Symbolism, Imagery, Allegory
Trial by fire and trial by water: that's exactly what Gabriel Oak is willing to go through in his love for Bathsheba Everdene. Now to be fair, he doesn't actually know that he's helping Bathsheba when he saves her farm from fire. But the second time around, he runs out into a lightning storm to protect her harvested crops from rain because he wants what's best for her.
The symbolism of what's happening isn't lost on him either: "Oak suddenly remembered that eight months before this time he has been fighting against fire in the same spot as desperately as he was fighting against water now—and for a futile love of the same woman" (38.3).
The last line here is especially telling, since Bathsheba is already married and Oak knows that he'll never have a chance with her. That's what makes his love so much better than that of the other men in Bathsheba's life, though. Oak is willing to love her even when he can't be with her. Troy and Boldwood, on the other hand, both disappear from her life when things aren't going well.