144  THE  PETROGRAPHY  OE  THE  ISLAND  OE  CAPRAJA,  [May  1 8 9 3 r 
]STo.  YII.  is  an  anamesite  from  Punta  del  Zenobito.  • 
Xo.  YITI.  is  a  piece  from  the  cone  of  scoria  in  Gala  Rossa. 
"When  in  place,  the  cavities  of  the  scoria  are  filled  with  the  secon¬ 
dary  mineral  4  bole.’  The  piece  analysed,  however,  was  a  fragment 
on  the  beach,  from  whose  pores  all  the  bole  had  been  leached  by 
the  action  of  the  sea.  It  was  deemed  more  advisable  to  analyse 
the  scoria  thus  free  from  bole,  as  a  separate  analysis  of  the  bole 
was  also  undertaken,  the  results  of  which  are  given  in  Ho.  IX. 
Roth  it  and  the  scoria  were  carefully  washed,  after  pulverization 
and  before  analysis,  so  as  to  eliminate  any  sodium  chloride  which 
might  have  been  absorbed  from  the  sea-water. 
Lastly,  I  ma3T  mention  the  occurrence  of  a  mineral  in  small 
quantities  just  north  of  Punta  del  Trattojo,  called  by  the  Caprajans 
‘  vitreol,’  and  used  by  them  for  healing  purposes.  It  is  found 
sometimes  in  a  silky,  fibrous  form,  and  sometimes  botryoidal;  it  is 
white,  except  when  tinged  yellow  from  traces  of  iron.  Qualitative 
analysis  showed  it  to  be  a  magnesian  alum. 
I  cannot  conclude  without  expressing  my  warmest  gratitude  to 
Herr  Prof.  Zirkel  for  the  kindly  interest  which  he  has  evinced  and 
the  valuable  assistance  which  he  has  given  me  during  my  work 
on  the  rocks  of  Capraja  ;  my  thanks  are  also  due  to  Herr  Dr. 
Lenk,  assistant  in  the  Mineralogical  Institute  at  Leipzig  ;  and  last, 
though  not  least,  to  Herr  Dr.  Rohrig,  for  his  willingness  to  set  aside 
other  work  in  order  to  complete  my  analyses. 
Discussion. 
Dr.  Du  Riche  Preller  gave  an  outline  of  the  leading  geological 
and  the  analogous  petrological  features  of  the  several  islands  of  the 
Tuscan  Archipelago,  of  Corsica,  Sardinia,  the  Carrara  Mountains, 
and  the  Maremma  Hills.  These  groups,  he  said,  were  the  remains 
of  the  old  post-Tertiary  and  subsequently  submerged  Tyrrhenian  Con¬ 
tinent,  which  connected  Southern  Prance  and  Liguria  with  Africa  : 
the  continuance  of  the  ancient  Alpine  4  greenstone  ’-chain  and  the 
curved  axis  of  the  Alps  being,  moreover,  demonstrated  by  the  pre- 
Silurian  serpentines  of  the  various  islands.  Dr.  Preller  showed 
that,  with  the  significant  exception  of  the  Trias,  which  only  appeared 
in  the  Carrara  Mountains,  and  of  the  Cretaceous  Series,  the  Tuscan 
Archipelago,  conjointly  with  Corsica,  Sardinia,  and  the  Maremma 
Hills,  included  every  formation  from  pre-Silurian  to  post-Tertiary, 
and  that  the  eruption  of  the  andesitic  rocks  of  Capraja  probably 
took  place  in  the  early,  and  that  of  the  lava  in  the  same  island  in 
the  more  recent  post-Tertiary  period. 
The  President  also  spoke. 
