426  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bill.  225. 
the  pr<  vailing  rock  across  the  valley,  and  at  Bangor  and  Blount  Springs, 
on  the  Louisville  and  Nashville  Railroad,  there  are  extensive  quarries 
which  have  been  worked  for  many  years  to  supply  rock  for  fluxing 
purposes  to  the  furnaces  of  the  Birmingham  district.  Analyses  Nos. 
2,  3,  1,  5,  6,  7,  8,  and  9,  on  p.  132,  show  the  composition  of  average 
samples  from  these  quarries;  5  to  9,  inclusive,  arc  of  carload  samples. 
From  Brooksville  to  the  Tennessee  line  a  great  thickness  of  this 
limestone  is  exposed  along  the  western  escarpment  of  Sand  Mountain, 
below  the  sandstones  of  the  Coal  Measures,  which  there  cap  the 
mountain.  In  this  area  the  river  runs  near  the  foot  of  the  mountain 
and  would  afford  the  means  of  transportation. 
In  similar  manner  the  lower  Carboniferous  limestone  outcrops  along 
the  western  flank  of  Lookout  Mountain  in  Little  Wills  Valley,  from 
near  Attalla  to  the  Georgia  line,  and  south  of  Attalla  it  forms  the 
lower  part  of  the  escarpments  of  Blount  and  Chandlers  Mountain. 
The  Alabama  Great  Southern  Railroad  passes  very  near  to  the  out- 
crop from  the  Georgia  line  down  to  Springville,  Ala.  South  of 
Springville  large  outcrops  occur  in  Shades  Valley,  and  at  Trussville 
are  quarries  which  have  supplied  the  Birmingham  furnaces.  Analyses 
10  to  17,  inclusive,  p.  132,  are  of  material  from  Trussville;  and  analyses 
12  to  17,  inclusive,  represent  average  samples  from  carload  lots  deliv- 
ered to  furnace. 
In  Murphrees  Valley  the  main  outcrop  of  this  rock  is  on  the  western 
side,  and  quarries  at  Compton  have  for  many  years  been  worked  to 
supply  the  Birmingham  furnaces.  Analyses  18,  19,  and  20  of  the  rock 
from  these  quarries  show  somewhat  varying  composition,  but  by 
proper  selection  suitable  material  could  easily  be  obtained. 
In  the  valleys  lying  east  of  Shades  Valley  and  in  parts  of  Shades 
Valley  itself  this  formation  becomes  one  of  prevailing  shales  and 
sandstones  and  the  limestones  are  of  limited  occurrence  and  of  inferior 
quality. 
Trenton  limestone. — The  Trenton  limestone  outcrops  in  Alabama  in 
three  principal  areas.  In  the  Tennessee  River  Valley  some  of  the 
smaller  streams  which  flow  into  the  river  from  the  north,  like  Flint 
River,  Limestone  Creek,  Elk  River,  Bluewater  Creek,  and  Shoal 
Creek,  have  eroded  their  valleys  into  the  Trenton  limestone.  These 
areas  are  crossed  at  only  a  few  points  by  the  railroads  leading  out 
from  Huntsville  aiid  Florence,  and  no  commercial  use  has  as  yet  been 
made  of  the  rock. 
In  the  narrow  anticlinal  valleys  below  enumerated  erosion  has  in 
most  cases  sunk  the  floors  of  the  valleys  into  Cambrian  strata,  and,  as 
a  consequence,  the  Trenton  limestone  occupies  a  narrow  belt  on  each 
side,  near  the  base  of  the  Red  Mountain  ridges.  But  since  a  fault 
usually  occurs  on  one  side  of  these  valleys,  the  Red  Mountain  ridges 
and  the  accompanying  Trenton  limestone  are  more  fully  represented 
