ines that any
really intelligent start has been made upon its solution. The men
who really gave practical effect to the vague theories which others
set up--in aircraft the Wrights, Santos-Dumont, and Count Zeppelin;
in submarines Lake and Holland--are either still living, or have
died so recently that their memory is still fresh in the minds of
all.

In this book the author has sketched swiftly the slow stages by
which in each of these fields of activity success has been attained.
He has collated from the immense mass of records of the activities
of both submarines and aircraft enough interesting data to show the
degree of perfection and practicability to which both have been
brought. And he has outlined so far as possible from existing
conditions the possibilities of future usefulness in fields other
than those of war of these new devices.

The most serious difficulty encountered in dealing with the present
state and future development of aircraft is the rapidity with which
that development proceeds. Before a Congressional Committee last
January an official testified that grave delay in the manufacture of
airplanes for the army had been caused by the fact that types
adopted a scant three months before had become obsolete, because of
experience on the European battlefields, and later inventions before
the first machines could be completed. There may be exaggeration in
the statement but it is largely true. Neither the machines nor the
tactics employed at the beginning of the war were in use in its
fourth year. The course of this evolution, with its reasons, are
described in this volume.

Opportunities for the peaceful use of airplanes are beginning to
suggest themselves daily. After the main body of this book was in
type the Postmaster-General of the United States called for bids for
an aerial mail service between New York and Washington--an act urged
upon the Government in this volume. That service contemplates a
swift carriage of first-class mail at an enhanced price--the
tentative schedule being three hours, and a postage fee of
twenty-five cents an ounce. There can be no doubt of the success of
the service, its value to the public, and its possibilities of
revenue to the post-office. Once its usefulness is established it
will be extended to routes of similar length, such as New York and
Boston, New York and Buffalo, or New York and Pittsburgh. The mind
suggests no limit to the extension of aerial service, both p