766 
SIE  CHAELES  LTELL  OX  THE  STEECTrEE  OF  LAVAS 
back  down  a wooded  and  rocky  alpine  valley,  while  on  the  opposite  or  northern  side,  the 
wildest  and  most  magnificent  scenery  of  the  V al  del  Bore  lies  at  our  feet.  To  our  right 
are  the  precipices  of  the  Serra  del  Solfizio  extending  to  Zoccolaro ; and  to  the  left,  the 
vast  pinnacled  and  craggy  promontories  of  rock,  which  jut  out  one  behind  the  other, 
below  the  Montagnuola,  presenting  themselves  in  all  then  grandeur.  Looking  up,  we  see 
the  summit  of  Etna  with  its  wreath  of  white  vapour  streaming  in  the  wind,  while  every 
other  portion  of  the  sky  is  a deep  blue.  The  landscape  is  lighted  up  by  a bright  sunshine 
almost  every  autumnal  morning,  but  soon  after  noon  a body  of  fieecy  clouds,  formed  first 
in  the  lower  region,  rises  up  slowly  and  rolls  into  the  higher  valley,  hiding  from  riew  in 
succession  the  leading  features  of  the  scene,  but  disclosing  fr’om  time  to  time  some 
momentary  glimpses  of  objects  which  had  just  vanished  from  the  sight,  until  the  whole 
are  enveloped  in  one  dense  veil  of  mist. 
In  order  fully  to  appreciate  the  depth  and  width  of  the  two  gaps  made  by  the  tvN'o 
valleys  above  alluded  to,  especially  by  the  Valle  del  Tripodo, — ^breaks  in  the  other- 
wise continuous  southern  rim  of  the  Caldera, — it  is  necessary  to  look  at  them  from  a 
distance,  or  out  at  sea  otf  Aci  Gastello.  By  their  aid  we  see  into  the  interior  of  the 
Val  del  Bove,  from  points  where,  but  for  these  openings,  that  valley  would  be  quite  shut 
out  from  view. 
The  erosion  of  the  Valle  del  Tripodo  is  still  going  on;  and  here  we  have  an  oppor- 
tunity of  studying  a small  inland  delta  at  its  mouth,  and  of  learning  by  means  of  it  how 
much  matter  has  been  brought  down  in  a given  time,  or  during  the  sixty-six  years  which 
have  elapsed  since  1792,  when  a powerful  fiow  of  lava  crossed  the  lower  extremity  of 
the  narrow  valley  and  suddenly  put  a stop  to  all  further  transportation  of  allurium  to 
lower  levels. 
The  waters  of  the  torrent,  even  when  most  swollen,  no  sooner  arrive  at  the  margin  of 
the  lava,  than  they  are  instantly  absorbed  by  its  spongy,  scoriaceous  crust,  and  by  the 
superficial  rents  and  grottos  in  which  it  abounds.  The  engulfed  waters  continue  their 
course  underground,  but  the  mud,  sand,  and  boulders  are  all  left  behind,  and  already 
form  a deposit,  which  may  be  called  an  inland  delta  (see  the  point  marked  “ delta,’’ 
Map,  Plate  L.).  This  deposit  is  several  hundred  feet  long,  100  or  more  broad,  and 
judging  from  the  shape  of  the  ground,  30  or  40  feet  deep.  It  proves,  on  the  one 
hand,  how  much  erosion  has  gone  on  in  httle  more  than  half  a centm-y;  and  on  the 
other,  how  entirely  all  aqueous  action  ceases  in  areas  once  covered  nith  fresh  lava,  and 
where  a superficial  drainage  is  turned  into  a subterranean  one.  The  deep  ra'\ine-like 
valleys  of  S.  Giacomo  and  Cava  Secca,  occurring  about  two  and  a half  miles  to  the 
south-east  of  the  V alle  del  Tripodo,  may  in  like  manner  have  been  excavated  by  running 
water,  and  the  process  is  still  in  full  operation.  Of  this  I became  fully  aware  in  October 
1858,  when,  after  heavy  rains,  I beheld  the  turbid  waters  which  di-ain  them  rushing 
dovm  like  Alpine  torrents,  and  saw  and  heard  repeated  avalanches  of  stones  and  mud 
descending  from  their  steep  sides,  as  well  as  from  the  precipices,  in  Avhich  they  terminate 
abruptly  at  their  upper  ends ; for  they  are  not  continued  upAvards,  like  the  valleys  of 
