vanhisf.i  DISCUSSIONS    OF    PRINCIPLES.  511 
ther,  much  that  was  written  before  the  present  decade  is  as  good  work 
in  proportion  to  the  light  at  hand — the  only  proper  method  of  compar- 
ison— as  any  since.  The  only  way  to  get  well  on  a  road  or  to  a  goal  is 
to  start.  Also  it  must  be  insisted,  in  opposition  to  Whitney  and  Wads- 
worth,  that  stratigraphy  and  classification  are  possible  without  paleon- 
tology. Both  of  these  preceded  this  branch  of  geological  science,  and  . 
paleontology  is  useful  only  as  it  is  guided  by  stratigraphy.  Forgetting 
this,  fossil  evidence  has  frequently  been  misused.  In  dealing  with  the 
pre-Cambrian  rocks  we  are  exactly  in  the  position  that  geologists  are 
among  the  post- Cambrian  rocks  where  fossil  evidence  is  lacking.  Each 
district  must  be  studied  stratigraphically  by  its  formations  and  discord- 
ances. The  lack  of  fossils  is  most  keenly  felt  in  correlation.  However, 
the  protests  of  Whitney  and  Wads  worth  against  many  of  the  subdi- 
visions of  the  pre-Cambrian  and  the  principles  upon  which  they  were 
made  are  well  founded. 
As  to  the  supposed  invariable  aqueous  succession  of  Hunt,  the  writer 
can  only  say  that  so  far  as  he  is  familiar  with  North  America  he  knows 
of  no  region  in  which  this  succession  does  occur  in  its  fullness ;  while 
every  complex  region  with  which  he  is  familiar  contradicts  it  at  one  or 
more  fundamental  points.  As  one  illustration  among  many  which  might 
be  mentioned,  the  Labradorian,  supposed  to  be  a  part  of  the  invariable 
succession,  is  demonstrated  beyond  all  question  to  be  an  eruptive  rock. 
Large  areas  of  this  rock  are  associated  with  or  underlie  the  earliest 
pre-Cambrian  and  it  also  occurs  in  the  form  of  great  flows  in  series  as 
late  as  the  Keweenawan.  The  whole  scheme  is  one  which  is  highly 
theoretical  and  seems  to  have  been  evoked  by  laboratory  study  rather 
than  from  a  consideration  of  the  actual  rock  successions  within  the 
pre-Oambrian  in  the  field.  The  chance  that  a  scheme  evolved  in  this 
manner  should  accord  with  the  facts  of  the  world  is  indefinitely  small. 
PRINCIPLES  APPLICABLE   TO   ALGONKIAN    STRATIGRAPHY. 
The  clearest  discussion  of  the  principles  which,  from  the  writer's 
point  of  view,  are  most  applicable  to  the  classification,  correlation,  and 
mapping  of  the  pre-Cambrian  rocks  are  the  structural  and  lithological 
principles  enunciated  by  Irving,  Pumpelly,  and  Dale.  Accepting  these 
in  the  main,  a  few  supplementary  remarks  may  be  made. 
In  the  stratigraphical  work  of  the  past,  methods  have  oftentimes 
been  defective.  Instead  of  giving  close  lithological  descriptions  of  a 
series  of  rocks,  noting  carefully  the  relations  of  the  different  strata,  in 
case  they  are  found  to  have  strata,  to  each  other,  and  giving  a  detailed 
account  of  the  relations  which  actually  obtain  between  the  series  con- 
sidered and  surrounding  series,  writers  have  too  often  called  the  rocks 
of  regions  far  distant  from  the  original  localities  to  which  the  terms 
have  been  applied  Laurentian,  Huronian,  etc.  Sometimes  this  is  done 
,on  the  ground  that  a  series  as  a  whole  has  a  certain  color;  which  has 
