The _Archimedes_, after taking her ammunition on board, had steamed out seaward so as to get a good offing where she might fire her guns without the risk of hitting any passing craft; and, by the time Bob had come on deck again from inspecting the machinery, she was well beyond the Nab light and far out into the waters of the Channel. On the order being presently given to fire, the machine-guns went popping away, to test how many shots they can fire off in a minute--the report of some of them sounding like an asthmatic old gentleman with a very bad cough. "What a funny noise!" cried Bob--"Rover barks just the same when he's asleep and dreaming!" "Indeed!" said the young lieutenant, more intent, however, on watching a party of blue-jackets getting ready a big gun for firing in the bows than paying much attention to Bob. "Look out there, youngster!" "What are they going to do, eh?" asked Bob--"all those sailors there!" "Why, fire one of our forty-three ton guns; so you'd better look out for squalls. Have you got any cotton-wool about you?" "No," answered Bob. "What for?" "To put in your ears, so as to deaden the noise of the report," said the lieutenant. "I've got some, though, so it doesn't matter. Here's a bit to stick in your ears--you'd better take my advice, it'll save your tympanum!" Bob did not know what he meant; but he put the cotton-wool in his ears, as desired, on seeing Captain Dresser and some other officers standing near doing the same, and that the lieutenant was not "taking a rise out of him," as at first he was inclined to think. The enormous gun, carrying a charge of two hundred and eighty pounds of powder, with a shot weighing nearly a quarter of a ton, was now loaded; when the officer directing the operation ordered all persons to move away from the vicinity of the weapon, which was about to be fired for the first time--at least on board the _Archimedes_. Everybody retreated behind the armoured screen bulkhead that formed a sort of "shelter trench" across the deck; for, if an accident should happen in the way of an unexpected explosion, refuge might be had there from any flying fragments. Everybody, as has been said, at once, on the order being given, sought this retreat--everybody, that is, but Bob, who, instead of stepping back like the others, stepped forwards. At the same moment the signal was given, "Fire!" A terrific report followed, as if the ship and all its contents were blown up, there being none of the reverberating sound, like that usually heard when heavy guns are fired, as of an express train rushing at speed through the air; but a dull, hollow, sullen, sharp roar, succeeded by the heavy swish of some body, or something, falling into the water alongside, while a thick smoke hung over the deck like a pall. "By Jingo!" exclaimed the Captain, "the gun has burst!" CHAPTER NINETEEN. BOB GETS "BLOWN UP."