"An earthquake, Carnes?" exclaimed the doctor as the operative described the happenings. "Wait a few minutes, will you?"

In five minutes he was back on the telephone.

"It was no earthquake, old dear, whatever it may have been. I have examined the records of all three of the Bureau's seismographs. None of them record even a tremor. What are you going to do?"

"Whatever you say, Doctor. I'm out of my depth already."

"Let me think a moment. All right, listen. Go back to Charleston as quickly as you can and get in touch with the commanding officer at Fort Moultrie. I'll have the Secretary of War telephone him and give him orders. Get troops and go to the scene of the catastrophe. Allow no one near it. Proclaim martial law if necessary. Stop all road and rail traffic within a radius of two miles. Arrest anyone trying to pa.s.s your guard lines. I'll get a plane from Langley Field and come down on the run. Is that all clear?"

"Perfectly, Doctor. By the way, the President suggested that you bring Dr. La.s.sen with you."

"Since it wasn't an earthquake, he wouldn't be of much value. However, I'll bring him if I can get hold of him. Now start things moving down there. I'll get some apparatus together and join you in five hours; six at the outside. Have a car waiting for me at the Charleston airport."

Carnes commandeered a pa.s.sing car and drove back to Charleston. He made a wide sweep to avoid the disturbed area and went direct to Fort Moultrie. Dr. Bird had been good at his word. The troops were a.s.sembled in heavy marching order when the detective arrived. A few words to the commanding officer was sufficient to set the trucks loaded with soldiers in motion. Carnes, accompanied by the colonel and his staff, went direct to the scene of the catastrophe.

He found a hole in the ground, a hundred feet wide and a quarter of a mile long, sunk to a depth of fifty feet. He shuddered as he thought of what would have happened had the Presidential train been in the center of the devastated area instead of at the edge. The edges of the hole were ragged and sloping as though the earth had caved in to fill a huge cavern underground.

State and local authorities were already on the ground, striving to hold back sightseers. They were very glad to deliver their responsibility to the representative of the federal government. Carnes added their force to that of the military. In an hour a cordon of guards were stationed about the cavern while every road was picketed two miles away. Fortunately there had been no loss of life and no rescue work was needed. The earth-shaking had been purely a local matter, centered along the line of the railroad track.

There was nothing to do but wait, Carnes thought furiously. He had worked with Dr. Bird long enough to have a fair idea of the scientist's usual lines of investigation.

"The first thing he'll want to do is to explore that hole," he mused.

"Probably, that'll mean some excavating. I'd better get a wrecking train with a crane on it and a steam shovel here. A gang of men with picks and shovels might be useful, too."

He hurried to the railroad officials. The sight of his gold badge had the desired result. Telegraph keys began to click and telephones to ring. Carnes was sorely tempted to explore the hole himself, but he resisted the temptation. Dr. Bird was not always pleasant when his colleagues departed from the orders he had given.

The morning pa.s.sed, and the first part of the afternoon. Two wrecking trains stood with steam up at the edge of the hole. Grouped by the trains were a hundred negroes with shovels and picks. Carnes sat at the edge of the hole and stared down into it. He was roused from his reverie by the sound of a motor.

From the north came an airplane. High over the hole it pa.s.sed, and then swerved and descended. On the under side of the wings could be seen the insignia of the Air Corps. Carnes jumped to his feet and waved his hat. Lower came the plane until it roared across the cavern less than a hundred feet above the ground. Two figures leaned out and examined the terrain carefully. Carnes waved again. One of the figures waved a hand in reply. The plane rose in the air and straightened out toward Charleston.

"We'll have the doctor here in a few minutes now," said Carnes to the Colonel. "It might be a good plan to send a motorcycle out along the Charleston road to bring him in. We don't want the guards to delay him."

The colonel gave an order and a motorcycle shot off down the road. In half an hour it came sputtering back with a huge Cadillac roaring in its wake. The car drew up and stopped. From it descended two men. The first was a small, wizened figure with heavy gla.s.ses. What hair age had left to him was as white as snow. The second figure, which towered over the first, was one to merit attention anywhere.

Dr. Bird was as light on his feet and as quick and graceful as a cat, but there was nothing feline about his appearance. He stood well over six feet in his stockings and tipped the beam close to the two hundred mark. Not one ounce of fat was on his huge frame. So fine was he drawn that unless one looked closely he would never suspect the weight of bone and muscle that his un.o.btrusive tweed suit covered.

Piercing black eyes looked out from under s.h.a.ggy brows. His face was lean and browned, and it took a second glance to realize the tremendous height and breadth of his forehead. A craggy jutting chin spoke of stubbornness and the relentless following up of a line of action determined on. His head was topped with an unruly shock of black hair which he tossed back with a hand that commanded instant attention.

His hands were the most noteworthy thing about the famous Bureau scientist. Long slender hands, they were, with slim tapering fingers--the hands of an artist and a dreamer. The acid stains that marred them could not hide their slim beauty, yet Carnes knew that those hands had muscles like steel wire and that the doctor boasted a grip that could crush the hand of a professional wrestler. He had seen him tear a deck of playing cards in half and, after doubling, again in half, with as little effort as the ordinary man would use in tearing a bare dozen of the cards. As he climbed out of the car his keen black eyes swept around in a comprehensive glance. Carnes, trained observer that he was, knew that in that one glance every essential detail which it had taken him an hour to place had been accurately noted and stored away in the doctor's mind. He came forward to the detective.

"Has anything happened since you telephoned me?" was his first question.

"Nothing, Doctor. I followed your instructions and also a.s.sembled a crew of men with excavating tools."

"You're improving, Carnes. This is Dr. La.s.sen. This is a little out of your line. Doctor, but you may see something familiar. What does it look like to you?"

"Not like an earthquake, Bird, at all events. Offhand I would say that a huge cavern had been washed in the earth and the ground had caved in."

"It looks that way. If you are right, we should find running water if we dig deep enough. Have you been down in the hole, Carnes?"

"No, Doctor."

"Then that's the first thing to do. You have ropes, of course?"

Carnes called to the waiting gang of negroes and a dozen of these hurried up with ropes. Dr. Bird slung a rope around his body under his arms and was lowered into the hole. The rope slackened as he reached bottom. Carnes lay on his stomach and looked over the edge. Dr. Bird was gingerly picking his way across the ground. He turned and called up.

"Carnes, you and La.s.sen can come down if you care to."

In a few minutes the detective and the volcanologist joined him in the cavern. The top surface of the ground was rolled up into waves like the sea. The sides of the hole were almost sheer. The naked rock was exposed for thirty feet. Above the rock could be seen the subsoil, and then the layer of top soil and vegetation. Dr. Bird was carefully examining the rock wall.

"What do you make of these, La.s.sen?" he asked, pointing to a row of horizontal striations in the rock. The volcanologist studied them.

"They might be water marks but if so they are different from any that I have seen before," he said doubtfully. "It looks as though some force had cut the rock away in one sharp stroke."

"Exactly. Notice this yellow powder on the ridges. Water would have washed it away."

Dr. Bird stepped forward to the wall and idly attempted to pick up a pinch of the yellow powder he had referred to in his fingers. He gave an exclamation of surprise as he did so. The powder was evidently fast to the wall. He drew his knife from his pocket and pried at the stuff.

It fell readily. He sc.r.a.ped again and caught a speck of the falling powder in his hand. He gave a cry of surprise, for his hand sank as though borne down by a heavy weight. With an effort he lifted his hand and examined the substance.

"Come here, Carnes," he said. "Hold your hand up to catch some of this powder as I sc.r.a.pe it off."

The detective held up his hand. Dr. Bird pried with his knife and a shower of dull yellow particles fell. Carnes' hand sank as though the bits of dust had been a lead bar. He placed his other hand under it and with an effort lifted both hands up a few inches.

"What on earth is this stuff, Doctor?" he cried. "It's as heavy as lead."

"It's a great deal heavier than lead, Carnesy, old dear. I don't know what it is. I am inclined to think you did a wise thing when you sent for me. La.s.sen, take a look at this stuff. Did you ever run into anything like it?"

The aged volcanologist shook his head. The yellow powder was something beyond his ken.

"I have been poking around volcanos all my life," he said, "and I have seen some queer things come out of the ground--but nothing like that."

Dr. Bird poked tentatively at the substance for a moment, his brow furrowed in lines of thought. He suddenly threw back his shoulders in a gesture of decision.

"Send a gang of excavators down here," he cried. "Never mind the power shovel at present."

Down the ropes swarmed the gang of negroes. Dr. Bird indicated an area at one end of the cavern and directed them to dig. The blacks flew to work with a will. The top soil and subsoil were rapidly tossed into buckets and hauled to the surface. When bare rock lay before them, the negroes ceased their efforts.