rise, steam

烝 is composed of 丞(to assist) and the BuShou of 火(fire). 丞 depicts a man being lifted by two hands, which has the meaning of ascending, water gets heat from fire will turn to ascending vapour. The original meaning of 烝 is water vapour, but such meaning has been replaced by 蒸, now 烝 is mainly used to describe something multitudinous.