BURDEN or BURTHEN. (1) A load, both literally and figur atively (A.S. byrthen, from beran, to bear) ; the carrying capacity of a ship; in mining and smelting, the tops or heads of stream work which lie over the stream of tin, and the proportion of ore and flux to fuel in the charge of a blast-furnace. In Scots and English law, an encumbrance on real or personal property. (2) An accompaniment to a song, or the refrain of a song (Fr. bourdon, a droning, humming sound) ; hence a recurrent topic, as "the burden of a speech."