From some point far overhead a musical humming became audible. It was not the rasping roar of an aËroplane motor, but a deep, truly melodious note that seemed to grow rapidly in volume. The soft-voiced conversations on the upper deck were hushed. Every one listened to the strange sound from above. It grew and became clear and distinct. The source seemed to come nearer. At last the sound came from a spot directly overhead, then passed over and toward the Narrows.

A cold breeze beat down suddenly. It was not a cool sea breeze, but a current of air coming down from directly above the Coney Island steamer. It was actively, actually cold. A chorus of exclamations arose, full of the wit of the American a-holidaying.

"Br-r-r-r! I feel a draft!"

"Say, Min, are you givin' me the cold shoulder?"

"Sadie, d'you want to borrow all of my coat or only the sleeve?"

And one young man caused a ripple of laughter by remarking:

"Feels like my mother-in-law was around somewhere."

People hastened to put on such wraps as they had with them. On the lower decks there arose a sound of tired voices, saying with variations only in the names called:

"Johnnie, button up your coat. It's getting cold."

The cold wave lasted only for a few moments, however. As the steamer forged ahead the strata of cold air seemed to be left behind, and the humming sound grew fainter. If the passengers on the boat had listened, they might have heard a faint splash in the water behind them, but as it was the sound went unnoticed. The humming died away. The boat went on and docked, and the passengers dispersed to their homes. Every one of them woke the next morning to find himself or herself locally celebrated.

Half an hour after the Coney Island boat had docked a tramp steamer was nosing her way out of the Narrows. She was traveling at half speed, the air was clear, the channel was well buoyed, and there seemed no possibility of any harm or danger befalling her. The lookout leaned over the bow negligently, watching and listening to the indignant interchange of whistle signals between two small tugs in a dispute over the right of way. He dropped his eyes and stiffened, then turned toward the pilot house and shouted frantically, but too late. The shout had hardly left his lips before there was a shock and grinding sound, mingled with the raucous shriek of rent and tormented iron plates. The tramp steamer shuddered and stopped, and began to sink a trifle by the head. At the first intimation of danger the man on the bridge had ordered the water-tight doors, closed, and now he rang for full speed astern. The tramp swung free of the unknown obstruction, but the two bow compartments were flooded and the steamer's stern was lifted until the propeller thrashed helplessly in a useless mixture of air and water. Her whistle bellowed an appeal for help. "Want immediate assistance!"

Half a dozen tugs, including the two that had been quarreling by whistle, responded to the stricken steamer's call. Their small sirens sent cheery messages promising instant aid, and they began to tear across the water toward her. One tug reached the helpless vessel's side. A second rushed up and began to pull the unwieldy tramp away from the unknown obstacle. The lights of a third could be seen very near, when there was a crash and a frantic bellow from the tug. It also had struck the obstruction against which the tramp had run. The tramp bellowed anew.

A destroyer shot down the river with a searchlight unshipped, her crew standing by to rescue any persons who could be reached by lifeboats. She swung up and saw the tramp being hauled and pulled at by busy, puffing tugs. The long pencil of light danced over the surface of the water to find the derelict or wreck that had caused the trouble. Back and forth it swept, and then stopped with a jerk as if the operator could not believe his eyes.

Floating soggily in the water of New York harbor, in late August—the hottest time of the year—a wide cake of ice lay glistening under the searchlight rays! The harbor waves ran up to the edge of the ice cake and stopped. Beyond their stopping point the surface was still and glassy. The cake floated heavily in the water and showed no sign of cracks or fissures. It was evidently of considerable thickness.

A second searchlight reËnforced the first. The two white beams moved back and forth, incredulously examining the expanse of ice. It was hundreds of yards across. At last one of the beams passed something at the center of the cake and hastily returned to the thing it had seen. Rising calmly and quietly from what seemed to be a small crater at the center of the ice cake, a plume of steam floated placidly into the air. It was a huge plume, precisely like the flowing of a white ostrich feather, rising from a small orifice in the center of the mass of frozen sea water.

A wail from the siren of the tug that had run against the ice cake caused the searchlights to turn in its direction. The engine had ceased to run and a cloud of escaping steam was pouring from the tug's funnel. Men on the deck gesticulated frantically. The destroyer ran as close as the commander dared, and he shouted through a mega-phone. It was impossible to distinguish words in the confused shouts that came back from half a dozen throats at once, but the searchlights soon showed the cause of the excitement. The men on the tug pointed over the side. The small harbor waves rolled unconcernedly up to a point some twenty feet from the stern of the tug, but there they stopped abruptly. The tug had become inclosed in the ice floe. As those on the destroyer watched, the twenty feet became thirty and the thirty forty. The ice cake was increasing in size with amazing rapidity.

A boat put off from the destroyer, and the commander shouted to the crew of the tug to take to the ice. There was a moment's hesitation, and then they jumped over the side and ran to the edge of the floe. The lifeboat touched the edge and was instantly frozen fast, but the sailors managed to break it free again by herculean efforts. It went back to the destroyer, whose wireless almost instantly began to crackle. Two other destroyers dashed down from the Brooklyn Navy Yard and turned their searchlights on the strange visitor in the harbor. The semaphore of the first destroyer on the scene began to flash, and the three lean naval craft began to circle around the huge ice cake, warning away all other craft and constantly measuring and re-measuring the size of the mass of ice. One of the destroyers at last slipped outside the Narrows and stayed there, patrolling back and forth to keep other vessels from running foul of the strange and as yet inexplicable phenomenon.

By daybreak the Battery was a black mass of people. They looked eagerly toward the Narrows, but could see nothing but a wall of mist, from which the gray shape of a destroyer now and then emerged. High in the air, however, the plume of steam was visible. It was now more than a thousand feet high and was dense and white. The first rays of the sun had gilded the top, while the ground below was still dim and dark, but now it rose in calm and quietness to an unprecedented height, mystifying the people who looked at it and causing a sudden silence to fall upon them all. A warm, moist sea breeze had blown in from the ocean during the night and had been changed to fog as it passed over the expanse of ice, so that the ice itself was hidden from view, but the tall plume of steam told of some mysterious menace to humanity that the crowd assembled at the Battery feared without understanding.

As the mass of people watched the supremely calm column of steam rising high in the air of that August morning, newsboys began to circulate among them, their strident cries sounding strangely among the silent multitude. The Narrows were frozen solidly from shore to shore, and all entrance to and egress from New York harbor was blocked. Small craft could go out behind Staten Island through the Kill van Kull, and some vessels could use the other channel which goes from the East River into the Sound, but the great Ambrose Channel—-one-third the size of the Panama Canal—and the broad opening that made New York the greatest port on the Atlantic coast was closed. The growth of the ice cake had greatly lessened, so that it could be predicted that it would not expand far beyond its present size, but its origin and the means by which it resisted the disintegrating effect of the August warmth were utterly unknown. The cause of the plume of steam from the center of the ice cake was an unfathomable mystery.

Suddenly, from the empty sky, there came a deep, musical humming. Instinctively people looked up. The humming grew louder and more distinct, while curious eyes swept the sky.

Then a black speck appeared below one of the fleecy white clouds and dropped toward the earth. A thousand feet, two thousand feet it fell, then checked and hung steadily in the air. Those who looked with the naked eye could only discern that it seemed like a wingless black splinter suspended above the earth, but those who had glasses saw the whir of dark disks above a black, stream-lined body. A small cabin was placed amidships, and a misshapen globe hung from chains below. It was still for several minutes. The passenger or passengers seemed to be inspecting the earth below, and particularly the ice cake, with deliberation and care. Then it began to rise with the same deliberation and certainty, swung around, and sped off with incredible speed toward the northeast. The humming sound grew fainter and died away, but the crowd standing on the Battery began to murmur with a nameless sense of fear.