CLAYS    OF    WESTERN    KENTUCKY    AND    TENNESSEE.         419 
The  following  analysis  of  the  Pottertown  clay  was  made  by  A.  M.  PetenQ 
Analysis  of  Pottertown  clay,  Kentucky. 
Silica 57. 840 
Alumina ::o.  340 
Iron  peroxide I .  I  si  1 
Lime Oil 
Magnesia 0/30 
Potash tils 
Soda 510 
Water,  etc 9.442 
100.000 
TENNESSEE. 
Holloiv  Rock,  Carroll  County. — About  2  miles  west  of  the  town,  near  the  railroad,  is  a  small 
pit  of  white,  lean,  siliceous  clay.  It  is  found  in  horizontal  layers  and  if  taken  out  when 
dry  it  breaks  along  the  bedding  plane.     An  area  25  by  40  feet  has  been  opened  up. 
One  mile  farther  west  is  another  pit,  in  which  occurs  a  bluish-pink,  highly  plastic  clay 
free  from  grit.  It  is  shipped  to  Nashville.  The  clay  is  exposed  in  a  gully  30  feet  long  and 
50  feet-wide,  and  is  overlain  by  3  feet  of  Lafayette  and,  above  this,  by  2  feet  of  Columbia  loam. 
TERTIARY  CLAYS  ABOVE  THE  PORTERS  CREEK. 
The  valuable  clays  which  occur  in  great  amount  and  variety  in  the  Gulf  embayment  area 
of  western  Kentucky  and  Tennessee  are  principally  found  in  the  lower  Tertiary.  In  Tennes- 
see the  area  is  restricted  to  a  narrow  belt  of  country  10  to  20  miles  wide  lying  just  west  of 
the  Porters  Creek  clay  belt  and  can  be  traced  across  the  State  by  a  line  of  stoneware  and 
fire-brick  plants  and  pits  which  ship  clays  elsewhere  to  be  made  into  the  finished  product. 
In  Kentucky  the  clays  extend  over  a  much  wider  belt,  but  they  are  confined  within  the 
limits  of  the  lower  Tertiary 
KENTUCKY. 
The  Tertiary  clays  of  Kentucky  are  still  practically  undeveloped.  Most  of  the  clays  now 
being  mined  are  shipped  out  of  the  State. 
Dr.  R.  H.  Loughridge,&  who  made  a  comprehensive  study  of  the  Jackson  Purchase 
region  of  Kentucky,  gave  in  his  report  the  analyses  of  41  different  clays.  Tests  of  the  most 
important  were  made  in  the  Rookwood  Pottery,  of  Cincinnati,  Ohio,  and  the  results  are 
given  in  the  right-hand  columns  of  the  table  of  analyses  (p.  420). 
Wickliffe,  Ballard  County. — One  of  the  most  extensive  clay  deposits  of  Ballard  County 
outcrops  in  the  ravines  and  along  the  new  railroad  east  of  Wickliffe.  Similar  clay  is 
exposed  in  the  river  bluffs  between  Wickliffe  and  Laketon.  Near  the  surface  it  is  gray,  but 
it  becomes  whiter  below.     It  makes  a  good  fire  brick  and  fancy  decorated  brick. 
The  thickness  of  the  deposit  is  ascertained  in  the  railroad  section  1  mile  east  of  Wick- 
liffe.    The  section  is  as  follows: 
Section  of  clay  deposit  1  mile  east  of  Wickliffe,  Ky. 
Feet. 
Loess 30 
Lafayette  sand  and  gravel 2° 
Black,  rotten  clay,  containing  fragments  of  lignitized  wood,  bark,  and  logs ...       h 
White  plastic  clay 30 
Fine  quicksand ° 
Sand  rock,  bottom  of  cut. 
Samples  of  clay  from  this  horizon  have  been  made  into  fire  brick  and  tested  in  the  iron 
furnaces  at  Birmingham,  Ala.,  where  they  are  said  to  have  stood  a  higher  degree  of  heat 
than  any  other  brick  used  at  the  furnaces. 
oJackson  Purchase  region:  Kentucky  Geol.  Survey,  p.  107. 
b  Jackson  Purchase  region:  Kentucky  Geol.  Survey. 
