572  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.         [bull.  260. 
A  dark-gray  sandy  shale  has  been  extensively  quarried  1J  miles 
northeast  of  Horseheads  for  the  manufacture  of  brick.  The  shale  is 
mixed  with  glacial  clay  in  the  proportion  of  two  parts  of  the  former 
to  one  of  the  latter.  The  output  of  the  factory  is  about  50,000  bricks 
per  day. 
At  Elmira  a  large  brick  factory  is  operated  which  makes  a  high- 
grade  brick  from  the  valley  clay  combined  with  the  sandy  shales 
furnished  by  the  quarries  just  east  of  the  city. 
The  same  quarries  which  furnish  brick  shale  at  Elmira  supply 
thin-bedded  sandstone,  which  is  used  extensively  for  foundation  work 
in  the  city  and  to  a  small  extent  for  other  purposes. 
