About three in the morning
According to the daily custom on board the Nautilus , its air should have been renewed four hours ago ; but I did not suffer much , although Captain Nemo had not yet made any demand upon his reserve of oxygen . My sleep was painful that night ; hope and fear besieged me by turns : I rose several times . The groping of the Nautilus continued . About three in the morning , I noticed that the lower surface of the iceberg was only about fifty feet deep . One hundred and fifty feet now separated us from the surface of the waters . The iceberg was by degrees becoming an ice-field , the mountain a plain . My eyes never left the manometer .