underclay
/ (ˈʌndəˌkleɪ) /
noun
a grey or whitish clay rock containing fossilized plant roots and occurring beneath coal seams. When used as a refractory, it is known as fireclay
Words nearby underclay
undercast,
undercellar,
undercharge,
underclass,
underclassman,
underclay,
underclothes,
undercoat,
undercoating,
undercompensate,
undercool
Example sentences from the Web for underclay
It rests on the underclay b b', filled with roots of trees in situ, and it supports a growing forest (C D).
A Manual of Elementary Geology |Charles Lyell.These roots were Stigmaria, and the stuff into which they penetrated was an underclay.
I wish Ehrenberg would undertake a microscopical hunt for infusoria in the underclay and shales; it might reveal something.
More Letters of Charles Darwin Volume II |Charles Darwin