It was even possible that at a certain depth the walls of the Nautilus might be crushed in like an eggshell, and the whole machine made as flat as two leaves of paper pasted together.
Perfectly conscious of the nature of the tremendous risk they were about to run, Marston, Morgan, and Murphy quietly bade their friends a short farewell and were lowered into the manhole.

The Nautilus having room enough for four, Belfast had been expected to be of the party but, feeling a little sea sick, the Professor backed out at the last moment, to the great joy of Mr.Watkins, the famous reporter of the _N.Y.
Herald_, who was immediately allowed to take his place.
Every provision against immediate danger had been made.

By means of preconcerted signals, the inmates could have themselves drawn up, let down, or carried laterally in whatever direction they pleased.

By barometers and other instruments they could readily ascertain the pressure of the air and water, also how far they had descended and at what rate they were moving.

The Captain, from his bridge, carefully superintended every detail of the operation.