The scientific kite-flyer will find much to tempt him into the field
of electricity; and will be able, not only to duplicate Dr. Franklin's
historic experiment of bringing down sparks from the heavens, but
may go far beyond this, taking advantage of the greater knowledge of
electricity at his disposal and the superior apparatus. In the summer
of 1885, Alexander McAdie, at the Blue Hills Observatory, got strong
sparks at the earth's surface from a wire connected with a kite
whose surface had been coated with tinfoil so as to form an electric
collector. He also, by the brightness and increased lengths of the
sparks obtained, proved that the electric force in the atmosphere is
very greatly increased with the approach of thunder clouds; and
also that this force increases steadily as the kites reach greater
altitude, and _vice versa_. Indeed Mr. Eddy and others who have
conducted similar experiments, have found the electric force so strong
at certain altitudes as to make the manipulation of the conducting
wire a source of considerable danger.
On October 8, 1892, Mr. Eddy made an important advance in electrical
experiments with kites, by using a collector quite separate from the
kites themselves, which were merely used in tandem to support the line
on which the collector was swung and raised to any desired altitude.
By this arrangement any accident that might befall one of the kites is
less likely to ruin the whole experiment.
Much experience with the kite-collector has convinced Mr. Eddy that
there is always in the air overhead, at all times of the year and
in all weathers, an abundant, practically a boundless, supply of
electricity. It has never yet happened to him to send his collector up
to even so low a height as four hundred feet without getting a spark
in his discharge-box at the earth. He has discovered, however, that
the greater the amount of moisture in the air, the greater is the
height to which he must send the collector before getting the first
spark. There is no doubt that large quantities of electricity might
be obtained by hoisting large collectors, supported by strong flying
tandems, to considerable altitudes, and drawing off the supply at
the earth by means of a system of transformers which would lower the
electricity from the dangerously high tension at which it discharges
down the wire, to a voltage that could be handled with safety. In his
experiments thus far, Mr. Eddy has discharged the copper wire leading
from his collector into a wooden box containing a pasteboard wheel
with darning-needle axle and tinfoil edges. The axle is grounded, and
the copper wire from the collector placed near the tinfoil periphery
of the wheel, so as to discharge its sparks through the intervening
distance, and by the shock cause the wheel to turn.