530  PRE-CAMBRTAN    GEOLOGY    OF    NORTH   AMERICA. 
passing  into  each  other  by  almost  insensible  gradations.  Careys 
Islands,  west  of  Wolstenholme  Sound,  are  composed  of  a  gneissose 
mica  schist,  formed  of  successive  layers  of  quartz  granules  and  jet- 
black  mica.  The  mica  schist  passes  into  white  gneiss.  On  the  islands 
yellow  and  white  sandstones  are  also  found  in  small  quantity,  repos- 
ing upon  the  granitoid  rocks. 
Liebee,23  in  1860,  describes  gneisses,  granites,  labradorites,  etc., 
found  at  various  localities  on  the  coast  of  Labrador. 
Dawson,24  in  1861,  describes  the  Laurentian  rocks  exposed  on  the 
coast  cliffs  of  Murray  Bay.  At  one  place  the  succession  includes 
gneiss,  white  quartz  rock,  impure  limestone,  and  hornblende  slate, 
but  the  beds  are  so  inverted  that  little  reliance  can  be  placed  on 
apparent  superposition.  The  crystalline  limestone,  dolomite,  and 
serpentine  are  together  14  feet  thick.  The  Silurian  rocks  rest  uncon- 
formable upon  the  Laurentian  beds. 
Richardson,25  in  1870,  describes  the  Laurentian  and  Labradorite 
rocks  on  the  north  shore  of  the  lower  St.  Lawrence.  The  Laurentian 
gneiss  has  sometimes  little  appearance  of  stratification.  The  dips 
are  high,  approaching  the  vertical.  The  Labradorite,  with  moderate 
dips,  rests  unconformably  upon  the  Laurentian.  At  one  place  there 
occurs  in  the  gneiss  a  bed  12  feet  thick  of  coarsely  crystalline  lime- 
stone. The  Labradorite  rocks  have  a  wide  extent.  Both  the  Lau- 
rentian gneiss  and  the  Labradorite  are  cut  by  granitic  veins. 
Richardson, 2,;  in  1872,  reports  on  the  prefossiliferous  rocks  in  the 
country  north  of  Lake  St.  John.  They  are  classified  under  two  heads : 
First,  Laurentian  gneiss,  including  a  little  crystalline  limestone; 
second,  crystalline  schists,  consisting  of  chloritic  and  epidotic  rocks, 
with  dolomites,  serpentines,  and  conglomerates.  The  Laurentian 
occupies  much  the  largest  area  of  country  and  includes  gneissic  rocks 
cut  by  granite  veins,  limestones,  quartzites,  and  hornblende  rocks. 
The  limestones  and  quartzites  are  comparatively  unimportant,  but 
the  former  is  said  to  be  in  thickness  not  less  than  500  or  600  feet. 
The  rocks  of  the  second  class  immediately  succeed  the  Laurentian 
near  the  north  end  of  Lake  Abatagomaw.  Large  expanses  of  the  con- 
glomerate of  this  series  are  composed  entirely  of  rounded  fragments 
of  Laurentian  gneiss  of  gray  and  red  colors.  In  some  places,  without 
close  examination,  the  conglomerate  might  be  mistaken  for  the  Lau- 
rentian gneiss.  Sandstones  and  shales  are  met  with  which  show  lines 
of  deposition.  It  is  remarked  that,  whatever  the  geological  horizon 
of  this  series  of  rocks,  it  will  be  prudent  for  the  present  to  withhold 
an  opinion  until  further  investigations  are  made.  The  only  indica- 
tion as  to  the  geological  age  of  this  series  is  given  by  an  obscure  fos- 
sil occurring  in  a  limestone  which  Billings  thinks  is  a  coral. 
Bell,27  in  1877,  reports  on  explorations  between  James  Bay  and 
Lakes  Superior  and  Huron.     The  rocks  are  described  as  Huronian 
