45 G  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull. 225. 
Probabli  extension  of  the  industry. — As  noted  in  the  earlier  portion 
of  this  paper,  the  cement  deposits  have  been  developed  only  from  near 
Reading,  Pa.,  to  a  few  miles  from  Stewartsville,  N.  J.  Most  of  the 
readily  accessible  cement  land  between  these  points  has  been  taken 
up  by  the  cement  companies  or  is  being  held  at  impossible  prices  by 
the  owners.  Under  these  circumstances  it  seems  probable  that  few 
additional  plants  can  be  profitably  established  in  the  district  now 
developed,  and  that  the  growth  of  the  industry  here  will  be  brought 
about  by  extending  the  district.  A  few  notes  on  the  distribution  of 
the  same  cement  beds  in  adjoining  areas  may  therefore  be  of  interest 
to  those  desiring  to  engage  in  the  manufacture  of  Portland  cement 
from  materials  of  the  Lehigh  district  type. 
Northeast  of  Stewartsville,  N.  J.,  the  cement  beds  outcrop  at  fre- 
quent intervals  in  the  Kittatinny  Valley  all  the  way  across  New  Jersey, 
and  a  few  miles  into  Orange  County,  N.  Y.  The  exact  locations  of 
these  deposits,  with  numerous  analyses  of  the  cement  rocks,  are  given 
in  the  Annual  Report  of  the  State  Geologist  of  New  Jersey  for  1900, 
pages  41-95.  Many  detailed  maps  in  this  report  show  the  outcrops 
very  precisely. 
Southwestward  from  Reading  the  Trenton  beds  outcrop  in  a  belt 
crossing  Lebanon,  Cumberland,  and  Franklin  counties,  Pa.,  passing 
near  the  towns  of  Lebanon,  Harrisburg,  Carlisle,  and  Chambersburg. 
In  Maryland  the  Trenton  rocks  occur  in  Washington  County,  while  in 
West  Virginia  and  Virginia  they  are  extensively  developed.  The  dis- 
tribution of  these  rocks  in  Virginia  is  discussed  in  the  following  paper. 
Throughout  this  southern  extension  of  the  Lehigh  rocks,  the  Tren- 
ton is  not  everywhere  an  argillaceous  limestone,  but  it  is  frequently 
so,  and  it  is  always  very  low  in  magnesium  carbonate.  It  is  therefore 
probably  safe  to  say  that  in  southern  Pennsylvania,  Maryland,  West 
Virginia,  and  Virginia  the  Trenton  rocks  are  everywhere  good  Port- 
land cement  materials,  though  in  some  cases  they  will  require  pure 
limestone,  and  in  other  places  clay,  to  bring  them  to  proper  composition. 
