QUEBEC    NORTH    AND    WEST    OF    ST.    LAWRENCE    RIVER.  455 
middle  section  is  undoubtedly  Lower  Laurentian.  The  rocks  met 
with  include  great  thicknesses  of  gneiss,  for  the  most  part  clearly 
stratified,  with  well-defined  strike  and  dip;  masses  of  hornblende 
rock  and  diorite,  grading  into  slate  or  schist ;  large  and^  important 
bands  of  crystalline  limestones,  and  groups  of  calcareous  strata  as- 
sociated with  mica  slates  and  workable  masses  of  magnetic  iron  ore. 
These  rocks  are  clearly  interstratified.  Apparently  five  distinct  bands 
of  crystalline  limestone  are  met  with,  separated  by  reddish  granitic 
and  dark  hornblendic  gneisses.  The  rocks  of  the  eastern  section  con- 
sist chiefly  of  gneiss,  but  associated  with  this  are  coarsely  granular 
limestones.  The  horizontal  limestones  of  the  Lower  Silurian  by  a 
fault  are  brought  into  abrupt  vertical  contact  with  the  Laurentian 
gneiss. 
Vennor,22  in  1874,  further  describes  Frontenac,  Leeds,  and  Lanark 
counties.  The  five  belts  of  crystalline  limestones  mentioned  in  the 
previous  report  are  described  in  detail.  Eozoon  occurs  abundantly 
in  places. 
Vennor,23  in  1876,  gives  a  further  report  on  the  rear  portions  of 
Frontenac  and  Lanark  counties.  Two  sections  are  given,  representing 
the  limestones  as  interstratified  with  the  quartzites  and  gneisses.  The 
rocks  are  classified  into  five  groups :  I,  Mica-schist  group ;  II,  Dolo- 
mite and  slate  group ;  III,  Diorite  and  hornblende  schist  group ;  IV, 
Crystalline  limestone  and  hornblende  rock  group;  V,  Gneiss  and 
crystalline  limestone  group.  A  sixth  group,  described  in  a  previous 
report,  occupies  the  front  portion  of  Lanark  County.  Each  of  the  five 
groups  has  many  subordinate  phases  of  rocks;  they  occupy  distinct 
and  separate  positions,  but  it  is  not  known  whether  they  represent  one 
or  more  formations. 
Vennor,24  in  1877,  states  that  there  is  in  eastern  Ontario  and  the 
adjoining  portions  of  Quebec  an  Azoic  formation,  consisting  of  sye- 
nite and  gneiss(?),  without  crystalline  limestone,  in  which  there  is 
but  little  indication  of  stratification.  On  it  has  been  unconformably 
deposited  a  great  system  of  gneisses,  schists,  slates^  crystalline  lime- 
stones, and  dolomites,  in  the  higher  member  of  which  Eozoon  is  found. 
The  limestone  occurs  in  four  principal  belts.  Logan's  Huronian  and 
Upper  Laurentian  are  both  considered  to  belong  to  the  second  divi- 
sion, which  is  for  the  present  called  the  Upper  Laurentian.  Inter- 
stratified with  several  of  the  bands  of  limestone  are  labradorite  rocks. 
No  evidence  is  found  for  making  these  a  distinct  system.  The  Huro- 
nian and  Hastings  series  are  simply  an  altered  condition,  in  their 
westward  extension,  of  the  lower  portion  of  the  upper  system. 
Vennor,25  in  1878,  reports  on  the  counties  of  Renfrew,  Pontiac,  and 
Ottawa.  Referring  to  the  work  of  previous  years,  it  is  said  that  the 
rocks  of  divisions  B  and  C  of  the  Hastings  series  are  really  the  west- 
ern extensions  of  the  diorites,  hornblende  schists,  and  mica  slates  of 
