ts pierced, even then the rest would be
sufficient to hold her up at least for a day or two. These bulkheads
were constructed of heavy sheet steel, and extended from the very bottom
of the ship to a point well above the water-line. Necessarily there were
openings in them in order to make possible communication between the
different parts of the ship. These openings were the size of an ordinary
doorway and fitted with heavy steel doors--not hinged doors, but panels,
sliding closely in water-tight grooves on either side of the opening.
There were several ways of closing them; but once closed they offered a
resistance as solid as that of the bulkheads.

The method of opening and closing them was one of the many marvels of
modern engineering. The heavy steel doors were held up above the
openings by a series of friction clutches. Up on the bridge were
switches connected with powerful electro-magnets at the side of the
bulkhead openings. The operation of the switches caused each magnet to
draw down a heavy weight which instantly released the friction clutches,
so that the doors would slide down in a second or two into their places,
a gong ringing at the same time to warn anyone who might be passing
through to get out of the way. The clutches could also be released by
hand. But if for any reason the electric machinery should fail, there
was a provision made for closing them automatically in case the ship
should be flooded with water. Down in the double bottom of the ship were
arranged a series of floats connected with each set of bulkhead doors.
In the event of water reaching the compartment below the doors, it would
raise the floats, which, in their turn, would release the clutches and
drop the doors. These great bulkheads were no new experiment; they had
been tried and proved. When the White Star liner _Suevic_ was wrecked a
few years ago off the Lizard, it was decided to divide the part of her
which was floating from the part which was embedded in the rocks; and
she was cut in two just forward of the main collision bulkhead, and the
larger half of her towed into port with no other protection from the sea
than this vast steel wall which, nevertheless, easily kept her afloat.
And numberless other ships have owed their lives to the resisting power
of these steel bulkheads and the quick operation of the sliding doors.

As for the enormous weight that made for the _Titanic's_ stability, it
was, as I have said, contained chiefly