"That is our steam siren." "What is that, sir ?" said Bob again--"I don't understand you." "It's the siren," explained the other, "a thing like the steam-whistle, for signalling to passing ships." "It makes an awful row," cried Bob.

"Don't you think so, sir ?" "It does," said the lieutenant laughing.

"A great row!" "Why do they call it a siren, though ?" inquired the insatiable Bob.
"The `sirens' I've read of in my lessons at school used to be mermaids that sang so sweetly and made such beautiful music, as they played on their harps or lyres, that they lured poor mariners to destruction!" "But doesn't our siren make beautiful music ?" asked the lieutenant in a joking way.

"It is loud, it is true; but don't you think it sweet ?" "No," answered Bob, most emphatically.

"It isn't! It is more like a thousand wild bulls all with the toothache and roaring with pain!" "That's not a bad description," said the other, laughing heartily again.
"Hullo, though, they are going to fire now! Don't you see they've just run up a red flag on that spar we have forward as an apology for a mast ?" "I see," replied Bob, concentrating his attention on the preparations being made around for testing the machine-guns and larger weapons with which the vessel was armed, long cylindrical shot, ribbed with brass bands, being piled by the side of the various batteries, and nicely-made cases of cartridges placed ready for the hoppers of the Nordenfeldts and Gatlings.