VARIOLITE  OE  THE  LLEYN. 
165 
Yol.  49.] 
Fig.  3.  Breccia,  from  a  small  quarry  on  the  hillside  west  of  Careg  (north  of 
Aberdaron),  probably  due  to  flow.  The  fragments  show  a  tendency 
to  fluxion-structure :  they  are  bordered  by  small  incipient  spheru- 
litic  formations,  within  a  thick  deposit  of  opacite.  The  part  left  clear 
is  mainly  palagonite,  probably  an  altered  basic  glass.  A  small  crystal 
of  felspar  is  contained  within  one  fragment.  (Magnified  8  diam.) 
Fig.  4.  From  rock  on  the  beach,  at  the  eastern  part  of  the  isthmus  of  Dinas- 
fach.  A  breccia,  including  fragments  of  a  spherulitic  andesite  and  of 
slate  or  argillite.  The  radial  structure  represents  the  spherulitic 
fragments,  consisting  mainly  of  felspar.  The  dotted  parts  represent 
pseud omorphic  dolomite.  The  darker  shaded  fragments  consist  of 
argillite.  The  part  between  the  fragments  represents  mainly  pala¬ 
gonite,  and  the  rock  is  probably  a  flow-breccia.  (Magnified  30  diam.) 
Fig.  5.  Variolite,  from  the  cliff  north  of  Porth  Oer.  The  spherulites  shown  on 
the  right  of  the  figure  have  a  central  part  darkened  by  ferrite,  and 
are  contained  within  rings  of  granular  deposit,  somewhat  similar  to 
the  boundaries  in  the  specimen  which  was  described  from  Arran  by 
Prof.  Bonney  (see  p.  156).  This  structure  passes  gradually  to  the 
part  without  distinct  spherulites,  shown  on  the  left  of  the  drawing. 
The  groundmass  here  consists  of  granular  opacite,  and  of  felspar  - 
microliths.  (Magnified  15  diam.) 
Fig.  6.  Exterior  zone  of  a  spheroid  from  near  Porth-din-lleyn,  south  of  the 
lifeboat-house.  This  part  of  the  spheroid  shows  incipient  spherulitic 
structure  in  the  form  of  non-radial  aggregates,  which  in  many  cases 
are  grouped  around  felspar-microliths.  The  slide  is  crossed  by  a  vein 
filled  with  a  secondary  deposit  or  palagonite.  The  small  group  of 
spherules  to  the  left  of  the  vein,  which  is  less  shaded  in  the  drawing, 
is  seen  under  polarized  light  to  be  pseudomorphosed,  showing  the 
bright  pi nk-and -green  colours  of  dolomite.  (Magnified  20  diam.) 
Discussion. 
Prof.  Judd  complimented  the  Authoress  on  the  evidently  great 
amount  of  labour  and  patient  research  devoted  to  this  investigation. 
He  thought  the  occurrence  of  the  spherulitic  structure  round  the 
surfaces  of  ‘  pillow-like  masses  ’  similar  to  those  described  by 
Prof.  Dana  was  exceedingly  interesting,  especially  when  one  con¬ 
sidered  the  probably  very  great  antiquity  of  these  Caernarvonshire 
rocks.  He  thought,  also,  the  suggestion  that  early  crystallized 
magnetite-grain 3  had  formed  the  nuclei  of  the  spherulites  was  a 
very  interesting  and  probable  one. 
Mr.  Harker  expressed  satisfaction  at  the  further  discovery  of 
variolites  in  Britain — rocks  presenting  interesting  points  of  resem¬ 
blance  to  those  known  in  Savoy,  Hesse,  and  Bavaria.  He  anticipated 
that  the  detailed  researches  of  the  Authoress  would  throw  light  on 
the  nature  of  these  spherulitic  structures  in  basic  igneous  rocks. 
Prof.  Bonnet  said  he  believed  that  the  variolite  described  by  the 
Authoress  was  the  third  example  in  the  United  Kingdom,  that 
discovered  by  Mr.  Blake  in  Anglesey  being  the  first,  and  that  found 
by  Prof.  Cole  in  Ireland  the  second.  He  referred  to  the  question  of 
the  origin  of  spherulites,  and  stated  his  opinion  that  this  paper,  the 
fruit  of  much  labour,  would  prove  a  valuable  contribution  to  our 
knowledge  of  the  subject. 
Prof.  Hull  and  Prof.  J.  F.  Blake  also  spoke. 
