UNDERCLAY
Source: 567
Un″der‐clay′ (?), n. (Geol.) A stratum of clay lying beneath a coal bed, often containing the roots of coal plants, especially the Stigmaria.
Source: 567
Un″der‐clay′ (?), n. (Geol.) A stratum of clay lying beneath a coal bed, often containing the roots of coal plants, especially the Stigmaria.