smith]  CEMENT    BESOUBCES    OF    ALABAMA.  427 
on  the  unfaulted  side,  which  is  the  eastern  side  in  all  except  Mur- 
phrees  Valley.  While  the  Trenton  forms  practically  a  continuous 
belt  along  the  undisturbed  side,  extensive  areas  are  sometimes  found 
on  the  faulted  side  also.  This  is  the  case,  for  instance,  at  Vance,  on 
the  Alabama  Great  Southern  Railroad,  where  the  rock  is  quarried 
for  flux  for  the  furnace  of  the  Central  Iron  Company  at  Tuscaloosa. 
Analysis  1  of  the  second  table  on  p.  432  shows  its  composition  here. 
Other  series  of  analyses  from  lower  ledges  in  the  quarry  show  only 
1.22  per  cent  of  silica,  but  more  magnesia. 
In  cases  where  erosion  has  not  gone  so  deep  as  to  reach  the  Cam- 
brian the  Trenton  may  be  found  extending  entirely  across  the  valleys. 
This  is  the  case  in  the  lower  part  of  Browns  Valley  from  Brooksville 
to  beyond  Guntersville.  Above  Guntersville  the  Trenton  is  seen  mainly 
on  the  eastern  side  of  the  valley.  The  river  touches  these  outcrops  at 
many  points,  and  at  Guntersville  the  railroad  connecting  that  city  with 
Attalla  would  afford  an  additional  means  of  transportation.  No  devel- 
opments have  }^et  been  made  in  this  area. 
The  valley  separating  the  Warrior  from  the  Cahaba  coal  field  is 
known  as  Roups  Valley  in  the  southern  and  as  Jones  Valley  in  the 
northern  part.  In  these  the  Trenton  occupies  a  narrowT,  continuous 
belt,  usually  near  the  base  of  the  eastern  Red  Mountain  ridge,  though 
in  places  it  is  high  up  on  the  ridge  and  even  at  its  summit,  as  at  Gate 
City,  where  the  quarries  of  the  Sloss  Iron  Company  are  located. 
Many  analyses  of  the  rock  from  this  quarry  have  been  made,  and  sev- 
eral are  given  in  the  second  table  on  p.  432  (Nos.  2,  3,  4,  5,  6). 
In  Murphrees  Valley  the  continuous  belt  of  the  Trenton,  as  above 
explained,  is  on  the  western  side,  while  the  faulted  remnants  are  on 
the  eastern  side.  No  quarries  have  been  opened  in  the  Trenton  lime- 
stone here,  but  the  Louisville  and  Nashville  Railroad  goes  up  the  val- 
ley as  far  as  Oneonta  and  would  afford  means  of  transportation. 
In  Cahaba  Valley,  which  separates  the  Cahaba  coal  field  from  the 
Coosa  coal  field,  the  Trenton  is  well  exposed  on  the  eastern  side  for 
the  entire  length  of  the  valley  from  Gadsden  down.  It  expands  into 
wide  areas  near  the  southern  end,  where  it  has  been  quarried  for 
lime  burning  at  Pelham,  Siluria,  Longview,  Calera,  and  other  places 
on  the  line  of  the  Louisville  and  Nashville  road.  Analyses  7,  8,  and 
9  of  the  table  on  p.  432  show  the  composition  of  the  rock  in  this  region. 
The  Central  of  Georgia  and  the  Southern  railroads  cross  this  belt 
about  midway  of  its  length  at  Leeds,  in  Jefferson  County,  and  near  its 
northern  end  it  is  crossed  by  the  Louisville  and  Nashville  Railroad, 
where  a  quarry  at  Rock  Springs,  on  the  flank  of  Colvin  Mountain, 
supplies  the  rock  for  lime  burning.  Analyses  10  shows  the  character 
of  the  rock  at  this  point. 
At  Pratts  Ferry,  on  the  Cahaba  River,  a  few  miles  above  Genter- 
ville,  in  Bibb  County,  the  Trenton  limestone  makes  high  bluffs  along 
