He indicated a group of Admiralty experts, both naval and civilian, gathered round Brian Strong's gadget on the quarter-deck. Sir John smiled. "They'd jump still more if a tinfish got us," he added. The seaplane had already been given orders to attack. It was indeed a lucky chance that she had left Calshot under active service conditions. In addition to two torpedoes designed for use against surface craft, she was equipped with four delayed-action bombs, each capable of being set to explode at any depth between four and twenty-four fathoms. It was with weapons of the latter type that the seaplane was about to deal drastically with her submerged foe. The latter was the submersible cruiser that had recently bombed Portsmouth and Southampton. She was now proceeding up-channel intent upon causing a little annoyance at Dover. Unfortunately for her, she was unaware of the presence of the seaplanes; but she had spotted the slowly moving _Cariad_ and had marked her down for an easy prey. The light cruiser had swung gently through eight points of the compass. Captain Parr had purposely refrained from ordering increased speed lest the submarine might "smell a rat". On her part, the Rioguayan craft was not able to gain on the cruiser, but was hanging on in the hope that the _Cariad_ would again alter helm and thus present a target that was almost impossible to be missed by the deadly torpedo. During the conversation between Sir John Pilrig and the Captain of the _Cariad_, Brian Strong had rejoined Peter, who had been closely questioned by the experts concerning the anti-aircraft device. In complete ignorance of the presence of the Rioguayan submarine, the group of experts transferred their attention to the seaplane that had detached herself from her consorts and was now hovering in wide circles over the clearly-defined hull of her lawful prey. A dark object dropped from the fuselage, quickly followed by another, their impact with the water throwing up a tall column of spray. "What is that fellow doing?" began Uncle Brian, but before he could complete the sentence a muffled roar shook the air. A thick cloud of greasy black smoke shot up, mushroom-shaped... the rush of subsiding water hurled high above the normal surface deadened the long-drawn-out reverberations of the explosion.... The _Cariad_ rolled lazily to the wash caused by the violent displacement of hundreds of tons of water. It seemed an interminable time before the straight snout and the net-cutting device of the Rioguayan submersible rose for a brief interval above the pool of oil--sufficient for the _Cariad_ to establish the certainty that the craft was not a British one. The submarine had been hit right aft, the explosion completely shattering the hull abaft the Diesel-engine room. The for'ard portion was, however, still practically intact.