"On the trail of the gold!" gasped Carnes. "Surely, Doctor, you don't think--"

"Once in a while, old dear," replied the Doctor with a chuckle, "which is more than anyone in the Secret Service does. You might tell Bolton that I said that, but hang up quickly if you do. I don't want the wires of my telephone melted off. No, Carnesy, I have no miraculous inspiration as to where that gold is coming from; I just have a plain old-fashioned hunch, and that hunch is that we are going to have lots of fun and more than our share of danger before we see Washington again.

After you get through bearding Bolton in his den, you might call the Chief of the Air Corps and ask him to have a bomber held at Langley Field subject to my orders. If he squawks any, I'll talk to him."

He turned to a telephone which stood on his desk and lifted the receiver.

"Get Mr. Lambertson on the wire," he said. "He is the chief technician of the Pyrex Gla.s.s Works at Corning, New Jersey."

The _U.S.S. Minneconsin_ steamed out of New York harbor and headed down toward the lower bay. On her forward deck rested a huge globe. The bottom quarter of the sphere was made of some dark opaque substance but the upper portion was transparent as crystal. Through the walls could be seen a quant.i.ty of apparatus resting on the opaque bottom portion. Two mechanics from the Bureau of Standards were making final adjustments of one of the pieces of apparatus, which resembled a tank fitted with a piston geared to an electric motor. From the tank, tubes ran to four hollow pipes, an inch and a half in diameter, which ran through the skin and extended thirty inches from the outer skin of the twenty-foot sphere. Dr. Bird stood near talking with the executive officer of the ship and from time to time giving a brief word of direction to the mechanics.

"It's safer than you might think, Commander," he said. "In the first place, that globe is not made of ordinary gla.s.s; it is made of vitrilene, a new semi-malleable gla.s.s which was developed at the Bureau and which is being made on an experimental scale for us by the Pyrex people. It is much stronger than ordinary gla.s.s, and is not sensitive to shock. It is also perfectly transparent to ultra-violet light, being superior even to rock crystal or fused quartz in that respect. The walls, as you have noticed, are four inches thick, and I have calculated that the ball will stand a uniform external pressure of thirty-five hundred atmospheres, the pressure which would be encountered at a depth of about twenty miles. I believe that it will stand a squeeze of six thousand tons without buckling, and it is impossible to fracture it by shock. It could be dropped from the top of the Woolworth Building, and it would just bounce."

"It seems incredible that it could stand such a pressure as you have named."

"My figures are conservative ones. Lambertson calculated them even higher, but we allowed for the fact that this is the first large ma.s.s of the material to be cast, and lowered them."

"But suppose your lifting cable should break?" objected the naval officer. "The outfit weighs a good many tons."

"You notice that the lower quarter is made of lead. The specific gravity of the entire globe when sealed up tight with two men in it is only a little more than unity. In the water its weight is so little that a three-inch manilla hawser would raise it, let alone a steel cable. I have another safety device. Granted that the cable should snap, I can detach the lead from it and it would shoot to the surface like a rocket."

"How long can you remain under water in it?"

"A week, if necessary. I have an oxygen tank and a carbon dioxide removing apparatus which will keep the air in good condition. The globe is electrically lighted, and can be heated if necessary. Should my telephone line become fouled and broken, I have a radio set which will enable me to communicate with you. I can't see that it is especially dangerous; not nearly as much so as a submarine."

"What is your object in going down, if I may ask?"

"To take pictures and to explore the wreck if we can. The globe is equipped with huge floodlights and excellent cameras. The salvage people are having a little trouble and we are trying to help them out."

"You mentioned exploring. Can you leave the globe while it is under water?"

"Yes. There is a locking device for doing so. A man in a diving suit can enter the lock and fill it with water. Once the external pressure is released he can open the outer door and step out. Coming back, he seals the outer door and the man inside blows out the lock and compressed air and then the inner door can be opened. It is the same principle as a torpedo tube."

A jangle of bells interrupted them and the _Minneconsin_ slowed down.

Commander Lawrence stepped to the rail and gave a sharp order to the navigating officer on the bridge. The bells jangled again and the ship's engines stopped.

"We are almost over the buoy, Doctor," he said.

Dr. Bird nodded and spoke to the two mechanics. With a few final touches to the apparatus they emerged from the globe and Dr. Bird entered.

"Come on, Carnes," he called. "No backing out at the last minute."

Carnes stepped forward with a sickly smile and joined the Doctor in the huge sphere.

"All right, boys; close her up."

The mechanics swung the outer door into place with a crane. Both the edge of the door and the surface against which it fitted had been ground flat and were in addition faced with soft rubber. Bolts were fastened in the door which pa.s.sed through holes in the main sphere, and Dr. Bird spun nuts onto them and tightened them with a heavy wrench. He and Carnes lifted the smaller inner door into place and bolted it tight. Dr.

Bird stepped to the telephone.

"Lower away," he directed.

From a boom attached to the _Minneconsin's_ forward fighting top, a huge steel cable swung down, and the latch at the end of the cable was closed over a vitrilene ring which was fastened to the top of the sphere. The cable tightened and the globe with the two men in it was lifted over the side of the battleship and lowered gently into the water. Carnes involuntarily ducked and threw up his hand as the waters closed over them. Dr. Bird laughed.

"Look up, Carnes," he said.

Carnes gasped as he looked up and saw the surface of the water above him. Dr. Bird laughed again and turned to the telephone.

"Lower away," he said. "Everything is tight."

The globe descended into the depths of the sea. Darker and darker it grew until only a faint twilight glow filled the sphere. A dark bulk loomed before them. Dr. Bird snapped on one of his huge floodlights and pointed.

"The _Arethusa_," he said.

The ill-fated vessel lay on her side with a huge jagged hole torn in her fabric amidships.

"That's where her boilers burst," explained the Doctor. "Luckily we have a hard bottom to deal with. Let's see if we can locate any of Mitch.e.l.l's sea serpents."

He turned on other flood lights and swept the bottom of the sea with them. The huge beams bored out into the water for a quarter of a mile, but nothing unusual was to be seen. Dr. Bird turned his attention again to the wreck.

"Things look normal from this side," he said after a prolonged scrutiny.

"I'll have the _Minneconsin_ steam around it while we look it over."

In response to his telephone orders the ship above them swung around the wreck in a circle, and Carnes and the Doctor viewed each side in turn.

But nothing of a suspicious nature made its appearance. The sphere stopped opposite the hole in the side and Dr. Bird turned to Carnes.

"I'm going to put on a diving suit and explore that wreck," he said. "If there ever was any danger, it isn't apparent now; and I can't find out anything until I get inside."

"Don't do it, Doctor!" cried Carnes. "Remember what happened to the other divers!"

"We don't know what happened to them, Carnes. No matter what it was, there is no danger apparent right now, and I've got to get into that ship before I can get any real information. We could have lowered an under-sea camera and learned as much as we have so far."

"Let me go instead of you, Doctor."

"I'm sorry to refuse you, old dear, but frankly, I wouldn't trust your judgment as to what you had seen if you went alone; and we can't both go."

"Why not?"

"If we both went, who would work the air to let us back in? No, this is a one-man job and I'm the one to do it. While I am gone, keep a sharp lookout, and if you see anything unusual call me at once."

"How can I call you?"