vanhise.]  EASTERN   ONTARIO    AND    WESTERN    QUEBEC.  31 
crystalline  limestones  have  been  found  in  the  interior  of  the  gneiss 
country,  these  have  been  proved  to  occur  in  the  superficial  condition  of 
shallow  troughs,  and  not  as  bands  interstratified  in  the  gneiss  itself. 
The  lower  noncalcareous  Lauren tian  is  a  great  series  of  crystalline 
rocks,  not  only  highly  metamorphosed,  but  most  intricately  contorted. 
In  the  entire  area  studied  the  gneiss  and  syenite  are  by  far  the  most 
abundant  rocks,  while  gneisses  with  interstratified  crystalline  lime- 
stones occupy  but  a  comparatively  limited  area,  and  this  only  toward 
the  margins  of  the  former.  The  relative  volumes  of  the  two  distinct 
sets  of  rocks,  that  is,  the  gneisses  with  the  crystalline  limestones,  bear 
about  the  same  relations  to  the  volume  of  gneiss  and  syenite  that  the 
comparatively  narrow  belt  of  the  Silurian  does  in  this  section  of  country 
to  both  of  these  together. 
There  is  thus  in  these  old  crystalline  rocks  a  great  uncalcareous  di- 
vision and  a  smaller  calcareous  one.  The  first  of  these  may  be  further 
subdivided  into  a  stratified  and  unstratified  portion,  of  which  the  latter 
is  undoubtedly  the  lowest  and  oldest.  As  shown  by  the  map,  north 
and  northwestward  of  the  line,  at  the  base  of  the  gneiss  and  limestone 
series,  there  are  numerous  and  repeated  troughs  of  the  lower  member 
of  this  division  which  separate  out  over  the  great  fundamental  gneiss 
system  in  a  most  irregular  manner,  and  it  is  these  that  have  given  rise 
to  the  supposition  that  the  older  gneiss  and  syenite  is  interstratified 
with  the  crystalline  limestone.  The  three  great  subdivisions  in  east- 
ern Ontario  are,  then,  first,  a  great  gneissic  and  syenitic  series  without 
limestone;  second,  a  thinner  gneissic  series  with  labradorites  and  lime- 
stones; and,  third,  Lower  Silurian  (Potsdam  to  Trenton).  The  thick- 
ness of  the  upper  series,  exclusive  of  the  fundamental  gneiss,  is  placed 
tentatively  as  from  50,000  to  60,000  feet.  No  attempt  is  made  to  esti- 
mate the  thickness  of  the  underlying  gneiss  and  syenite  series. 
Bell,27  in  1878,  reports  on  geological  researches  north  of  lake  Huron 
and  east  of  lake  Superior,  including  lake  Nii>issing.  He  finds  the  rocks 
along  the  whole  northeast  coast  of  Georgian  bay,  a  distance  of  125  miles, 
to  belong  to  the  Laureutian  series.  They  consist  principally  of  varie- 
ties of  gneiss,  occasionally  interstratified  with  bands  of  hornblendie  and 
micaceous  schists.  The  crystalline  limestones  are  also  found,  as  well 
as  stratified  diorites,  trap  rocks,  and  granite  veins.  The  rocks  have 
no  uniform  strike  and  are  contorted  into  many  anticlinals  and  syncli- 
nals. The  crystalline  limestones  of  Georgian  bay  and  lake  Nipissing  are 
regarded  as  belonging  in  three  and  possibly  more  crystalline  bands. 
Associated  with  the  limestone  are  sometimes  found  chert,  conglomerate, 
quartzite,  and  magnetic  iron  ore.  A  junction  of  the  granite  with  the 
Huronian  quartzite  and.  hornblende  schist  is  mentioned. 
Wilkins,28  in  1878,  describes  near  the  Grand  Trunk  station  of  Slian- 
nonville,  about  three-quarters  of  a  mile  north  of  the  village,  a  gray  and 
green  slate  conglomerate  which  much  resembles  the  slate  conglomerate 
of  lake  Huron  belonging  to  the  Huronian  system.    The  base  of  tins 
