506  PRE-CAMBRIAN   GEOLOGY   OF   NORTH   AMERICA. 
bearing  Silurian  rocks  are  seen  to  rest  uncon forma bly  on  a  gneissoid 
series  between  Stillwater  and  Uniacke  station  on  the  Halifax  and 
Windsor  Railway,  and  near  the  village  of  Sherbrooke,  in  Guysboro 
County.  This  series  of  Huronian  rocks  is  composed  of  beds  of  gneiss, 
interstratified  with  micaceous  schists,  schist  conglomerate,  beds  of 
true  quartzite,  and  grits.  The  gneiss  is  sometimes  porphyritic,  and 
the  upper  beds  are  almost  always  conglomeratic,  holding  pebbles  and 
masses  of  schists,  grits,  and  conglomerates,  which  are  found  in  this 
series.  This  older  series  rests  unconformably  upon  the  Laurentian. 
The  contacts  are  visible  on  the  Halifax  and  Windsor  Railway,  near 
New  Stillwater  and  Mount  Uniacke  stations.  The  gold-bearing  Silu- 
rian strata  are  also  found  to  repose  unconformably  upon  the  Lauren- 
tian.    This  contact  is  also  observed  near  Mount  Uniacke  station. 
Silliman,50  in  18G4,  finds  that  the  gold-bearing  rocks  of  Nova 
Scotia  extend  along  the  Atlantic  coast  for  250  miles,  from  Cape 
Sable  to  Cape  Canso.  These  rocks  are  hard,  slaty  ones,  which  are 
sometimes  micaceous  schists,  and  occasionally  granitic.  When  strati- 
fied they  are  always  found  standing  at  a  high  angle,  sometimes 
almost  vertical,  and  in  the  main  with  an  east-west  course.  The  zone 
of  metamorphic  rocks  varies  in  width  from  G  to  8  miles  at  its  eastern 
extremity  to  40  or  50  at  its  widest  part,  the  area  covered  being  about 
G,000  square  miles.  While  no  fossil  evidence  has  been  found  in  any 
of  these  slates,  opinion  seems  to  favor  the  belief  that  they  belong 
to  the  Silurian  age,  but  as  yet  no  place  has  been  found  where  the 
rocks  next  higher  in  the  geological  column  may  be  seen  resting  upon 
them.  The  most  noticeable  rock  of  the  gold  region  is  a  dark-gray 
massive  rock,  which  resembles  a  trap,  but  which  is  really  a  granular 
quartzite.  It  has  three  well-defined  planes  of  cleavage,  by  which  it 
breaks  into  very  irregularly  shaped  masses.  This  rock  is  of  enor- 
mous thickness,  and  is  undoubtedly  the  fundamental  or  basement 
rock  of  the  region. 
Selwyn,51  in  1872,  in  studying  the  gold-bearing  slates,  believes  that 
they  belong  to  the  Primordial-Silurian  epoch.  As  evidence  of  this 
is  given  the  discovery,  in  the  slates  of  Ovens  Bluffs,  of  numerous 
specimens  of  the  genus  Eophyton. 
The  granite  impresses  this  author  as  of  strictly  indigenous  charac- 
ter, and  neither  a  granitoid  gneissic  series  of  Laurentian  age  nor  an 
intrusive  mass.  The  line  of  contact  with  the  Silurian  and  Devonian 
leaves  no  doubt  of  its  posterior  origin,  but  whether  intrusive  or  meta- 
morphic in  situ  is  perhaps  uncertain. 
Robb,52  in  1876,  finds  that  a  massive  syenite  and  associated  crystal- 
line rocks  have  a  rather  widespread  distribution  in  Cape  Breton.  At 
some  points  the  Carboniferous  rocks  are  brought  into  contact  with 
the  syenite,  but  at  a  few  points  there  are  interposed  metamorphic 
calcites,  argillites,  and  quartzites,  associated  with  dolomites  and  other 
