SUMMARY    OF   GENERAL  LITERATURE.  79 
rentian  character  are  there  so  intimately  associated  with  others  of 
equally  typical  Huronian  characters,  and  the  two  kinds  are  in  such 
constant  alternation,  that  in  mapping  them  they  could  not  be  sepa- 
rated, and  are  therefore  all  classed  as  Archean  or  pre-Cambrian. 
Whitney  and  Wadsworth,15  in  1884,  after  a  very  wide  but  dis- 
proportionate review  of  the  literature  of  the  pre-Potsdam  rocks, 
conclude  that  it  is  impossible  for  any  unprejudiced  worker  in  this 
department  of  science  to  peruse  with  care  the  pages  given  and  not 
be  obliged  to  admit  that  the  geology  of  a  large  portion  of  this  coun- 
try, and  especially  that  of  Canada  and  New  England,  is  in  an  almost 
hopeless  state  of  confusion.  The  belief  is  justified  that  our  chances 
of  having  at  some  future  time  a  clear  understanding  of  the  geological 
structure  of  northeastern  North  America  would  be  decidedly  im- 
proved if  all  that  Avere  written  about  it  were  at  once  struck  out  of 
existence.  While  not  desiring  to  conceal  the  fact  that  some  of  the 
problems  presented  in  the  course  of  the  study  of  the  older  rocks  are 
extremely  difficult,  it  is  clearly  proved  that  want  of  knowledge,  want 
of  experience,  and  a  desire  to  produce  sensational  theories  have 
brought  about  this  condition  of  confusion. 
In  reference  to  Azoic  rocks,  there  are  several  classes  to  which  this 
term  may  be  applied.  First,  it  may  be  applied  to  strata  once  fossilif- 
erous  in  which  the  evidences  of  life  have  disappeared.  Second,  rocks 
may  be  azoic  even  if  laid  down  when  life  was  existing  on  the  globe, 
provided  the  local  conditions  were  not  favorable  to  its  development  at 
the  particular  locality  under  consideration.  Third,  rocks  must  neces- 
sarily- be  azoic  when  formed  or  originating  under  conditions  in- 
compatible with  the  existence  of  life.  Such  was  the  original  crust 
of  the  earth  and  the  volcanic  eruptive  rocks.  Fourth,  we  may 
have  rocks  formed  under  such  conditions  as  were  not  inimical  to  life, 
but  yet  azoic,  because  life  had  not  begun  to  exist  on  the  globe  at  the 
time  of  their  deposition.  These,  according  to  our  view,  would  be 
the  rocks  properly  designated  by  the  term  Azoic,  and  the  body  of 
rocks  having  this  character  might  properly  be  called  the  Azoic  sys- 
tem. And  we  think  that,  in  view  of  what  has  here  been  set  forth,  no 
one  will  deny  that  it  is  important  that,  if  there  are  such  rocks,  they 
should  have  a  special  designation,  and  that  the  term  Azoic  would  be 
a  proper  one  to  apply  to  them. 
This,  however,  is  exactly  what  was  done  by  Foster  and  Whitney  in 
1850,  when  they  gave  the  name  Azoic  system  to  a  body  of  strata, 
originally — in  part,  at  least — of  sedimentary  origin,  which  did  not 
show  by  their  character  that  life  could  not  have  existed  at  I  he  time 
of  their  deposition,  but  which  proved,  on  examination,  1<>  be  en- 
tirely destitute  of  fossils,  and  which,  moreover,  were  found  every- 
where to  underlie  unconformably  other  stratified  formations  which 
were  recognized  as  containing  the  lowest  known  forms  of  organic  life. 
