EXPLANATION  OF  PLATES  II.  &  III. 
la  Plate  II.  the  very  characteristic  weathered  surfaces  of  the  fused  granite 
of  the  Cuiliin  Hills  is  represented,  all  the  figures  being  of  the  natural  size. 
Fig.  1.  Shows  a  mass,  probably  from  near  the  edge  of  an  inclusion,  in  which 
the  most  perfect  flow-structure  is  exhibited.  The  fine  bands,  which 
are  slightly  different  in  colour,  can  in  places  be  seen  to  be  formed  of 
drawn-out  spherulites.  Microscopic  examination  shows  that,  in  this 
case,  the  phenocrysts  have  been  almost  completely  absorbed  in  the  glass. 
Fig.  2.  A  somewhat  similar  banded  spherulite,  in  which  the  bands  have,  by  the 
movements  of  the  molten  mass,  been  made  to  assume  beautiful 
puckerings  and  contortions,  so  well  exemplified  in  some  of  the  rhyo¬ 
lites  of  Hungary,  the  Ponza  Islands,  and  many  other  districts. 
Fig.  3.  A  very  striking  example  of  a  banded  mass,  with  spherulites  of  very 
different  sizes,  drawn  out  and  crushed.  This  rock  greatly  resembles 
certain  varieties  of  rhyolite  from  Obsidian  Cliff. 
Fig.  4.  A  rock  showing  the  puckered  banding  in  union  with  large  spherulites, 
which  are  sometimes  ‘  lithophyses.’ 
Fig.  5.  Very  characteristic  ‘  hollow  spherulites,’  exposed  by  weathering. 
(In  the  last  two  figures  the  phenocrysts  of  the  original  granite  are  very  con¬ 
spicuous  and  stand  out  in  relief.) 
In  Plate  III.  microscopic  sections  of  the  altered  minerals  and  the  spherulitic 
growths  of  these  inclusions  are  represented. 
Fig.  1.  Shows  quartz-crystals  with  large  glass  enclosures,  the  crystals  being 
much  cracked,  while  in  places  the  surrounding  glass  has  penetrated 
along  and  opened  out  the  cracks. 
Fig.  2.  Shows  a  quartz-crystal  which,  by  the  corrosive  action  of  the  glass  pene¬ 
trating  along  cracks,  has  been  broken  into  four  fragments.  The 
action  of  these  fragments  under  polarized  light  shows  that  they  are 
parts  of  the  same  crystal. 
Fig.  3.  A  greatly  cracked  quartz-crystal  which  has  had  developed  around  it  a 
shell  of  secondary  ‘  pyrogene  ’  quartz.  The  secondary  quartz  is 
seen  filling  a  crack  which  traverses  both  crystal  and  matrix.  The 
secondary  and  original  quartz  show  perfect  continuity  in  polarized  light. 
Fig.  4.  Two  orthoclase-crystals,  twinned  and  untwinned,  with  ‘  contraction- 
rifts,’  along  which  secondary  felspar-substance  has  been  developed. 
Fig.  5.  Ort hoclase-crystal  similarly  altered,  but  with  a  nucleus,  probably  con¬ 
taining  stone- cavities  originally,  which  has  been  completely  fused. 
(Figures  1-5  are  represented  as  seen  with  a  power  magnifying  30  diameters.) 
Fig.  6.  Small  oligoclase-crystal  lying  in  a  mass  of  glass  containing  trichites, 
now  converted  into  hydrous  iron  oxide  ;  many  of  these  are  attached  to 
the  edges  of  the  felspar. 
Fig.  7.  Section  of  one  of  the  largest  of  the  complex  spherulites,  natural  size; 
the  dark  parts  represent  the  ordinary  spherulitic  growths  (see  fig.  8), 
and  the  paler-coloured  portions  the  ‘  trichitic  spherulites  ’  (see  fig.  9). 
These  spherulitic  growths  radiate  from  and  enclose  smaller  spheru¬ 
lites  and  the  original  phenocrysts  of  the  granite. 
Fig.  8.  Ordinary  spherulitic  growths  forming  the  smaller  dark  portion  of  this 
spherulite,  and  showing  radiating  and  concentric  structure,  with 
numerous  scattered  grains  of  magnetite  which  give  them  their  dark 
colour  ;  magnified  30  diameters. 
Fig.  9.  Trichitic  spherulitic  growths,  with  similar  radiating  and  concentric 
structure,  which  make  up  the  larger  part  of  the  spherulite.  High 
powers  show  that  the  pale  creamy  tint  is  due  to  innumerable  trichites 
which  have  been  converted  into  brown  oxide  of  iron.  The  figure 
shows  a  tuft  seen  with  a  magnifying  power  of  30  diameters. 
Fig.  10.  Spherulite,  with  nucleus  of  micropegmatitic  granite  ;  natural  size. 
Fig.  11.  Nucleus  of  micropegmatitic  granite  magnified,  showing  the  sur¬ 
rounding  vitrified  crust  with  crystals  of  pyrites. 
Fig.  12.  Spherulites,  natural  size,  with  two  nuclei  of  micropegmatitic  granite. 
Fig.  13.  Enlargement  of  the  upper  and  larger  of  these  nuclei,  with  its  glassy 
crust.  (It  is  this  granite  mass  which  is  shown  as  seen  under  the 
microscope  in  the  figure  on  p.  189.) 
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