Washingtonfor me and I took it. It was Haggerty on the wire. He followed yourprecious secretary from the Bureau of Standards over to the PublicHealth Office and waited for her to come out. She stayed in thebuilding for about an hour and brought a bundle of papers with herwhen she returned. She walked toward the State, War and Navy Buildingand Haggerty followed.
"On Pennsylvania Avenue, she was stopped by two men whom Haggertydescribes as dark, swarthy, bearded Europeans of some sort. He triedto overhear their conversation but it was in a language which he didnot recognize. He got only one word. The girl called one of them'Denberg.'"
"Denberg!" cried the doctor, "Why, he's one of the Young Labor crowd,but he's in Atlanta."
"He was, Doctor, but I telephoned Atlanta, and found that he had beenreleased last month. After several minutes of talk the two men andyour secretary went off together in perfect amity with Haggertyfollowing. The trio got into a waiting car and Haggerty trailed themin a taxi. They drove around town rather aimlessly for some time andthen left the car and walked. Haggerty was afraid he would lose themin the crowd so he closed in on them. He doesn't know what happenedexcept that he felt a sudden stab in his arm and everything wentblack. He recovered in the police station twenty minutes later but thebirds had flown."
"The devil!" cried Dr. Bird, consternation in his voice. "Of course,it's easy to see what happened. They spotted him and a confederateslipped a hypo into his arm. What worries me is the fact that they'vegot Thelma."
* * * * *
"I hope they kill her," snapped Carnes vindictively. "She was neverkidnapped in broad daylight. Haggerty says she went with them quitewillingly and talked and laughed with them. She has deserted, if shewasn't simply acting as a spy from the first. I didn't trust her atall."
"I hate to admit that my judgment is that rotten, Carnes, but theevidence certainly points that way. At that, I think I'll reservefinal judgment until later. Now, in view of what you have learned, Ihave a job for you."
"It's about time, Doctor. I have been rather useless with all thehigh-powered science that has been flying around here."
"Well, you'll be in your element now. We know that Denberg is looseand their capture of Thelma is no coincidence. I was pretty sure thatSaranoff and his gang were at the bottom of this; now I am certain.They must have introduced something onto the marshes last night whichcaused the trouble. They could not have come overland very well, forthe place is too well patrolled. Had they come by air, they would haveattracted attention, even had they used a Bird silencer on theirmotor, for they couldn't muffle their propeller, especially on atakeoff, and there are plenty of men here who would have recognizedit. You might check up on that, but I am confident that they came bywater. Launches and boats are continually passing up and down theChesapeake and its tributaries and one more could easily have escapednotice. The Bush River is at the far end of the Michaelville range andit is navigable for craft of light draft at high tide. Find outwhether any strange craft were seen in the vicinity of the provingground last night. If you draw a blank, go to Perryville and Havre deGrace and see what you can find out there. I have a hunch that theirbase is more likely to be up the Susquehanna than down toward thecoast. Above all, Carnes, don't approach the proving ground by waterto-night and don't get near the mouth of the Bush River."
"All right, Doctor. What are you going to do?"
"I'm going down on the swamp and collect samples. Oh, don't look soworried. I know just what I am up against and I will have adequateprotection. I'll be in no danger and you would just be in the way.Toddle along, old dear, and report to me by telephone as soon as youhave learned anything."
"As you say, Doctor. You'll hear from me the minute I do."
* * * * *
When Carnes had left, Dr. Bird climbed into the waiting car and wasdriven back to the hospital. Captain Murdock greeted him with asmiling face.
"I don't know how you got on to that treatment, Dr. Bird," he said,"but it is doing the men good. The worst cases haven't been affectedmuch, one way or the other, but the progress of the malady in the mildcases from the stables has been completely checked. I think they havea chance now."
"They'll be all right if the destruction and coagulation of tissuehadn't progressed too far before you checked it, Captain. Treat themnow for simple lung cauterization and they ought to get well."
"I have some more of those crystals dissected out, Doctor."
"Keep them in the dark until Mr. Davis comes after them. I want totake a few of them back to Washington for study."
"You expect another attack to-night, Doctor?"
"Yes, sometime after sundown."
"What, in heaven's name, is it?"
"Heaven has nothing to do with it, Captain; the stuff comes from thedevil's regions and it is the product of a Russian chemist, who Isometimes believe is verily the devil himself. How it's done and whatit is, I haven't found out yet, but I am going to investigate a littleto-night. The effect is what you have seen. Are you familiar with thevarious forms of oxygen?"
"The forms of oxygen? Why, there is only one, oxygen gas. Wait aminute though, there is another form, ozone. Are there any more?"
"None that have been previously listed and studied, but at least oneother form exists. Those crystals are pure oxygen."
"Impossible! Oxygen is a gas at all ordinary temperatures."
* * * * *
"Yes, a gas, but one whose density varies. Oxygen, to which wechemists assign the formula O_{2}, meaning that its molecule consistsof two atoms of oxygen, has a weight of 32 grams per gram molecule.Ozone, to which we assign the formula O_{3}, meaning that its moleculecontains three atoms of oxygen, weighs fifty per cent more or 48 gramsper gram molecule. This new form has a density less than water, buttremendously greater than any known gas. I have not yet been able todetermine its structure, so I will have to assign to it the formula,O_{x}, meaning an indefinite number of atoms per molecule. The onlyname which suggests itself is oxyzone, a combination of oxygen andozone.
"The stuff is a polymerization, or condensation, to speak roughly, ofthe oxygen of the air. The oxygen takes this form which the lungscannot assimilate except with great difficulty and with great damageto the tissues. The oxyzone will break down rapidly under theinfluence of sunlight or of any ray whose wave-length is shorter thanindigo. As a result, it disappears as soon as the sun is up and itwill reappear after dark. That is why I suggested X-rays as atreatment. They have a very short wave-length and will penetratetissues and affect the particles in the lungs themselves. Once thematerial is removed from the lungs, the cauterization of the tissueceases and it is merely a matter of slow recovery."
"It is a marvelous discovery, Doctor. I can foresee great uses for itin medical science if a way can be found to produce it."
"Just now we are much more interested in stopping its production thanin producing it. Carry on with the line of treatment I have prescribedand be ready for a busy time to-night."
* * * * *
From the hospital, Dr. Bird made his way to the headquarters buildingwhere he conferred with Colonel Wesley on the measures being taken toclear the proving ground of all persons not strictly necessary for itsguarding. The commanding officer, when he learned Dr. Bird's plans,wished to send guards with him, but the doctor promptly vetoed thescheme.
"My assistant, Mr. Davis, won't be able to fix up more than two masksbefore dark, Colonel," he said, "and you would just be condemning mento death to send them with me into that fog without proper protection.I can see that you are anxious to know what is causing it, but I'm notready to tell just yet. I had given your medical officer enoughinformation to enable him to treat the hospital cases scientifically,and to-morrow or the next day I hope to be able to tell you all aboutit. Now, if you'll pardon me, I'm going to the laboratory to see howMr. Davis is getting along. It will be dark in three-quarters of anhour and I hope that everyone will stay unde
r cover as much aspossible."
Davis looked up as Dr. Bird entered the laboratory.
"I'll have the masks completed in an hour, Doctor," he said, "but Idon't know how much value they will be. If the oxygen polymerizesbefore it enters the body, these masks ought to stop it, but if itpolymerizes under the influence of heat and moisture in the lungs,they will be useless."
"I'll have to take a chance on that, Davis. From the description ofthe fog, I strongly suspect that the process takes place outside thebody. Have you had your supper?"
"No, Doctor."
"Neither have I. I'll go over to the