What does "underclay" mean?
Underclay: A stratum of clay lying beneath a coal bed, often containing the roots of coal plants, especially the Stigmaria.
Sources
- Webster's Unabridged Dictionary, 1913 edition (public domain, via GCIDE / Project Gutenberg).
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- Published: 2026-07-17T00:00:00-07:00 · Modified: 2026-07-17T00:00:00-07:00