“I’d like to drop that hundred-pounder on to a Zeppelin!” said one of the aviators.  All the population of London would like to see him do it.  And Fritz, the submarine, does not like to see the shadow of man’s wings above the water.

Seaplanes and destroyers carry the imagination away from the fleet to another sphere of activity, which I had not the fortune to see.  An aviator can see Fritz below a smooth surface; for he cannot travel much deeper than thirty or forty feet.  He leaves a characteristic ripple and tell-tale bubbles of air and streaks of oil.  When the planes have located him they tell the hunters where to go.  Sometimes it is known that a submarine is in a certain region; he is lost sight of and seen again; a squall may cover his track a second time, and the hunters, keeping touch with the planes by signals, course here and there on the look out for another glimpse.  Perhaps he escapes altogether.  It is a tireless game of hide and seek, like gunnery at the front.  Naval ingenuity has invented no end of methods, and no end of experiments have been tried.  Strictest kept of naval secrets, these.  Fritz is not to be told what to avoid and what not to avoid.

Very thin is the skin of a submarine; very fragile and complicated its machinery.  It does not take much of a shock to put it out of order or a large charge of explosives to dent the skin beyond repair.  It being in the nature of submarines to sink, how does the hunter know when he has struck a mortal blow?  If oil and bubbles come up for some time in one place, or if they come up with a rush, that is suggestive.  Then, it does not require a nautical mind to realize that by casting about on the bottom with a grapnel you will learn if an object with the bulk and size of a submarine is there.  The Admiralty accept no guesswork from the hunters about their exploits; they must bring the brush to prove the kill.

With Admiral Crawford I went to see the submarine defences of the harbour.  It reminded one of the days of the drawbridge to a castle, when a friend rode freely in and an enemy might try to swim the moat and scale the walls if he pleased.

“Take care!  There is a tide here!” the coxswain was warned, lest the barge should get into some of the troubles meant for Fritz.  “A cunning fellow, Fritz.  We must give him no openings.”

The openings appear long enough to permit British craft, whether trawlers, or flotillas, or cruiser squadrons, to go and come.  Lying as close together as fish in a basket, I saw at one place a number of torpedo boats home from a week at sea.

“Here to-day and gone to-morrow,” said an officer.  “What a time they had last winter!  You know how cold the North Sea is—­no, you cannot, unless you have been out in a torpedo boat dancing the tango in the teeth of that bitter wind, with the spray whipping up to the tops of the smoke-stacks.  In the dead of night they would come into this pitch-dark harbour.  How they found their way is past me.  It’s a trick of those young fellows, who command.”