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CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  190k 
[BULL.  260. 
About  8  miles  east  of  Columbus,  on  the  Columbus  and  Tusca- 
loosa road,  the  hills  of  the  Tuscaloosa  formation  first  appear.  Ou 
the  hill  near  the  8-mile  post  the  highly  stratified  clay  interbedded 
with  various  colored  sands  outcrops  on  the  side  of  the  road. 
One  mile  south  of  Strongs,  on  the  Illinois  Central  Railroad,  on 
the  Monroe  and  Clay  line,  the  railroad  has  cut  into  the  Selma  clay 
to  a  depth  of  15  feet. 
Eutaw  sands  extend  west  of  the  town  of  Aberdeen  for  2  miles. 
Here  the  post-oak  lands  begin,  and  the  regular  prairie  soils  one-half 
mile  farther  west.  There  are  no  outcrops  of  the  Selma  from  Aberdeen 
to  Prairie  station.  The  first  outcrop  found  southwest  of  Aberdeen  is 
rd  Strongs.  There  are  very  few  outcrops  of  the  Selma  chalk  here  or 
farther  south. 
The  following  four  analyses  of  samples  of  limestone  from  vari- 
ous points  in  Oktibbeha  County,  Miss.,  were  made  by  Prof.  W.  F. 
Hand,  State  chemist: 
Analyses  of  Selma  Limestone,  Oktibbeha  County,  Miss. 
Average, 
Silica  (Si02) 
Alumina  ( AL03)  
Iron  oxide  (Fe203) 
Lime  carbonate  (CaC03) 
Magnesium  carbonate  (MgC03) 
Water 
1. 
2. 
3. 
4. 
2.89 
2.33 
3.03 
2.  55 
I  1.53 
1.72 
1.92 
1.96 
94.10 
94.35 
93.60 
94. 07 
1.84 
1.82 
1.64 
2. 12 
.36 
.44 
.42 
.52 
2.70 
1.78 
94.03 
1.85 
.44 
The  following  analysis  is  an  old  one  made  by  Doctor  Hilgard  a  on 
a  sample  of  the  Selma  chalk  from  near  Okolona,  Chickasaw  County, 
Miss.  Of  the  material  reported  as  "  insoluble  "  probably  about  two- 
thirds  was  silica,  the  remainder  being  alumina  and  iron  oxide. 
Analysis  of  limestone  from  Okolona,  Miss. 
Insoluble  (mostly  silica,  Si02) 10.  DO 
Alumina    (Al2Os) 1.96 
Iron  oxide  (Fe,03) 1.42 
Lime  (CaO) &  45.  70 
Magnesia  (MgO) c  .  88 
Alkalies    (K20,   Na20) .57 
Carbon  dioxide   (C02) 35.73 
Water  and  organic 2.84 
a  Report  on  the  Geology  of  Mississippi,  p.  101.     1860. 
"Lime  carbonate   <CaC03).  81.77. 
c  Magnesium  carbonate  (MgC03),  1.84. 
