618  PRE-CAMBKIAN    GEOLOGY   OF   NORTH   AMERICA. 
The  only  locality  where  the  possible  (Coleman  would  say  probable) 
existence  of  a  second  unconformable  sedimentary  series  was  suggested 
by  the  facts  observed  was  on  the  Queensboro  road  east  of  Madoc, 
Ontario.  It  is,  however,  still  uncertain  whether  or  no  the  conglomer- 
ate here  developed  marks  the  base  of  an  overlying,  infolded,  uncon- 
formable series. 
In  Logan's  original  classification  of  the  Laurentian  this  term — ■ 
apart  from  the  Upper  Laurentian,  which  was  proved  to  be  composed 
essentially  of  anorthosite  intrusions — included  two  series  differing  in 
character,  namely,  the  lower  orthoclase  (Fundamental)  gneiss  and 
the  Grenville  series.  Now  that  investigations  have  shown  that  these 
two  series  differ  in  origin,  one  being  essentially  a  great  development 
of  very  ancient  sediments,  and  the  other  consisting  of  great  bodies  of 
igneous  rock  intruded  through  them,  it  becomes  necessary  to  separate 
these  two  developments  in  drawing  up  a  scheme  of  classification. 
As  the  great  intrusions  of  gneissic  granite,  forming  what  has  been 
termed  the  "  Fundamental  gneiss,"  have  an  enormously  greater  areal 
development  than  the  overlying  sedimentary  series,  constituting,  as 
they  do,  a  very  large  part  of  the  whole  northern  protaxis,  the  commit- 
tee recommends  that  the  term  "  Laurentian  "  be  restricted  to  this  great 
development  of  igneous  gneisses.  The  nomenclature  suggested  for  the 
pre-Cambrian  rocks  of  this  eastern  region  will  thus  conform,  so  far  as 
the  use  of  this  term  is  involved,  with  that  suggested  by  the  special 
committee  for  the  Lake  Superior  region.0 
For  the  overlying  sedimentary  series  the  committee  recommends 
the  adoption  of  the  name  "  Grenville  series,"  as  it  is  the  name  origi- 
nally given  by  Logan  to  the  series  as  typically  developed  about  the 
township  of  Grenville,  in  the  "Original  Laurentian  area,"  on  the 
north  shore  of  the  Ottawa  River,  in  the  Province  of  Quebec,  between 
the  cities  of  Montreal  and  Ottawa.  The  term  "  Hastings  series,"  in 
the  opinion  of  the  committee,  should  be  abandoned  as  a  serial  name, 
seeing  that  the  development  to  which  this  name  was  applied  by  Logan 
is  merely  the  Grenville  series  in  a  less  altered  form,  as  Logan  in  giv- 
ing the  name  had  conjectured  was  probably  the  case.  The  committee, 
however,  thinks  that  it  may  in  some  cases  be  advantageously  employed 
as  a  qualifying  term  to  designate  the  less  highly  altered  phase  of  the 
Grenville  series,  which  may  thus  be  referred  to  as  the  "  Hastings 
phase  "  of  the  Grenville  series. 
In  Canada  this  Grenville  ^  series  everywhere,  on  going  north,  is 
invaded  by  and  frays  away  into  the  great  Laurentian  batholiths, 
while  in  the  Adirondacks  it  is  cut  to  pieces  by  the  great  intrusions  of 
that  area,  which,  when  worked  out  in  detail,  may  prove  also  to  have 
a  more  or  less  similar  batholithic  form. 
a  See  Jour.  Geology,  February-March,  1905. 
