750 
SIE  CHAELES  LTELL  OX  THE  STErCTEEE  OF  LAVAS 
sider  which  of  two  propositions  is  the  more  likely  to  be  true ; first,  the  one  adranced  by 
M.  Elie  de  Beaumoat,  that  a large  portion  of  the  strata  in  the  nucleus  of  Etna,  as  seen 
in  the  Val  del  Bove,  and  now  dipping  at  an  angle  of  28°,  had  an  oidginal  slope  of  only 
5°  or  6°,  the  remaining  20°  or  22°  being  due  to  upheaval;  or  secondly,  the  converse  of' 
the  above,  namely,  that  23°  may  have  been  the  original  average  inclmation,  and  that 
the  additional  5°  or  6°  may  have  been  gained  by  subsequent  movements, — in  other  words, 
a fifth  part  alone  of  the  whole  dip,  save  in  a few  exceptional  cases,  may  be  ascribable  to 
elevation. 
In  favour  of  the  doctrine  that  the  lavas  and  tuffs  of  Etna  have  been  subjected  to  dis- 
turbing forces,  two  arguments  have  been  advanced ; first,  it  is  said  that  the  rocks  of 
fusion,  as  well  as  those  composed  of  fragmentary  materials,  are  inclined  in  many  places 
at  angles  steeper  than  those  at  which  they  could  possibly  settle  on  the  slope  of  a volcanic 
cone  ; 2ndly,  that  in  the  V al  del  Bove  alternate  strata  of  rocks  of  both  kinds  preserv  e a 
uniform  thickness  and  parallelism  over  exceedingly  wide  spaces,  entire  sets  of  them  pre- 
serving their  parallelism  at  points  where  they  are  all  bent  at  once,  and  made  to  assume 
a new  position  with  quite  a different  dip  (see  below,  p.  763).  I shall  begin  by  considering 
the  first  of  these  arguments,  the  only  one,  according  to  my  observations,  to  which  any 
real  weight  can  be  attached. 
The  steepest  dip  of  beds  in  the  modern  or  highest  cone  of  Etna  amormts  to  39°;  the 
most  considerable  which  I saw  in  Vesmius  was  on  the  exterior  of  a small  cone,  then  in 
the  process  of  growth  (October  and  November  1857),  where  the  slope  was  42°;  hut  in 
that  case,  as  before  stated,  p,  737,  I believe  the  scorise,  which  were  red-hot,  and  which 
formed  a sheet  of  matter  glowing  like  lava  after  it  had  fallen,  to  have  been  in  such  a 
state  of  semifusion  as  to  be  capable  of  becoming  agglutinated  or  soldered  together. 
Every  observer  will  grant  that  the  dip  of  nine-tenths  of  the  lavas,  tufis,  and  agglome- 
rates seen  in  sections  of  the  Val  del  Bove,  fall  short  of  the  angles  above  alluded  to,  and 
that  by  far  the  larger  part  of  them  are  under  30°.  The  steepest  inclination  which  I 
measured  was  in  the  outlying  rock  in  the  Val  del  Bove,  called  Finocchio  Infeiiore,  where 
the  beds,  consisting  of  red  scoriae,  with  a few  intercalated  layers  of  lava,  dip  at  one 
point,  at  angles  as  high  as  from  45°  to  47°,  towards  the  N.W.,  whereas  other  beds  near 
them,  and  separated  only  by  a dike,  dip  from  30°  to  38°  N.E.  The  scoriae  here  are  of 
such  a nature  as  might  originally  have  had  a very  steep  dip,  and  they  are  traversed  by 
so  many  dikes,  some  vertical,  others  many  degrees  out  of  the  perpendicular,  that  no 
geologist  would  deny  that  local  fracture  and  subsequent  dislocations  may  have  operated 
as  disturbing  causes,  to  say  nothing  of  the  possibility  of  such  an  outlier  ha'ving  had  its 
position  altered  bodily  by  that  subsidence,  and  those  explosions  to  which  we  refer,  in 
part  at  least,  the  origin  of  the  great  valley. 
[In  the  lofty  escarpment  of  the  Serra  del  Solfizio,  near  the  Montagnuola,  the  beds  of 
lava,  scoriae,  and  fragmentary  matter  (the  latter  greatly  preponderating  in  volume  over 
the  lava)  are  horizontal,  or  nearly  so,  in  the  upper  half  of  the  precipice,  while  in  the 
lowest,  800  or  1000  feet,  they  have  a steep  inward  dip  away  fi'om  the  Val  del  Bo’se. 
