van  msR.j  EASTERN    UNITED    STATES.  429 
two  granites,  one  of.  .which  is. more  ancient  than  the  elastics  and  the 
other  intriisives  within  these.  According  to  Emmons  the  ancient  form 
is  predominant,  but  occasionally  granite  has  been  projected  through 
fissures  like  other  intrusive  rocks. 
The  great  discovery  that  regularly  laminated  rocks  are  produced  by 
the  metamorphism  of  eruptive  rocks  as  well  as  from  sedimentary  rocks 
naturally  carried  the  discoverer  too  far  in  the  application  of  the  princi- 
ple. Emmons  included  in  the  metamorphic  igneous  rocks  many  mica- 
schists,  talcose  slates,  and  limestones  for  which  he  gave  no  evidence 
whatever.  Lieber's  discrimination  between  the  metamorphic-igneous 
and  metamorphic-sedimentary  rocks  was  much  more  satisfactory.  But 
Emmons's  general  statements  as  to  the  small  value  of  lamination  alone 
in  rocks  as  an  evidence  of  origin  and  the  method  of  stratigraphical 
work  in  the  crystalline  rocks  can  hardly  be  improved  upon  at  the  pres- 
ent day.  Says  this  writer:  Rocks  of  igneous  origin  are  often  massive, 
but  also  are  frequently  laminated,  and  laminated  rocks  are  frequently 
called  stratified,  but  this  latter  term  should  be  restricted  to  the  sedi- 
mentary rocks.  The  metamorphic  rocks  are  excluded  from  the  sedi- 
mentary classification  because  all  rocks  may  become  metamorphic,  and 
a  stratum  metamorphic  in  one  locality  may  not  be  metamorphic  in 
another.  The  highest  proof  of  the  age  of  rocks  is  the  order  of  super- 
position. When  this  method  can  be  applied  it  is  paramount,  but  pale- 
ontology may  be  used  subject  to  proper  principles. 
The  Primitive  rocks  from  Emmons's  point  of  view  are  all  igneous; 
with  aqueous  rocks  begins  the  Azoic,  the  oldest  sedimentaries,  and 
above  the  Azoic  are  rocks  which  in  the  past  have  been  regarded  as  Azoic, 
but  are  found  to  be  fossiliferous ;  that  is,  they  constitute  the  Taconic  sys- 
tem. We  have  here  a  definite  theory  as  to  the  order  of  development  of 
the  earth,  the  primitive  rocks  being  wholly  pyrocrystalline,  the  Azoic 
stratified  rocks  being  earlier  than  the  dawn  of  life,  and  the  Taconic 
rocks  being  the  fossiliferous  rocks  earlier  than  the  Potsdam. 
NOTES. 
1  First  Annual  Report  on  the  Geology  of  the  State  of  Maine,  Charles  T.  Jackson. 
Augusta,  1837,  pp.  vm,  9-128;  24  plates. 
-  Sketch  of  the  Geology  of  Portland  and  its  Vicinity,  Edward  Hitchcock.  Bost. 
Soc.  Nat.  Hist.,  Journal,  vol.  i,  1834-37,  pp.  306-347;  with  a  geological  map. 
3  Third  Annual  Report  on  the  Geology  of  the  State  of  Maine,  Charles  T.  Jackson. 
Augusta,  1839,  pp.  xiv  and  1-276. 
4  General  Report  upon  the  Geology  of  Maine,  Charles  H.  Hitchcock.  Preliminary 
Report  upon  the  Natural  History  and  Geology  of  the  State  of  Maine,  pp.  146-328. 
r>  Reports  on  the  Geology  of  Maine,  Charles  H.  Hitchcock.  Seventh  Annual  Report 
of  the  Secretary  of  the  Maine  Board  of  Agriculture,  pp.  223-312,  323-332,  345-352, 
377-382,  388-395,  404-413,  422-430;  map. 
e  The  Geology  of  Portland,  Charles  H.  Hitchcock.  Proc.  Am.  Assoc.  Adv.  Sci., 
vol.  xxii,  pp.  163-175. 
7  Geology  of  the  Region  about  the  Head  Waters  of  the  Androscoggin  River,  Maine, 
J.  H.  Huntington.     Ibid.,  26th  meeting,  pp.  277-286. 
