One of the most interesting departments of Minella, as this great building was called, was that which contained the measurers of time. I was somewhat surprised that this department should exist, for I had admired every day the power the Limanorans had of telling to a minute fraction the passage of time. Their sense of time seemed to me to make watches and clocks superfluous. Even when the sky was clouded over and no heavenly body or light to be perceived, they could tell the exact fraction of the day or night that had passed, as I tested again and again by the watch I had brought with me. Their knowledge of the natural signs of the time of day or year had become instinctive and automatic through long centuries of daily use. The position and state of the petals of flowers would at any moment by day or night, by shine or cloud, reveal to them the time. So would the temperature of anything they touched, or, if it were highly contractile, its size. But these external signs were quite unnecessary. They had not to go beyond the sensations of their own bodies to tell the time or season. They knew by the intensity of the magnetism in them, by the acuteness of their senses, by the amount of energy they could command. But their experiments needed far more exactness than even their senses could afford. Time had to be counted in their science not by mere seconds, but by the hundred-thousandth, or even the millionth, part of a second. One old-fashioned measurer of time was based on the length of a wave of sound as it passed through a vessel of water. The length of the vessel contained a round number of moltas (their smallest measure of length, perhaps about the millionth part of an inch); the vibration in the water reflected a bright light through a microscope and camera combined; and a photograph of the pulsations imprinted itself on a strip of irelium that kept moving with lightning swiftness across the focus; this strip was divided into minute sections, each of them corresponding to a lenta or millionth part of a second and numbered in order up to a million. A newer clock had its principle based on the length of a wave of light in a vacuum. Another and more convenient clock, or rather watch, consisted of an electric battery that kept a light irelium tongue vibrating; this latter controlled a graduated mechanism which pointed out on a face the exact lenta in the time of day that it was. It was small enough to be carried about on the person like a watch.