With a quick spring, Dorothy was first on a chair, and then on the table beside her brother. She bent to inspect the crystal hemisphere, looked at it from various points, and then both of them began examining the construction of the lamp shade.

“It’s hermetically sealed above?” said Tom finally, a note of inquiry in his voice.

“It seems to be,” answered Dorothy briefly. “Tom, jump down, will you, and let Mr. Hamerly come up here. Jim, will you and Mr. Swenton see if you can find another lamp shade like this in the storeroom.”

We returned from our errand, bearing a duplicate of the shade which we had found on a shelf. Dorothy, who by this time had come down from the table where Hamerly and Tom still stood, took the shade from my hands and held it to the light.

“This shade is nothing but ordinary glass. There’s nothing unusual about it,” she exclaimed. “The effect of the shade up there must be due to a gas inside.”

As Tom and Hamerly leaped from the table to inspect the shade, I seized the opportunity to ascend, and mounting, gazed through the hemispherical glass. A strange world met my eyes. Everything seen through the glass was bent around at extraordinary angles. Tom’s legs, seen below the shade, were perfectly natural and upright, but his torso, seen through the shade, was bent like the body of a Japanese contortionist engaged in extremest posturing. The straight line of the door casing beyond was broken short off where the line of the shade intersected it, and the top of the casing appeared in a wholly different place. As I gazed, I struggled to think what common everyday thing acted in much the same way. Eureka, I had it.

“Why, whatever is inside this globe bends everything seen through it, something as a spoon is bent in a glass of water or an oar in a pond,” I cried.

Hamerly looked up. “That’s about right, Orrington. Or better yet, you could say it bends the things you see, as the hot gases rising from a chimney bend everything behind them into wavy lines. Haven’t you ever watched the queer waviness that shows in a wintry atmosphere above chimneys, when you look over them?”

“Many a time,” I replied.

“Well, that’s just the same type of thing we have here. When you look across a chimney, where hot gases from a fire are coming off, you are looking from air through lighter gases (for such hot gases are lighter than cold air) to cold air again. That extreme bending of light rays that we call refraction is the reason why we hope we have a new gas.”

“If we can test the gas to find out what it is, it ought to be a big lift in finding out what really happened,” I said, as I descended from the table.

“That won’t be hard at all,” interrupted Dorothy. “We’ll test it with the spectroscope in the next room. Here comes Tom now, with the apparatus to catch and confine the gas.”

With glass tubes and air pumps, with platinum and flame, they strove for half an hour, Tom, Hamerly, and Swenton together. Dorothy threw in a quiet word of suggestion now and then, but the most of the time she stood back with me. This was a matter for experts, and left nothing for me to do. As we waited, I asked Dorothy two questions. “Where do you think the gas came from? Has it been here since Heidenmuller’s death?”

“I think it must have been,” answered Dorothy. “If, as I imagine, we have an unknown gas here, it is probably one of the products left behind from the metal destroyed by the terrific force used by the man. When the substance that gave the force, energy, or whatever you call it, escaped through the broken valve of the cigarette case, this gas was formed from the changed metal and, as it was lighter than the air, some of it rose and filled the shade, the rest floated upward and out through some crevice. When the man destroyed the Alaska or any of the other vessels, the same thing probably occurred—the metal of the ship changed to a gas which floated up into the air with extreme rapidity. The gas must be to air as oil is to water, that is, it can’t diffuse or mix with it, any more than oil can mix with water. Otherwise it wouldn’t have stayed all these months in the lamp shade.”

Just then Tom came towards us with a glass tube, a foot long and an inch or two wide, in his hand. In each end was sealed a bit of silvery metal.

“Platinum,” I said, as I looked at them.

“Yes,” said Tom laughing, “Mrs. Rosnosky taught you to know platinum when you see it. Just look through this.”

He held the tube before us, and the same magic bending of the lines showed as we gazed. The tube was filled with the gas that I had seen in the shade above.

“That’s as pretty a piece of work as I ever did,” said Tom approvingly. “Transferred it without allowing practically a particle of air to get in. Now we’re ready to try the current on it, and then the spectroscope.”

Rembrandt might well have painted the picture that I beheld, to hang beside the “Lesson in Anatomy” that dominates the old Museum at the Hague. A striking group of four bent above the shining tubes and polished mountings of the spectroscope. Tom, eager, with his fine lean face showing the highest power of receptivity to new ideas, mouth mobile but firm, with an ever present tendency towards an upward lift of the corners; Hamerly, careful thoughtful scholar, in our college slang “a little on the grind type,” extremely bald, his glasses perched judicially on his rather prominent nose, his face showing the lines of deep and strong thought; Swenton, faithful and efficient follower, a man who would always be led, would never spring by any conceivable chance from the narrow channels where his lot had chained him; Dorothy, Maxima et Optima, now commanding by reason of her swift flying intellect, now yielding to her dreams as she had an hour or two ago in the hansom cab, and, when yielding, most womanly, most thoroughly feminine of her sex. Faceted like a diamond, she shone upon the world through every facet, and every line, plane and angle showed a new beauty, a new grace.

The four stood eagerly intent upon the little tube before them, as they connected it with a huge coil which stood near. That done, everything was ready to throw the switch which would send the electric current leaping from one platinum pole to another, penetrating the gas in the tube, heating it, changing its action, forcing it to submit to the current’s tremendous force.

“All ready?” asked Tom, as he straightened up from the last adjustment. “Swenton, you turn off the lights and I’ll put on the current here.”

As the lights went out, and we heard the sound of the throwing of the switch, Dorothy stepped back by me. A low buzz grew swiftly in intensity, and then a simultaneous cry broke from us all. Within the tube a soft blue came slowly from out the dark, the blue of early dawn on quiet waters, as we gazed it turned darker, more brilliant; now it was the deep, steel blue of the biting autumn day, now the deep, blue black of velvet tropic night. Every change, every hue was lighted by the rarest and most exquisite effulgence man could conceive. No glory bound to earth it seemed, rather an unearthly brilliancy, perhaps such radiance as led the three kings, Gaspar, Melchior and Balthazar, to the manger where the young child lay. It awed us all.

“That is beyond anything I ever saw,” said Hamerly at length, breaking the silence. “I have observed every known gas under the influence of current, but never anything like this.”

“Nor I,” said Tom. “But there may be no time to spare. Let’s try it with the spectroscope.”

As Tom and Dorothy bent over the instrument, I asked Hamerly, “What do you expect to find from the spectroscope? What does it do?”

“It breaks down light,” answered Hamerly, “by means of a prism, as a prismatic chandelier or a prismatic glass thermometer throws the spectrum of a sunbeam on the floor, breaking the white light of the sun into a shifting mass of color that changes from red, through orange and green to violet. Every different glowing gas gives off a slightly different light. We can tell by the spectroscope whether the light from this gas is the same as any we have known before, or whether it is different. If the light waves sent out are unlike any recognized before, we can be sure we have a new gas.”

Tom was turning a screw, with his eye glued to a small telescope. “Change that tube a bit to the right, Hamerly,” he said, and it was changed. “Now a bit higher. No, not so high, a bit lower now. There you are.”

He gazed long and intently, then rose, motioning Hamerly in silence to take his place. Dorothy followed Hamerly, and Swenton followed her. I ended, but I could distinguish nothing save some lines crossing a scale placed within the tube. As I rose from the stool, Tom reached up to throw on the lights. As he faced around, Hamerly met him with outstretched hand.

“It is only given to a handful of scientists in a century,” he said, “to find a new element, to discover one of those units from which the world is made. I believe you have done it this afternoon.”

“It is a new, elementary gas,” said Dorothy. “You found it, Tom, when you climbed that table.”

“Much good it will do me, so far as that goes,” remarked Tom. “So far as we know, all there is of it in the world is in this tube. I don’t know how to produce any more, and I can’t publish anything about it, for it would interfere with our search for the man.”

“You have no right to say that it’s no use,” said Dorothy. “Again and again as we have gone on, the slightest unexpected things have come to mean the most. I believe this tube of unknown gas may be a most important link in the chain.”

“All right,” said Tom. “Just as you say. You can be sure I wasn’t going to throw it into the waste basket.”

While Swenton cleared away, the rest of us went into the wooden room. Hamerly passed across and opened one of the wooden shutters. “The fog is lifting,” he said.

We looked out and saw that the other side of the street was gradually becoming visible. Dorothy seated herself by the window, and we joined her.

“I don’t know that there could be a better time,” I began, “than right here and now, to find out just where we are. For my part, I want to understand the relation between the new gas and all that has gone before. If we bring all our information together, won’t there be a better chance to get a line on our next move?”

“We have two things in our hands,” said Tom thoughtfully. “This tube of gas here and the cigarette case. We know that the ships really disappeared, because Jim has been to the bottom of Portsmouth Harbor and seen the men that lie there. We know by the same token that this force kills, by a sort of paralysis, every man whom it attacks. Oh, that reminds me,” he exclaimed, checking himself. “Let me see that cigarette case again, if you will, Hamerly?” The case once in his hand, he looked it over with minute care. “Insulated within the paraffin by caema, don’t you think?” he asked Dorothy.

After a brief inspection she also nodded. “That’s caema, all right.”

“Never mind caema, now, whatever it is,” I said. “Let’s go on with the business. What else do we know?”

Hamerly took up the tale. “We know to a reasonable certainty that Dr. Heidenmuller was the first man who found the source of this power, and that he died when it accidentally was let loose. We know that some of this substance, probably in powder form like radium, was kept in the leather cigarette case, insulated by paraffin and caema.” He paused.

“We know,” went on Dorothy, “that when the man who is trying to stop all war uses this force, a tremendous amount of radio-active energy is generated, enough to affect reflectoscopes half around the world.”

“We know there is something which is even more than all those things,” I broke in. “We know there is a man who is slaughtering men by the hundreds, in pursuit of his ideal, and that it is our business, in more ways than one, to run him down. How will the data we have on hand enable us to do that?”

As I spoke, Dorothy was sitting looking meditatively out of the window. The fog had lifted a little more. Hamerly straightened in his chair.

“Miss Haldane,” he said, “if you will look straight across the street from where you are sitting, you can see the spot from which the sign fell on the day that Dr. Heidenmuller died.”

Dorothy turned in her chair, and we all crowded about her. Hamerly pointed across the road. There, against the brick wall of an old house, blackened by the smoke of many sooty years, two small rectangles showed in light relief against the surrounding darkness. The sight of those spots, where the supports to the sign had once stood, brought the whole horror of it home to me more forcibly than anything else. The very smallness, the homeliness of the thing drove it in. The accumulated effects of the charged electroscopes, of the wave-measuring machine, of the bodies on the ocean’s floor, of Dr. Heidenmuller’s death, and of the gas we had just found, rose to their very crest in those small, light gray spots, less sullied than the rest of the wall.

“And there is where the wooden sign fell down, and its iron supports disappeared,” said Tom reflectively. “Jove, I’d like to have seen it happen. If anybody had seen it, though, he wouldn’t have believed his eyes.”

We were still standing, peering out through the rising mist, when Dorothy spoke out excitedly. “That’s the next clue, there’s nothing else that will do so well,—the hunt for disappearing iron.”

“What good will that do?” said Tom. “We know where iron has disappeared, and we’ve run everything down as far as we could. It isn’t likely that Heidenmuller or the man went around shooting off signs for fun.”

“Of course not,” answered Dorothy impatiently. “But don’t you see the man must have had a laboratory, or lodgings, anyway, somewhere in London, if he got his data and his power from Dr. Heidenmuller here. When Dr. Heidenmuller let his discovery get away from him, it killed him, and caused all the metal which it reached to disappear. Now, the man hasn’t been killed by his weapon, unless it happened very recently, but it’s perfectly possible that he might have allowed some of his magic substance to escape without injury to himself. If that happened, it would destroy any metal at hand. If we could find some place where iron disappeared, we might get a direct clue to the whereabouts of the man. It’s worth trying, anyway.”

“I’m sure it is,” I cried. “Tom, you old doubter, speak up and admit Dorothy knows twice as much about it as you and I put together.”

“I guess not,” said Tom firmly. “There may be something in this, if we could get track of everything that bore on disappearing iron, London over; but,” he went on, “talk about a needle in a hay stack. You went up against a hard enough proposition in running down Heidenmuller’s laboratory here, but this new deal is far worse. You can’t advertise.”

“No, I don’t see how you can,” remarked Dorothy, a trifle discouraged.

“Oh, this thing’s easy enough,” I broke in. “I wish everything was as simple. Inside of two days, I’ll have all the information that London holds with regard to disappearing iron.”

“How can you get it?” cried the three in unison.