Their makrakousts were instruments which by means of electric currents and magnetism could make a beam of light transmit any sound to its source, or make the ear gather in the same way whatsoever sounds were filling the air at any point on its course. I knew when I saw a steady flash in any direction that the sound of some point was getting tapped by one of these instruments. Each had an apparatus for laying and keeping fixed its luminous telegraph-wire along which it received and transmitted. An application of this in the gossip-telegraph enabled them to listen to the comedy of life as it went on in any one of the adjacent islands of the archipelago. Their mikrakousts used the same means for gathering the faint sounds which echoed from the clouds or through the upper regions of the atmosphere and turning them into loud notes, which might be recorded, analysed, and interpreted. Their magnifying power was quite equal to that of the clirolan. Faint buzzings of insects at vast distances could be collected and made as loud as thunder. It was even applied to cosmic sounds that impinged on the atmospheric envelope of the earth. Mikrakoustic balloons rose into the upper air, and after gathering whatever faint sounds wandered thither from outside the world, were drawn back again to divulge their secrets; eavesdroppers of the cosmos they were, and perchance in some future age they would enable the Limanoran to listen to voices from other worlds or even to communicate with the dwellers there. A more immediate and practical advantage of these instruments was found in medicine. They told in clear accents the unexpected or dangerous changes in the tissues or organs of any man’s system. They were used in the weekly medical inspection, which every member of the commonwealth underwent. When the keen eye, aided by the camera-microscope, could detect nothing abnormal in the body, the mikrakoust would tell the examiner’s ear of some obstruction or deleterious change; he knew the normal sounds of healthy action in every part when they were magnified thousands of times by this instrument, and every departure from them readily caught the ear. All the citizens were trained to use it as an aid in diagnosis, so that they might be able to locate in the system any beginning of disease. It was part of the training of my ear to use the mikrakoust and to interpret its physiological revelations.