It was indeed a gigantic one, and capable of exercising enormous pressure. When I passed outside, however, and pressed down the levers which controlled it, I knew at once by the whishing sound that there was a slight leakage, which allowed a regurgitation of water through one of the side cylinders. An examination showed that one of the india-rubber bands which was round the head of a driving-rod had shrunk so as not quite to fill the socket along which it worked. This was clearly the cause of the loss of power, and I pointed it out to my companions, who followed my remarks very carefully and asked several practical questions as to how they should proceed to set it right. When I had made it clear to them, I returned to the main chamber of the machine and took a good look at it to satisfy my own curiosity. It was obvious at a glance that the story of the fuller’s-earth was the merest fabrication, for it would be absurd to suppose that so powerful an engine could be designed for so inadequate a purpose. The walls were of wood, but the floor consisted of a large iron trough, and when I came to examine it I could see a crust of metallic deposit all over it. I had stooped and was scraping at this to see exactly what it was when I heard a muttered exclamation in German and saw the cadaverous face of the colonel looking down at me.