[Illustration: Bending over the instrument was a young officer, his head practically covered with a metal cap fitted with receivers.]
"We can now complete our tour of inspection," remarked Captain Brookes, "since the presence of yonder craft interferes somewhat with our preparations. Bring Mr. Stockton with you."
"Very good, sir," replied Gerald, and in a few minutes the captain and his two protégés were descending the steep iron ladder that communicated with that part of the ship below the armoured deck.
Being below the water-line the place was lighted by electric lamps, while every bulkhead and partition was traversed by a maze of wires, hidden by metal casings, each painted in distinctive colours.
At length Captain Brookes stopped before a sliding steel door and beckoned Gerald and Jack to enter. The two chums found themselves in a small lobby, their progress barred by a door similar to the one they had just entered. Carefully closing the outermost door their guide proceeded to slide back the other panel, disclosing a small room lighted only by the fitful bluish sparks emanating from an electrical machine. Bending over the instrument was a young officer, his head practically covered by a metal cap fitted with receivers similar to those worn by telephone exchange operatives.
"This is our wireless room," said the captain, raising his voice to make it audible above the succession of sharp reports like the crack of a whip. "No overhead gear to be carried away in action or in a gale; our wireless messages are received by an electrical current passing through water. The apparatus is merely an extension of the submarine signalling system. We are in touch with our agents at Swanage in England, Plougastel in Brittany, Cape Cod in the U.S.A., and ere long with Sydney, N.S.W., and Antofagasta in Chili. Thus we are well informed of events that are likely to call for our intervention."
"Then that is how you learned the result of your experiments with the Zietan, is it not?" asked Tregarthen.
"A shrewd guess, only it happens to be wrong," replied Captain Brookes. "However, I'll enlighten you on this point."
From the wireless room he led the way for'ard, between walls of steel that doubtless contained more wonders of mechanical triumph. Passing the cable lockers he dived down a narrow hatchway, leading still deeper into the bowels of the ship, till he arrived at the door of a wedge-shaped room corresponding with the bow of the vessel. Here was a table on which were several electrical coils and a pair of dials resembling galvanometers.
"Here you are," continued the captain. "What do you make of this contrivance?"