Someone pointed me at this 1896 article by George Griffith, with illustrations by Fred T. Jane (of Jane's Fighting Ships fame), which I somehow managed to miss when I checked the first volume of Pearson's Magazine for scientific romances. The reason probably being that it isn't so much a scientific romance as a "prediction" of military technology. I've just scanned it and put it on line, please tell me if you spot any errors etc. in the text before I link to it properly.
