But before we were half-way across the intervening stretch of water a dull "boom" resounded astern of us, and a length of some fifty feet of wharf face suddenly leapt outward and fell with a heavy splash into the water, followed, about half a minute later, by a second "boom" and splash, then a third, fourth, fifth, and so on, until the entire wharf was completely destroyed and the whole place a ghastly, fire-swept ruin.
