There were also four windows reserved for projecting a searchlight into the outer darkness. The inner side of the bell corresponded in curvature with the outer, so that the adventurers had no flat flooring on any side to stand upon, but this caused little inconvenience, since the walls were abundantly provided with hand and foot holds, enabling the inmates to maintain themselves in almost any position they could wish.
After a while they passed below the range of daylight, and then they turned on the searchlight. The storage batteries which supplied energy for the searchlight and the propellers served also to operate an apparatus for clearing the air of carbonic acid, and De Beauxchamps had carefully calculated the limit of time that the air could be kept in a breathable condition. This did not exceed forty-eight hours--but as we have seen they had no intention of remaining under water longer than twenty hours at the utmost.
When the bell entered the night of the sea-depths they passed into an apparently lifeless zone, where the searchlight, projected now on one side and now on another, revealed no more of the living forms which they had encountered above, but showed only a desert of solid transparent water. Here, amid this awful isolation, they experienced for the first time a feeling of dread and terror. An overpowering sense of loneliness and helplessness came over them, and only the stout heart of Cosmo Versál, and his reassuring words, kept the others from making the signal which would have caused the bell to be hastily drawn back to the Ark.
"M. De Beauxchamps," said Cosmo, breaking the impressive silence, "to what depth have we now descended?"
"A thousand fathoms," replied the Frenchman, consulting his automatic register.
"Good! We have been only thirty minutes in reaching this depth. We shall sink more slowly as we get deeper, but I think we can count upon reaching the bottom in not more than four hours from the moment of our departure. It will require only two hours for them to draw us back again with the powerful engines of the Ark, especially when aided by our propellers. This will leave fourteen hours for our explorations, if we stay out the limit that we have fixed."
