Hastings' Dictionary of the Bible (1898)
LEAD, a metal known to the ancients from a very early period, and alluded to in Ex 15:10 on account of its weight. It is mentioned several times in Scripture as entering into the process of purifying more precious metals, Jer 6:29; Eze 22:18, Ruth 4:20; for which purpose quicksilver is now used. The words of Job 19:24, "That they were graven with an iron pen and lead in the rock for ever!" refer to the custom of pouring molten lead into letters
carved in the rock in order to make them more striking to the eye.