1  o  s  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull.  225. 
the  river  for  several  miles,  and  is  in  most  convenient  position  for  easy 
quarrying. 
Marble  work-  have  in  former  days  been  established  here  and  should 
be  again  put  in  operation,  since  the  marble  is  of  fine  quality  and  beau- 
tifully variegated.  No  analyses  are  available,  but  there  is  no  doubt 
that  much  of  the  rock  is  sufficiently  low  in  magnesia  to  be  lit  for  use 
in  cement  making.  Cahaba  River  and  a  short  spur  from  the  Mobile 
and  Ohio  Railroad  would  afford  transportation  facilities  for  this  deposit. 
In  Big  Wills  Valley,  which  separates  Sand  and  Lookout  mountains, 
the  Trenton  limestone  occupies  perhaps  25  square  miles,  but  it  is 
crossed  only  by  the  railroad  connecting  Gadsden  with  Guntersville. 
No  analyses  are  available. 
In  the  great  Coosa  Vallej-  region  the  Trenton  outcrops  are  found 
mostly  on  the  western  border  near  the  base  of  Lookout  Mountain,  as 
in  Broomtown  Valley,  and  in  other  valleys  extending  south  toward 
Gadsden.  While  these  belts  have  been  utilized  in  the  past  for  the  old 
Gaylesville,  Cornwall,  and  Round  Mountain  furnaces,  and  possibly  for 
some  furnaces  now  in  blast,  no  analyses  are  available. 
Similarly,  farther  south,  along  this  western  border  of  the  Coosa 
Valley,  and  running  parallel  with  the  Coosa  coal  field  in  Calhoun,  St. 
Clair,  and  Shelby  counties,  there  are  numerous  long,  narrow  outcrops 
of  Trenton  limestone.  The  Calcis  quarry  of  the  Tennessee  Coal,  Iron 
and  Railroad  Company,  on  tke  Central  of  Georgia  Railroad,  near  Ster- 
ritt,  is  upon  one  of  these  outcrops,  and  furnishes  limestone  with  a  very 
low  and  uniform  percentage  of  silica  and  magnesium.  Analyses  11, 
12,  13,  14,  15,  and  16  exhibit  the  quality  of  the  rock  as  received  at  the 
Ensley  Steel  Works,  but  care  is  taken  at  the  quarry  to  select  ledges 
low  in  silica  and  magnesia,  and  the  analyses  therefore  represent  only 
the  selected  ledges  and  not  the  average  run  of  the  quarry  as  a  whole. 
Near  Talladega  Springs,  Marble  Valley,  and  Shelby  are  other  occur- 
rences of  the  rock,  and  a  quarry  a  few  miles  east  of  Shelby  furnace 
has  for  many  years  supplied  that  furnace  with  its  flux.  The  quality 
of  the  material  here  is  shown  by  analyses  17,  18,  19,  and  20. 
The  Cambrian  limestones  contain  generally  a  very  considerable  pro- 
portion of  magnesia,  and  for  this  reason  are  not  suited  for  Portland- 
cement  manufacture,  though  admirably  adapted  for  furnace  stone. 
Along  the  eastern  border  of  the  Coosa  Valley,  near  its  contact  with 
the  metamorphic  rock,  there  is  a  belt  of  limestone  which,  in  places,  is 
a  white  crystalline  marble  of  great  purity,  as  is  shown  by  analyses  1  to 
7,  inclusive,  of  the  table  on  p.  133.  The  Louisville  and  Nashville  Rail- 
road, from  Calera  to  Talladega,  passes  close  to  this  belt  at  many  points. 
This  marble  has  been  quarried  at  several  places  for  ornamental  stone. 
It  is  mentioned  here  because  it  is  near  the  railroad  and  its  description 
completes  the  account  of  the  limestone. 
