WHICH  HAVE  CONSOLIDATED  ON  STEEP  SLOPES. 
753 
Evidence  of  pseudo-parallelism  and  want  of  uniform  thicJcness  of  the  beds 
forming  the  escarpments  of  the  Val  del  Bove. 
M.  Elie  de  Beaumont,  in  his  celebrated  Essay  on  Mount  Etna  before  cited,  has  repre- 
sented the  escarpments  of  the  Val  del  Bove  as  being  composed  of  many  hundreds  of 
perfectly  regular  beds,  formed  alternately  of  rocks  of  fusion  and  of  fragmentary  and 
pulverulent  materials.  He  describes  the  thickness  of  the  beds  as  varying  from  a few 
inches  to  several  yards,  but  averaging  about  6 feet  each,  the  fragmentary  beds  being  gene- 
rally, though  not  always,  thicker  than  the  lavas.  At  the  same  time,  he  insists  on  the 
remarkable  uniformity  in  thickness  and  parallelism  of  the  several  members  of  this  whole 
series,  and  their  continuity  for  great  distances,  a fact  adduced  as  confirmatory  of  the 
doctrine  that  the  beds  were  originally  horizontal,  and  were  afterwards  brought  by 
upheaval  into  their  present  position.  The  same  author  states,  that  “ the  most  general 
and  the  most  conclusive  character  of  the  numerous  beds  of  fused  and  fragmentary  mat- 
ter consists  in  this,  that  they  are  liable,  all  of  them,  to  be  bent  together  as  they  pass  in 
several  difierent  (Erections,  from  a nearly  horizontal  position  to  an  inclination  of  from 
25°  to  30°,  without  either  theh  structure  or  their  thickness  being  altered  with  any 
degree  of  regularity*.”  The  volcanic  strata  are  therefore  likened  by  him  to  the  regular 
sedimentary  formations  which  have  undergone  great  flexures  in  mountain  chains. 
To  begin  with  the  northern  escarpment  of  the  Val  del  Bove,  we  obtained  (Signor  G. 
G.  Gemmellaeo  and  I)  a good  general  view  of  the  precipices  composing  it,  from  Monte 
Finocchio  Inferiore  and  its  neighbourhood.  First  we  turned  our  attention  to  part  of  the 
nearly  vertical  clifi*  immediately  N.E.  of  our  station,  where  the  height  exceeds  1000  feet. 
It  was  called  by  om-  guide  the  Serra  di  Cerrita,  and  is  part  of  the  Concazze.  We  could 
count  in  this  part  as  many  as  sixty  beds,  more  solid  and  prominent  than  the  rest,  which 
we  had  no  doubt  were  lavas  or  rocks  of  fusion,  and  we  recognized  in  the  series  many 
marked  deviations  from  parallehsm.  One  case  in  particular  was  very  conspicuous,  for  a 
single  bed  of  rock  [a,  fig.  19),  the  thickness  of  which  we  estimated  roughly  at  40  feet, 
was  represented  or  replaced,  at  the  distance  of  a few  hundred  yards  westwards,  at  h,  by 
Pig.  19. — Want  of  uniformity  in  thicJcness  in  stony  layers  in  northern  escarpment  of  Val  del  Bove, 
* “ Le  caractere  le  plus  general  et  le  plus  concluant  de  ces  nombreuses  assises  de  matieres  fondues  et  de 
matieres  fragmentaires  qui  alternent  pour  former  le  noyau  de  la  gibbosite  centrale  de  I’Etna  m’a  paru  con- 
sister  en  ce  cpJelles  sont  sujettes  a s'injlechir  toutes  ensemble,  en  passant  dans  plusiev/rs  directions  diverses, 
d' mie  position  a peu  pres  horizontale  a une  inclinaison  de  25°  a 30°,  sans  que  leur  structure  ni  leur  epaisseur 
en  soient  alterees  d'une  maniere  constante.”  The  italics  are  in  the  original.  Mem.  pour  servir,  &c.,  pp.  130, 
131.  Again,  we  find,  p.  165,  “ I’uniformite  d’epaisseur  et  I’exacte  paraUelisme  que  conservent  au  milieu 
d’ inflexions  varices,”  &c. 
5f2 
