"Remains constant. Seventy miles an hour. Dying down a little,"

answered Graves.

"The death line now runs from Wilmington, South Carolina, straight to Augusta, Georgia," the Vice-president pursued. "Every living thing that this gas has encountered has been instantly destroyed. Men, cattle, birds, vermin, wild beasts. The gas is invisible and inodorous. These gentlemen believe it may be a form of hydrocyanic acid, but of a concentration beyond anything known to chemistry, so deadly that a billionth part of it to one of air must be fatal, otherwise it could not have traveled as it has done. Warnings have been broadcasted, but there are no stocks of chemicals that might counteract it. Flight is the only hope--flight at seventy miles an hour!"

His voice shook. "This gas has been loosed, as you told us, upon the wings of the hurricane that came through the Florida Strait. What are the chances of its reaching Washington?"

"Mr. Vice-president, if the wind continues, and this gas has sufficient concentration, it should be in Washington within the next eight hours." Graves replied. "If the wind changes direction, however, this gas will probably be blown out to sea, or into the Alleghanies, where it will probably be dissipated among the hills, or by the foliage on the mountains. I'm not a chemist--"

"No, sir, and I am not consulting you as one," answered old Tomlinson.

"A death belt several hundred miles in length and three or four hundred deep has already been cut across this continent. We are faced with wholesale, unmitigated murder, on such a scale as was never known before. But we are an integral part of America, and Washington has no more right to expect immunity than our devastated Southern States. The question we wish to put to you is, can you trace the exact course taken by the hurricane?"

"I can, Mr. Vice-president," answered Graves. "It originated somewhere in the West Indian seas, like all these storms. We've been getting our reports almost as usual. Our first one came from Na.s.sau, which was badly damaged. The storm missed the Florida coast, as many of them do, and struck the coast of South Carolina--in fact, we received a report from Charleston, which must have almost coincided with your first report of the gas."

"If the storm missed the Florida coast, it follows that the gas was not discharged from any point on the American continent," said Tomlinson. "From some point off Florida--from some island, or from a plane or from a ship at sea."

"Not from a ship at sea, Mr. Vice-president," interposed the head of the Chemical Bureau. "To discharge gas on such an extensive scale would require more s.p.a.ce than could be furnished by the largest vessel, in my opinion."

"In all probability the gas was 'loaded,' so to say, onto the gale somewhere in the Bahamas," said Graves. "That seems to me the most likely explanation."

Vice-president Tomlinson nodded, and picked up one of the latest telegraphic dispatches, as if absently.

"Gentlemen," he said, "the Invisible Death has already reached Charlotte."

He picked up another. "Reported Abaco Island, Bahamas, totally wrecked by storm. All communication has ceased," he read. He turned to d.i.c.k and spoke as if inspired. "Captain Rennell, there is your destination," he thundered. "They've betrayed themselves. We've got them now. You understand?"

"By G.o.d, sir! It's from Abaco Island, then, that those devils have been carrying on their game of wholesale murder!"

Suddenly a contagion of enthusiasm seemed to sweep the whole a.s.semblage. Every man was upon his feet in an instant, white, quivering, lips opened for speech that trembled there and did not come.

It was Secretary Norris spoke. "The Vice-president has. .h.i.t the mark,"

he said, with a dramatic gesture of his arm. "Yes, they've betrayed themselves. Their headquarters are on Abaco Island. It's one of the largest in the Bahamas." He turned to the Secretary for the Navy. "You can rush the fleet there, sir?" he asked.

"Within forty-eight hours I'll have every vessel that can float off Abaco Island."

"I'll concentrate all airplanes. Take your flight, Captain Rennell.

We'll stamp out that nest of murderers if we blow Abaco Island to the bottom of the sea. It can be done!"

"It can be done, sir--with Luke Evans and his invention," answered d.i.c.k.

CHAPTER VII

_On the Trail_

Three hours later, about the time when the war council rose after completing its plans, a sudden shift of the wind blew the poison gas out to sea, just when it appeared certain that it would reach the capital of the nation.

The southern half of Virginia had been swept over. Operators, telegraph and telephone, staying at their posts had sent in constant messages that had terminated with an abruptness which told of the tragic sequel. Yet, at that distance from its source, the intensity of the gas had been to some extent dissipated.

Poisonous beyond any gas known, so deadly as to make hydrocyanic gas innocuous in comparison, still as it was swept northward on the wings of the wind, there had been an increasing number of non-fatal casualties. The most northernly point reached by the gas was Richmond, and here some fifty per cent of those stricken had suffered paralysis instead of death.

But a new element had been injected into the situation. Even the heroic courage shown by the populace in the beginning had had its limits. The morning after the news of the Invisible Death's advent was made public mobs had gathered in all the large cities of the East, demanding surrender.

The submerged elements of crime and disorder had come to the surface at last. Committees were formed, with the avowed object of yielding to the Invisible Emperor, and averting further disaster. In Washington, a city of the dead, half the members of Congress and the Senators had gathered in the ruined Capitol, to debate the situation.

There were rumors of an impending march on the White House, of a coup d'etat.

The action of the Government was prompt. Five hundred loyalists were enrolled, armed, and posted round the White House: every avenue of approach was commanded by machine-guns. Meanwhile the news was spread by radio that the headquarters of the Invisible Emperor had been located, and that a strong bombing squadron was being dispatched to destroy it.

The entire fleet was to follow, and it was confidently antic.i.p.ated that within a little while the Terror would be at an end.

Those at the white House were less sanguine. There was none but realized the diabolical strength of their antagonists.

"Everything depends upon the outcome of the next forty-eight hours, and everything depends on you, Rennell," said Secretary Norris to d.i.c.k, as he stood beside his plane. Behind him his flight of a dozen airships was drawn up.

"Find them," added the Secretary; "cover Abaco Island with the black gas, and the navy and the marines will wipe up the mess that you leave behind you. G.o.d help you--and all of us, Rennell!"

He gripped d.i.c.k's hand and turned away. d.i.c.k was very sober-minded as he climbed into his c.o.c.kpit. He knew to the full how much depended upon himself and Luke Evans. Already the shouts of the insurgents were to be heard at the ends of the barriers, commanded by the machine-guns, and patrolled by the enlisted volunteers.

Negro mobs were building counter-barricades of their own with rubble from the fallen edifices. Civil war might be postponed for eight-and-forty hours, but after that unless there was news of victory, the whole structure of civilization would be smashed irreparably.

It was up to d.i.c.k and Luke Evans, and they had a.s.sumed such a responsibility as rarely falls to the lot of man in war.

d.i.c.k was to lead the flight in a two-seater Barwell plane. This was one of the latest types, and had been hurriedly adapted to the purpose for which it was to be used. d.i.c.k himself occupied the rear seat, with its dual controls, and the gun in its armored casing. In front sat old Luke Evans, in charge of the black gas projector.

His famous camera box, containing a minute quant.i.ty of gas in slow combustion, and projecting the black searchlight, had been built into the plane. In the rack beside him were a number of the black gas bombs, each of which, dropped to earth, would release enough gas to cover a considerable area with darkness. Both Luke and d.i.c.k wore respirators filled with charcoal and sodium thio-sulphate, and beside d.i.c.k a cage containing three guinea-pigs rested.

These little rodents were so sensitive to atmospheric changes that a quant.i.ty of hydrocyanic acid too minute to affect a man would produce instantaneous death on them.

From its hiding-place off the Virginia coast the American fleet was steaming hotly southward toward Abaco Island, cruisers, destroyers, submarines. That Abaco was British territory had simply not been considered in this crisis of history.

The twelve airships that followed d.i.c.k's contained enough bombs to put the headquarters of the Invisible Empire out of business for good. The naval guns would complete the same business.

All day d.i.c.k and Luke Evans flew southwestward. At first glance, everything appeared normal. The catastrophe that had fallen upon the land was visible only in the shape of the lines of tiny figures, extending for miles, that choked all the roads radiating out of the princ.i.p.al cities. It was only when they were over the southern portion of Virginia that the ravages of deadly gas became apparent.

Flying low, d.i.c.k could see the fields strewn with the bodies of dead cattle. Here and there, at the doors of farmhouses, the inmates could be seen, lying together in gruesome heaps, caught and killed instantaneously as they attempted flight. Here, too, were figures on the roads. But they were figures of dead men and women.

They strewed the roads for miles, lying as they had been trapped--men, women, children, horses, mules, and dogs. The spectacle was an appalling one. d.i.c.k set his jaws grimly. He was thinking that the Council had let Von Kettler escape. He was thinking of Fredegonde. But he would not let himself think of her. She deserved no more pity than the rest of the murderous crew.

Over the Carolinas the conditions were still more appalling. Here deadly gas had struck with all its concentrated power. A city materialized out of the blue distance, a factory town with all chimneys spiring upward into the blue, a section of tall buildings intersected by canyonlike streets, around it a rim of trim houses, bungalows, indicative of prosperity and comfort. And it was a city of the dead.