476 
CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull.  225. 
Of  the  57  clay  yards  mentioned  in  Hopkins's  report,  over  two-thirds 
use  shale,  wholly  or  in  part,  making  a  product  chiefly  of  red  brick, 
hut  also  paving  and  pressed  brick. 
QUATERNARY  CLAYS. 
These  clays  are  limited  to  the  river  terraces,  of  which  three  are  well 
marked  along  Beaver  and  Ohio  rivers.  One  lies  200  to  250  feet  above 
river  level,  and  is  well  exposed  between  Rochester  and  New  Brighton 
and  at  Doctor  Heights,  but  farther  west  on  the  Ohio,  to  State  line, 
is  represented  only  by  very  small  remnants.  Another  terrace  lies 
about  100  feet  lower,  and  on  this  are  built  most  of  the  river  towns — 
New  Brighton,  Fallston,  Beaver,  Monaca,  Shippingport,  and  George- 
town. A  third  terrace,  100  feet  lower  than  the  one  just  described,  lies 
from  30  to  50  feet  above  river  level,  and  usually  is  inundated  by  spring 
floods. 
Of  these  three  terraces,  the  highest  and  lowest  produce  clays  which 
being  generally  impure  and  frequently  sandy,  are  chiefly  adapted  to 
the  manufacture  of  common  brick,  though  pressed  brick,  and  even 
crude  pottery  are  made  when  the  clays  are  fine  and  homogeneous. 
Often  they  are  mixed  with  shale,  producing  excellent  results.  So  far 
as  known,  clay  deposits  of  value  have  not  been  discovered  on  the  inter- 
mediate terrace.  A  terrace  of  the  same  elevation  as  the  highest  one 
mentioned  above,  and  probably  of  the  same  age,  occurs  between  Rac- 
coon Creek  and  Logtown  Run.  New  Sheffield  is  situated  upon  it.  That 
this  terrace  might  in  depth  also  carry  red -brick  clays  seems  probable, 
but  exploitation  is  hindered  by  lack  of  transportation  facilities. 
An  important  deposit  has  been  worked  on  the  highest  terrace  near 
New  Brighton  and  Rochester.  At  the  former  place  the  deposit,  which 
was  used  for  terra  cotta,  and,  by  mixing  with  Lower  Kittanning  clay, 
for  flower  pots,  shows  the  following  composition: 
Analyses  of  terrace  days. 
Si02 
A1203 
Fe203 
Ti02 
CaO 
MgO 
Alkalies 
Water 
Total 
1.  Mendenhall  &  Chamberlin  Works. 
2.  Elverson  &  Sherwood  Works. 
Both  analyses  from  Second  Geol.  Survey,  Pennsylvania,  Rept.  MM,  p.  257 
Per  cent. 
46. 160 
26. 976 
7.214 
.740 
2.210 
1.520 
3.246 
11.  220 
99.  286 
Per  cent. 
67.  780 
16.  290 
4.570 
.780 
.600 
.727 
2.001 
6.340 
99.  088 
A.  S.  McCreath,  analyst. 
