724 
SIE  CHAELES  LTELL  ON  THE  STEUCTUEE  OF  LAVAS 
consumed  some  of  the  richest  land  in  Sicily.  At  the  same  time  changes  were  observed 
in  the  form  of  the  highest  cone  and  crater  of  Etna.  In  November  some  of  the  lava 
which  issued  from  below  the  cone  called  Centenario,  was  seen  to  lam  in  a canal,  or 
beneath  an  arched  crust  of  solid  scoriee,  where  the  sm-face  had  cooled  and  solidified. 
The  united  breadth  of  the  several  lava-streams  must  have  equalled  two  Enghsh 
miles,  if  measured  in  a north  and  south  direction  towards  the  eastern  or  lower  limits  of 
the  Val  del  Bove,  and  then’  length  was  about  six  miles. 
All  January,  February  and  March,  1853,  intermittent  explosions  and  ejections  of 
scoriae  took  place  in  the  Val  del  Bove,  and  so  late  as  the  26  th  of  April  the  lava  was  still 
seen  piling  itself  up,  one  stream  over  another,  in  the  district  of  Zapinelh ; nor  was  it  till 
the  27th  of  May,  1863,  more  than  nine  months  from  the  date  of  its  commencement, 
that  this  memorable  eruption  ceased. 
In  regard  to  the  temperature  of  the  advancing  lava,  those  currents,  says  Dr.  Mer- 
cuRio,  which  were  fluid  (by  which  he  eridently  means  those  which  were  not  greatly 
encumbered  on  their  surface  and  sides  with  scorise  and  stony  fragments),  radiated  so 
much  heat,  that  trees  caught  fire  and  were  consumed  at  the  distance  of  several  paces, 
whilst  other  currents,  which  he  compares  to  a heap  of  moring  stones,  enveloped  the  fn-iit- 
trees  with  detached  fragments  along  their  borders,  so  that  they  were  not  even  scorched. 
So  slowly  indeed  was  the  heat  conducted  through  the  scoriaceous  materials,  that  some 
of  the  trees  actually  vegetated  anew,  and  burst  forth  a second  time  into  flower  [ihid.). 
The  depth  of  the  lavas  varied  from  8 to  16  feet,  but  as  successive  streams  were  often 
piled  one  over  another,  they  attained  double  and  treble  that  thickness  in  some  spots, 
and  near  the  Portella  they  seemed  to  me  to  reach  a height  of  150  feet. 
There  can  be  little  doubt  that  the  various  apertures  (figs.  1,  2,  and  3,  Plate  L.)  which 
emitted  lava  in  August  1852,  each  of  which  were  formed  successively  at  lower  and  lower 
levels,  beginning  at  a great  height  and  not  far  below  the  Torre  del  Filosofo,  were  all  of 
them  in  connexion  with  the  axis  or  highest  crater  of  Etna ; for  tliis  crater  sent  forth 
from  time  to  time,  from  the  commencement  of  the  eruption  to  near  its  close,  dense 
clouds  of  vapour,  and  occasionally  red-hot  scoriae. 
Burnt  area. — A singular  event  of  peculiar  geological  interest  occui’red  some  weeks 
after  the  27th  of  May,  when  to  all  appearance  the  flooring  of  lava  had  entirely  ceased, 
and  when  all  the  currents  had  become  encrusted  over  mth  so  fii'm  a covering  of  scoriae 
that  the  inhabitants  could  walk  upon  them  with  safety.  Within  a certain  area  (marked 
as  the  “burnt  area”  on  the  Map,  Plate  L.),  six  or  seven  hundred  yards  in  diameter,  and 
situated  between  Zafarana  and  Ballo,  all  the  fruit-trees  and  rines  were  struck  dead  as  if 
by  lightning.  The  ground  exhaled  no  hot  gases,  and  the  vegetation  did  not  sufier  in  the 
space  intervening  between  the  parched-up  area  and  the  recent  lava,  which  was  only  a 
few  hundred  yards  distant.  Dr.  Giuseppe  Gemmellaro  has  suggested  as  the  most  natu- 
ral explanation  of  this  phenomenon,  that  the  lava  must  gradually  have  made  its  way 
through  underground  passages,  until  coming  beneath  the  fields  alluded  to,  its  heat 
dried  up  the  roots  of  the  plants.  It  is  well  known  that  vaults  and  tunnels  abound 
