AREA   NORTH   AND    NORTHEAST   OP   LAKE    HURON.  423 
intimately  intermingled  with  the  eruptives,  and  is  regarded  as  a  con- 
centration by  differentiation  from  the  eruptive  magma.  Cutting  both 
the  Huronian  and  the  included  nickel-bearing  eruptives  are  masses  of 
fine-grained  pinkish  biotite  granite,  sending  apophyses  into  the  sur- 
rounding rocks.  This  granite  is  found  to  have  been  intruded  in  two 
eruptions.  The  youngest  rocks  of  the  Sudbury  district  are  olivine  dia- 
bases, which  occur  in  dikes,  cutting  all  the  other  rocks  of  the  district. 
Barlow  and  Ferrier,42  in  1898,  discuss  the  relations  and  the 
structure  of  certain  granites  and  associated  arkoses  on  Lake  Temis- 
caming.  An  examination  of  the  contact  of  the  granite  and  arkose 
shows  a  gradual  and  distinct  passage  of  the  granite  into  the  arkose. 
Microscopically  also  there  may  be  seen  evidence  of  the  decomposition 
of  the  feldspars  of  the  granite,  the  breaking  up  of  the  feldspar  and 
quartz,  and  finally  the  rearrangement  and  assortment  of  the  material 
by  water,  indicating  a  gradual  transition  from  the  granite  to  the 
arkose. 
The  arkose  is  regarded  as  a  Huronian  sediment  derived  from  and 
deposited  on  the  granite.  This  is  regarded  as  the  only  instance  at 
present  known  in  which  the  material  composing  the  Huronian  elastics 
can  be  clearly  and  directly  traced,  both  macroscopically  and  micro- 
scopically, to  the  original  source  from  which  it  has  been  derived. 
Ells,42e  in  1907,  gives  a  summary  account  of  the  geology  of  New 
Brunswick.  A  comparison  of  the  nomenclature  and  classification  of 
Bailey  and  Matthew  in  1870-71  with  that  of  Ells  in  1907  is  as  follows : 
1870-71.  1907. 
Laurentian Pre-Cambrian,  in  part  igneous  and 
in  part  altered  Silurian  and  De- 
vonian. 
Huronian :  Kingston,  Coldbrook,  Coastal Pre-Cambrian  witb  associated  ig- 
neous masses. 
Cambrian,  St.  Jobn  group Cambrian,  Etcheminian,  division  0 
at  base,  Cambrian  divisions  1,  2, 
and  3. 
Barlow,43  in  1899,  describes  the  geology  of  the  area  of  the  Nipis- 
sing-Temiscaming  map  sheets,  comprising  portions  of  the  district  of 
Nipissing,  Ontario,  and  the  county  of  Pontiac,  Quebec. 
Laurentian  and  Huronian  rocks  occupy  most  of  the  area.  These 
do  not  include  a  few  small  isolated  inliers  of  crystalline  limestone 
and  gneissic  rocks  which  resemble  the  Grenville  rocks  to  the  south 
and  southwest,  These  are  so  small  in  quantity  that  they  are  not 
mapped.     Their  relations  to  the  Huronian  are  not  discussed. 
The  Laurentian  rocks  occupy  two-thirds  of  the  area  of  the  two 
sheets.  While  probably  representing  in  part  the  first-formed  crust  of 
the  earth,  and  therefore  the  basement  upon  which  the  Huronian  rocks 
were  laid  down,  the  Laurentian  has  undergone  successive  fusions  and 
recementations  before  reaching  its  present  condition.  It  is  now  a 
complex  of  plutonic  rocks  which,  in  general,  show  irruptive  relations 
