"He sends 'O K Q ten,'" he said.

Eldridge turned to the reporters.

"That means that the subst.i.tution of the smaller Leyden jar for one of the larger reduced the sending power of this instrument just ten miles," said he. "My crew has quite simply moved slowly forward until it caught our sending here."

"Next," he instructed Simmons, "see if you can communicate with Monsieur X."

The operator speedily reported his success at that. Eldridge removed his gla.s.ses and polished their lenses.

"Thus, gentlemen," said he, "from our circle of two-hundred-mile radius we have eliminated a strip ten miles wide. Naturally if this weakened sending reaches only one hundred and ninety miles, and our antagonist receives our messages, he must be nearer than one hundred and ninety miles. We will now further reduce the strength of our sending and try again."

The younger men present broke into a shout,

"Good work!" somebody cried. They crowded about, keenly interested in this new method of man-hunting. Only Darrow, tipped back in his chair against the wall, seemed unexcited.

To Jack's whispered question he shook his head.

"It's ingenious," he acknowledged, "but he's on the wrong track." That was as far as he would explain, and soon dropped into a slight doze.

Throughout the greater part of the night the experiment continued. Battery by battery the sending power of the instrument was weakened. Mile by mile the special train drew nearer until, by catching the prearranged signal, it determined just how far the new sending reached. Then Simmons tried Monsieur X. As the latter invariably answered, it was, of course, evident that he remained still in the narrowing zone of communication. It was fascinating work, like the drawing of a huge invisible net.

The reporters on the morning papers mastered only with difficulty their inclination to stay. They had to leave before their papers went to press, but were back again in an hour, unwilling to lose a moment of the game. A tension vibrated the little office. Only Percy Darrow dozed alone in the corner, leaning back in his wooden armchair.

At near four o'clock in the morning Simmons raised his head after a long bout of calling to announce that he could get no reply from Monsieur X.

"He's got tired of your fool messages," remarked the _Register_ man. "And I don't wonder! Guess he's gone to bed."

Eldridge said nothing, but replaced the Leyden jar he had but just removed.

"Try one," said he.

"I get him," reported Simmons, after a moment.

"Send him anything plausible and rea.s.suring," commanded Eldridge hastily.

He turned to his small and attentive audience in triumph. "Thus, gentlemen," he announced, "we have proven conclusively that our man is located between forty and fifty miles from New York. If we draw two circles, with this building as center, the circ.u.mference of one of which is fifty, the other forty miles away, we define the territory within which the malefactor in question is to be found."

The people in the room crowded close about the table to examine the map upon which Professor Eldridge had drawn the circles.

"There's an awful lot of country--some of it pretty wild," objected the _Bulletin_ man. "It will be a long job to hunt a man down in that territory."

"Even if it were as extensive a task as a hasty review of the facts might indicate," stated Eldridge, "I venture to a.s.sert that enough men would be forthcoming to expedite such a search. But modifying circ.u.mstances will lighten the task."

"How's that?" asked the _Banner_ man, speaking for the others' evident interest.

"We have no means of surmising the method by which this man succeeds in arresting vibratory motions of certain wave-lengths," said Eldridge didactically, "any more than we are able to define the precise nature of electricity. But, as in the case of electricity, we can observe the action of its phenomena. Two salient features leap out at us: one is that these phenomena are limited in time; the other that they are limited in s.p.a.ce.

The latter aspect we will examine, if you please, gentlemen.

"The phenomena have been directed with great accuracy (a) at the Atlas Building; (b) at this city and some of its immediate suburbs. The peculiarity of this can not but strike an observant mind. How is this man able, at forty or fifty miles distance, to concentrate his efforts on one comparatively small objective? We can only surmise some system of insulating screens or focal mirrors. I might remark in pa.s.sing that the existence of this power to direct or focus the more rapid ethereal vibrations would be a discovery of considerable scientific moment. But if this is the method employed, why do we not cut a band of vibratory nullifications, rather than touch upon a focal point?"

"Repeat softly," murmured the irrepressible _Register_ man.

"Why," explained Eldridge patiently, "are not the people and buildings between here and the unknown operator affected? The only hypothesis we are justified in working upon is that the man's apparatus is at a height sufficient to carry over intervening obstacles. This hypothesis is strengthened by the collateral fact that the territory we have just determined as that within which he must be found lies in the highlands of our own and neighboring states. We may, therefore, eliminate the low-lying districts within our radius."

Percy Darrow opened one eye.

"Perhaps he's up in a balloon," he drawled languidly; "better take along an aeroplane."

Eldridge cast on him a look of cold scorn. Darrow closed the eye.

CHAPTER XVII

DRAWING THE NET

The "zone of danger", as the _Bulletin_ named it, was immediately the scene of swarming activities. Besides the expedition immediately despatched by the interests backing the investigation, several enterprising newspapers saw a fine chance for a big scoop, and sent out much-heralded parties of their own. The activities of these were well reported, you may be sure. Public interest was at once focused rea.s.suringly on the chances of finding the annoying malefactor to-day or to-morrow; there no longer existed a doubt that he would be found. The weight of dread was lifted, and in the reaction people made light of the inconveniences and fun of the menacing messages that now came in by the dozen.

[Ill.u.s.tration: "Let Eldridge do his best."]

It was necessary to take extraordinary precautions against thieves and fire; the people took them. It was needful to slacken business in order that the congestion of the rush hour might not again prove tragic; business was slackened. People were willing to undergo many things, because, after all, they were but temporary. The madman of the Catskills would sooner or later be found; his pernicious activities brought to a conclusion. The country to be searched was tremendous, of course, but the search was thorough.

The public delivered itself joyously to a debauch of rumors and of "extras". The insistent alarms of danger, trickling in slowly from the outside world, dried up in the warmth of optimism. Only the more thoughtful, to a few of whom these warnings came, coupled them with Monsieur X's repeated threats, and walked uncertain and in humility.

Percy Darrow did not interest himself in the search, nor did he desert his post in the wireless office. There he did nothing whatever. Jack Warford stayed with him, but immensely bored, it must be confessed. Once he suggested that if Darrow had nothing for him to do that afternoon, he thought he would like to go out for a little exercise.

Darrow shook his head.

"You may go, if you want to, Jack," said he, "but if you do I'll have to get some one else. This isn't much of a job, but I may need you any moment."

"All right," agreed Jack cheerfully. "Only I wish you'd let a fellow know what to expect."

Darrow shook his head. The two now practically lived in the office.

Neither had taken his clothes off for several days. They slept in their chairs or on the lounge. Darrow read the various messages from the Unknown, glanced over the newspapers, and dozed.

Thus there pa.s.sed two days of the search. On the third day the intermittent phenomena and the messages suddenly ceased. This fact was hailed jubilantly by all the papers as indicating that at last the quarry had become alarmed by the near-coming search. From the contracted district still remaining to be combed over, n.o.body was permitted to depart; and so closely was the cordon drawn by so large a posse that it was physically impossible for any living being to slip by the line.

Thus even if Monsieur X, convinced that at last his discovery was imminent, should destroy his apparatus or attempt to move it and himself to a place of safety, he would find his escape cut off. Thousands of men were employed, and thousands more drafted in as volunteers to render this outcome a.s.sured.

It was an army deployed in an irregular circle and moving inward toward its center. Men of the highest executive ability commanded it, saw to its necessary deliberation, eliminated all possibility of a confusion through which any man could slip. The occasion was serious, and it was taken seriously.

Of the outcome no one in touch with the situation had a moment's doubt.

The messages and the phenomena had continued to come from the danger zone.

It was of course evident that they could not have been sent from any portion of the zone actually searched and occupied by the searchers. The remaining portion of the zone, from which they were still coming, had been completely surrounded. After that the manifestations had ceased.

Therefore, Monsieur X must be within the beleaguered circle. To add to the probabilities, as Eldridge pointed out, the remaining district compa.s.sed the highest hills in the zone--a fact on all fours with his hypothesis.

On the appointed morning the army moved toward the center. Men beat the ground carefully, so close to one another that they could touch hands. As they closed in, the ranks became thicker. Animals of many kinds, confused as the ranks closed in on them, tried to break through the cordon and were killed. Captains held order in the front row, that the army might not become a crowd. Birds, alarmed by the shouting, rose and wheeled.