1) A rock, chiefly consisting of carbonate of lime, used to make quicklime.
The mortar used by bridge masons had two basic components, lime and sand. Its preparation involved converting the lime into quicklime which was done in a kiln, often a very primitive pit kiln. At that stage it was very volatile and dangerous to transport so the operation was usually carried out close to the place of work. Much of that is explicit in the masons' contract for Catterick Bridge: 1422 [they] schalle gett lymstane and birne itte … and make thair lymkilns … and fynde and make carriage of sand als mekylle as thaim nedes …and schalle fynd apone thair owne cost als mykylle wode and coles broghte one the grounde as wille suffys … to the birnynge of alle the lymkilnes.