The Norfolk weekly news-journal., 1910-04-29

than seventy miles in diameter can be
seen through the big 36.inch Lick tel.
escope. If the transit can be observed
at Mount Hamilton, we shah know
more about the nature of the nucleus
after May Is than we do now.
Astronomers are also interested in
the possibility of ascertaining new
facts concerning the comets tail. So
little do they fear any harm from our
passing through the comets tail that
they are almost praying for the tail
to be long enough to reach the earth.
Two other comets have had tails so
long that the earth passed through
them. The first time this happened
was in 1919, the second time was in
1861. No harm was done, even the
astronomers did not know what had
happened until after it was over
They are on the watch this time, and
if we pass through the tail of Hal
ley's comet in May, the phenomena
will be subjected to the most careful
scientific observation.
Much unsCientifiC speculation as to
the danger from the comets tail has
been INDUCED in by a number of writ
ers. The worst offender in this re.
speCt is the French astronomer, Ca.
mile Flammarion. America has a
dozen astronomers more able than he,
yet none is gifted with so vivid an
imagination nor so facile a pen, nor
has any of them a scientific conscience
quite so elastic as Flammarion's.
FIammarons Bad Dream.
He has described at length the dan
gers from three sources: First, the
acetylene gas present in a comets
tail; second, the hydrogen, and third,
the cyanOgen. The danger from the
first two he pictures as due to the
possibility of explosion from contact
with the earth's atmosphere. Now it
is well known that the light of
comets tail is largely of electrical orr
gin and that electrical discharges
must be constantly taking place there
in. Were either hydrogen or acety.
lene present in large quantities in a
comets tail, the electrical discharges
would ignite it long before it could
reach the earth.
AS to the poisoning of the earth's
atmosphere by Cyanogen gas from the
tail, Flammarion again drew on his
imagination. 1t was not known until
a few weeks ago that cyanogen was
present in Halley's comet, and the
cyanogen present was in the comets
head, not in its tail. Even so, the
amount of cyanogen is too small to
produce the effect described. Profes.
Sor Frost says:
THE density of the tail Of comet
is about that of the vacuum in an
electric bulb, and there could not pos
sibly be enough poisonous gas in it
to hurt fly"
Some notion of the small weight
of the entire comet, tail and head
may be reached thus: The motion of
the comet is seriously altered by the
attraction of the planets, but the
course of the planets is not measur.
ably disturbed by the comet, About
May 2 Venus will considerably affect
the comets movement. Theoretical
ly, the comet in turn should alter
slightly the course of Venus. An
American astronomer will attempt to
measure the perturbation-as it is
called-of Venus. If he can do this
he can then determine the weight of
Halley's comet in tons, a fact not
now known. The weight Is known to
be small so small indeed that very
few astronomers believe the effect on
Venus can be measured Even the
man who has undertaken the measure.
ment is doubtful of success.
Will There be TaiI7
In nearly all of its former appear.
ances Halley's comet exhibited a tail
during the whole time it remainsd Wis.
ible. In 1885, however the tail sud.
denly disappeared when the comet
was nearest the sun. Later, when
the comet on its outward journey was
about $50 million miles from the sun
1t formed new tail very unlike the
first, If a similar event occurs this
time there will be no tail for us to
see on May IS. Whether the comet
will behave as it did in 1885 cannot
be told until after April 20, the day
on which the comet reaches perhelion. !
Up to date the comet has behaved in |
normal fashion. At this return II
was first discovered photographically !
by Wolf of Heidelberg September II,
1903.
The photograph showed the comet |
within a few minutes arc OF the posi-
ton predicted by Cowell and Cromme.
lin. II one knows that the diameter
Of the moon is about thirty minutes,
he can see that the comet missed its !