes  at  an  angle  of  30°,  and  on  its  eastern 
side,  where  in  the  steep  part  the  slope  is  50°,  the  height  above  c is  no  less  than  70  feet. 
The  ridges  (Nos.  2,  3,  and  4)  are  respectively  40,  30,  and  25  feet  above  the  mtervening 
depressions.  Nearer  the  Portella,  we  find  some  of  the  fianks  of  these  ridges  inclined  at 
60°;  and  at  certain  points,  where  there  had  been  landslips,  they  w-ere  pei'pendicular  and 
even  overhanging.  In  such  cases,  the  arrangement  consists  of,  first,  one  or  more  kregular 
outer  layers  of  scoriaceous  lava,  2 or  3 feet  thick  in  all,  and  then,  2ndly,  beneath  or 
within  that  outer  crust,  several  concentric  layers  of  compact  rock,  each  from  6 to  10 
inches  thick,  of  the  usual  Etnean  type,  exhibiting  crystals  of  felspar  in  a grey  base,  with 
olhine  and  titaniferous  iron,  and  a few  crystals  of  augite.  These  interior  stony  layers 
we  observed  in  one  case  inclined  at  an  angle  of  more  than  70°. 
Passing  up  from  the  Portella  (see  Map,  Plate  L.),  we  came  to  the  hill  of  Calanna, 
