vanhisb.]  LAKE    HURON    TO    LAKE    TEMISCAMANG.  35 
morphosed  sedimentaries.  That  this  series  is  newer  than  the  granite- 
gneisses,  is  indicated  by  the  fact  that  the  intricate  structure  of  the 
lower  Laurentian  is  not  simulated  by  the  clastic  rocks.  Apparently  the 
latter  has  undergone  earlier  and  more  intense  orographic  movements 
than  the  former. 
SECTION  II.  FROM  NORTH  CHANNEL  OF  LAKE  HURON  TO  LAKE 
TEMISCAMANG. 
LITERATURE. 
Bigsby,31  in  1821,  gives  the  earliest  geological  account  of  the  north 
shore  of  lake  Huron.  He  found  north  of  the  North  channel  two  scries 
of  rocks,  one  of  granite,  gneiss,  and  trap,  which  was  placed  by  him 
with  the  Primitive ;  the  other,  without  mentioning  distinct  characters, 
he  called  the  Transition  formation. 
Murray,32  in  1845,  finds  Primary  and  Metamorphic  rocks  to  com- 
prise the  whole  country  to  the  north  of  lake  Simcoe  and  the  northeast- 
ern 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,33  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)  fossilifer- 
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  (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  conglomeratic  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  opin- 
ion that  this  rock  is  equivalent  to  the  Niagara  of  New  York.  That 
these  limestones  are  unconformable  with  the  slates  appears  almost  cer- 
tain, 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,34  in  1847,  having  visited  Echo  lake  and  the  Bruce  mine,  finds 
the  rocks  of  the  North  channel  to  consist  of  sandstone,  talcose  slate, 
limestone,  all  metamorphosed  by  trap  rock.  The  slate  contains  some 
pebbles  of  primitive  rock,  and  thus  approaches  a  conglomerate.  The 
limestone  at  Echo  lake  shows  original  stratification,  and  is  traversed 
