Of the three, Curtis was most inured to an environment that was unusual and weird, and he it was who first noticed that the barge was altering its position with regard to the white discs of light which the lamps of the automobile formed in the mist, and a splash caused by the falling plank confirmed his frenzied doubt.
One glance showed what had happened.

Already they were ten or twelve feet from the quay, which stood fully two feet above the deck of the barge.

Even while the fantastic notion flashed through his mind, a shoreward jump barely achievable by a first-rate athlete became a sheer impossibility.
"Good Lord!" he cried, almost laughing with vexation.

"The barge has been cast off from her moorings!" Devar and McCulloch greeted the discovery with appropriate remarks, but the situation called for deeds rather than words.

The cumbrous craft was swinging gayly out into the stream, displaying a light-hearted energy and ease of motion which would certainly not have been forthcoming had it been the object of her unwilling crew to get her under way.
The whereabouts of Brodie and the automobile were still vaguely discernible by two fast converging luminous circles now some twenty yards distant, and the fact was painfully borne in on them that in another few seconds this landmark would be swallowed in a sea of mist and swirling waters.
Curtis, accustomed to the vagaries of Chinese junks in the swift currents of the Yang-tse-Kiang, adopted the only measures which promised any degree of success.