Teddy put his hand comfortingly on Evelyn's shoulder.

"There isn't anything I can say, Evelyn," he said awkwardly, "except that I couldn't have loved him more if he'd been my own father, and it hurts me terribly to have him go like this."

Evelyn looked up.

"Teddy," she said bravely, trying to hold back her sobs, "I've been fearing this for a long time, but—I can't believe it wasn't caused by that fearful Varrhus."

"The professor did work very hard over that problem," admitted Teddy.

"I don't mean that the work he did caused his heart to fail. I mean I think Varrhus killed father." Evelyn's eyes were dark and troubled as she looked at Teddy Gerrod.

"But, Evelyn, why do you think such a thing? You knew his heart was weak."

Tears came again into Evelyn's eyes, but she forced them back determinedly.

"Will you go upstairs and look at his fingers—inside? I was—crossing his hands—on his breast. Please look."

Teddy went soberly up the stairs to where the professor lay quietly on the bed he was occupying for the last time. Teddy turned back the sheet that covered the figure and looked at the gentle old face. A lump came in his throat, and he hastily turned his eyes away. He lifted the sheet until the professor's thin hands came into view. He looked, at the fingers, then lifted one of the white hands and examined the inside. Small but deep burns disfigured the finger tips. When Teddy went down-stairs his face was white and set, and a great anger burned in him.

"You are right, Evelyn," he said grimly. "Where is the bracelet he was holding when he was found?"

"On the acids table. He was lying beside it when—when I saw him." Evelyn was grief-stricken, but she forced herself to be calm. "Do you think you know what happened?"

"I'm not sure."

Teddy went quietly into the laboratory and found the massive silver bracelet lying where Evelyn had said. He looked at it carefully before he touched it, and when he lifted it it was in a pair of wooden tongs.

"That thermo-couple, Evelyn, please. And start the small generator, won't you?"

The two worked on the bracelet for half an hour, then stopped and stared at each other, their suspicions confirmed.

"Varrhus," said Teddy slowly. "Varrhus caused your father's death. This earth has gotten too small for both Varrhus and me to live on."

"He knew father could wreck his plans," Evelyn said in a hard voice, "and he wished to rule the world. So he killed my father."

Teddy's lips were compressed.

"Before God," he burst out, "before God, I'm going to kill Varrhus!"

The bell rang, and in a moment the commandant of the forts was ushered in.

"Mr. Gerrod, Miss Hawkins," he nodded to them, and then said: "They tell me Professor Hawkins is dead. The Narrows are frozen over again. Hampton Roads is frozen over. Charleston is frozen over. The Panama Canal is frozen over! There's no steam plume to blow up. Washington is worried. They're calling me to clear out the channel. The navy department is going crazy. If it were a case of fighting men I'd know something, but I can't fight a chemical combination. What's to be done, since the professor is dead? Who on earth can fill his place?"

He looked from one to the other, already beginning to show the strain under which he was laboring.

"Professor Hawkins," said Teddy quietly, "was murdered by Varrhus some four hours ago."

"Murdered! Varrhus has been here!"

"No, Varrhus has not been here, but we may be able to trace him. I'll get the police. Then we'll talk about ice floes. We know Varrhus' method now. We'll soon be able to anticipate him."

"But in the meantime," the commandant snapped angrily, "he'll play the devil with the world."

"We'll play the devil with him when he is caught," said Teddy evenly. "I've no intention of letting Varrhus get away. Just now there's a possibility of catching him in the ordinary way. He mailed a present to the professor, an antique bracelet. Ancient jewelry was the professor's hobby. He examined the bracelet and died.

"I heard he was dead," said the commandant restlessly. "The paper said heart failure."

"So did the doctor." Teddy took down the receiver of the telephone. "Give me police emergency, please."

In a few moments he hung up again. The statement that Professor Hawkins had been murdered and that there was a chance of catching Varrhus was all he needed to say. Hardly five minutes had passed before the commissioner of police himself was in the room with two of his keenest men.

"You'll have to explain what happened," he said at once to Teddy. "When news of the professor's death came I phoned at once to the doctor mentioned in the paper and asked if there were any possibility of foul play. To tell the truth, I'd been rather afraid something like this might happen. What was it?"

"Varrhus electrocuted the professor by an antique bracelet."

He handed over the ornament. The commissioner examined it gingerly.

"Nothing funny about this except the workmanship."

"And the surface," said Teddy. His set calm was surprising himself. "It looks as if it had been lacquered. That's Varrhus' secret."

"What is it? A powerful battery?"

Teddy turned to the materials with which he and Evelyn had been working.

"I'll show you. Here's an instrument that measures the resistance of a given coil. This is one of the professor's evaporation machines for producing low temperatures quickly. He evaporates ether in this sheath that surrounds this oven and objects in the oven are cooled far below freezing point. Look at this coil of silver wire. We measure the resistance at room temperature. One hundred and twenty ohms. It is very fine wire. We put it in the cooling oven and set the engines going——" For some minutes there was silence while the small electric pump thumped and rattled. "Now we'll take the coil out. The thermometer inside the oven says twelve below zero." Teddy handled the small coil of silver wire with thick gloves. "We'll measure the resistance again. Fourteen and a half ohms resistance, approximately. Low temperatures decrease resistance and increase the conductivity of metals. You see?"

"Yes, but why——"

"The inside of that bracelet is nine hundred degrees below zero. The whole thing is coated with Varrhus' lacquer, which, in this case, radiates all the heat from the inside out, leaving it incredibly cold within. That cold makes the silver conduct electricity better."

"Well?"

"At eight hundred degrees below zero Fahrenheit silver has no measurable resistance to the passage of an electric current. Now watch."

Teddy laid the bracelet on top of a frame wound with many turns of glistening copper wire. He threw on a switch, and a small generator at one side of the laboratory began to run with a humming purr.

"Eddy currents are whirling all around that bracelet. A strong current is running in an endless circle in that closed circuit of silver, nine hundred degrees below zero. Silver at that temperature offers no resistance to an electric current. Closed circuits have been left at that degree of cold for over four hours, and at the end of that time the electric current was still flowing round and round like a squirrel in a cage."

Teddy picked up the bracelet with a pair of wooden tongs. He took a second pair in his other hand. Rubber handles insulated the tongs from their handles.

"There's a current flowing around the inside of this bracelet. There was one flowing around it when the professor received it in the mail. He opened it with his bare hands, suspecting nothing. I open it with these insulated tongs. Watch."

He jerked on the two tongs. The bracelet parted at the catch, and a dazzling, blinding flash of light appeared with a sharp crackle at the parting.

"I made the current jump the gap. The professor took it through his body and it killed him. Are you satisfied?"

"God!" said the commissioner of police, aghast.

"The box and wrapper," said one of the men who had come with the commissioner. "Let us have the box and wrapper the bracelet came in and we'll get the man that mailed it. But we'll handle him with tongs, too, when we close in on him."

They took what they wanted and left. Teddy turned to the commandant.

"Now, sir, we'll see what can be done about the new berg. You say there's no plume of steam. Have you had an aËroplane fly above it to make sure?"

"Yes. The pilot says the whole ice cake is covered with mist, except for a round spot in the middle, but there's no sign of a steam plume."

Teddy nodded at Evelyn.

"No holes in this cold bomb. I wonder what happens to all the heat that comes in?"

"Father mentioned that he expected something of the sort, but didn't say what he thought could be done about it."

"The same as we did with the other, I suppose," said Teddy reflectively. "Only this time we'll have to blast down to the bomb and then break it up."

"I'll set men to work if you'll find the bomb," said the commandant.

"Almost any one could find it," Teddy remarked, "but there are going to be some queer difficulties when you get near the cold bomb. If you'll allow me, I'd like to be at hand when it is broken up. I may really be of use there."

He began to pick out instruments he thought he might need. Among other things he took what seemed to be two silvered globes with small necks. They were Dewey bulbs. Several low-temperature thermometers and a thermocouple connected with a delicate galvanometer completed his preparations.

The two men left the house and started for the launch that would take them to the forts. On the way Teddy was asking crisp questions about the explosives he could have placed at his disposal, quite ignorant of what was happening at that moment in Jacksonville.

The river there was a mass of ice from one shore to the other. All the little reedy islands and the swampy shores were frozen solidly. To see the slender palm trees rising from icy shores, their reflections visible on the narrow strip of mist-free ice that ran along the shores of the river was an anomaly. To see fur-clad tourists stepping out of the tropical foliage to step gingerly out on the ice "just to say they'd done it" was even more strange. At the moment, however, interest centered on a little group of soldiers out in the central clearing in the cloud of mist. They were bundled in furs and swathed in numberless garments until they looked like fat penguins or some strange arctic animals. A major of engineers was waving them to the right and left, forward and back until they stood at equal distance around the clearing. Each man moved backward until the mist that rose gradually from the ice reached his waist. Then, at a whistle signal from the major, they began to move forward toward a common center. The major had reasoned that the cold bomb must be precisely underneath the exact center of the clearing, and this was a rough-and-ready means of finding that center. They advanced toward each other, and as they went nearer the center of the clearing the cold grew more intense. Infinitesimal ice crystals glittered in little clouds where the moisture of their breath froze instantly in the terrific cold. At a second whistle from the major they halted. They formed a fairly even circle about forty yards across. Each man began to stamp and fling his arms about to keep from freezing in that more than frigid atmosphere. No man could have stood that cold, no matter how hardy he might be, for more than a very few moments. The major trotted around the circle, marking the place where each man stood. Four small sledge loads of explosives stood out in the clearing. The major intended to blast down toward the cold bomb with them.

The major was marking the position of the last man, completing his circle under which the cold bomb must lie, when a peculiar tremor was felt by every man there. It was not like the shiver of an earthquake or the reverberation of an explosion. It was an infinitely shrill vibration that a moment later was followed by a creaking sound that seemed to come from the center of the ice cake. The men on the ice stopped their stamping and swinging of arms to listen in instinctive apprehension.

The center of the circle around which they stood seemed to rise in the air. The ice on which they stood was shivered into tiny fragments. A colossal and implacable roar filled the air, and a great sheet of flame of the unearthly tint of a vaporized metal rose to the heavens. The swathed and bundled soldiers were annihilated by the blast. A great hole five hundred feet across gaped in the center of the ice cake. Jacksonville shook from the concussion, and the plate-glass windows of its stores and office buildings splintered into a myriad tiny bits that sprinkled all its streets with sharp-edged, jagged pieces.

Teddy Gerrod, all unconscious of the fate of those who had attempted to meddle with the Jacksonville ice cake, went on out to bare and blast open the cold bomb that blocked New York harbor.