It was one of the masters of physical force who manipulated the keys. He was controlling and harmonising the vast power that was concentrated in Rimla, and, instead of the demoniac jarring of the engines and machinery which I had been accustomed to in the industrial centres of other lands, the sounds of the marvellous vault made sweet concord that ever varied with the transference of power from purpose to purpose. He was the pointsman of the numberless railroads of energy, and at the same time the musician of the titanic workshop. His will disciplined and guided both the generation and the distribution of all the force of the island. Our troop took the place of that which had been on guard through the sunset and twilight, and separated in pairs throughout the valley, each pair taking under its charge one section of the labyrinthine movement. My comrade, Ooriel, the cousin of Thyriel, was a youth of splendid build, the strength of his upper limbs seeming almost bovine, his shoulders and arms not too large for his size, yet giving the impression of gigantic power. I soon saw how much he could do. We were to inspect the generators of force underneath the dome. He first led me to the various streams which came leaping down the slopes and cliffs. One of them from some cause only to be ascertained at the cone of Lilaroma was swollen into a yellow torrent that threatened to overflow its lava banks and flood the valley. In a moment he saw the danger, and rushed to the wing-dam dividing the upper course and controlling the amount of water which should flow down to its various wheels and the amount which unused should find its way to the great exit. He found that the separating barrier had lost its automatic motion through the sudden increase of the overflow and the intrusion of a huge boulder that had come down like a battering-ram upon it. He set me to guide the machinery and power that moved the dam to suit the strength of the current, and then, fixing a narrow irelium shield in the bottom of the channel, he leapt into the torrent. The shield, I could see, keeping erect just above him, shed the stones and boulders to this side and that. Thus protected he raised a huge hammer which he had taken with him and by three or four well-directed blows split the obstacle into half a dozen pieces; he then bent down and removed them out of the way, and suddenly I felt the steering-gear begin to work, and saw the dam swing round into the channel leading to the centre of force, whilst the bulk of the torrent found its way into the exit, which was deeper and broader. The danger was past; but a moment’s hesitation, either in order to bring up the heavier tools or to call other assistance, would have ruined many of the great works upon the levels below and stopped the whole of the operations of Rimla for several days.