CHAPTER  IV. 
AREA  NORTH  AND  NORTHEAST  OF  LAKE  HURON,  IN- 
CLUDING THE  ORIGINAL  HURONIAN  DISTRICT. 
SUMMARY  OF  LITERATURE. 
Bigsby,1  in  1821,  gives  the  earliest  geological  account  of  the  north 
shore  of  Lake  Huron.  He  found  north  of  the  North  Channel  two 
series  of  rocks,  one  of  granite,  gneiss,  and  trap,  which  was  placed  by 
him  with  the  Primitive ;  the  other,  without  mentioning  distinct  char- 
acters, he  called  the  Transition  formation. 
Murray,2  in  1845,  finds  Primary  and  Metamorphic  rocks  to  com- 
prise the  whole  country  to  the  north  of  Lake  Simcoe  and  the  north- 
eastern shores  of  Lake  Huron.  The  rocks  are  similar  in  appearance 
to  the  masses  which  compose  the  Thousand  Isles,  and  include  granite, 
syenite,  and  gneiss,  as  well  as  a  coarse  micaceous  sandstone,  which 
at  one  place  presents  evidence  of  stratification. 
Logan,3  in  1847,  finds,  after  passing  over  63  miles  of  lower  meta- 
morphic or  syenitic  gneiss  on  the  Ottawa,  after  leaving  the  Mattawa 
(nearing  Lake  Temiscamang),  a  succession  consisting  of  (1)  chloritic 
slates  and  conglomerates,  (2)  greenish  sandstones,  and  (3)  f ossifer- 
ous limestones.  The  conglomerates  often  hold  pebbles  and  bowlders, 
sometimes  a  foot  in  diameter,  of  the  subjacent  gneiss,  from  which  they 
are  chiefly  derived.  So  indurated  is  the  rock  that  the  fracture  breaks 
across  the  pebbles.  The  sandstone  is  of  a  sea-green  color,  and  appears 
to  be  composed  of  quartz  and  feldspar,  with  occasional  flakes  of  mica. 
The  volume  of  formation  1  is  probably  not  less  and  may  be  very 
much  more  than  1,000  feet,  while  that  of  the  sandstone  is  between 
400  and  500  feet.  Formation  3,  fossiliferous  limestone,  is  often  con- 
glomeratic at  its  base,  containing  pebbles,  fragments,  and  bowlders 
of  the  sandstone  beneath  in  a  calcareous  cement.  Some  of  the  harder 
beds  abound  in  chert,  and  many  of  them  are  fossiliferous,  the  organic 
remains  leading  to  the  opinion  that  this  rock  is  equivalent  to  the 
Niagara  of  New  York.  That  these  limestones  are  unconformable 
with  the  slates  appears  almost  certain,  but  whether  the  intermediate 
sandstones  are  conformable  with  one  or  both  of  these  can  not  be 
asserted,  nor  can  it  be  asserted  that  the  slates  are  conformable  with 
the  gneiss. 
Locke,4  in  1847,  having  visited  Echo  Lake  and  the  Bruce  mine, 
finds  the  rocks  of  the  North  Channel  to  consist  of  sandstone,  talcose 
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