That made me smile, and I broke off the conversation."

  The others had risen with a single movement.

  "There's no need to say that you can rely on us," Barsac declared on behalf of them all. "But we must have weapons...."

  "Weapons? ..." Camaret repeated with a smile. "What for? ... I don't think there's even one of them here. None the less, you need not be uneasy, gentlemen. We can use other methods."

  "Methods able to resist the Palace guns?"

  "Those and many other tilings. If it occurred to me to destroy the whole town, I could do it in an instant. But I hardly think we shall be reduced to that extremity. The Palace guns will remain silent, be assured of that.

  "Not only does Killer realize my power, and realize, too, that most of the Factory is shell proof, he will take care not to destroy it, for he knows that his whole power is based on it He's more likely to try to get in with living agents. But he will not succeed."

  As though in response to his declaration, they heard heavy blows corning from the floor beneath.

  "What did I tell you?" said the engineer, smiling gently. "There they are, attacking the door. But I can guarantee that it's solidly built."

  "But if they bring a cannon to bear on it?" asked Barsac, only half reassured by the engineer's calm.

  "Even so it would not be easy to break it down," replied the latter. "But to bring one of the palace guns on to the quay, that would take time, and we've only got to deal with a battering ram wielded by human arms. Using that, they could batter for a century without getting any further. Still, if you care to come with me, you can be present at the edge of the siege. I think the sight will interest you."

  They went back to the workshop and crossed it without stopping. The machines were in action now, but the men were not showing their usual zeal. Grouped together, they were discussing the news they had heard, and the place showed a certain disorder easily explicable in the light of recent events, and to which Camaret closed his eyes.

  Having crossed the workship, they climbed a spiral staircase and reached the platform of a tower; the only difference between this and that of the Palace was that it was surmounted by that inexplicable metal pylon whose tip rose more than a hundred yards into the air. Like the Palace tower, too, it was provided with a cycloscope placed between the supports of the pylon; Camaret asked his companions to enter this.

  "This cycloscope," he explained, "does not cover a range of several miles like the one I built for Harry Killer. Thanks to a series of mirrors placed obliquely along the top of the Factory wall, we can observe what happens in our immediate vicinity. From here you can see the outer face of the surrounding wall right down to its foot."

  The Esplanade, the quay, and the circular road were indeed visible in the cycloscope whose images, though much smaller than those of the Palace instrument, were much clearer. Through the lenses they saw a number of men, several carrying ladders, running all round the Factory wall, while about thirty others were still exhausting themselves in fruitless efforts against the door.

  "As I foresaw," said Camaret. "They're going to launch an attack. Now this should really begin to get interesting."

  The attack was certainly beginning. Already several ladders had been reared against the wall, and on these were a number of the Merry Fellows. Reaching its crest, several of them grasped it unsuspiciously.

  The scene changed at once. Scarcely had they touched the top of the wall when these men exhibited the most frightful contortions. Hanging from the crest, as though their arms were glued to the wall, they danced the devil of a jig, like jumping jacks when someone pulls the strings.

  "That's stupid of them," explained Camaret "The edge of the wall is completely covered with a metal which I invented, a hundred times as good a conductor as copper. I sent an alternating current of suitable voltage through it and you see the result."

  While he was giving that explanation, the attackers on the lower ladders had seized the legs of the men above them, whose frantic movements they could not understand. At once these reckless fellows performed the same antics, to the complete bewilderment of their companions who had not followed their example.

  "But why don't those lunatics simply let themselves drop oil?" asked St. Berain.

  "They can't, the poor devils," Marcel Camaret explained. "They'll stop fixed to the wall as long as I wish. ... But I can do even better."

  He grasped a switch. At that moment the ladders were overthrown, as though thrust back by an invisible hand, and the men who had been holding them tumbled pellmell, leaving on the wall only those human bunches of grapes who were fastened to it and who continued to struggle desperately.

  "I won't be responsible for any damage," remarked Camaret gently. "This has happened under your eyes-would you like to know how it was done?"

  When they all agreed, he continued:

  It's quite simple. In my opinion force, whatever its nature, consists of nothing but different kinds of vibrations in the ether. It is generally agreed that light can be considered as a series of vibrations between certain limits of frequency, and that electrical phenomena are a different series of vibrations separated from the first by an interval supposed to appertain to other vibrations whose nature is unknown. Without finally deciding, I incline to believe that these last have some relation with heat. However this may be, I know how to produce them and use them to obtain somewhat strange results, like those of which I have just given you proof."

  During this brief explanation, the human grapes continued their fantastic dance.

  "That little game has lasted long enough," he said, throwing over another switch.

  At once the human jumping-jacks dropped off the walls and fell thirty feet to its base, where they remained motionless. After a moment of understandable hesitation, their comrades decided to come and carry them off.

  "End of the first act," Camaret announced in his usual voice. "I don't think it's ended to Harry Killer s benefit; already about thirty of his men are out of action. Suppose we next deal with the lunatics who so stupidly persist in clamouring at the door?"

  He seized a telephone transmitter. "Are you ready, Rigaud?" he asked.

  "Yes, Sir," replied a voice audible everywhere in the cycloscope.

  "Send!" ordered Camaret.

  As if in direct obedience to his order, a strange-looking implement at once emerged and moved away from the base of the tower. It was some sort of vertical cylinder, the end facing the ground expanded to form a large cone.

  At the other end four screws, one horizontal and three vertical, spun with dazzling speed. This strange contrivance soared into the air, moving away from the exterior wall. When it was several yards high, its course became horizontal, and it rigorously followed the Factory boundary.

  But already, following this first contrivance, had come a second, then a third, then others. Camaret's guests could count twenty which, at regular intervals, left the tower like birds leaving the nest and in turn completed the same manoeuvre.

  "Those are my wasps'," said Marcel Camaret, slightly stressing the possessive pronoun. "I'll explain later how they are steered. For the time being, just watch them at work."

  Again he lifted the telephone transmitter. "A warning, Rigaud," he said.

  Then, speaking to his new friends, "After all, why should I kill those poor devils who've done nothing to me? A warning will do, if they're willing to accept it."

  Since their attempt had been halted, the attackers who had tried to scale the wall had stayed motionless. Carrying away their comrades who were out of action several had certainly been killed or at least badly injured. They had evacuated the circular road and had gathered together on the Esplanade, at a respectful distance from the Factory, and were staring at its wall in bewilderment.

  On the other hand those who were attacking the door had not interrupted their work. They were obstinately battering at the portal, which didn't seem to be much damaged, with a great beam which about forty strong arms w
ere swinging. In circling the boundary, the wasps, as Marcel Camaret called them, passed one after another over this group, which paid no attention to them.

  Suddenly an explosion sounded from one of the wasps, and a hail like machine-gun bullets covered the ground, over a circle about a hundred yards across.

  At the noise, the men who were swinging the ram looked up. They had not yet understood what caused it when a second explosion sounded from another of the contrivances as it reached them; the explosion was followed, like the first, by a machinegun hail.

  This time the field of fire was nearer and several men were hit by the projectiles. The others did not wait. Dropping the ram, they gathered up the wounded and ran away as fast as their legs could carry them.

  The onlookers could hardly believe their eyes. Each wasp, after being fired, had obediently returned into its nest at the foot of the tower. Then, having been reloaded, it set off to regain its place in the general circle.

  "I don't think we need trouble about those fellows," said Marcel Camaret. "So if it would please you, by any chance, to visit the Factory. ..."

  CHAPTER VII

  BLACKLAND FACTORY

  His guests were only too ready to accept.

  "We shall come back here when we've finished our tour of the Factory," said Camaret, "but first notice its general layout. You see it covers a rectangular surface about 250 yards wide by about 300 yards along the river. Its area is roughly twenty acres: its western part, about three fifths of the rectangle, is devoted to gardens."

  "Why gardens?" broke in Amedee Florence.

  "They give us part of our food, the rest comes from outside. So it's only the remainder, about a hundred yards wide, with an entrance on the quay, which forms the Factory itself. At its centre, over a length of about 250 yards, the workshops and my own quarters are grouped at the foot of that central tower. So at each end there's a space of about 60 yards where a broad street, perpendicular to the river, separates two rows of workmen's quarters. As each row includes seven houses, and each house has four storeys, including the ground floor, we have 120 dwellings."

  "What's the size of your staff?" asked Barsac.

  "Exactly a hundred men, but several are married and there are some children. As you can see, the workshops are only one storey high and they are covered with a thick layer of turfed soil. So shells would be almost powerless a gainst them. Now you know the general layout, we can go down, if you wish, and make a detailed visit."

  Before accepting that invitation, Camaret's audience threw a last glance around. There was no change in the situation. The wasps were still making their circular promenade, and the attackers, rendered wise by experience, did not dare enter the zone of peril. Reassured, the party followed the engineer off the platform.

  Under his leadership, they first visited the part of the tower which he called the hive, whence the twenty wasps had emerged from as many cells; between these was placed their reserve ammunition. They then traversed a series of workrooms, the fitting shop, mill, forge, foundry, and so forth, and emerged in the gardens, on the side nearest the Palace.

  The high wall around the Factory hid this from them. But when they had gone about fifty yards from thewall, the crest of Harry Killer's tower came into sight. At once an explosion sounded from its top and was followed by the characteristic whine of a bullet passing over their heads. They recoiled hurriedly.

  "The fool! . . ." Camaret murmured calmly; then, without halting, he simply raised his arm.

  The sign was followed by a violent hissing. His guests instinctively turned towards the Factory, but Camaret pointed to the Palace. The cycloscope which crowned its tower had vanished.

  "That will teach him," said the inventor. "I've got aerial torpedoes, too! Indeed, I've got more than he has, because I made them. As for the cycloscope, I'll build another, that's all."

  "But, Monsieur," asked Amedee Florence. "As you've got these projectiles which you call aerial torpedoes, why don't you use them against Harry Killer?"

  For a moment Camaret stared at the man who had asked the question, and again a bewildered look came into his eyes.

  "Me! . . ." He said at last in a dull voice. "Me, to destroy my own workl ..."

  Without pressing the point, Amedee Florence exchanged a glance with his companions. With all Ins high qualities, this remarkable man certainly had one chink in his armour, and that chink was pride.

  They walked on in silence. The Palace had learned its' lesson. No other attack was made upon them as they went on through the garden.

  "Now we're coming to the interesting part," said Camaret, as he opened a door. "This used to be the power unit, the motor and steam engine and boiler which we fed with wood, for want of any other fuel. That was quite a business, for the wood came some distance, and we used a great deal of it. Fortunately that didn't last long. As soon as the river was flowing, fed by the rainfall I had produced, the hydroelectric station began to work; I had meantime built it about six miles up-stream. Now we no longer use this archaic equipment, and smoke-no longer gushes from that useless chimney. We're quite satisfied to meet all our needs from the energy which the generating station sends us."

  They followed Camaret into another room.

  "Here," he explained, "and in the next rooms, which are filled like this with dynamos, alternators, transformers and coils, this is the realm of the thunderbolt. It is here we use and transform the main current which the station sends us."

  "What?" cried Florence, amazed. "You were able to bring all these machines here?"

  "Only a few of them," replied Camaret, "most of them we built ourselves."

  "Still, you'd have needed the raw materials," Florence objected. "How the devil did you get them in the midst of' the desert?"

  "Weill" said Camaret, who had paused thoughtfully as if this point were quite new to him, "you are right, Monsieur Florence. How could the first machines have come here, as well as the raw materials we used for the others? I've never considered that side of the question, I must admit. I asked for them, and I got them. I didn't look any further. But now you draw my attention to it...."

  "And what a sacrifice of men, to bring all that across the desert, until you had the heliplanes."

  "That is true," admitted Camaret, who had turned rather pale.

  "And the money? For all that must have swallowed up the cash" Florence asked in a tone of familiar boldness.

  "The money?" babbled Camaret "Yes, the money. Certainly you must be rich?" "Me! . . ." Camaret protested. "I don't think I've had five centimes in my pocket since I came here."

  "Then?"

  "It's Harry Killer. . . ." Camaret began timidly.

  "True enough, but where did he get it? Is he a millionaire, your Harry Killer?"

  Camaret extended his arms in token of his ignorance. This question seemed to have demoralized him, and again his eyes took on that lost expression devoid of any living emotion. Foreseeing the possible answer to the question put to him so brusquely, a problem quite different from those he usually had to solve, he felt a sort of faintness before the unsuspected horizons which opened out before him. He seemed so completely lost that Dr. Chatonnay took pity on him.

  "That's a point we can clear up later with the others," he said. "But now don't let's dwell on it all day, let's get on with our visit."

  As if to drive away too pressing a thought, Camaret passed his hand over his forehead and silentiy entered the next room.

  "Here," he said, in a voice still touched by emotion, "these are the compressors. We make much use of liquid air and other gases. As you know, every gas can be liquefied, so long as it's sufficiently compressed and the temperature is low enough, but as soon as the liquids are left to themselves, they warm up and more or less quickly regain their gaseous state. Then if they're in a closed receptacle, they exert so great a pressure on its casing that it flies into fragments.

  ' "One of my inventions has changed all that. In fact, I have discovered a substance which is compl
etely antidiathermic, completely impermeable to heat. The result is that a liquefied gas, air for example, in a container made of this substance will always keep the same temperature. So it remains liquid and never has the slightest tendency to explode. This invention has enabled me to produce several others, notably the long-range heliplanes which you know about."

  "Which we know about I . . ." exclaimed Amedee Florence. "You may say we know about them only too well! Then it was you who made them, too?"

  "And who did you think made them?" asked Camaret, suddenly assailed by a new attack of his inordinate pride.

  As he spoke, however, his emotion gradually vanished. Soon no trace of it remained, and he had quite regained his self-control when he continued:

  "My heliplanes have three special features, their stability, their takeoff, and their motive power; I will give you a brief idea of them.

  "Let's begin with the stability. When a bird meets the thrust of a sudden squall, it does not need calculations to regain its equilibrium. Its nervous system or rather what the physiologists call its reflexes, comes into action and it balances quite instinctively. For the stability of my mechanical birds to be automatic, I wanted to give them a similar system of reflexes. As you have seen, they are provided with two wings placed at the top of a pylon fifteen feet high, based on the platform for the motor, the pilot, and the passengers. That arrangement results in a marked lowering of the centre of gravity.

  "But the pylon is by no means fixed in relation to the wings. Unless it is securely held, by the directional or altitudinal rudders, it is free to oscillate slightly in all directions about the vertical. So if, apart from the action of the rudder, the wings dip sideways or forwards, the pylon is forced by its own weight to tend to produce a new angle with them. This movement at once brings into action weights free to slide parallel or perpendicular to the wings, which meantime are warped appropriately. This immediately, and automatically, corrects the accidental oscillations of the heliplane."