Without a moment's hesitation Crosthwaite telegraphed for full speed, at the same time ordering the quartermaster to port helm.
A mile and a half away could be discerned the elongated conning-tower and partly housed twin periscopes of a large submarine, although why in broad daylight the unterseeboot--for such she undoubtedly was--exposed her conning-tower above the surface was at first sight perplexing.
With the for'ard 4-inch quick-firer loaded and trained upon the meagre target the Calder leapt forward at a good 24 knots, ready at the first sign of the submerging of the submarine to send a projectile crashing into and pulverizing the thin steel plating of her conning-tower.
So intent was the lieutenant-commander upon his intended prey that he had failed to notice the proximity of a black-and-white can buoy now almost on the starboard bow. It was not until Sefton reminded him of the fact that he realized that the destroyer was doing her level best to pile herself upon the Haisborough Sands--a feat that the German submarine had already accomplished to the rage and mortification of her officers and crew.
Listing violently outwards, the destroyer swung round clear of the treacherous shoal, and for the first time Crosthwaite was aware of the ignominious predicament of the unterseeboot.
"The beggar may have a broadside torpedo-tube," he remarked to his subordinate as he ordered the Calder to be swung round, bows on to the stranded craft, speed having been reduced to give the destroyer more steerage-way. "Give her a round with the for'ard gun. Plank a shell a hundred yards astern."
The shot had the desired effect. The conning-tower hatch was thrown open, and the head and shoulders of a petty officer appeared. For a few moments he hesitated, looking thoroughly scared, then his hands were extended above his head.
In this position of surrender he remained, until, finding that the destroyer made no further attempt to shell the submarine, he emerged from the conning-tower. Two officers followed, and then the rest of the crew--twenty-two all told. The officers stood upon the steel grating surrounding the conning-tower, for the tide had now fallen sufficiently to allow the platform to show above water. The rest of the crew, wading knee-deep, formed up in a sorry line upon the after part of the still submerged hull, and, with uplifted hands, awaited the pleasure of their captors.
"Fetch 'em off, Mr. Sefton," ordered the lieutenant-commander. "Half of 'em at a time."
The sub hastened to order away the boat. As he did so Dr. Stirling nudged him and whispered in his ear: