ver, which Edison hopes to improve still further. In addition
to the two great inventions of the phonograph and incandescent lamp,
which we have dwelt upon here, many more stand to his credit. In fact,
he has been the greatest client the patent office ever had, nearly one
thousand patents having been issued in his name. At the age of
sixty-three, he shows no sign of falling off in either mental or
physical energy, and no doubt more than one invention has yet to come
from Llewellyn Park before he quits his great laboratory forever.

No one can ever guess at the future of electrical invention. The recent
marvelous development of the wireless telegraph, by which the impalpable
ether is harnessed to man's service, is an indication of the wonders
which may be expected in the future. It was our own Joseph Henry who, in
1842, discovered the electric wave--the "induction" upon which wireless
telegraphy depends. He discovered that when he produced an electric
spark an inch long in a room at the top of his house, electrical action
was instantly set up in another wire circuit in the cellar. After some
study, he saw and announced that the electric spark started some sort of
action in the ether, which passed through floors and ceilings and all
other intervening objects, and caused induction in the wires in the
cellar. But wireless telegraphy was made a commercial possibility not by
any great scientist, but by a young Italian named Marconi. Already
experiments with wireless telephony are going forward, and another half
century may see all the labor of the world performed by this wonderful
and mysterious force which we call electricity.

* * * * *

From earliest times, man has longed to navigate the air. He has watched
with envy the free flight of birds, and has tried to imitate it, usually
with disastrous results. The balloon, of course, enabled him to rise in
the air, but once there, he was at the mercy of every wind. More
recently, balloons fitted with motors and steering gear have been
devised, which are to some extent dirigible; but the real problem has
been to fly as birds do without any such artificial aid as balloons
provide.

Experiments to solve this problem were begun several years ago by
Professor S. P. Langley, of the Smithsonian Institution, under
government supervision, and pointed the way to other investigators. He
proved, theoretically, that air-flight was possible, provided sufficien