The lamp consists of a crescent-shaped stone with a concavity, in which there is animal oil and a line of crushed moss as a wick.
"My Attainment of the Pole"
Frederick A. Cook
The seas, with boulders of ice, rolled up over our crest and into the concavity of the berg, leaving no part safe.
"My Attainment of the Pole"
Frederick A. Cook
They were on the brink of one of those subterranean wells, or "rinks," common in that part of the country, whose dangerous concavity is concealed by a light crust of earth; and only by the sudden sinking of the support beneath him is the unwary traveller apprised of the peril.
"The White Squaw"
Mayne Reid