LETTER   OF   TR  ANSMITTAL. 
Department  of  the  Interior, 
U.  S.  Geological  Survey, 
Division  of  Geologic  Correlation, 
Washington,  I).  6'.,  January  30,  1892. 
Sir:  I  have  the  honor  to  transmit  herewith  a  memoir  by  Pro!'.  0.  R. 
Van  Hise  on  the  Archean  and  Algonkian  of  North  America,  prepared 
for  publication  as  a  bulletin. 
The  Division  of  Geologic  Correlation  was  created  for  the  purpose  of 
summarizing  existing  knowledge  with  reference  to  the  geologic  forma- 
tions of  North  America,  and  especially  of  the  United  States;  of  dis- 
cussing the  correlation  of  formations  found  in  different  parts  of  the 
country  with  one  another  and  with  formations  in  other  countries ;  and 
of  discussing  the  principles  of  geologic  correlation  in  the  light  of  Amer- 
ican phenomena.  The  formations  of  each  geologic  period  were  assigned 
to  some  student  already  well  acquainted  with  them,  and  it  was  ar- 
ranged that  he  should  expand  his  knowledge  by  study  of  the  literature 
and  by  field  examination  of  classic  localities,  and  embody  his  results  in 
an  essay.  The  general  plan  of  the  work  has  been  set  forth  on  page  10 
of  the  Ninth  Annual  Report  of  the  Survey,  and  on  pages  108  to  113  of 
the  Tenth  Annual  Report,  as  well  as  in  a  letter  of  transmittal  of  Bul- 
letin No.  80. 
The  present  essay  is  the  seventh  of  the  series,  having  been  preceded 
by  essays  on  the  Carboniferous  and  Devonian,  the  Cambrian,  the  Cre- 
taceous, the  Eocene,  the  Neocene,  and  the  Newark  systems;  prepared 
severally  by  Messrs.  Williams,  Walcott,  White,  Clark,  Dall  and  Harris, 
and  Russell,  and  constituting  Bulletins  80,  81,  82,  83,  84,  and  8~). 
The  voluminous  literature  of  the  pre-Cambrian  rocks  of  North  Amer- 
ica is  abstracted  in  a  thorough  manner,  being  classified  fortius  purpose 
primarily  by  geographic  districts  and  secondarily  by  dates.  The  di- 
vision of  the  rocks  into  two  great  classes,  the  Archean  and  Algonkian, 
taxonomically  coordinate  with  the  periods  under  which  the  fossil- 
iferous  clastic  rocks  are  classified,  is  then  advocated  and  set  forth  at 
length.  As  these  rocks  do  not  contain  fan n as  available  for  purposes  of 
correlation,  their  classification,  both   major  and   minor,  is  necessarily 
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