Upon this fact Mr.Gibbs based his theory of making an entrance to the lake.
A climbing party, larger than the previous one, set out for the iceberg, carrying with them, on several sledges, a long and heavy iron rod, which was a piece of the extra machinery on the Dipsey, and some explosives of a special kind.
When the iceberg had been reached, several of the party ascended with a hoisting apparatus, and with this the rod was hauled to the top and set up perpendicularly on a central spot at the summit of the iceberg, the pointed end downward, and a bomb of great power fastened to its upper end.

This bomb was one designed to exert its whole explosive power in one direction, and it was so placed that this force would be exerted downward.

When all was ready, the electric-wire attachment to the bomb was carried down the iceberg and carefully laid on the ice as the party returned to the Dipsey.
Everybody, of course, was greatly interested in this experiment.
The vessel was at least two miles from the iceberg, but in the clear atmosphere the glittering eminence could be plainly seen, and, with a glass, the great iron rod standing high up on its peak was perfectly visible.

All were on deck when Mr.Gibbs stood ready to discharge the bomb on top of the rod, and all eyes were fixed upon the iceberg.
There was an explosion--not very loud, even considering the distance--and those who had glasses saw the rod disappear downward.

Then a strange grating groan came over the snow-white plain, and the great iceberg was seen to split in half, its two peaks falling apart from each other.