Incidental

Directions: Some words in the passage below have been highlighted. Select the best meaning for the corresponding word.

Primitive man was probably more concerned with fire as a source of warmth and as a means of cooking food than as a source of light. Before he discovered less laborious ways of making fire, he had to preserve it, and whenever he went on a journey he carried a firebrand with him. His discovery that the firebrand from which the torch may well have developed, could be used for illumination, was probably incidental purpose of preserving a flame.

Lamps too, probably developed by accident. Early man may have had his first  conception of a lamp while watching a twig of fibre burning in the molten fat dropped from roasting carcass. All he had to do was to fashion a vessel to contain fat and float a lighted reed in it. Such lamps, which were made of hollowed stones or sea-shells, have persisted in identical form up to quite recent times