Five minutes after two o'clock
The chances of immediate and unforeseen danger , it is true , had been somewhat diminished by all these precautions . The risk , nevertheless , was fearful . The slightest accident or even carelessness might easily lead to the most disastrous consequence . Five minutes after two o'clock , the manhole being closed , the lamps lit , and everything pronounced all right , the signal for the descent was given , and the Nautilus immediately disappeared beneath the waters . A double anxiety now possessed all on board the _ Susquehanna _ : the prisoners in the Nautilus were in danger as well as the prisoners in the Projectile . Marston and his friends , however , were anything but disquieted on their own account , and , pencil in hand and noses flattened on the glass plates , they examined carefully everything they could see in the liquid masses through which they were descending . For the first five hundred feet , the descent was accomplished with little trouble .