82
THE YPRES TIMES
extended it as two separate branches of the usual standard dimensions, one to a chamber
under the main summit and the other to a similar chamber beneath a spoil bank known
as the Caterpillar. Both, it may here be stated, were completed and charged in October,
1916, and were turned over to relieving Australian tunnellers a month later.
Meanwhile, following the reverse of April 25th, shallow defensive galleries 30 feet
apart, well manned by listeners, were maintained between the bridge and Trench 42.
From them, by explosion of several camouflets, successive attempts of the enemy to
again approach our lines were frustrated. No doubt some of this hostile shallow mining
was intended to divert attention from his real counter-offensive. This was nothing
less than a carefully matured scheme which, had it succeeded, would not only have
undoubtedly spelled ruin to our own local plans but might well have jeopardized the
far-reaching project of which they formed a part. Credit for its failure must be ascribed
partly to a piece of inexcusable Teutonic carelessness and partly to some rather neat
deductive reasoning by its immediate prospective victims.
About the middle of May, 1916, listeners began to report a mysterious noise from
the shallow gallery in front of Trench 39, known as No. ro Adit. It was quite unlike
any previously heard, and might be described as a sort of indistinct tapping, the intervals
between strokes accelerating from slow to very fast. It would stop abruptly and then,
after a few minutes silence, be repeated. Sometimes it ceased altogether for days at a
time, only to recommence and keep recurring for possibly twelve hours at a stretch.
At first it attracted no particular attention. Then as a week slipped by, it began to
excite anxious curiosity. The most expert listeners were detailed to report. Records
were kept of each repetition and its duration. Officers and other ranks racked their
brains for a solution of the mystery. After a painstaking investigation with two geo-
phones, the Company's direction-finding specialist located its apparent point of origin
twenty feet in front of No. 10 Adit, some hundred beyond its entrance. An N.C.O.,
about the same time, hit on the explanation that would account for its peculiar nature,
his theory being that it proceeded from a windlass revolved about an unoiled axle by
the free unwinding of a rope. Realizing that, if this were the case, the enemy must be
carrying on a deep offensive operation of his own through the medium of a winze or
underground shaft, the O.C. at once took action. Assuming each tap represented a
revolution of the supposed windlass, and being aware what the latter probably measured
in circumference, he deduced therefrom the corresponding depth of shaft it served.
A small gallery was broken out from No. 10 Adit and driven towards the sound's pro
jected origin. Extraordinary precautions were taken to carry on the work noiselessly,
nobody with a tendency to sneeze or cough being allowed near it. After progressing
eighteen feet the sound was audible to the naked ear. A six hundred pound ammonal
charge was then placed in position, tamped and exploded. The blast wrecked a
portion of No. 10 Adit, but the damage was soon made good and another gallery was
immediately pushed out towards the camouflet in order to investigate its result. It
was not, however, until June 26th that the tool operated by one of our tunnellers suddenly
came in contact with solid wood. Following standing orders, he immediately put out
his candle and reported to the officer on duty. Carefully prying loose some timbers, the
latter flashed a torch into the aperture. As expected, it disclosed a chamber which
had housed the tell-tale windlass and which formed a head-house for the enemy's shaft.
Walls and roof consisted of heavy pit props held together with iron dogs. The structure
itself was intact, but its entrance had been destroyedprobably by its original owners.
The shaft, constructed of sheet iron plates, was full of quicksand which had poured in
through the portion wrecked by our mine.
It now became urgently necessary to determine how far the enemy's gallery had
penetrated beyond our front line, for if he had extensive workings at depth, he could
be relied on, with certainty, to make strenuous efforts at recovering them from some
neighbouring tunnel. Calculations showed the damaged shaft's probable depth as
being between 30 and 35 feet. A point in the Berlin Sap at a corresponding level was
