240  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.  86. 
metamorphism  due  to  the  baking  of  sedimentary  rocks  by  heat  and  water, 
while  quartzite  consists  of  graius  of  flinty  sand  fused  together.  The 
preponderant  rocks  are  thick  bands  of  slate  and  quartzite  having  a 
general  northeast  and  southwest  strike  and  highly  inclined.  Whether 
the  mica  schists  and  gneiss  of  cape  Canso,  and  Queen's  and  Shel- 
bnrne  counties,  and  the  chloritic  beds  of  Yarmouth  are  to  be  regarded 
as  more  metamorphosed  members  of  the  Lower  Silurian  slates  or  are; 
still  older  deposits  remains  uncertain.  Granite  is  found  in  several 
places  in  the  region  in  large  masses  projecting  through  the  slates  and 
quartzites,  and  adjacent  to  the  granite  these  rocks  are  replaced  by 
gneiss  and  mica-slate  or  other  more  highly  metamorphosed  rocks.  The 
metamorphism  of  the  rocks  must  have  occurred  prior  to  the  Carbonifer- 
ous period,  and  there  is  no  doubt  that  the  granite  rocks  have  been  the 
agent  in  effecting  it,  if  they  are  not  themselves  portions  of  the  strati- 
lied  beds  completely  molten  and  forced  up  by  pressure  against  and  into 
the  fissures  of  the  neighboring  unmelted  rocks.  Whatever  view  is* 
taken  as  to  the  age  of  the  granitic  rocks,  it  is  certain  that  they  are 
strictly  Hypogene,  that  is,  they  belong  to  deep-seated  foci  of  subter- 
ranean heat  and  are  not  superficial  products  of  volcanic  action,  bun 
were  probably  at  one  time  deeply  buried. 
Campbell,49  in  1863,  divides  the  gold-bearing  slates  into  a  lower  or"' 
quartzite  group  and  an  upper  or  clay  slate  group. 
Hind,50  in  1869,  finds  in  the  Waverly  beds  of  the  gold-bearing  rocks 
obscure  fossils,  which  are  regarded  as  evidence  that  these  rocks  prob- 
ably lie  near  the  base  of  the  Lower  Silurian,  perhaps  being  the  equiva-: 
lent  of  the  Potsdam  or  lower  part  of  the  Galciferous. 
Hind,51  in  1870,  describes  the  series  of  gneissic  and  granitic  rocks' 
which  are  said  to  extend  as  an  interrupted  axis  from  the  Gut  of  Canso 
to  the  Tusket  islands.    These  have  heretofore  been  regarded  as  erup- 
tives,  because  dikes  of  granite  are  frequently  found  in  the  quartzites 
which  are  supposed  to  be  Silurian,  and  also  fragments  of  quartzites  and 
slates  are  imbedded  in  the  granites  near  the  contacts.     It  is,  however, 
concluded  that  the  granite  is  a  sedimentary  deposit  resting  unconform- 
ably  below  the  slates  and  quartzites. ,   The  chief  proof  of  the  aqueous 
origin  of  the  granitic  rocks  is  the  abundance  of  water- worn  pebbles  and 
bowlders,  and  this  not  only  near  the  junction  of  the  quartzites  bill 
remote  from  these  rocks.     These  pebbles  are  symmetrically  arranged, 
showing  the  dip  of  the  gneiss.    They  are  often  smooth  and  rounded 
but  masses  of  schists  are  also  contained  which  do  not  present  roundec 
edges.    The  granites  or  gneisses  are  seen  to  break  through  the  gold 
bearing  series  in  many  places,  but  they  are  regarded  as  brought  up  bi 
faulting;  but  in  certain  places  on  the  line  of  the  Halifax  and  Windso; 
railroad  the  gneisses  were  in  a  plastic  state  when  the  uplift  took  place 
for  veins  are  found  squeezed  into  the  cracks  and  interspaces  of  th< 
thinly  bedded  gold  bearing  rocks. 
The  sequence  of  formations  is  Upper  Silurian,  Lower  Silurian,  Cam 
