CHAPTER XII.
ENGINEER SERKO'S ADVICE.
Thomas Roch has started work and spends hours and hours in a wooden shed on the left bank of the lagoon that has been set apart as his laboratory and workshop.

No one enters it except himself.

Does he insist upon preparing the explosive in secret and does he intend to keep the formula thereof to himself?
I should not wonder.
The manner of employing Roch's fulgurator is, I believe, very simple indeed.

The projectile in which it is used requires neither gun nor mortar to launch it, nor pneumatic tube like the Zalinski shell.

It is autopropulsive, it projects itself, and no ship within a certain zone when the engine explodes could escape utter destruction.