He pursued his employment with perfect impunity; the darkness covered him from observation; no one disturbed him by approaching the solitary scene of his operations; and of the two sentinels who were placed near the part of the wall which was the centre of all his exertions, one remained motionless at the most distant extremity of his post, and the other paced restlessly backwards and forwards on the rampart, singing a wild, rambling song about war, and women, and wine, which, whatever liberty it might allow to his organs of perception, effectually hindered the vigilant exercise of his faculties of hearing.
Brick after brick yielded to the vigorous and well-timed efforts of Ulpius.

He had already made a cavity, in an oblique direction, large enough to creep through, and was preparing to penetrate still further, when a portion of the rotten material of the interior of the wall suddenly yielded in a mass to a chance pressure of his iron bar, and slowly sunk down inwards into a bed which, judging by such faint sounds as were audible at the moment, must have been partly water, and partly marshy earth and rotten brick-work.

After having first listened, to be sure that the slight noise caused by this event had not reached the ears or excited the suspicions of the careless sentinels, Ulpius crept into the cavity he had made, groping his way with his bar, until he reached the brink of a chasm, the depth of which he could not probe, and the breadth of which he could not ascertain.
He lingered irresolute; the darkness around him was impenetrable; he could feel toads and noisome animals crawling over his limbs.

The damp atmosphere of the place began to thrill through him to his very bones; his whole frame trembled under the excess of his past exertions.
Without light, he could neither attempt to proceed, nor hope to discover the size and extent of the chasm which he had partially laid open.

The mist was fast vanishing as the night advanced: it was necessary to arrive at a resolution ere it would be too late.
He crept out of the cavity.