From the exterior of the ship these two ports appeared like the huge eyes of some gigantic monster; and, in truth, this was the purpose they served.

Fal Sivas called my attention to a small, round metal object about the size of a large grapefruit that was fastened securely just above and between the two eyes.

From it ran a large cable composed of a vast number of very small insulated wires. I could see that some of these wires connected with the many devices in the control room, and that others were carried through conduits to the after part of the craft.

Fal Sivas reached up and laid a hand almost affectionately upon the spherical object to which he had called my attention. "This," he said, "is the brain."

Then he called my attention to two spots, one in the exact center of each crystal of the forward ports. I had not noticed them at first, but now I saw that they were ground differently from the balance of the crystals.

"These lenses," explained Fal Sivas, "focus upon this aperture in the lower part of the brain," and he called my attention to a small hole at the base of the sphere, "that they may transmit to the brain what the eyes of the ship see. The brain then functions mechanically precisely as the human brain does, except with greater accuracy."

"It is incredible!" I exclaimed.

"But, nevertheless, true," he replied. "In one respect, however, the brain lacks human power. It cannot originate thoughts. Perhaps that is just as well, for could it, I might have loosed upon myself and Barsoom an insensate monster that could wreak incalculable havoc before it could be destroyed, for this ship is equipped with high-power radium rifles which the brain has the power to discharge with far more deadly accuracy than may be achieved by man."

"I saw no rifles," I said.

"No," he replied. "They are encased in the bulkheads, and nothing of them is visible except small round holes in the hull of the ship. But, as I was saying, the one weakness of the mechanical brain is the very thing that makes it so effective for the use of man. Before it can function, it must be charged by human thought-waves. In other words, I must project into the mechanism the originating thoughts that are the food for its functioning.

"For example, I charge it with the thought that it is to rise straight up ten feet, pause there for a couple of seconds, and then come to rest again upon its scaffolding.

"To carry the idea into a more complex domain, I might impart to it the actuating thought that it is to travel to Thuria, seek a suitable landing place, and come to the ground. I could carry this idea even further, warning it that if it were attacked it should repel its enemies with rifle fire and maneuver so as to avoid disaster, returning immediately to Barsoom, rather than suffer destruction.

"It is also equipped with cameras, with which I could instruct it to take pictures while it was on the surface of Thuria."

"And you think it will do these things, Fal Sivas?" I asked.

He growled at me impatiently. "Of course it will. Just a few more days and I will have the last detail perfected. It is a minor matter of motor gearing with which I am not wholly satisfied."

"Perhaps I can help you there," I said. "I have learned several tricks in gearing during my long life in the air."

He became immediately interested and directed me to return to the floor of his hangar. He followed me down, and presently we were poring over the drawings of his motor.

I soon found what was wrong with it and how it might be improved. Fal Sivas was delighted. He immediately recognized the value of the points I had made.

"Come with me," he said; "we will start work on these changes at once."

He led me to a door at one end of the hangar and, throwing it open, followed me into the room beyond.

Here, and in a series of adjoining rooms, I saw the most marvellously equipped mechanical and electrical shops that I have ever seen; and I saw something else, something that made me shudder as I considered the malignity of this man's abnormal obsession for secrecy in the development of his inventions.

The shops were well manned by mechanics, and every one of them was manacled to his bench or to his machine. Their complexions were pasty from long confinement, and in their eyes was the hopelessness of despair.

Fal Sivas must have noted the expression upon my face; for he said quite suddenly, and apropos of nothing else than my own thoughts, "I have to do it, Vandor; I cannot take the risk of one of them escaping and revealing my secrets to the world before I am ready."

"And when will that time come?" I asked.

"Never," he exclaimed, with a snarl. "When Fal Sivas dies, his secrets die with him. While he lives, they will make him the most powerful man in the universe. Why, even John Carter, Warlord of Mars, will have to bend the knee to Fal Sivas."

"And these poor devils, then, will remain here all their lives?" I asked.

"They should be proud and happy," he said, "for are they not dedicating themselves to the most glorious achievement that the mind of man has ever conceived?"

"There is nothing, Fal Sivas, more glorious than freedom," I told him.

"Keep your silly sentimentalism to yourself," he snapped. "There is no place for sentiment in the house of Fal Sivas. If you are to be of value to me, you must think only of the goal, forgetting the means whereby we attain it."

Well, I saw that I could accomplish nothing for myself or his poor victims by antagonizing him, and so I deferred with a shrug. "Of course, you are right, Fal Sivas," I agreed.

"That is better," he said, and then he called a foreman and together we explained the changes that were to be made in the motor.

As we turned away and left the chamber, Fal Sivas sighed. "Ah," he said, "if I could but produce my mechanical brain in quantities. I could do away with all these stupid humans. One brain in each room could perform all the operations that it now takes from five to twenty men to perform and perform them better, too-much better."

Fal Sivas went to his laboratory on the same level then, and told me that he would not require me for a while but that I should remain in my quarters and keep the door open, seeing that no unauthorized person passed along the corridor toward the ramp leading to his laboratories.

When I reached my quarters, I found Zanda polishing the metal on an extra set of harness that she said Fal Sivas had sent to me for my use.

"I was talking with Hamas's slave a little while ago," she remarked, presently.

"She says that Hamas is worried about you."

"And why?" I asked.

"He thinks that the master has taken a fancy to you, and he fears for his own authority. He has been a very powerful man here for many years."

I laughed. "I don't aspire to his laurels," I told her.

"But he does not know that," said Zanda. "He would not believe it, if he were told. He is your enemy and a very powerful enemy. I just wanted to warn you."

"Thanks, Zanda," I said. "I shall be watchful of him, but I have a great many enemies; and I am so accustomed to having them that another, more or less, makes little difference to me."

"Hamas may make a great difference to you," she said. "He has the ear of Fal Sivas. I am so worried about you, Vandor."

"You mustn't worry; but if it will make you feel any better, do not forget that you have the ear of Hamas through his slave. You can let her know that I have no ambition to displace Hamas."

"That is a good idea," she said, "but I am afraid that it will not accomplish much; and if I were you, the next time I went out of the building, I should not return. You went last night, so I suppose that you are free to come and go as you will."

"Yes," I replied, "I am."

"Just as long as Fal Sivas does not take you to the floor above and reveal any of his secrets to you, you will probably be allowed to go out, unless Hamas makes it a point to prevail upon Fal Sivas to take that privilege away from you."