For I had seen ours being mined; I had seen the entrance of the great irelium tube into the earth, ring within ring, and its slow but inevitable work from day to day and week to week. The principle of this leomoran or earth perforator had been found by investigation of the anatomy and method of work of the pholas or rock-boring shell, partly chemical, partly mechanical. The edge of the lowest ring was like a sharp-toothed file that, as it rotated by means of power applied from the centre of force, wore its way gradually into the rock, the ridges of the file being as hard as the diamond. An inner ring-file was attached to it on the inside, and between the two was let down a certain chemical compound, which by the friction of the files produced little explosions in the rock below and thus quickened the process. Other ring-files followed in the same way. Another chemical compound, differing according to the character of the rock to be attacked, was let down in the space within the concentric rings, and rapidly decayed the rock so that it ascended like a column of thick black smoke. After all the ring-files were at work, the leomoran needed little guidance; for by an application of the principle of the spectroscope, its use of the chemicals according to the nature of the rock became automatic. As soon as the volatilised mineral that ascended out of the rings changed its character, the beams of light that passed through it changed the spectrum; and the new spectrum influenced a certain solution that controlled a thread, and this thread set free a stream of the proper chemical compound down the leomoran. A still more striking use of the spectrum was the linoklar or spectroscope analyst and recorder. It analysed the vapours that ascended from the tubes, and recorded their spectra on a moving strip of irelium that was guided by the descent of the leomoran into the earth. Thus anyone could see what strata were passed through in any given time and the extent of the strata. But the linoklar did much more than this; whenever it struck any vein that had the much-desired irelium in it in any quantity, its spectrum released a spring which opened a small tube; through this streamed the irelium vapour into a cavity of the earth, where by means of a purifier it deposited only the pure metal. There was less demand for the other metals, gold, silver, platinum, tin, copper, iron. But there was also an arrangement for separating and depositing their volatilised forms in other cavities. Thus they were able to have more than they required of the metals, and especially of irelium, the most precious because the most adaptable of all.