in antiquity, a species of divination performed with stones. Sometimes the stone called sideritis was used: this they washed in spring-water. water in the night by candle-light; the person that consulted it was to be purified from all manner of pollution, and to have his face covered; this done, he repeated divine prayers, and placed certain characters in an appointed order; and then the stone moved of itself, and in a soft gentle murmur, or (as some say) in a voice like that of a child, returned an answer. By a stone of this nature, Helena is reported to have foretold the destruction of Troy.