"There were iron brackets every few yards, holding blubber lamps"
Whale Blubber
Creative Commons Attribution Share AlikeWhale Blubber - Credit: Susanna Haas

Whale blubber was melted down and used as oil in lamps as far back as the 1700s, but it was very expensive. In the 19th century, cheaper oils such as kerosene (or naptha, as it is known in Lyra's world) replaced whale blubber as lamp oil.