"I suppose I have. It is necessary to experiment, and having good cause to try my device upon a German ship, I proceeded to do so. I am fully aware of the results it occasioned while I kept the Zietan under the influence of the Z-rays."
"However did you manage to know that?" asked Tregarthen. "Have you put into any port since leaving the Tyne?"
"I have neither put into port nor have I entered into communication with any vessel excepting your yacht, so obtaining information by those means is entirely out of the question. How I did find out the results of my experiment I will inform you shortly. But to return to this device. You will doubtless have observed that there are two pairs of pointers? Those with a black disc are merely deterrents. Any vessel that persists in forcing an action after receiving the stern warning given by these pointers has only herself to blame for the consequences; for the moment the pointers with the red disc are superimposed upon the others the fate of the Olive Branch's antagonist is sealed."
"How?" asked Gerald, with ever-growing interest.
"The conjunction of the red-disced pointers release a super charge of electricity—which I term the ZZ-rays—and her magazines are instantly exploded."
"In that case why do you require guns on board? I understood you to say that you expected to have her armament in position in the course of a few days."
"Chiefly as a matter of precaution. The slightest defect in a terminal, switch, or wire might throw the whole of the electrical apparatus out of gear. But there is another danger I have to guard against—the danger of annihilation from the sky. This device you see here has taken me fifteen years of unremitting toil and thought to perfect, and perfected it is as far as my original plans were concerned. But within recent years the advent of the airship and aeroplane has tended to revolutionise warfare. In order to negative the possible ill results of the ZZ-rays to the vessel that releases them the indicator board is arranged so that the minimum range is nine miles. Thus I can put a vessel out of action at any distance between nine and eighteen miles. The Z-rays, having a comparatively low electro-motive force, can be brought into play at a distance of two miles, without danger to the Olive Branch's delicate mechanism. It consequently follows that to use the rays within the distance of 1,000ft.—the effective range of an airship—the consequences would be disastrous to us. I therefore have to rely on other means. Now I think I have explained the contents of the conning-tower pretty fully, so we will resume our tour."
"But what are these for?" asked Tregarthen, pointing to a triple row of metal studs fixed to a mahogany board on the side of the conning-tower.
"To control the gun fire. When the ordnance is installed I'll explain their use. But we will now ascend to the flying bridge."
With the wind howling over this exposed position like a veritable tornado Gerald was glad to gain the shelter of a diminutive chart-house. Here was the electrical steering apparatus, but, to his unbounded astonishment, Tregarthen found that the place was untenanted, the only other occupants of the bridge being a lieutenant and a seaman, both of whom, glass in hand, were scanning the horizon.