ortance, the
tubular boiler and the compound engine being introduced. These have
developed into the cylindrical, multitubular boiler and the triple
expansion engine, in which a greater percentage of the power of the
steam is utilized and four or five times the work obtained from coal
over that of the old system. The side-wheel was continued in use in the
older ships until this period, but after 1870 it disappeared.

It has been said that the life of iron ships, barring disasters at sea,
is unlimited, that they cannot wear out. This statement has not been
tested, but the fact remains that the older passenger ships have gone
out of service and that steel has now taken the place of iron, as
lighter and more durable.

Something should also be said here of the steam turbine engine, recently
introduced in some of the greatest liners, and of proven value in
several particulars, an important one of these being the doing away with
the vibration, an inseparable accompaniment of the old style engines.
The Olympic and Titanic engines were a combination of the turbine and
reciprocating types. In regard to the driving power, one of the recent
introductions is that of the multiple propeller. The twin screw was
first applied in the City of New York, of the Inman line, and enabled
her to make in 1890 an average speed of a little over six days from New
York to Queenstown. The best record up to October, 1891, was that of the
Teutonic, of five days, sixteen hours, and thirty minutes. Triple-screw
propellers have since then been introduced in some of the greater ships,
and the record speed has been cut down to the four days and ten hours of
the Lusitania in 1908 and the four days, six hours and forty-one minutes
of the Mauretania in 1910.

The Titanic was not built especially for speed, but in every other way
she was the master product of the shipbuilders' art. Progress through
the centuries has been steady, and perhaps the twentieth century will
prepare a vessel that will be unsinkable as well as magnificent. Until
the fatal accident the Titanic and Olympic were considered the last
words on ship-building; but much may still remain to be spoken.

CHAPTER XXVII. SAFETY AND LIFE-SAVING DEVICES

WIRELESS TELEGRAPHY--WATER-TIGHT BULKHEADS--SUBMARINE
SIGNALS--LIFE-BOATS AND RAFTS--NIXON'S PONTOON--LIFE-PRESERVERS AND
BUOYS--ROCKETS

THE fact that there are any survivors of the Titanic left to tell the
story of the terrible catastrophe