As best as I can make out from the photo, the inscription on the tombstone reads:
JACOB KOHLER DIED APRIL 27, 1870 AGED 82 Y 8 M 10 D ELISABETH wife of JACOB KOHLER DIED DEC 17, 1868 AGED 76 Y 2 M 27 D
Further information about headstones in this cemetery, and the original source data for the image above, are available at http://www.rootsweb.com/~ohrichla/Cem-Clay.htm.