It was then five in the morning; and at that moment a shock was felt at the bows of the _Nautilus_. I knew that its spur had struck a block of ice. It must have been a false manœuvre, for this submarine tunnel, obstructed by blocks, was not very easy navigation. I thought that Captain Nemo, by changing his course, would either turn these obstacles or else follow the windings of the tunnel. In any case, the road before us could not be entirely blocked. But, contrary to my expectations, the _Nautilus_ took a decided retrograde motion. “We are going backwards?” said Conseil. “Yes,” I replied. “This end of the tunnel can have no egress.” “And then?” “Then,” said I, “the working is easy. We must go back again, and go out at the southern opening. That is all.” In speaking thus, I wished to appear more confident than I really was. But the retrograde motion of the _Nautilus_ was increasing; and, reversing the screw, it carried us at great speed. “It will be a hindrance,” said Ned. “What does it matter, some hours more or less, provided we get out at last?” “Yes,” repeated Ned Land, “provided we do get out at last!” For a short time I walked from the saloon to the library. My companions were silent. I soon threw myself on an ottoman, and took a book, which my eyes overran mechanically. A quarter of an hour after, Conseil, approaching me, said, “Is what you are reading very interesting, sir?” “Very interesting!” I replied. “I should think so, sir. It is your own book you are reading.” “My book?” And indeed I was holding in my hand the work on the Great Submarine Depths. I did not even dream of it. I closed the book and returned to my walk. Ned and Conseil rose to go. “Stay here, my friends,” said I, detaining them. “Let us remain together until we are out of this block.” “As you please, sir,” Conseil replied. Some hours passed. I often looked at the instruments hanging from the partition. The manometer showed that the _Nautilus_ kept at a constant depth of more than three hundred yards; the compass still pointed to south; the log indicated a speed of twenty miles an hour, which, in such a cramped space, was very great. But Captain Nemo knew that he could not hasten too much, and that minutes were worth ages to us. At twenty-five minutes past eight a second shock took place, this time from behind. I turned pale. My companions were close by my side. I seized Conseil’s hand. Our looks expressed our feelings better than words. At this moment the Captain entered the saloon. I went up to him. “Our course is barred southward?” I asked. “Yes, sir. The iceberg has shifted and closed every outlet.” “We are blocked up then?” “Yes.” CHAPTER XVI WANT OF AIR Thus around the _Nautilus_, above and below, was an impenetrable wall of ice. We were prisoners to the iceberg. I watched the Captain. His countenance had resumed its habitual imperturbability.