a bed of coal.
Why Is The Word “Root” In “Root Beer”?Is root beer the world's most oddly named carbonated beverage ... we don't know, that award might go to 7-up, but we're going to explore the naming of this soft drink regardless. What, after all, is the root in root beer?
Origin of coal seam
First recorded in 1840–50
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for coal seam
The mining engineer, Monsieur Arnaud, was of opinion that on sinking deeper into the coal-seam a better quality would be met with.Cruise of the 'Alert'|R. W. Coppinger