Abstract
The group of Buddhist stone images of Oya Hill which is in the suburbs of Utsunomiya City is the oldest one among cave statures in Japan (made in the 9th century). The stone images are carved on the wall surface of the large cave in porous green tuff.
At the present time, the stone images are considerably damaged as a result of active weathering through the centuries.
So the National Commission for Protection of Cultural Properties is intending to repair the damage and to check further deterioration.
The author has made clear that the active weathering is caused by capillary water which derived from the ground water, and has found that the elimination of the ground water is effective for the conservation of the stone images.
