"Two points on the port bow, sir," was the prompt reply.
In anxious suspense officers and crew waited for the Portuguese vessel to come within range of vision. Quickly the daylight grew brighter. A slight mist that hung around in low, ill-defined patches began to lift. The sea, still high, rendered it difficult to locate a vessel at any considerable distance from the British auxiliary cruiser.
Presently Osborne went to the voice-tube communicating with the engine-room. His observant eye had noticed that the Portchester Castle's funnels were throwing out considerable volumes of smoke. Since it was imperative that she should conceal her approach until the last possible moment, he requested the Engineer-lieutenant to exercise a little more care in the stokeholds. A minute or two later the black volumes of smoke gave place to a thin haze of bluish vapour.
"There she is!" exclaimed Webb. "By Jove, they've bagged her! She's hove-to."
The tramp, a vessel of about 2000 tons, was lying motionless and showing almost broadside on to the oncoming Portchester Castle. As yet there was no sign of the pursuing submarine.
By the aid of the binoculars the British officers could just discern the red and green mercantile ensign of Portugal being slowly lowered from the vessel's ensign-staff. The Douro had surrendered: would the Portchester Castle be in time to save her from being sunk, or merely able to witness her final plunge, and experience the mortification of finding that the lawless U-boat had submerged into comparative safety?
For some seconds the silence on board the Portchester Castle was broken only by the swish of the water against her bows, the muffled thud of the propeller shaftings, and the clear incisive tones of the range-finding officer as the distance rapidly and visibly decreased betwixt the ship and the supposed position of the German submarine.
Presently, upon the rounded crest of a roller appeared the elongated conning-tower and a portion of the deck of the U-boat. She was forging gently ahead, and was just drawing clear of the bows of the Douro.
The situation was a delicate one. If the German commander's attention were wholly centred upon his capture it might be possible that the submarine would increase her distance sufficiently to enable the Portchester Castle to send a shell into her without risk to the Portuguese vessel. If, on the other hand, the approaching succourer were sighted by the Huns, the submarine would have time to go astern, close hatches under the lee of the Douro, and dive.
Five thousand yards.