The Saint Paul globe. (St. Paul, Minn.) 1896-1905, 1901-01-13

Portland, Me. Instead of two boxes
there is one, with curved walls; and
tail with surfaces convex to the wind
taking the place of the lower box. 1t
is more powerful but less steady than
the Hargrave kite, and when used in a
tandem is usually sent aloft as the leader,
with the HargraVe kites below to give
stability In addition to their proportion
of lifting power.
The Great Blue Hill-its summit the
division between two towns, Canton and
Milton, on the dividing line Of which the
Observatory StandS-commandS a beauti-
full panorama of sea and plain, from Cape
Ann, 46 miles seward, to Grand Monad-
mock mountain, GO miles distant in the
west A kite flight from its summit IS
not only picturesque but an impressive
spectacle; but the course Of the expert
ments has many times been Interrupted
by the loss of kites and instruments, the
lines parting and the kites travelling on
the wind to every part of the great plain
below. Sometimes they are recovered by
the observers, but often they go SO great
distance that they can be followed only
through the telescope, and getting them
back depends upon their return by some
person who happens to find them when
they light. Not long ago one was carried
to bingham, twelve miles distant, at
rate of about a mile a minute, as was
determined by timing it through a glass.
Sometimes they come to the ground with
such violence that they are utterly
wrecked, instrument and ALL but usual
ly they light So gently that, If found
again, both kite and instrument are little
or not at all injured.
Steel piano wire is used as String" as
the best combination Of strength and
Hghtness. The windlass on which the
line is reeled, however, presented the
most difficult problem of all in the first
experiments. If one winds a bit of string
loosely about the finger number of
times, the pressure, as every one knows,
Will finally become intolerable. In the
same way the gathering coils of the steel
wire eXerted such force on the wooden
drum first used that it was literally
crushed out Of shape, and the heads Of
the bolts holding together the ends were
torn off by the tremendous pressure.
Finally a modificat ton of Lord Kelvin g
steam pow er windlass for deep sea sound
ing was devised by Mr. Ferguson, which
after many experiments has proved en-
! trely successful. Simply stated, the
| principle is a pulley over which the kite
| wire is conveyed to a storage drum, the
| coils on which are thus projected from
| the strain of the kite. The pull of the
| kite Is sufficient to unwind the drum
the power is used to draw the wire back
The length of wire paid out and the
| pressure eXerted-nccesSary to be known
| in order to calculate how many more
| kites, if any, can be safely added to
| the tandem-are automatically registered
| Kites are attached from time to time
as the wire tends TO sag more and more
and to approximate, near the windlass,
| a horizontal line. Each additional kite
| therefore after the first is released ex-
| erts its power partly in sustaining the
main line and taking off the strain from
| the leader, and partly only in elevating
%hn
called meteorograph, is combination
contrived to include, compactly and with
the least possible weight, the various
| self-recording instruments which are
| used to investigate the aerial conditions.
| Formerly 1t was suspended from the
| wire. but 1t was found that greater
| steadtness could be secured if 1t were at
| tached directly to it; and this is now
done The meteorograph includes an
| thermometer. for recording continuously
| on a cylinder of paper the velocity of the
| wind, the direction of which is deter
| mined by the observations taken every
minute from below, or at night Is more
roughly calculated by the shift of the
wire at the windlass; an alcohol Their
mometer, the contraction or expansion
OF which constantly changes the curative
of the tube itself, furnishing a second
continuous record; MICROSCOPE, consist,
ing of little bundle of human hair-one
|
purpose-which lengthens in moist and
shortens In dry air currents; and a self
recording barometer to ascertain atmos-
pheric pressure and hence the height in
clouds or at night. In clear weather and
in the daytime the height of the kite is
determined by observation of the angle
and from the length OF the wire, after
eliminating the error caused by the sag
g1ng. averaging about 2 per cent
Ordinarily kite fight at Blue Hill
lasts from six to eight hours, though it
may continue throughout a day or even
the night. For some time the flights
nave taken place monthly, on several
successive days. in order to study the
changing weather conditions at different
heights. The last was Dec. 80 The sta
tistics of kite flights at the observatory
are conveniently given in the small table
prepared by Mr.. Rotch, as follows:
Average
Height of Greatest
Flight In Height in
Numbar of feet a hove foot hove