All this time Madge had been breathing naturally and comfortably inside her helmet as she traveled along the bed of the bay. She was so unconscious of any difficulty that she was beginning to believe that she was, in truth, a mermaid, and that water, and not air, was her natural element. Suddenly she felt a little uneasy, as though the windows of her room had been closed for too long a time. It was nothing, she was sure. The stifling sensation would pass in another second. At this moment Captain Jules gazed hard at Madge. He had never forgotten his charge for a moment. But all seemed well with her, and the captain thought he saw ahead of him something that was well worth investigating. He dropped on his knees in the soft mud. With him he had a small hammer and a fork, not unlike a gardener's. Shining through some green sea moss so soft and fine that it might have been the hair of a water-baby, Captain Jules had espied some glittering shells. To his experienced eye the glow was that of mother-of-pearl. It is the mother-of-pearl shell that usually covers the precious pearl. The old sailor set to work. Madge was eagerly watching him, when once again the faint stifling sensation swept over her. Surely it was not possible to faint in a diving suit. Besides, Madge's heart was beating so furiously with excitement that it was small wonder she could not get her breath. She believed that Captain Jules was about to discover a wonderful pearl. He had wrenched the shells free and was trying to open them. Madge stood some feet away from him, quivering with excitement. "'And the sea shall give up its treasures'," she quoted softly to herself as she watched. The next moment her hands made an involuntary movement in the water. Had she been on land her gesture would have meant that she was fighting for breath. To her horror she realized that she was slowly suffocating. Something must have happened to her air-pump above the water. She was not faint from any other cause, but was getting an insufficient supply of fresh air. At this moment Madge proved her mettle. She remembered Captain Jules's injunction, "Keep a clear head under the water and there is nothing to fear." She knew the signal for more fresh air, and gave two hard, quick pulls on her life line. Then she waited. Relief would surely come in a moment. For the first and only time since their descent to the bottom of the bay Captain Jules had temporarily neglected Madge. He certainly had not expected to find any pearls in so unlikely a place as Delaware Bay; yet the shells he held in his hand were most unusual. The thrill of his old occupation seized hold of the pearl fisher. His big hands fairly trembled with emotion. He felt, rather than saw, Madge jerk her life line twice, but it never dawned on him that her signal for more air might fail to be answered.