the air, speeds will be reached that are impossible on
land or sea. As civilisation extends--this is of course a
truism--there grows with it a need for speedier travel; and we have
seen land and sea transit striving to meet this demand. But both have
reached, or are rapidly reaching, a limit of speed--a limit imposed by
the need to carry their passengers and goods on a remunerative basis.
On the sea, by burning excessive quantities of coal, it is possible to
add a few knots to the speed of a great liner. But then the problem
becomes one of profit and loss; while with trains--so nearly under
existing conditions have they reached a limit of speed--that a
difficulty is experienced, even on long runs, and under favourable
circumstances, in saving a minute here and there. It is not of course
to be assumed, when the spur of a greater necessity comes, that land
and sea transit will fail altogether to increase their existing
speeds. There is the mono-rail system of land traction, electrically
propelled, which has yet to be tested in a practical way; while on the
sea, perhaps, under pressure of competition, and with an increasing
demand for greater speeds, it may be possible to adapt with advantage,
even on large craft, some principle of the hydroplane.

But by way of the air, granted even a speeding-up on land and sea,
should go the high-speed traffic of the future. By a greater
efficiency in lifting surfaces and by reductions in the resistance a
craft offers to its own passage through the air; by the provision of
systems which will permit a pilot to reduce plane-area when his
machine has gained altitude and he desires a maximum speed; by the
equipping of craft with motors developing thousands of horse-power for
a very low weight--by such means, and by a general improvement in
design, it should be possible, eventually, to attain flying speeds of
150, 200, and even 250 miles an hour. From London to New York by air
liner, in less than twenty hours; such, for instance, should be an
attainment of the future.

It seems probable, in the development of the commercial aeroplane, we
shall have machines for touring and for pleasure flights--craft not of
large size but in which efforts are made to obtain a greater
reliability and comfort. Then it appears likely that aircraft may
reach a practical use as carriers of mails and of light express goods;
first of all in localities, and under conditions, which favour
specially an aerial trans