we not hear that report?"

"Too hard for me," said Ardan. "Give it up!"

The three friends gazed at each other for a while with countenances
expressive of much perplexity. Barbican appeared to be the least
self-possessed of the party. It was a complete turning of the tables
from the state of things a few moments ago. The problem was certainly
simple enough, but for that very reason the more inexplicable. If they
were moving the explosion must have taken place; but if the explosion
had taken place, why had they not heard the report?

Barbican's decision soon put an end to speculation.

"Conjecture being useless," said he, "let us have recourse to facts.
First, let us see where we are. Drop the deadlights!"

This operation, simple enough in itself and being immediately undertaken
by the whole three, was easily accomplished. The screws fastening the
bolts by which the external plates of the deadlights were solidly
pinned, readily yielded to the pressure of a powerful wrench. The bolts
were then driven outwards, and the holes which had contained them were
immediately filled with solid plugs of India rubber. The bolts once
driven out, the external plates dropped by their own weight, turning on
a hinge, like portholes, and the strong plate-glass forming the light
immediately showed itself. A second light exactly similar, could be
cleared away on the opposite side of the Projectile; a third, on the
summit of the dome, and a fourth, in the centre of the bottom. The
travellers could thus take observations in four different directions,
having an opportunity of gazing at the firmament through the side