Clement quotes B30 and B31 in the same context. His complete text reads:
"Now that [Heraclitus] recognized that the world which is uniquely characterized by the totality of substance is eternal, is evident when he says:
The world, the same for all, neither any god nor any man made; but it was always and is and will be, fire ever-living, kindling in measures and being extinguished in measures. [B30]And that he believed it to be generated and destructible is indicated by the following words:
Turnings of fire: first, sea; of sea, half is earth, half lightning flash. [B31a]-- He says in effect that, by reason and good which rule everything, fire is turned by way of air into moisture, the seed, as it were, of creation, which he calls sea; and from this, again, come earth and heaven and what they contain. He shows clearly in the following words that they are restored again and become fire:
Sea is dissolved and measured into the same proportion that existed at first. [B31b]And the same holds for the other elements" (Barnes 122).