[ 703  ] 
XXXII.  On  the  Structure  of  Lavas  which  have  consolidated  on  steep  slopes;  with 
EemarJcs  on  the  Mode  of  Origin  of  Mount  Etna^  and  on  the  Theory  of  “ Craters  of 
Elevation^  By  Sir  Chaeles  Lyell,  F.B.S.,  JD.C.L. 
Eeceived  June  10, — Read  June  10,  1858*. 
CONTENTS. 
Paet  I. 
Page 
THE  STEHCTUEE  OE  MODERN  LAYAS  WHICH  HAVE  CON- 
GEALED ON  STEEP  SLOPES  ON  MOUNT  ETNA 705 
Preliminary  remarks  on  tlie  characters  commonly  attributed  to  laras  which  have 
consolidated  on  steep  slopes,  and  on  the  theory  of  “ Craters  of  Elevation  ” ...  705 
Recent  shower  of  ashes,  September  1857,  from  the  summit  of  Etna  709 
Alluvial  deposits  and  external  featimes  of  the  coast  along  the  eastern  base  of 
Etna  709 
Highly  inclined  stony  lava  of  Aci  Eeale  711 
Section  of  lava  of  the  year  1689,  inclined  at  35°,  in  the  Cava  Grande  716 
Structure,  aspect,  and  inclination  of  the  lavas  of  the  great  eruption  of  1852-53  ...  719 
Narrative  of  the  eruption 720 
Burnt  area 724 
Gigantic  parallel  ridges  near  the  PorteUa  of  Calanna  726 
Steeply  inclined  branch  of  the  lava  of  1852  at  the  head  of  the  valley  of 
Calanna  730 
Obliteration  of  the  junction-lines  of  successive  and  overlying  lava-streams  732 
Steeply  inclined  modem  lava  in  the  Cava  Secca  near  Zafarana  733 
Compact  Lava  of  modem  date,  inclined  at  35°,  below  the  Cisterna  734 
* [This  paper  was  read  to  the  Royal  Society  on  the  10th  of  June,  1858,  and  a full  abstract  of  it  was  printed 
in  the  ‘ Proceedings  ’ for  that  month.  In  September  of  the  same  year  I revisited  Naples  and  Sicily,  for  the 
sake  of  re-examining  certain  points  in  the  geology  of  Vesuvius  and  Etna,  devoting  five  weeks  to  the  explo- 
ration of  the  latter  mountain.  The  additional  facts  and  inferences  obtained  at  that  time  have,  by  leave  of 
the  Council,  been  embodied  in  the  present  memoir ; all  the  newly -intercalated  passages  being  marked  by 
Irackets,  thus  [ ],  or  such  as  are  simply  recasts  of  the  original  MS.,  thus  cg[  ]s).  By  comparing  the  abstract 
published  in  June  (Proceedings  of  the  Royal  Society,  June  10th,  1858)  last  with  the  present  memoir,  it  'will 
be  seen  that  they  agree  with  each  other  in  all  essentials,  whether  of  fact  or  theory.] 
MDCCCLVIII.  4 Z 
