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

computed position by perhaps one
tenth of the diameter of the moon.
This is a small error and such accu-
rate prediction OF the comets position
is really a remarkable triumph OF
mathematical astronomy.
September Is the comet was first
observed usually by Professor Burn
ham of the Yerkes observatory. At
that time the comet was about $50 mil
lion miles away from the sun. Professor
Barnard with the Yerkes telescope
studied the appearance of the comet
from September II to November IA.
The average measurements showed
the diameter of the comet to be at
that time 1900 miles. The bright
ness and size increased until on Feb
ruary 10, 1910, the diameter of the
head was $4,000 miles and the length
of the tail was five million miles.
Thus far the indications are for a
brilliant appearance.
Will be a Spectacle.
1t is true that the brightness Of a
comet usually diminishes with each
return. Halley's comet, however, dates
back at least 24O b. G. 1t has been
of such striking brilliance in compare.
lively recent times that it is not like.
ly to prove disappointing now. The
earth, comet and sun will be in rela-
lively better positions now than they
were in 1885. May the earth and
comet are forty-five million miles
aaprt, and as the sun rises two hours
after the comet, the latter should then
be at its best.
We must judge of former appear
ance of the tail of Halley's comet from
verbal descriptions and from draw
ings. 1t was only in 1890 that the
first really successful work was done
in photographing a comet. That work
was performed by Professor Barnard
at the Lick observatory. Photography
has revealed many details Of comet
structure wholly beyond the eye OF
the best observer. Photographs of
the same comet taken several hours
apart show that condensations and
other peculiarities move rapidly out.
ward. At first their velocity Is a few
miles second; later, far out in the
tail, the motion is often fifty miles a
second. This proves conclusively that
the particles in a comets tail on one
night are not those of the next night.
OF what tilmy lightness then. is the
material of the tail, since the rapid
motion of such bulky mass does not
soon cause the comet to utterly waste
away?
According to Prof. J. j. See, IL the
tail is long enough to reach the earth.
we may expect "a faint phosphores-
cent glow in the midnight skies of
Europe and the evening skies of the
eastern states" II any such effect Is
visible it can be seen here, providing
there are no heavy clouds. Since the
tail Will be curved we shall not enter
1t until some time after the transit
begins. At precisely what time one
should be on watch 1t Is impossible
now to say, perhaps from 7:40 o'clock
p m.
No Chance Of Collision.
On March % the comet passed be-
hind the sun. Some time must elapse
before it gets far enough from the sun
to be visible in the morning. 1t will
remain visible in the morning from
early April until May 1S. May 8 the
comet rises two hours before the sun.
About April 10 to Is the comet was
visible to the naked eye. From May
10 1t will again be visible in the eve
ming until about the latter part OF
June. Powerful telescopes may keep
track of it until 1911, but in June prac.
tically all of us will bid Halley's com.
ct farewell.