sent to start
screening in widening circles, while--on the off-chance that there
really was a wreck on the bottom--a pair of trawlers were sent to drag
about the bottom under the messy patch with an 'explosive sweep.'

"My diagnosis was quite correct as far as it went, but it did not go
quite far enough; still--by the special intervention of the sweet little
cherubim who sits up aloft to keep watch o'er the life of poor Jack--my
plan of operation was quite as sound as if I had all the facts of the
case spread out before me. Had the U-boat really been lurking round
waiting for a pot at some of the ships trying to save his supposed
remains--something that we never gathered any definite evidence on--our
screening tactics would probably have prevented his success; while the
trawlers, with their sweep, furnished the best antidote for the little
surprise party that he already _had_ prepared for us.

"Scarcely had the trawlers entered the oily area than the jar of a heavy
under-sea explosion jolted against the bottom of the _Flash_, which, a
thousand yards distant, was just beginning to work up to full speed.
Almost immediately three or four other explosions followed, coming so
close together as to make one rippling detonation of tremendous
violence. An instant later I saw several columns of grimy foam shoot
skyward, two or three of them so close together that they seemed to
'boil' into each other as they spilled and spread in falling. Although
neither of the trawlers appeared to be immediately over any of the
explosions, both of them received terrific shocks. One of them I
distinctly saw rear up till it seemed almost to be balanced on its
rudder-post as a round hump of green water drove under it, while the
scuppers of the other spurted white as they cleared the flood that a
spreading foam geyser had thrown upon the deck. It seemed impossible
that either of them could survive such shocks as I knew they must have
received, and I fully expected to see nothing better than two foundering
wrecks emerge from the smother which hovered above the scene of the
explosions. Imagine my surprise, then, when two junk-like profiles (they
were both of the marvellously sea-worthy 'Iceland trawler' type) came
bobbing serenely into sight again, and I noted with my glass that
neither appeared to have suffered serious damage. On the score of lives,
a tom-cat has nothing the best of a trawler. If it had been otherwise
our whole fleet of them--and t