van  HisE.]  EASTERN    UNITED    STATES.  403 
tion  as  sediments  of  one  kind  or  another,  and  to  the  more  or  less  com- 
plete obliteration  of  the  bedding  planes  by  excessive  metamorphism. 
The  beds  of  magnetic;  ore  occur  in  different  horizons  of  the  middle 
group,  but  never  occur  in  the  highest  or  lowest.  In  this  same  gronp 
the  beds  of  crystalline  limestone  appear  generally  to  be  at  a  slightly 
higher  horizon  than  the  magnetite  beds.  The  highest  gneissic  and 
schistose  group  corresponds  very  well  in  character  with  the  Montalban 
system  of  Hunt.  These  rocks  are  like  those  of  Trenton  and  West- 
chester counties  in  New  York.  Among  the  eruptive  rocks  are  placed 
those  which  occur  in  dikes,  such  as  diorite,  diabase,  kersantite,  and 
porphyry. 
Britton,  143  in  1888,  describes  as  occurring  in  the  Archean  of  New 
Jersey  an  organic  form,  apparently  algae,  to  which  he  applies  the  name 
Archwophyton  neivberryanum. 
Nason,  144  in  1890,  describes  the  Archean  of  New  Jersey.  Here  are 
found  four  types  of  rock :  The  mount  Hope  type,  a  foliated  magnetitic 
gneiss,  the  magnetite  sometimes  largely  replaced  by  hornblende,  with 
little  mica;  the  Oxford  type,  foliated  hornblende- gneiss,  magnetite  and 
biotite  in  places  almost  wholly  replacing  the  hornblende ;  the  Franklin 
type,  a  less  foliated  biotite-gneiss;  the  Montville  type,  white  or  crys- 
talline limestone.  The  Franklin  type  differs  from  the  mount  Hope  and 
Oxford  types  in  that  the  quartz  and  feldspar  are  usually  in  sharply 
angular  grains,  which  contrast  with  the  roundish  grains  of  these  min- 
erals in  the  first  two  types.  The  crystalline  limestone  is  placed  under 
the  Archean  only  provisionally.  As  there  are  apparently  many  reasons 
why  it  should  be  considered  of  more  recent  origin,  there  is  greater 
reason  for  supposing  that  if  a  part  of  it  proves  to  be  Archean  all  will 
not.  This  rock  is  found  at  Montville,  Wanaque,  Pequest  furnace, 
Jenny  Jump  mountain,  Oxford  church,  and  Mendham.  No  actual  con- 
tacts between  the  different  groups  have  been  found.  The  distribution 
of  the  various  types  is  described  in  detail.  Whether  the  gneisses  are 
sedimentary  or  eruptive  has  not  been  ascertained,  but  there  are  many 
localities  in  which  true  eruptive  granitic  rocks  inclose  within  their 
masses  fragments  of  the  adjacent  schistose  and  gneissic  rocks.  Also 
in  the  Archean  is  frequently  found  gabbro  which  is  almost  certainly 
of  igneous  origin.  Graphite  is  found  to  be  widely  separated  in  the 
Archean  rocks.  At  one  place,  commencing  at  the  old  graphite  mine 
near  South  bridge,  it  is  found  continuously  for  35  miles.  A  similar 
rock  has  been  found  at  Iona  island  in  the  Hudson  river,  35  miles  north-* 
east.  Another  line  is  found  on  Bald  hill,  and  a  third  graphite  gneiss 
is  found  on  a  hill  east  of  Pomp  ton  station  and  in  part  of  the  range  of 
Ramapo  mountains.    Also,  graphite  occurs  at  other  places. 
Nason,145  in  1891,  describes  the  relations  of  the  white  and  blue  lime- 
stones of  Sussex  county,  New  Jersey.  They  are  found  to  grade  into 
each  other  at  many  points.    The  white  limestone  is  always  associated 
I  with  later  granitic  eruptions.     In  passing  away  from  a  boss  or  dike 
