I had never thought of it before, but I now resolved to be upon my guard.

Indeed, I thought that this halt would mark the termination of our walk; but I was mistaken, for, instead of returning to the Nautilus, Captain Nemo continued his bold excursion.

The ground was still on the incline, its declivity seemed to be getting greater, and to be leading us to greater depths.

It must have been about three o'clock when we reached a narrow valley, between high perpendicular walls, situated about seventy-five fathoms deep.

Thanks to the perfection of our apparatus, we were forty-five fathoms below the limit which nature seems to have imposed on man as to his submarine excursions.
I say seventy-five fathoms, though I had no instrument by which to judge the distance.