171 
CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,    1903. 
[bull.  225. 
than  fire  clay  alone.  Accordingly  the  shale  overlying  and  underlying 
the  day  beds  in  the  Allegheny  formation  is  used  considerably  in  the 
brick  industry  of  this  region.  Generally  it  is  the  shale  nearest  the 
Lower  Kittanning  clay  which  is  most  extensively  employed.  For 
example,  the  Fallston  Fire  Clay  Company  use  the  shale  between  the 
Lower  Kittanning  clay  and  the  Clarion  coal;  the  Vanport  Brick  Com- 
pany uses  the  same  shale  and  also  that  between  the  Darlington  and  the 
Lower  Freeport  coals.  As  shown  by  analysis  No.  1  below,  there  seems 
little  doubt  but  that  higher  shales  might  be  utilized  also,  if  necessary. 
No  analysis  from  Beaver  County  can  be  given. 
A  nalyses  of  clay  and  shale. 
Silica  (total) 
Alumina 
Water  (combined)  . 
( )xide  of  iron 
Lime 
Magnesia 
Potash 
Soda 
H20  (TTncombined) 
Total 
1. 
2. 
Per  cent. 
Per  cent. 
58.20 
49.  30 
22.47 
24.00 
6. 15 
9.40 
5.  63 
8.40 
.62 
.56 
.98 
1.60 
3.08 
3.91 
.42 
.19 
1.65 
1.20 
99.  20 
98.54 
Per  cent. 
57.  45 
21.06 
5.90 
7.54 
.29 
1.22 
3.27 
.39 
1.90 
99.02 
Per  cent. 
55.60 
24.  34 
6.75 
6.11 
.43 
.77 
3.00 
.09 
2.65 
99.  74 
Per 
cent. 
57.15 
20.26 
5.  50 
7.54 
.  90 
1.62 
3.05 
.  58 
2.70 
99.30 
No.  1.  Shales  and  fire  clays  mixed,  from  the  T.  B.  Townsend  Brick  Company,  Zanes- 
ville,  Freeport  shales  and  Kittanning  fire  clays.     Lord,  analyst. 
No.  2.  Shale  from  Waynesburg  Brick  and  Clay  Manufacturing  Company,  from  the 
Middle  Kittanning  (Darlington  ?)  horizon.     Lord,  analyst. 
No.  3.  Shale  from  the  Ohio  Paving  Company,  Columbus,  Ohio,  mined  at  Darlington, 
Ohio,  on  Lower  Kittanning  horizon,     Average  sample.     Lord,  analyst. 
No.  4.  Shale  and  fire-clay  mixture,  from  the  A.  O.  Jones  Company,  Zanesville,  Ohio, 
from  the  Kittanning  horizon.     Lord,  analyst. 
No.  5.  Shales  used  by  Bucyrus  Brick  and  Terra  Cotta  Company,  mined  at  Glouster, 
Ohio,  on  horizon  of  Cambridge  limestone.    Average  sample.    Lord,  analyst. 
Con emaugh  formation. — These  rocks  extend  from  the  top  of  Upper 
Freeport  coal  to  the  base  of  Pittsburg  coal,  making  an  interval  of 
about  510  feet.  The  base  of  this  formation,  which  practically  is 
the  horizon  of  the  Upper  Freeport  clay,  lies  375  feet  above  Beaver 
River  at  Beaver  Falls  and  dips  southward  to  275  feet  above  Ohio  at 
Beaver,  to  175  at  Freedom,  thence  becoming  lower  toward  Pittsburg. 
From  275  feet  at  Beaver,  it  drops  westward  to  265  at  Vanport,  235  at 
Industry,  225  at  Phillis  Island,  and  then  rises  to  325  at  State  line. 
The  river  bluffs  do  not  rise  much  above  this  elevation,  and  therefore 
catch  only  the  lower   portion  of  the  Conemaugh  formation,  but  it 
