a bright spark, the gleam of a lucifer. Guillaume was lighting a candle.
Pierre recognised his broad shoulders, and from that moment he simply had
to follow the flickering light along a walled and vaulted subterranean
gallery. It seemed to be interminable and to run in a northerly
direction, towards the nave of the basilica.

All at once the little light at last stopped, while Pierre, anxious to
see what would happen, continued to advance, treading as softly as he
could and remaining in the gloom. He found that Guillaume had stood his
candle upon the ground in the middle of a kind of low rotunda under the
crypt, and that he had knelt down and moved aside a long flagstone which
seemed to cover a cavity. They were here among the foundations of the
basilica; and one of the columns or piles of concrete poured into shafts
in order to support the building could be seen. The gap, which the stone
slab removed by Guillaume had covered, was by the very side of the
pillar; it was either some natural surface flaw, or a deep fissure caused
by some subsidence or settling of the soil. The heads of other pillars
could be descried around, and these the cleft seemed to be reaching, for
little slits branched out in all directions. Then, on seeing his brother
leaning forward, like one who is for the last time examining a mine he
has laid before applying a match to the fuse, Pierre suddenly understood
the whole terrifying business. Considerable quantities of the new
explosive had been brought to that spot. Guillaume had made the journey a
score of times at carefully selected hours, and all his powder had been
poured into the gap beside the pillar, spreading to the slightest rifts
below, saturating the soil at a great depth, and in this wise forming a
natural mine of incalculable force. And now the powder was flush with the
flagstone which Guillaume has just moved aside. It was only necessary to
throw a match there, and everything would be blown into the air!