398 
DE.  C.  CALLAWAY  ON  THE  ORIGIN  OF  THE 
[Aug.  1893, 
33.  The  Origin  of  the  Ckystalline  Schists  of  the  Malvern  Hills. 
By  Charles  Callaway,  D.Sc.,M.A.,  F.G.S.  (Bead  April  26th, 
1893.) 
[Abridged.] 
Contents. 
Page 
I.  Introduction  . . . 
II.  Confirmation  from  other  Sources  of  some  Points  in  the  Authors 
former  Papers  . 
III.  Stages  of  Metamorphism  . . . 
(1)  Decomposition  and  Corrosion. 
(2)  Reconstruction. 
IV.  Classification  of  the  Malvern  Schists  . 
(A)  Simple  Schists. 
(B)  Injection-Schists. 
(a)  Of  Primary  Injection. 
(b)  Of  Secondary  Injection. 
V.  How  far  the  Schists  indicate  their  Origin  . 
VI.  The  Nature  of  the  Shearing  . •••; . ••• 
VII.  Discussion  of  the  Question  whether  there  has  been  a  Mixing  of  the 
Original  Magmas  . 
VIII.  The  Chemical  Changes . . • . 
IX.  Secondary  Consolidation  . 
X.  Summary  . 
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422 
422 
I.  Introduction. 
The  crystalline  rocks  of  Malvern  are  of  exceptional  importance  to 
the  student  of  the  problems  of  metamorphism,  inasmuch  as  the 
causes  in  operation  have  acted  with  comparative  feebleness,  and 
thus  have  not  obliterated  the  earlier  stages  of  their  work.  Hence 
we  are  able  in  numerous  sections  to  observe  the  details  of  the 
process  by  which  a  massive  igneous  rock  has  been  converted  into  a 
well-foliated  schist. 
In  my  first  paper  1  on  the  subject,  I  gave  an  outline  of  the  mode 
in  which  some  of  the  schists  had  been  formed.  In  the  second,2  I 
described  the  most  important  mineral  changes  that  occur  at  the 
zones  of  shearing.  It  now  remains  to  work  out  certain  structural 
details,  to  meet  difficulties  arising  or  suggested  in  the  course  of  the 
enquiry,  and  to  classify  the  chief  varieties  of  schist  in  the  light  of 
their  mode  of  origin.  I  would  add  that  five  years’  study  of  these 
rocks  has  enlarged  my  belief  in  the  efficacy  of  dynamo-metamorphism, 
to  a  degree  which  I  should  hardly  have  conceived  possible  when  I 
presented  my  first  paper  to  the  Society  in  1887. 
In  the  present  communication,  it  will  be  unnecessary  to  refer  to 
minerals  which  do  not  play  an  essential  part  in  the  metamorphic 
process.  Apatite,  for  example,  does  not,  so  far  as  the  writer  has 
observed,  undergo  any  change.  Sphene,  garnet,  and  rutile  are 
1  Quart.  Journ.  Greol.  Soc.  vol.  xliii.  (1887)  p.  525. 
2  Ibid.  vol.  xlv.  (1889)  p.  475  ;  these  papers  will  (in  the  following  pages)  be 
referred  to  respectively  as  No.  I.  and  No.  II. 
