Meanwhile a party of men under Uncle Herbert's directions had bored and prepared a chamber in the rock to receive nearly the whole of the remaining blasting powder, a small quantity being retained to form a "necklace"—to use the professional term—to assist in the complete dismemberment of the rock.
The work of placing the charge into the receptacle was performed by my uncle, as he preferred to take the risk alone. At dead low water springs the lagoon still remaining tidal, he took the gig, with its dangerous freight, and rowed close to the low cliff that formed the barrier between the lagoon and the open sea. Working quickly, yet cautiously, he transferred the blasting powder to the chamber, and placed a double necklace in two parallel lines in grooves over the tongue of rock. The charge was to be fired by means of a time fuse, the length of the period between the lighting of the fuse and the explosion being timed at twenty minutes. A quarter of a mile off lay the whaler, well equipped with sounding lines and rods to take the depths of the newly formed channel, and the crew anxiously awaited the appearance of the gig.
Three hours after low water the fuse was lit, and my uncle rowed back to the whaler. All eyes were fixed on the spot where the explosion was to take place, and every one who possessed a watch consulted it with feverish attention.
The twenty minutes passed, yet no explosion occurred. Five more minutes, and still no result. We began to get anxious, and my father and his brother exchanged grave looks. At the expiration of half an hour they came to the conclusion that the fuse, by some means or the other, had been extinguished, and Uncle Herbert proposed to row back and find out the cause.
"No, no," replied my father. "Give it an hour at the very least," and reluctantly my uncle agreed to defer his visit to the scene of his failure.
Directly the hour was up he rowed towards the little channel, taking two more fuses with him, but hardly had he completed half the distance when a column of smoke and dust rose into the air, followed by a deep roar. Masses of rock flew in all directions, some falling close to the gig.
"Give way, lads!" shouted the bos'n excitedly, and, bending to their oars with a will, the men urged the whaler through the water at a great pace, the heavy boat overtaking the gig before Uncle Herbert had reached the opening of the little creek, much to his chagrin.
At the head of this creek, where formerly the tongue of hard rock had been, a channel twenty feet in width communicated with the sea, and already the flood tide was swirling through. With a loud cheer, the men pulled towards the gap.
"Easy now," said the bos'n; "there might still be shallow water"; and with the blades of the oars almost touching the walls of rock on either side, the whaler breasted the tide and gained the deep water beyond.
Here we anchored, and, paying out a long grass warp, the boat was allowed to drift back into the channel, where, by careful soundings, a depth of not less than one fathom was found throughout its entire length. The action of the explosive had not only blown away the rock, but had excavated a trench with an almost even bottom.