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HERR  V.  MADSEN  ON  SCANDINAVIAN 
[-Feb.  1893, 
7.  Scandinavian  Boulders  at  Cromer.  By  Herr  Victor  Madsen, 
of  the  Danish  Geological  Survey.  (Communicated  by  J.  W. 
Hulke,  Esq.,  E.B.S.,  For.Sec.G.S.  Bead  December  21st, 
1892.) 
During-  a  visit  to  England  in  the  autumn  of  1891,  I  took  the 
opportunity  of  making  a  short  excursion  to  Cromer  in  order  to  study 
the  interesting  geological  facts  presented  in  the  well-known  cliffs 
near  that  village. 
On  my  walks  along  these  cliffs  my  attention  was  especially  devoted 
to  the  boulders  which  occur  there,  for  I  thought  it  possible  to.  find 
some  which  might  with  certainty  be  referred  to  definite  localities  m 
Scandinavia.  The  greater  number  of  the  boulders  there  originate 
indeed,  as  I  expected,  from  disturbed  portions  of  the  Cretaceous  strata 
which  underlie  the  Drift  in  the  vicinity  of  Cromer,  so  that  it  is  only 
a  few  of  the  boulders  which  are  likely  to  be  of  Scandinavian  origin, 
and  of  these  again  only  a  small  number  can  be  definitely  referred  to 
their  parent  localities. 
Among  the  boulders  on  the  shore  a  little  west  of  Cromer  I 
succeeded  in  finding  a  ‘  porphyry  ’-boulder  which  I  supposed  had 
been  derived  from  the  south-eastern  part  of  Norway,  and  this 
supposition  was  subsequently  confirmed  by  Herr  E.  0.  Bjorlykke,  of 
the  "Norwegian  Geological  Survey,  to  whom  I  showed  the  boulder 
and  who  referred  it  to  the  neighbourhood  of  Christiania. 
This  boulder  measures  about  4|  X  3J  X  2  inches.  The  ground- 
mass  is  rather  decomposed  and  of  a  grey-violet  colour ;  in  it  are 
disseminated  crystals  of  felspar  which,  on  fresh  fracture,  show  the 
same  colour  as  the  groundmass,  while  those  on  the  surface  of  the 
boulder  have  become  somewhat  paler  by  decomposition.  The  sec¬ 
tions  of  the  crystals  are  fairly  rectangular,  sometimes  rhombic.  A 
large  rhombic  crystal  on  the  surface  of  the  boulder  measured  j  inch 
in  length  and  \  inch  in  breadth,  but  most  of  the  crystals  are  \  inch 
long  and  J  inch  broad.  Several  of  them  are  considerably  smaller, 
i.  e.  about  J  inch  in  both  dimensions. 
At  Cromer  I  called  on  Mr.  A.  Savin,  who  gave  me  permission  to 
examine  several  hundred  boidders  which  he  had  collected  in  the 
vicinity.  Among  them  X  found  two  which  I  thought  might  have 
come  from  Dalarne  in  Sweden,  and  those  Mr.  A.  Savin  was  kind 
enough  to  make  me  a  present  of.  They  were  the  only  two  in  the 
whole  collection  which  were  sufficiently  characteristic  to  be  un- 
hesitatinglv  referred  to  definite  localities  in  Scandinavia. 
One  of  these  boulders  is  a  4  porphyry’  with  greyish-brown  ground- 
mass,  in  which  are  seen  white  crystals  of  felspar  whose  greater 
dimensions  vary  from  ^  to  inch  and  less,  and  greenish,  partly  de¬ 
composed  hornblende-crystals  of  about  the  same  size.  It  does  not 
contain  macroscopically  visible  quartz.  Mr.  A.  Savin  had  taken  it 
out  of  Boulder  Clay  between  Cromer  and  Overstrand,  one  mile  south- 
