244  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  I  bull.  86. 
Faribault,64  in  1887,  reports  on  the  gold-bearing  area  of  southern 
Nova  Scotia.  These  rocks  occupy  6,000  or  7,000  square  miles.  They 
are  divided  into  a  granitic  division  and  a  lower  Cambrian  division. 
The  lower  Cambrian  rocks  include  quartzites,  clay-slates,  and  con- 
glomerates, and  are  estimated  to  have  a  thickness  of  15,000  feet. 
These  rocks,  always  greatly  altered,  are  much  more  so  when  cut  by 
masses  of  granite,  and  over  considerable  districts  have  been  rendered 
thoroughly  crystalline,  the  quartzites  passing  into  fine  gneissic  rocks, 
and  the  mica-slates  into  mica-schists.  Following  Campbell,  they  are 
divided  into  a  lower  or  quartzite  group,  11,000  feet  thick,  and  an  upj)er 
or  graphitic  and  ferruginous  slate  group,  about  4,000  feet  thick.  The 
first  of  these,  while  in  the  main  quartzite,  is  interstra titled  with 
numerous  bands  of  slates  and  one  or  two  of  conglomerate.  The  Cam- 
brian rocks  are  greatly  disturbed  from  their  original  horizontally, 
being  folded  into  a  series  of  sharp  parallel  undulations.  In  the 
more  altered  portions  the  planes  of  bedding  are  not  easily  distin- 
guished from  those  of  slaty  cleavage,  the  latter  often  being  more  dis- 
tinct. The  rocks  are  referred  to  the  Cambrian  upon  the  evidence  of  a 
single  fossil,  Eophyton.  The  group  is  analogous  in  some  respects  to 
Lawson's  lake  of  the  Woods  series.  The  granites  are  found  to  cut  the 
Cambrian  rocks  at  many  places,  and  at  times  are  associated  with 
gneisses.  At  the  edge  of  large  masses  the  granite  frequently  passes 
into  a  foliated  schistose  rock,  losing  its  crystalline  texture,  and  itself 
passing  insensibly  into  the  altered  sedimentary  rocks. 
Dawson  (Sir  William)65,  in  1888,  places  the  isolated  rocks  of  St. 
Anns,  mountain  in  the  lower  Lauren tian,  and  regards  it  as  probable 
that  rocks  of  this  kind  exist  in  the  northern  extremity  of  the  island. 
In  Nova  Scotia  proper  no  true  Laurentian  is  recognized,  the  rocks  here 
referred  by  other  observers  being  intrusive  granite  masses  of  much 
later  date  associated  with  altered  rocks. 
SUMMARY  OF   RESULTS. 
In  Nova  Scotia  and  Cape  Breton,  as  in  southern  New  Brunswick,  is 
a  great  variety  of  eruptive  and  intrusive  rocks,  both  basic  and  acid,  and 
of  varying  age.  It  is  also  plain  that  there  is  to  be  here  included  con- 
siderable masses  of  rocks  which  were  in  early  days  referred  to  the  Lau- 
rentian. The  intrusive  character  of  the  granites  was  appreciated  by 
Jackson  as  early  as  1832.  Since  that  time  the  only  observer  who  has 
not  agreed  with  this  conclusion  is  Hind,  who  strongly  maintains  that 
they  are  metamorphosed  sediments.  His  facts,  however,  clearly  dis- 
tinguishable from  his  theory,  point  to  an  eruptive  origin  of  the  granite. 
The  chief  fact  cited  in  favor  of  their  being  water- deposited  rocks  is  the 
presence  of  roundish  fragments  of  slates,  quartzites,  and  schists  remote 
from  the  contacts  with  these  rocks.  All  the  other  facts  given  by  him — 
i.  e.,  the  irregular  fashion  in  which  the  granite  veins  intrude  the  schists,- 
the  abundance  of  large  angular  fragments  of  these  schists  and  slates 
