Tom descended once more. The base of the telescoping aerial mast was in the forepart of the engine-room. A hand winch operated it much in the same manner that a fire department’s extension ladders are sent aloft. It did not take Tom long to extend the slender, yet pliant and strong steel spar heavenward to its fullest length. At its truck, or summit, was a pulley, through which halyards attached to the aerials had been rove. Jack had gotten these out while Tom had been busy below, and in a remarkably short time the slender antenna, or aerials, were strung from mast tip to deck. There were four separate wires of stranded phosphor bronze attached to wooden spreads, and properly insulated. From them a wire led back to the instruments attached to a table in the forepart of the cabin. The aerials being up Jack, after satisfying himself that everything was shipshape, made for the cabin. Seating himself at the wireless table he sent a signal crashing out into space. “S-K! S-K! S-K!” Then, after a pause:— “L-I.” There followed a period of listenings with the receiving switch over and the “watch-case” receivers closely clamped to the young operator’s ears. But no answer came. A worried look crept over Jack’s countenance. This silence was ominous. Once more he manipulated the key with nimble fingers. The spark squealing and crackling shot bluely hither and thither. But to the electrical appeals sent broadcast into the atmosphere, space vouchsafed no answer. CHAPTER III—THE CIPHER CODE A sudden break in the rhythmic pulse of the engine reached Tom’s alert ears at this instant. Without speaking he hastened from the cabin to the engine-room, using, for this purpose, a door cut in the forward bulkhead. He found that one of the cylinders was missing fire and traced the trouble to a badly sooted plug. While he was adjusting the trouble Jack stuck to his key. He would pound out his “S-K” call furiously for an interval, and then listen intently for even the faintest indication of a response. The lad tried various adjustments, of the potentiometer, which regulates the voltage and current supplied to the detector, and operated his receiving tuning coil in various ways. But though he tried for wave lengths from two hundred meters up to fifteen hundred, not a whisper came out of the void of silence about them. “I’ll call once more,” said the lad to himself in a determined voice, “it’s our duty to do all we can and keep at it all the time. Of course, if the _Sea King_ has met with a really serious disaster her wireless may be out of order and—Hullo! Here’s something coming now!” Something was coming, sure enough!