386  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.  86. 
eating  a  pitching  fold.  (3)  Such  a  correspondence  exists  between  the  stratifica- 
tion foliations  and  cleavage  foliations  of  the  great  folds  and  those  of  the  minute 
plications  that  a  very  small  specimen  properly  oriented  gives,  in  many  oases,  the 
key  to  the  structure  over  a  large  portion  of  the  side  of  a  fold. 
This  author  has  farther  ascertained  that  apparent  conformity,  which 
sometimes  exists  between  strata  really  unconformable,  may  be  due  to 
the  disintegration  of  the  earlier  series. 
Notwithstanding-  that  advantage  has  thus  been  taken  of  all  sources 
of  information,  the  problems  of  the  structure  of  western  Massachusettts 
have  been  found  so  difficult  that  it  has  taken  years  of  labor  of  a  num- 
ber of  men  to  build  up  correctly  the  stratigraphical  succession.  The 
labor  involved  in  this  work  and  the  relatively  small  size  of  the  area 
covered  show  that  before  any  accurate  map  of  the  whole  of  New 
England  can  be  presented  many  years  must  elapse,  although  it  may  be 
reasonably  hoped  that,  as  experience  accumulates,  the  application  of 
the  new  method  will  proceed  more  rapidly  than  in  the  decade  of  its 
inauguration. 
That  the  structural  mapping  of  the  crystalline  rocks  in  New  Eng- 
land is  less  extensive  than  in  some  other  parts  of  America  has  not  been 
due  to  a  lack  of  ability  or  industry  upon  the  part  of  the  workers  in 
this  region  as  compared  with  those  of  others,  but  rather  to  the  greater 
difficulty  of  the  problem.  This  region  is  one  in  which  repeated  dynamic 
movements,  accompanied  by  great  outbursts  of  igneous  material,  have 
occurred  until  late  in  Paleozoic  time. 
SECTION  II.      THE  MIDDLE   ATLANTIC   STATES. 
LITERATURE   OF  NEW  YORK. 
Pierce,88  in  1818,  describes  the  nucleus  of  Staten  island  as  consist- 
ing of  steatite,  which  stamps  the  formation  as  Primitive. 
Akerly,89  in  1820,  describes  a  section  running  from  Long  Branch,  in 
New  Jersey,  northward  to  New  Marlboro,  Ulster  county,  New  York. 
The  rocks  included  are  divided  into  principal  rocks,  metalliferous  rocks, 
basaltic  rocks,  and  alluvial  formations,  which  correspond  to  the  Ger- 
man terms  Primitive,  Transition,  Floetz,  and  Alluvial.  Staten  island 
has  a  rocky  base  composed  of  the  magnesian  order  of  rocks,  consisting 
of  serpentine,  steatites  or  soapstones.  Hoboken  is  of  the  same  nature 
as  Staten  island.  The  Highlands  of  New  York  consist  of  granitic 
rocks  belonging  to  the  primitive  class.  Gneiss  and  micaceous  schist 
are  the  most  prominent;  but  granite,  properly  speaking,  also  enters  into 
the  composition.  The  commencement  or  termination  of  any  of  these 
rocks  has  not  been  found,  and  as  they  graduate  into  one  another  they 
are  considered  the  same  formation.  At  Hell  Gate  the  rocks  are  gneiss 
and  micaceous  schist.  The  northern  part  of  New  York  island  is  of  the 
primitive  formation  and  includes  granite,  gneiss  and  limestone.  Crys- 
talline limestone  is  also  found  at  other  points.  All  these  rocks  are 
placed  in  the  primitive  formation  and  they  contain  no  organic  remains. 
