And the winds had been made as much the slaves of this people as the waves; for another great cavern that we visited was the storehouse of the energy of the winds. In every gorge and pass and gully around Lilaroma up almost to its crater had been erected immense windmills, which as they revolved generated electricity; this found its way from all points by massive cables buried in the earth to the conservator of energy in this second cave. Ooriel tested the wires to see that they were not leaking anywhere and tested the batteries for faults, and finding everything in good order, we passed into a third power treasury in the rock. This was vastest of all; for into it there poured the energy of the power-wells which was not needed by the private houses spread over the face of the island. As soon as the head of steam was shut off from the machinery or the tubes of any mansion, its whole force was turned upon an engine near the mouth of the well, which kept generating electric force day and night. The accumulation of energy in this cave of the wells would have been enough to supply ten times the power that Europe had ever used in her industries. In order to round off our tour of inspection, Ooriel led me to another but smaller cave which had just been fitted up with storage-batteries. This was the cave of the sun. For generations it had been contended that most of the power from the sun’s rays was lost, even when they reached the earth; and the inventors had at last worked out the problem of its utilisation. I had noticed as I flew over the country in a faleena vast gleaming spaces sparkling like gigantic diamonds in the sunlight. These were the reflectors which collected the sunbeams and concentrated their heat and light into power. Upon the slope of Lilaroma they utilised the miles of snow surface and gathered their gleam into a few heat-engines that sent the generated electricity into Rimla.