532 
ME.  J.  POSTLETHWAITE  ON  AN  INTENSIVE  [NoV.  1893, 
(now  in  the  Keswick  Museum  of  Local  Natural  History),  hut  it  has 
not  been  described  in  any  of  his  published  works.1  My  first  hurried 
visit  to  the  locality  took  place  in  the  spring  of  1890,  when  I  was 
engaged  in  preparing  a  paper  on  ‘  The  Metallic  and  other  Minerals 
surrounding  the  Skiddaw  Granite,’  and  on  that  occasion,  owing 
partly  to  the  faulted  nature  of  the  ground,  and  partly  to  the  imper¬ 
fect  examination  I  was  then  able  to  bestow  upon  it,  I  concluded 
that  the  intrusive  sheet  was  not  more  than  half-a-mile  in  length.  A 
more  thorough  examination  of  the  ground  on  a  subsequent  visit 
enabled  me  to  trace  it  over  a  mile  and  a  half  in  length,  and  on 
referring  to  J.  C.  Ward’s  map  I  found  that  there  was  still  an 
extension  of  the  sheet  to  the  east  of  Tarn  Kevin  which  I  had  failed 
to  discover. 
The  diabase  of  which  the  intrusive  sheet  is  composed  is  of  a  light 
grey  colour ;  it  varies  a  little  in  texture,  being  fine-grained,  hard 
and  compact  in  some  places,  and  in  others  moderately  coarse¬ 
grained.  The  rock  is  often  much  decomposed  near  the  surface. 
There  are  in  some  places,  associated  with  the  diabase,  a  good  deal 
of  opaque  white  quartz  and  some  calcite,  the  latter  occasionally 
filling  cavities  and  joints.  The  presence  of  the  quartz  and  calcite, 
and  the  knowledge  that  antimony  had  been  obtained  near  Kobin 
Hood,  led  me  at  first  to  believe  that  there  was  a  metallic  vein 
associated  with  the  diabase ;  further  investigation,  however,  proved 
that  this  opinion  was  incorrect,  the  vein-material  only  occurring  in 
irregular  patches.  Prof.  Bonney  submitted  a  fragment  of  the 
diabase  to  Mr.  Morris  W.  Travers,  of  University  College,  London, 
to  be  tested  for  antimony,  and  that  gentleman  ascertained  the 
presence  of  the  metal,  in  small  quantity,  in  the  calcite,  but  he  found 
that  the  rock-substance  of  the  diabase  did  not  appear  to  contain  any 
of  the  mineral.  It  is  probable,  therefore,  that  the  deposition  of  the 
quartz,  calcite,  and  antimony  has  been  the  result  of  thermal  action 
following  the  intrusion  of  the  diabase ;  and  the  thermal  action  seems 
to  have  been  most  intense  near  Kobin  Hood  House,  as  it  is  said  that 
about  20  tons  of  antimony  were  obtained  there  and  sent  to  market 
some  50  years  ago.  A  shaft  was  sunk  at  the  place,  and  a  level  was 
driven  some  distance,  partly  to  drain  off  the  water,  partly  for  the 
purpose  of  making  further  exploration,  but  apparently  without 
success.  Small  excavations  were  also  made  at  several  other  points 
along  the  course  of  the  intrusive  sheet,  but  the  ore  does  not  appear 
to  have  been  present  in  sufficient  quantity  to  warrant  further 
operations. 
About  300  feet  north  of  the  intrusive  sheet  of  diabase,  there  is  a 
parallel  bed  of  very  fine-grained  grit,  from  5  to  6  feet  in  thickness. 
The  materials  of  which  this  grit  is  formed  have  probably  been 
derived  to  some  extent  from  the  denudation  of  ore-bearing  veins,  as 
it  contains  a  very  high  percentage  of  silica,  with  small  quantities  of 
manganese,  antimony,  and  lead.  Minute  grains  of  these  minerals 
1  [I  find,  however,  that  it  is  mapped  by  the  Geological  Survey,  Sheet  101 
N.E.,  issued  to  the  public  about  the  end  of  April  of  the  present  year. — July  31st, 
1893.] 
