They could burn in a vacuum by means of oxygen furnished by themselves, as powder burns in the chamber of a gun, or as the volcanoes of the Moon continue their action regardless of the absence of a lunar atmosphere.
Barbican had therefore provided himself with rockets enclosed in strong steel gun barrels, grooved on the outside so that they could be screwed into corresponding holes already made with much care in the bottom of the Projectile.

They were just long enough, when flush with the floor inside, to project outside by about six inches.

They were twenty in number, and formed two concentric circles around the dead light.

Small holes in the disc gave admission to the wires by which each of the rockets was to be discharged externally by electricity.

The whole effect was therefore to be confined to the outside.