Evening star. [volume] (Washington, D.C.) 1854-1972, 1881-07-03


NefRhed-Their Orbits-The Ncbu
lar Hypothesis.
In the .Lowell lectures of the late Profcsso
Benjamin tterce, OF Harvard College, recently
published In book form under the title O
"Ideality In the Physical Sciences.r is a chap
ter treating OF the nature OF comets, from
OF special interest at the present time when
every one is talking OF the new visitor which
week: '''S'
The fin al stage OF the nebular history Is the
coDgealed star, OF which planet, satellite comet
and meteor are special forms, and which is des-
Ineo 10 become again. at last, a chaotic msss
They are simultaneous In existence, and not
belonging TO successive stages OF the history.
starting from common origin. they have
passed through q process OF differentiation,
ana are lifted for different functions They
may ali be regarded as bolides; and they nh
the CELESTIAL spaces with every c)ncelyao, e
variety OF magnitude, motion aud PHYSICAL as
pect.
The comet, from the strangeness OF fts an
pearance in the Inaccessible armament, his
been the tmmemor1al wonder and dreai
mankind. Ii has been the beard or tail OF 50 ne
invfs BILE monster. It has been the sword OF
some angry god. lt has been the pea OF tae
turies, writing IN the book or rate the death
Kings. the fall of empires, the speedy coming OF
.amineS ana peStilenceS and destru ctfye wars.
tt has been light which has filled the souls O
Philosophers with darkness. Even the great
Aristotle, with his clear b lief in nature an
MS contempt for superstition, could propose n }
Theory which was not a tissue OF gratuitous
and incorsequent hypothesis. He thought the
comet, with lis regular motions, 20 be phe.
nomenon like the Hitting and uncertain fIRis
Nevertheless. even In comstology whera
modern progress has been SO essentially aided
oy the discovery Of gravitaion and the in
ancient thinkers achieved some memorao!e
results. Passing by The researches OF the
Pytnagoreans, we need only refer co the
writings or Seneca 10 the first century OF the
Christian era IL know" writes Seneca. mo
nooler research, nor more useful science
tnan That which undertakes the study OF the
stars; out 10 perfect this science is 1t not ex-
pedient TO examine whether the nature OF
comets differs from that or the other celestial
coolies? III we reflect on their motions on
tneir viclssitudes or rising and setting. on
tneir light and brtll!ancy, we shall De struck
with the analogy which we perceive between
them ana these other bodies. We need an
exact history or the comets which have
hitherto appeared; for it Is their rarity OF
appearance which prevents our deciding upon
the regularity or their movement. We are ig-
ncrant whether, describing fixed ORBITS they
| intervals OF lime" This was the prediction OF
thoughtful genius. Modern astronomy, profit
Ing by The ancient suggestion, has demon
Slrated this, like many other truths the
Dwarf OF today who stands on the shoulders OF
me giant OF yesterday can see create r distance
than the giant.
The perfect comet combines nucleus and
tralD. The beauty belongs TO the train which
Is GfSGb5l8ntial and temporary; While the mass
| en1 density reside 10 the almost invisible bus
permanent nucleus. The solid nucleus moves
oieBt TO the same law of attraction which
| governs the motions OF any one OF the planets:
whereas each particle or the train moves in IT'S
own hyperbolc orbit, IN consequence OF a re-
| pusion from the sun, often two or three times
| as great as the ordinary SOAR attraction These
psItcies OF the train are electrified bodies, end
| nave the same electricity as that OF the sun;
tHe parccteS which are most highly electrified
! advance to the front edge or tue tai, while
those which are The least electrified fall back to
the rear. Some OF tie particles are electrified
| just enough TO balance the solar graylIaUion:
! so thar, after separating from the nucleus they
| btct me neutral TO the suns action and ND re
uniformly In straight lines. but without ceas-
! mg 10 oe pain Oh the tau. the particles which
the sun, but move 1n hyperbolIc orbits-in the
| opposite branch OF the hyperDola, however 10
that In which the repealed particles move.
This theory, In an imperfect state, was rudely
applied by Bessel to the tail OF Halley's comet.
| In 1885. But the comet discovered by Donati Ia
Is5s oneIed as me an opportunity as can be
| the beauty OF that comet! All the world stopped
/ In the street, when tt became visible after tWl.
light, and wondered at tt with bate1 breath A
| lew centuries ago 1t would have caused uni.
| Versal dlsmay. and men would have paled az
| the frightful portent Bur the Christian OF to-
day beholds it as the Ioveliest messen ger O,
Divine wisdom A multitude OF observ atoms
| were made upon the train as well as the head
| Ia ali civilized countries, and the theory or the
| tTain was sustained In every detail The eie-
gance OF the shape strictly conformed TO the
| ideal cor Instruction OF the geometer.
| Ii the nucleus OF comet were taken away
| the train would continue 10 move OIL through
space. uneisturbed by the loss OF its head. sin.
| gular as this phenomenon may seem II has be IN
| actually observed. At midday on the 2Sth OF
! February, 1S43, groups OF people in many of the
towns OF New England, especially az Portla I'D,
| collected at the corners OF the streets gazing
up toward the sun. Protecting their eyes In
| the shadows OF the houses they saw a br.luan
| object few degrees from the sun. Such mar
veions spectacle had never before been beheld.
few days later wonderfully brilliant tail OF
| comet was seen skirting the horizon soon at
| fer sunset and reaching more than one.third OF
the wa5 round the sky. WHAT we now saw was
tail without head, as We had before seen head
| amcst destitute OF tall. But head aud tall wer5
members OF the same comet.
In about two hours the comet OF 1913 went
! round the sun, from one side to the other. What
coulc have become OF the tail, which was reach.
ing out about hundred millions OF miles from
| the sun as far as TO the earth's orbit? There
have been those who have actually adopted the
| Inc, edible may say the imposSible-hy p oths =
Sis that the tail rotated through this immens;
circuit, developing centrifugal force which al
the united powers OF the universe could moi
have sustained. But no. The comet pracu
cally left its tail behind it and began to grow
Lew tail as ii receded from the sun. There
were thus two tails, nearly side by side, stretch
l iAs liOu OppuSile SUES Oh Inc sun IN nearly In.
same direction. The new tail began at tn,
head Of the comet; whereas the old deserted
| tail began without any head at some distance
| from the nucleus, and EXTENDED further from
the sun than the new tall
| The nucleus OF the comet is surrounded by 8
| mist, which Is called the coma, or hair; the
| name comet signifytng hairy star. the
| height OF the coma above the nucleus depend:
| On the mass CT the nucleus, and gives the
I, measure OF its weight; or, more exactly. the
least limit OF weight Which will suffice to 10 ain.
tain such height OF atmosphere. The nucleus
Is usually so closely surrounded by the dense
| times the mist RISES uncoyers the nucleus, and
leaves 1t with sharp stellar aspect. Toe lie ast
diameter determined at such tim IS may be lar ger
| than the actual one, but cannot be smaller.
| From the combination OF mass and diameter, the
! density Of the nucleus can be computed. In the
| case OF Donatts comet, the diameter OF the
| nucleus was perhaps not more than hundred
| miles, while the height OF the atmosphere eX-
! tended TO eighteen thousand miles. You may
| be surprised TO learn that the corresponding
density of The nucleus was at least equal 20
that OF iron. What an unexpected contrast is
| here presented to the prevalent notions con.
cerning the sun and the cometsl The solid sun
| Ia reduced by science to the state OF gas, while
the substance OF the ETHEREAL comet Is solid
| and heavy metal
In its approach to the sun the surface of the
| nucleus is rapidly heated; Ii is melted and vap.
| OIized and subjected TO frequent explosions
| the vapor rises In its atmosphere with well
| defined upper surface, which Is known to OBJ
servers as an envelope. Various envelopes, In.
| Guiding each other, are often observed.
The identification OF the c0metary mist Is
| analogous to that OF our own thuuder.ciond.
ANY portion OF the coma which has roooluod