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. The mixtures having been already carefully deposited in each barrel, nothing further need be done than to take away the metallic plugs which had been screwed into the bottom of the Projectile,
