770 
SIR  CTIARLES  LTELL  OX  THE  STEUCTERE  OF  LAVAS 
The  lateral  ravines  also,  mentioned  at  page  754,'  bear  testimony  to  the  removing  po^ver 
of  running  water,  since  the  Val  del  Bove  was  bounded  by  lofty  precipices. 
Even  the  torrent  in  the  suburbs  of  Giarre,  which  is  usually  diy,  and  the  channel  of 
which  slopes  towards  the  sea  at  an  angle  of  less  than  4°,  had  in  October  1857  carried 
to  some  distance  fragments  of  stone  9 feet  m diameter,  derived  from  the  older  drift  of 
its  banks.  What,  then,  may  not  have  been  the  force  of  running  water  in  the  woody 
zone,  where  the  mean  fall  is  7°  or  8°,  if  the  whole  drainage  of  the  eastern  slope  of  Etna, 
instead  of  being  as  now  subterraneous,  was  for  a time  superficial,  after  a suspension  for 
some  thousands  of  years  of  the  flowing  of  lava  1 
We  have  already  explained  wh)^,  in  the  present  state  of  the  Val  del  Bove,  no  denu- 
dation on  a large  scale  can  take  place.  The  obliteration  from  the  map  of  Sicily  of  the 
river  Amenano  by  the  lava  of  1669,  is  a good  illustration  of  the  antagonism  of  aqueous 
erosion  and  volcanic  activity.  Previous  to  1669,  the  inundations  of  that  river  were 
often  destructive  of  houses  in  Catania;  but  from  the  era  alluded  to,  the  waters  have 
always  made  their  way  underground,  and  flow  out  clear  and  transparent  from  the  extre- 
mity of  the  lava  in  the  harbour  of  the  great  city.  In  like  manner,  at  some  former 
period  there  may  have  existed  many  rivers  in  the  V al  del  Bove  like  those  now  draining 
the  Calderas  of  Palma  and  Tiraxana  in  the  Canaries,  and  like  them  they  may,  after 
uniting,  have  issued  by  one  principal  gorge ; yet  they  would  ineritably  be  all  effaced 
from  the  map,  and  the  gorge  filled  up  with  stony  matter,  whenever  the  time  arrived, 
during  a new  phase  of  eruption,  for  fresh  floods  of  lava  to  traverse  the  Caldera.Jso 
0 
Flood  0/1755  in  the  Val  del  Bove. 
The  only  well-authenticated  instance  of  a great  body  of  water  having  passed  Aom  the 
higher  region  of  Etna  through  the  Val  del  Bove  to  the  sea,  was  in  the  year  1755.  An 
eruption  had  taken  place  at  the  summit  of  the  volcano  in  the  month  of  March,  a season 
when  the  top  of  the  mountain  was  covered  with  snow.  The  Canon  Eecupero,  a good 
observer  and  a man  of  great  sagacity,  was  commissioned  by  Charles  of  Bouebox,  king 
of  Naples,  to  report  on  the  nature  and  cause  of  the  catastrophe.  He  accordingly  visited 
the  Val  del  Bove  in  the  month  of  June,  three  months  after  the  event,  and  fomid  that 
the  channel  of  the  recent  flood,  no  less  than  two  Sicilian  miles  broad,  was  still  strewed 
over  with  sand  and  fragments  of  rock,  to  the  depth  of  40  palms  *. 
The  volume  of  water  in  a length  of  one  mile  he  estimated  at  16  millions  of  cubic  feet, 
and  he  says  that  it  ran  at  the  rate  of  a mile  in  a minute  and  a half  for  the  first  twelve 
miles.  At  the  upper  end  of  the  Val  del  Bove,  all  the  pre-existing  inequalities  of  the 
ground,  for  a space  of  two  miles  in  length  and  one  in  breadth,  were  perfectly  le^■elled 
up  and  made  quite  even,  and  the  marks  of  the  passage  of  the  flood  were  traceable  from 
thence  up  the  great  precipice  (or  Balzo  di  Trifoglietto),  to  the  Piano  del  Eago,  or  highest 
X)latform.  Eecupero,  in  his  report,  maintains  that  if  all  the  snow  on  Etna,  which  he 
* The  falm  iu  use  iu  Sicily  is  10-^^  inches  English : eight  of  these  palms  make  one  canna,  and  720  caniie 
one  Sicilian  mile. 
