Sentence:  [W]e know from experience, that the light of a candle, lamp, or fire depends on, and emanates from the flame of each; and we alſo knw that this flame is nouriſhed and ſuſtained by a <WSD>pabulum</WSD> or fuel, which is conſumed or waſted, according to the quantity of light that iſſues from the flame; and that, when this food or fuel is exhauſted, the flame expires and yields no more light. 
Meaning of the word marked with <WSD> tags:  Material that feeds a fire.