GENERAL   ACCOUNT    OF    THE    PRE-CAMBRIAN    ROCKS.  53 
He  further  says  the  problem  of  the  pre- Cambrian  stratigraphy  has 
been  solved  "  in  a  decidedly  actualistic. direction."  While  Sederholm 
is  too  cautious  to  make  any  definite  correlations  with  the  Lake  Supe- 
rior region,  he  suggests  that  the  Jotnian  is  similar  to  the  Keweenawan 
of  North  America,  the  Jatulian  equivalent  to  the  Animikie  or  upper 
Huronian,  and  the  Kalevian  perhaps  similar  to  the  lower  Huronian 
of  Xorth  America.  This  suggested  likeness  is  even  greater  when  it  is 
remembered  that  what  was  originally  called  the  lower  Huronian 
is  now  divided  into  the  middle  and  lower  Huronian,  and  that  the 
Kalevian  is  divisible  into  two  unconformable  series. 
These  sedimentary  series  together  are  Algonkian.  Unconformably 
below  these  are  two  series  of  rocks,  the  upper  called  the  Ladogian, 
and  this  series  is  intruded  by  the  granites  and  gneisses  of  the  Katar- 
chean.  If  we  correlate  these  Avith  the  Archean  as  we  use  the  terms, 
we  may  have  in  Finland  two  divisions  of  the  Archean  which  cor- 
respond to  the  Keewatin  and  Laurentian.  The  essential  difference 
is  that  in  the  Ladogian,  equivalent  in  position  to  the  Keewatin,  the 
sedimentary  rocks  seem  to  be  more  important  relative^  than  in 
America. 
It  is  regarded  as  certain  that  some  of  the  granites  or  gneisses  have 
served  as  the  basement  upon  which  the  sediments  were  deposited,  that 
they  have  been  remelted  and  have  invaded  the  lower  portions  of  the 
sediments;  in  other  words,  there  has  been  subcrustal  fusion,  but  such 
rocks  are  regarded  and  mapped  as  distinctly  igneous  and  later  than 
the  sediments.  The  gneissose  structure  is  regarded  as  partly  original— 
that  is,  developed  before  the  solidification  of  the  rock — and  partly 
developed  secondarily  under  dynamic  pressure.  The  author  presents 
evidence  of  what  he  regards  as  partly  fused,  intermediate  phases 
between  the  granite  and  the  sediments.  No  evidence  was  found  that 
petrographic  character  can  serve  as  a  basis  for  stratigraphic  classifi- 
cation. 
These  conclusions  are  believed  to  cover  a  considerable  part  of 
"  Fenno-Scandia.,, 
RUSSIA   AND  CENTRAL  EUROPE. 
The  pre-Cambrian  of  Russia  and  central  Europe  has  for  the  most 
part  not  been  satisfactorily  subdivided  and  correlated,  but  it  is 
known  to  include  both  igneous  and  sedimentary  rocks  and  their 
metamorphosed  equivalents.  Algonkian  and  Archean  are  the  major 
divisions  for  the  pre-Cambrian  found  upon  the  official  geological 
map  of  France  published  in  1905  under  Michel  Levy  as  inspector- 
general,  and  compiled  by  a  committee  consisting  of  thirty-five  ideolo- 
gists of  that  country  with  the  assistance  of  a   committee  of  fifty 
