Evening star. [volume] (Washington, D.C.) 1854-1972, 1909-09-26
By Mary Proctor

are possible by ordinary spherical
balloons. while hundreds of miles may be trav-
ersed by dirigibles, and there is the prospect of
performing similar feats in aeroplanes the inn
portant problem of determining the astronom-
ical position of these craft becomes evident.
During the daytime, while the earth is in
view it is possible for an experienced aeronaut
to locate where he is by means of charts and at
night he can be guided more or less by the
lights of cities or towns. He also use the
friendly stars as his guides We can see in the
future classes formed for learning the Constella
| tons, especially the nine conspicuous "nauti-
cal" stars used by nautical men for determin-
ing their longitude at sea. Their names are
| Ariets, Aldebaran, Pollux, Regulus, Spica Vir-
ginis Antares, Affair, Fomalhaut, and Markab.
The true places of these stars for every day
in the year are given in the Nautical Almanac,
a valuable work published annually two or
three years in advance at the United States
Naval Observatory at Washington, for the
benefit of sea Captains engaged in long voyages.
Difficult to comprehend it may be- yet it is
a we'll known fact that the skilful navigator
who should be lost unknown sea, or in
the midst of the Pacific Ocean, can, by measur-
the distance between Arietis and the moon.
which often passes near it, determine at once
| not only the spot he is in, but his true CO rse
and distance to any known meridian or harbor
on earth.
THAT man." writes Sir John Herschel,
"by merely measuring the moons apparent dis
lance from a star, with little portable in
strument held in his hand, and applied to his
eye with unstable a footing as the deck of
ship, shall say positively within five miles
where he is on boundleSs ocean, cannot but
appear to persons ignorant of physical astron-
omy an approach to the miraculous. And yet,
the alternatives of life and death, wealth and
ruin. daily and hourly staked, with perfect
confidence, on these marvellous computations.
Captain Basil Hall relates that he had sailed
from San Bias on the west coast of Mexico, and
after voyage of eight thousand miles, occupy
| ing eighty-nine days, arrived off Rio Janeiro,
having in the interval passed through the
Pacific Ocean, rounded Cape Horn and crossed
the South Atlantic, without making any land
or seeing single sail on the voyage. Arrived
| within few days sail of Rio, he took set of
lunar observations. to ascertain his true po-
sition and the bearing of the harbor, and
shaped his course accordingly. AS result of
his calculations, he had to alter the course only
about a point in order to hit the entrance of
Rio. This was the first land he had seen for
three months, after crossing so many seas, and
being set backward and forward by innumer-
able currents and hard winds.
A Pilot of the Sky
FOR navigational purposes, it is just as i'm
portant to know exactly where one is when
travelling through the air, as it IS to sailor
when his ship is blowing the ocean. An able
book written for the benefit of aerial voyagers
has just been published by Professor Adolf
Marcuse, who in this way has assumed the
responsibility of being pilot of the sky.
He draws attention to the fact that aero
nauts should make themselves acquainted
with the ways and means for navigating the
air; for the subject will increase in importance
as the years 60 by. The instruments necessary
for the determination of longitude and latitude
are the level quadrant for the determination of
altitude, chronometer for recording Green
witch time, and a fluid compass for azimuth
observations. With no glimpse of the earth
beneath him. the only two facts he has in his
possession are his height from the ground and
the magnetic cardinal points.
In spherical balloon, this knowledge does
not inform him whether he is travelling in a
northerly southerly, easterly, or westerly direc-
ton. In dirigible he may head his craft in
the direction of any point of the compass;
but then his 1eeway will be unknown guam
tity, or he will soon find that his position in
relation to the earths surface is unknown.
Possibly better observations can be made.
however, from the platforms of dirigbles than
from the baskets of spherical balloons. In the
first place, the basket of balloon is seldom
steady, and is nearly always in state of slow
rotation. Again, the envelop above the OBJ
server cuts off a considerable portion of the
sky that would be available under or land
conditions; but, against this, he is in an ele-
waited position and his horizon is clearer. He
can form fair estimate of his position, whether
north. south east or west if he has knowl-
edge of the position in the sky of the constella-
thayr and OF DURING the of