New-York tribune., 1874-07-17
THE COMET AND Its CUANGES.

THE COMPUTATIONS EOR CURVATURE AfIhOAi-
MATEIY CORRECT AN INCREASE OF ONE
TWELFTH EACH DAY IN THE LENGTH OF THE TAIL
SINCE JULY 1-PRoBABIIITY THAT THE TAI.
WILL NOT DE VISIBLE WHEN NEAREST HE
EARTH - SATISFACTORY TELESCOPE oBsERvA-
TONS AT AN END.
To the Edttor Of The Tribune.
SIR: The clear sky Monday evening gave me
an opportunity many Of my predictions, and to
certain extent the theories upon which they were
founded. The position of the tail was wholly to the left
of the Omicron and Sigma OF Ursa Major and still
further to the lett last evening" so that consider 1t
demonstrated that the computations for curvature are
approximately correct In fact although the principal
part of the curvature directly u.s. aud therefore
mperceptbe, slight curvature was noticed on Monday
night by several observers the conyexy beng toward
tho right AS the comet Is moving toward the left this
Is an important fact for the curvature Is usually
seen like the bending backward OF a soldiers
plume. Last evening there seen curvature.
similar direction, but less In amount. The
length OF the tail on Monday evening was 200. This
is less than is shown upon the drawing published
In THE TRIBUNE of July founded upon the assumption
of straight tall aud somewhat less would have
been If had allowed for curvature The visible taI
was therefore I2O0O00O miles In length, increase
OF onetwenh each day since July l. corresponding
with that OF Donati's comet. Allowing q similar
increase for the next ten days the end OF the tail will
a. Last evening tho tail seen to a dis
tance OF $40 from the nucleus but it was
after the nucleus below the horizon II
the faint end OF the tail could be seen by
itself the general phenomena which predicted in THE
TRIBUNE of July from its approach would be visl
ble. But 1t has not developed the brightness which,
from the appearance OF the nucleus hoped; and
half OF the tail is By itself with so much difficulty
that after few days the ta will be excessively faint.
and 1t is probable that II will not be visible at all when
nearest us. The tail Of DonatPs comet had breadth
when brightest OF one fifth its length My own estimate
Of the breadth of the tail Of Coggas comet about the
18th inst led me adopt that the basis OF my
putations. Monday evenings observation showed Its
breadth TO be apparently little more than One-sxth
its length
The tail is still lying nearly right angles with the
line OF the yison the end of the tail being the
right angle, and nearer the head. The breadth,
or thickness, OF the tall nearly could measure
it, was 100000 miles The head or the comet is
lost IN the twilight and haze Of the horizon, having
last evening probably for the last time In this
hemisphere. The tail will change its aspect IL has
hitherto been straight and directed toward the
pointers" Of the Little Bear. have now the means OF
determining with considerable accuracy what its future
course and appearance VIII be-
OF the comet through the telescope viii no
longer be satisfactory Indeed persons generally
disappointed when they look through telescope any
comet which is visible to the naked eye. There two
reasons for tins. l. 1t is impossible 10 conceive
the image in the eye-peee at the distance
winch the comet itself appears to
be. Some people imagine the moon TO look the
of "a cart-wheel, others the dnner-pate or
Of penny but you could imagine IL 10 bo within six
inches OF your eye you would think IL looked about as
large the head OF PM On the other hand II you coud
imagine the head Of pin, held six inches from your
eye, to be distant as the mO0n 10 would look large
the II people who II through "A teIe-
could only imagine what they he al the dis
tance OF the stars the same view which now dlsaIp
points would equal II not surpass their expectations
O. When comets tail is 20' long, people wonder why
they do not the whole OF ii in telescope, and won
der why telescope cannot be made 10 show the whole
of it, just they the whole of 1t with the naked
distance of 60 feet, you get good OF the whole
house. Why should not "a telescope give You a
still better viewf Suppose that u magnifes times
that Is equivalent 10 bringing eye within one foot
OF the house III you wanted 10 a fly On the house
you would get good view Of him but you cannot sec
the whole house at that distance. II your telescope
manies TO times IL brings your eye within an inch OF
the house. so IN looking at object apparently large
TO the naked eye. Even tho lowest magnfying power
which be applied 10 large telescope Will bring Won
near II that you can see but extremely small part
of 1t. That portion Of comet which Is in the tel.
escOpe small that II by itself with the naked
eye II could hardly be distinguished from star In fhe
telescope you perceive the starry nucleus the coma
around IT, aud portion OF the tail stretching "A. far s
the field Of view viii permit Monday N ght there was
plainly visible another feature, the dark portion of the
tai immediately behind the nucleus II the nucleus
itself had intercepted the streams repeed by
show such envelopes In the coma of
DOnatPs comet such envelopes have boen distinctly
IN larger telescopes HENRY. NJ. PARKHuKsr
Nep- York, July lG, 1914