WHICH  HAVE  CONSOLIDATED  ON  STEEP  SLOPES. 
743 
I 
o 
can  be  more  striking  than  the  absence  here,  deep  in  the  internal  framework 
of  all  disturbance,  just  where  it  ought  to  have  been  most  manifest,  had  there 
truth  in  the  upheaval  theory ; since  as  we  climb  up,  we  are 
always  approaching  nearer  to  the  great  central  axis  or  highest  | g 
cone.  Lastly,  I found  a south-easterly  dip  at  angles  varying  ^ 
from  7°  to  15°  in  the  upper  mass,  800  or  1000  feet  thick,  | | 
composed  of  old  lavas  and  beds  of  fragmentary  matter  below  I 
the  Torre  del  Filosofo  and  Cisterna,  a state  of  things  irre-  g 
concileable,  so  far  as  1 can  see,  Avith  any  hypothesis  save 
that  of  a double  axis,  as  above  mentioned*. 
It  is  right,  however,  to  mention  in  this  place,  that  at  the 
upper  edge  of  the  precipice  under  the  Montagnuola  1 
obsers’ed  a slight  northerly  dip  in  certain  tuffs  and  lavas,  as 
shown  at  c,  fig.  16.  This  dip  1 ascertained  not  only  on  close 
inspection,  but  on  viewing  them  from  a distance  of  nine 
miles  east,  or  near  Bongiardo.  They  appear  to  be  a conti- 
nuation of  those  beds  which  are  seen  below  the  Cisterna  at 
h,  a,  but  as  the  natural  sections  are  not  complete  we  cannot 
prove  their  prolongation.  Such  an  exceptional  inclination 
towards  the  axis  of  Mongibello  may  suggest  the  idea  of  an 
independent  centre  of  eruption  at  or  near  the  site  of  the 
Montagnuola,  or  if  the  beds  belong  to  the  same  system  as 
a,  h,  they  may  have  been  slightly  tilted  by  movements  which 
accompanied  the  two  great  eruptions  to  which  the  older 
and  newer  craters  and  cones  of  the  Montagnuola  owe  their 
origin.  That  the  older  of  these  cones  was  due  to  eruption 
as  well  as  the  newer,  is  a conclusion  to  which  1 arrived  after 
exploring  it  in  1858,  and  Signor  G.  G.  Gemmellaro  tells 
me  that  since  1 was  there  he  has  \isited  it  and  has  come  to 
the  same  opinion.  It  must  at  least  be  admitted,  that,  had  the 
steep  dips  in  the  older  of  the  two  cones  been  due  to  upheaval, 
as  some  have  suggested,  the  beds  in  the  great  escarpment  at 
of  Etna, 
been  any 
I 
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1 
CO 
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tib 
• ^ 
* I had  the  pleasure  of  receiving  a letter,  dated  March  3,  1858,  from 
M.  Aeicii,  full  of  valuable  drawings,  illustrative  of  the  structure  of  Etna, 
which  has  been  published  in  the  15th  vol.  p.  117,  of  the  Gleological  So- 
ciety’s Quarterly  Journal  for  1859.  Among  other  sections,  that  distin- 
guished geologist  has  given  one  (fig.  6,  p.  121,  ibid.)  to  show  the  “ almost 
horizontal  position”  of  the  beds  high  up  or  in  the  middle  of  the  precipice 
of  the  Serra  Griannicola  observed  by  him  in  1834.  He  also  speaks  of  a 
double  axis  of  Etna,  the  older  one  to  the  east  of  the  present  centre,  but 
he  treats  the  subject  too  briefly  to  enable  me  to  judge  how  far  his  views  coincide  with  those  set  forth  in 
fig.  15,  p.  38. 
MDCfJCLVIII.  5 E 
I.  Lavas  and  scorise  with  south-south-easterly  dip.  c.  Same  with  northerly  dip 
