"Stop!" I called to the boatman. "Now, Eveena," I said, "I do not care to persist in this journey if it really distresses you. I wished to see so wonderful a work of engineering; but, after all, I have been in a much uglier and more wonderful place, and I can see nothing here stranger than when I was rowed for three-quarters of a mile on the river in the Mammoth Cave. In any case I shall see little but a continuation of what I see already; so if you cannot bear it, we will go back." By this time Esmo, who had been in the bows, had joined us, wishing to know why I had stopped the boat. "This child," I said, "is not used to travelling, and the tunnel frightens her; so that I think, after all, we had better take the usual course across the mountains." "Nonsense!" he answered. "There is no danger here; less probably than in an ordinary drive, certainly less than in a balloon. Don't spoil her, my friend. If you begin by yielding to so silly a caprice as this, you will end by breaking her heart before the two years are out." "Do go on," whispered Eveena. "I was very silly; I am not so frightened now, and if you will hold me fast, I will not misbehave again." Esmo had taken the matter out of my hands, desiring the boatman to proceed; and though I sympathised with my bride's feminine terror much more than her father appeared to do, I was selfishly anxious, in spite of my declaration that there could be no novelty in this tunnel, to see one thing certainly original—the means by which so narrow and so long a passage could be efficiently ventilated. The least I could do, however, was to appease Eveena's fear before turning my attention to the objects of my own curiosity. The presence of physical strength, which seemed to her superhuman, produced upon her nerves the quieting effect which, however irrationally, great bodily force always exercises over women; partly, perhaps, from the awe it seems to inspire, partly from a yet more unreasonable but instinctive reliance on its protection even in dangers against which it is obviously unavailing. Presently a current of air, distinctly warmer than that of the tunnel, which had been gradually increasing in force for some minutes, became so powerful that I could no longer suppose it accidental. Kevimâ being near us, I asked him what it meant. "Ventilation," he answered. "The air in these tunnels would be foul and stagnant, perhaps unbreathable, if we did not drive a constant current of air through them. You did not notice, a few yards from the entrance, a wheel which drives a large fan. One of these is placed at every half mile, and drives on the air from one end of the tunnel to the other. They are reversed twice in a zyda, so that they may create no constant counter-current outside." "But is not the power exerted to drive so great a body of air exceedingly costly?"