^

/

COSMOS:

A SKETCH

A PHYSICAL DESCRIPTION OF THE UNIVERSE.

ALEXANDER VON HUMBOLDT, f ^^l" ^^^ '

TRANSLATED FROM THE GERMAN,

BY E. C. OTTE AND B. H. PAUL, Ph. D., F.C.S.

Naturse vero rerum vis atque majestas in omnibus mc mentis fide caret, si quis modo
partes ejus ac non totam complectatur animo. — Plin., Hist, Nat., lib. yii., c. 1.

VOL. IV

NEW YORK:

HARPER & BROTHERS, PUBLISHERS,
329 & 331 PEARL STREET,

FRANKLIN SQUARE.

186G.

v:4

SUMMARY.

Vols. III. and IV.

GENERAL SUMMARY OF THE CONTENTS.

Special Results of Observation in the Domain of Cosmical Phenomena.^
Introduction.
Retrospect of the subject. Nature considered under a two-fold as
pect : in the pure objectivity of external phenomena, and in their inner
reflection in the mind. A significant classification of phenomena leads
of itself to their casual connection. Completeness in the enumeration
of details is uot intended, at least in the representation of the reflected
picture of nature under the influence of the creative power of imagina-
tidn. Besides an actual or external world, thei-e is produced an ideal
or an inner world ; filled with physical symbolic myths, difierent ac-
cording to race and climate, bequeathed for centuries to subsequent
generations, and clouding a clear view of nature. Fundamental im-
perfectibility of the knowledge of cosraical phenomena. The discovery
oi empirical laws, the insight into the causal connection of phenomena,
description of the universe, and theory of the universe. How, by means
of existing things, a small part of their genetic history is laid open. Dif-
ferent phases of the theory of the universe, attempts to comprehend the
order of nature. Most ancient fundamental conception of the Hellenic
mind : physiologic phantasies of the Ionian school, germs of the scien-
tific contemplation of nature. Double direction of the explanation of
natural phenomena, by the assumption of material principles (elements),
and by processes of rarefaction and condensation. Centrifugal revolu-
tion. Theories of vortices. The Pythagoreans ; philosophy uf meas-
ure and harmony, commencement of a mathematical treatment of phys-
ical phenomena. The order and government of the universe according
to the physical works of Aristotle. The communication of motion con-
sidered as the cause of all phenomena ; the tendency of the Aristotelean
school but little directed to the opinion of the heterogeneity of matter.
This species of natural philosophy bequeathed in fundamental ideas
and form to the Middle Ages. Roger Bacon, the Mirror of Nature of
Vincentz of Beauvais, Lt^er Cosmographicus of Albertus Magnus, Imago
Mundi of the Cardinal Pierre d'Ailly. Progress through Giordano Bru
no and Telesio. Clearness in the conceptions oi gravitation ^s mass at
traction, by Copernicus. First attempt at a mathematical application
of the doctrine of gravitation, by Kepler. The work on the Cosmos by-
Descartes ( Traits du Monde) nobly undertaken, did not appear until
long after his death, and only in fragments ; the Cosmotheoros of Huy-
gens, unworthy of the great name. Newton, and his work Philosophite
Naturalis Principia Mathematica. Endeavor toward a knowledge of
the universe as a Whole. Is the problem solvable of tracing back to
one principle all physical knowledge, from the law of gravitation to tho

IV GENERAL SUMMARY

formative activities in the organic and animated bodies ? VVhic has
been discovered does not by a long way exhaust the discoverable.
The iraperfectibility of empiric investigation makes the problem of ex-
plaining the changeability of matter from the forces of matter an indef'
inite one.

A. Uranological Portion of the Physical Description of the Uni
verse— p. 26-28.
Two sections, one of which comprises the heaven of fixed
stars; the other, our solar system — p. 26.

a. AsTROSNOsY ; Heaven of the fixed stars.

I. Tho realms of space, and conjectures regarding that which
appears to occupy the space intervening between the heaven-
ly bodies — p. 29-41.

II. Natural and telescopic vision — p. 49-72 ; Scintillation of the
stars— 73-83 ; Velocity of light— p. 84-88 ; Results of photom
etry — p. 89-102. Order of the fixed stars according to their
luminous intensity.

III. Number, distribution, and color of the fixed stars — p. 103-
139 ; Stellar clusters {stellar swarms) — p. 140-143 ; The Milky
pyay interspersed with a few nebulous spots — p. 144-151.

IV. New stars, and stars that have vanished — p. 151-160; Va-
riable stars, whose recurring periods have been determined —
p. 160-177; Variations in the intensity ot the light of stars
whose periodicity is as yet uninvestigated — p. 177-182.

V. Proper motion of the fixed stars — p. 182-185; Problematical
existence of dark cosmical bodies — p. 185-187; Parallax —
measured distances of some of the fixed stars — p. 187-194;
Doubts as to the assumption of a central body for the whole
sidereal heavens — p. 195-199.

VI. Multiple, or double stars — Their number and reciprocal dis
tances. Period of revolution of two stars round a common
center of gravity — p. 199-213.

VII. Nebulous spots. Are these only remote and very denso
clusters of stars? The two Magellanic Clouds, in which
crowded nebulous spots are interspersed with numerous stel-
lar swarms. The so-called black spots (Coal-sacks) of tha
Southern hemisphere — p. 13-53

B. Solar Region — p. 53-134.

I. The Sun considered as the central body — p. 59-88.

II. The Planets— p. 88-134.

A. General consideration of the planetary world — p. 88-134.

a. Principal Planets— p. 89-131.

b. Secondary Planets— p. 131-134.

B. Special enumeration of the planets and their moons as parta
of the solar system — p. 134.

Sun— p. 135-137.

OF CONTENTS. V

Mercury— p. 137, 138.
Venus— p. 138-141.
Earth— p. 141.

Moon of the Earth— p. 141-159.
Mars— p. 159, 160.
The small plane ts^p. 161 ; Flora, Victoria Vesta, Iris,

Metis, Hebe, Parthenope, Astraea, Egeria, Irene, Euno

mia, Juno, Ceres, Pallas, Hygeia ;
Jupiter— p. 165-168.

Satellites of Jupiter— p. 169, 170.
Saturn— p. 170-174.

Satellites of Saturn— p. 174, 175.
Uranus— p. 175, 176.

Satellites of Uranus— p. 176, 177.
Neptune— p. 177-180.

Satellites of Neptune— p. 180, 181.

III. The comets— p. 181-201.

IV. Ring of the zodiacal light— p. 201-204.

V. Shooting stars, fire-balls, meteoric stones — p. 204-226
Conclusion— p. 227-230.

Corrections and additions to vol. iii., p. xi., xii.
Index, p. 231-234.

Special analysis of the individual sections of the astronomical part of
the Cosmos.

a. AsTROGNOsy.

I. Cosmical space: Only isolated portions are measurable — p. 30.
Resisting medium, celestial atmosphere, cosmical ether — p. 31, note I,
and p. 33, note *. Radiation of heat by the stars — p. 35, note %. Tern
perature of space — p. 37-39. Limited transparency? — p. 48. Regu-
larly decreased period of revolution of the Comet of Encke — p. 39.
Limitation of the atmosphere ? — p. 40.

II. Natural and telescopic vision : Very different sources of light pre-
sent similar relations of refraction — p. 44. Different velocities of the
light of ignited solid bodies and that of frictional electricity — p. 45.
Position of the Wollastonian lines — p. 45. Influence of tubes — p. 43.
Optical means of distinguishing between direct and reflected light, and
the importance of the means to physical astronomy — p. 45. Limits of
ordinary vision — p. 48. Imperfection of the organ of vision ; false di-
ameter of the stars — p. 52. Influence of the form of an object upon the
minimum visual angle in experiments as to visibility ; necessity of a dif-
ference of luminous intensity of -^^ ; visibility of distant objects, posi-
tively and negatively — p. 48-56. On the visibility of stars by day wiih
the naked eye from wells or upon lofty mountains — p. 56. A feeble
light by the side of a stronger — p. 49, note *. Extending ray and star
tails — p. 52. On the visibility of the satellites of Jupiter by the naked
eye — p. 50. Undulation of the stars — p. 59. Commencement of tel-
escopic vision ; application to measurement — p. 60-62. Refractors of
great length — p. 63. Reflectors — p. 63. Day observations ; how strong
magnifying powers facilitate the findin^j of the stars by day — p. 66

VI GENERAL SUMMARY

Explanation of the sparkling and scintillation of the stars— p. 73. Ve-
locity of light — p. 79-88. Order of magnitude of the stars ; photomet-
ric relations and methods of measurement — p. 89-98. Cyanoraeter—
p. 97. Photometric order of the fixed stai's — p. 99-102.

III. Niimber, distribution, and color of the fixed stars; Stellar clusters
*nd the Milky Way : States of the sky which hinder or favor the de-
tection of stars — p. 103. Number of the stars ; how many may be seen
with the naked eye — p. 104. How many have been inserted in stellar
charts with determinations of position — p. 108. Conjectural estimation
of the number of stars which can be visible in the entire heavens with
our present powers of penetrating space — p. 105. Contemplative as-
trognosy of uncivilized people — p. 109. The Grecian sphere — p. 118.
The crystal sky — p. 123. False diameter of the fixed stars in telescopes
—p. 129. Smallest objects in the heavens which have yet been seea
— p. 130. Difierence of colors in the stars, and the changes which have
taken place in the colors since antiquity — p. 130. Sirius {Sothis) — p.
132. The four royal stars — p. 136. Gradual acquaintance with the
Southern heaven — p. 137. Distribution of the fixed stars, laws of rela-
tive accumulation, gauging — p. 138. Clusters and swarms of stars — p
140. The Milky Way— p. 143.

IV. Stars that have newly appeared and disappeared ; variable stars
and changes in the intensity of their light whose periodicity has not been
investigated: New stars in the last 2000 years — p. 151. Periodically
changeable stars: Historical particulars — p. 151. Color — p. 165. Num-
ber— p. 164. Order recognizable in apparent irregularity ; great dif-
ferences of brightness ; periods within periods — p. 167. Argelander's
table of the variable stars with commentary — p. 172. Variable stars
in undetermined periods {rj Arg0s, Capella, stars of the Ursae Major and
Minor) — p. 181. Reference to the possible changes of temperature on
the Earth's surface — p. 181.

V. Proper motion of the fixed stars, dark cosmieal bodies, parallax ;
doubts as to the assumption of a central body for the entire heaven of fixed
$tars: Change of the physiognomy of the sky — p. 182. Amount of the
proper motion — p. 184. Evidence in favor of the probable existence
of non-luminous bodies — p. 186. Parallax and measurement of the dis-
tance of some fixed stars from our solar system — p. 187. The aberra-
tion of light may be applied to the determination of the parallax of
double stars — p. 194. The discovery of the proper motion of the fixed
stars has led to the knowledge of the motion of our own solar system,
and even to the knowledge of the direction of this motion — p. 184 and
194. Problem of the situation of the center of gravity of the whole
heaven of fixed stars and central suns? — p. 196, and note t, P- 198, and
p. 199, note *.

VI. Double stars, period of revolution of two suns round a common
center of gravity : Optical and physical double stars — p. 200; number
— p. 201. Uniformity and difference of color ; the latter not the conse-
quence of optical deception, of the contrast of complementary colors—
p. 207, note *, p. 206, and p. 209, note *. Change of brightness— p. 209.
Multiple combinations (three to six fold) — p. 209. Calculated orbitual
elemeuts, half major axis and period of rotation in years — p. 213.

VII. NchulcCf Magellanic Clouds, and Coal-sacks : Resolvability of tho
nebulte; questions as to whether they are all remote and crowded

OP CONTENTS. Vll

clusters of stars ? — p. 13 (note $, p. 22, and p. 23, note *). Historical
particulars — p. 14 (note *, p. 28). Number of nebulae whose positions
are determined — p. 26 (notes * and +). Distribution of nebuUe and
clusters of stars in the northern and southern hemispheres — p. 27 ;
spaces poor in uebul®, and the maxima of accumulation — p. 28, and
note *. Configuration of nebulae : spherical, annular, spiral, and plan-
etary nebulae — p. 31. Nebula (cluster of stars) in Andromeda — p. 16-
31 (note t, p. 31); nebula in Orion's sword — p. 17-39 (notes *, p. 18,
t, p. 23, $, p. 36, *, p. 38, $, p. 39, and *, p. 40) ; large nebula round rj
ArgOs — p. 40 ; nebula in Sagittarius — p. 41 ; nebula in Cygnus and Vul-
pes ; spiral nebula in the northern Canes Venatici — p. 41. The two Ma-
gellanic Clouds — p. 43 (note *, p. 48). Black spots or Coal-sacks — p. 51.

/3. The Solar region; planets and their moons, ring of the zodiacal
light, and swarms of meteor-asteroids — p. 53-88.

I. The Sun considered as a central body : Numerical data — p. 59 (note
*, p. 59", and p. 62, note *). Physical constitution of the surface; en-
velopes of the dark solar globe ; Sun-spots, faculjE — p. 61. Diminutions
in the daylight recorded by the annalists ; problematic obscurations—
p. 73, and note. Intensity of the light in the center and at the edge
of the Sun's disk — p. 79, and note; also p. 81, note *. Correlation of
light, heat, electricity, and magnetism; Seebeck, Ampere, Faraday—
p. 84. Influence of the Sun's spots upon the temperature of our at-
mosphere— p. 80.

II. The Planets :

A. General comparative considerations :

a. Principal Planets :

1. Number and epoch of discovery — p. 89. Names, planetary
days (week), and planetary hours — p. 92, and note t; also
p. 94, note *.

2. Classification of the planets in two groups — ^p. 102.

3. Absolute and apparent magnitudes; configuration — p. 105.

4. Order of the planets and their distances from the Sun ; the
so-called law of Titius ; old belief that the cosmical bodies
which we now see were not all visible from the beginning ;
Proselenes — p. 106, note *, p. 108, and p. 120, note *.

5. Masses of the planets — p. 118.

6. Densities of the planets — p. 119.

7. Periods of sidereal revolution and axial rotation — p. 120.

8. Inclination of the planetary orbits and axes of rotation ;
their influence upon climate — p. 121, and note %, p. 126.

b. Secondary planets — p. 127

B. Special consideration; enumeration of the individual planets and
their relation to the Sun as central body.

The Sun— p. 135-137.

Mercury— p. 137, 138.

Venus; spots — p. 138-141.

The Earth; numerical relations — p. 141.

VIU GENEIAL SUMMARY

The Moon of the Earth ; produces light and heat ; ash-gray
or earth-light in the Moon ; spots ; nature of the Moon's
surface, mountains and plains, measured elevations ; pre
vailing type of circular configuration ; craters of elevation
without continuing eruptive phenomena;. old traces of
the reaction of the interior upon the exterior (the sur-
face) ; absence of Sun and Earth tides, as well of current!
as transportive forces, on account of the want of a liquid
element ; probable geognostic consequences of these re-
lations—p. 141-159.

Mars; ellipticity; appearances of surface altered by change

of the seasons — p. 159, 160.
The small planets— ^. 161, 162.
Jupit.er : periods of rotation ; spots and belts — p. 165-168.

Satellites of Jupiter — p. 169, 170.
Saturn : bands, rings, eccentric position — p. 170-174.

Satellites of Saturn — p. 174, 175.
Uranus— p. 175, 176.

Satellites of Uranus — p. 176, 177.
Neptune: discovery and elements — p. 177-181.

Satellites of Neptune— p. 181-201.

III. The Comets : with the smallest masses occupying immense
spaces ; configuration ; periods of revolution ; separation ; elements of
the interior comets — p. 181-201.

IV. The ring of the zodiacal light : Historical particulars. Intermit-
tence two-fold ; hourly and annual ? Distinction to be made between
the cosmical luminous process which belongs to the zodiacal light it-
self and the variable transparency of our atmosphere. Importance of a
long series of corresponding observations under the tropics at different
elevations above the sea from 9 to 12,000 feet. Reflection like that at
sunset. Comparison in the same night with certain parts of the Milky
Way. Question as to whether the zodiacal light coincides with the
plane of the Sun's equator — p. 201-204.

V. Shooting stars, fire-halls, meteoric stones : Oldest positively determ
med fall of aerolites, and the influence which the fall of ^Egos Potamos
and its cosmical explanations exercised upon the theories of the uni-
verse of Anaxagoras and Diogenes of Apollonia (of the later Ionic
school) ; force of revolution which counteracts the pc wer of the fall
(centrifugal force and gravitation) — p. 204-209, note \, p. 207, and p.
209, note *. Geometric and physical relations of meteors in sporadic
and periodic falls ; divergence of the shooting stars ; definite points of
departure; mean number of sporadic and periodic shooting stars in an
hour in different months — p. 209-214, note X, p. 210, and p. 211, note *.
Besides the stream of St. Laurentius, and the now more feeble Novem-
ber phenomenon, four or five other falls of shooting stars have been
discovered which very probably occur periodically during the yeai' —
p. 214, note *, p. 215, and p. 216, note *. Height and velocity of the
meteors — p. 217. Physical relations, color and tails, process of com-
bination, magnitudes ; instances of the firing of buildings — p. 217. Me-
teoric stones ; falls of aerolites when the sky is clear, or after the for-
mation of a small dark meteoric cloud — p. 220, note t, and p. 221, note *

OF CONTENTS. IX

Problematical abundance of the shooting stars between midnight and
the early hours of morning (hourly variations) — p. 222. Chemical re-
lations of the aerolites ; analogies with the constituents of telluric rock
—p. 223-226.

Conclusion : Retrospect -^f the undertaking. Limitation consistent
with the nature of a phv^sicav «iescription of the universe. Representa-
tion of the actual relations of cosmical bodies to each other. Kepler's
laws of planetary motion. Simplicity of the uranological problem in
opposition to the telluric, on account of the exclusion of material hete-
rogeneity and change. Elements of the stability of the planetary gy».
tern— p. 227-230.

A2

HUMBOLDT'S CORRECTIONS AND ADDITIONS

TO VOL. III.

Page 34, line 22.

Since the printing of that part of the Cosmos where a doubt is ex-
pressed as to whether it has been " shown with certainty that the posi-
tions of the Sun influence the terrestrial- magnetism," the new and ex-
cellent investigations of Faraday have proved the reality of such an in-
fluence. Long series of magnetic observations in opposite hemispheres
(c. g., Toronto in Canada, and Hobart Town in Van Diemen's Land),
show that the terrestrial magnetism is subject to an annual variation
which depends upon the relative position of the Sun and Earth.

Page 59, line 2.

The remarkable phenomenon of the undulation of stars has very re
cently been observed at Trier by very trustworthy witnesses, in Sirius,
between 7 and 8 o'clock, while near the horizon. See the letter of
Herrn Flesch, in Jahn's Unterhaltungen fur Freunde der Astronomic .

Page 132, line 21, note *.

The wish which I strongly expressed that the historical epoch in
which the disappearance of the red color of Sirius falls should be more
positively determined, has been partially fulfilled by the laudable in-
dustry of Dr. WSpcke, a young scholar, who combines an excellent ac-
quaintance with Oriental languages with distinguished mathematical
knowledge. The translator and commentator of the important Algebra
of Omar Alkhayyami, writing to me from Paris in August, 1851, says,
" I have examined the four manuscripts in this place of the Uranography
of Abdurrahman Al-Sufi, in reference to your suggestion contained in the
astronomical volume of the Cosmos, and found that a Bootis, a Tauri,
a Scorpii, and a Orionis, are all expressly called red; Sirius, on the
contrary, is not." Moreover, the passages refemng to it are uniformly
as follows in all the four manuscripts : " The first among its (Great
Dog) stars is the large, brilliant one in his mouth, which is represented
on the Astrolabium, and is called Al-jemaanijah.^' Is it not probable
from this investigation, and from what I quoted from Alfragani, that the
epoch of the change of color falls between the time of Ptolemaeus and
the Arabs.

Page 194, line 21.

In the condensed statement of the method by which the parallax of
the double stars is found by means of the velocity of light, it should ba

XII

HUMBOLDT S CORRECTIONS AND ADDITIONS.

eaid, The time which elapses between the moment in which the plane
tary secondary star is nearest to the Earth, and that in which it is most
distant from it, is always longer when the star passes from the point of
grsatest proximity to that of greatest elongation, than in the convers^,
when it returns from the point of greatest elongation to that of greatest
proximity.

Page 213, line 1.

In the French translation of the astronomical volume of the Cosmos^
which to my gi-eat gratification, M. H. Faye has again undertaken, this
learned astronomer has much enriched the section upon double stars
I had myself neglected to make use of the important treatises of M.
Yvon Villarceau, which were read at the Institute in the course of the
year 1849. (See Connaissance des Temps pour Van 1832, p. 3-128.)
I quote here from the table by M. Faye, of the orbital elements of eight
double stars, the first four stars, which he considers to be the most cer-
tainly determined :

Elements of the

Orbits of Double '

Stars.

1
Name and Magnitude.

Semi-
major
axis.

Eccen-
tricity.

Period of
revolution
in Years.

Name of the Calcu-
lator.

^ Ursae Majoris,
(4th and 5th Mag.)

3"-857
3"-278
2"-295
2"-439

0-4164
0-3777
0-4037
0-4315

58-262
60-720
61-300
61-576

Savary 1830.

J.Herschel..l849.

Madler 1847.

Y. Villarceau 1849.

p Ophiuchi,
(4th and 6th Mag.)

4"-328
4"-9C0
4"-800

0-4300
0-4445
0-4781

73-862
92-338
92-000

Encke...... 1832.

Y. Villarceau 1849.
Madler 1819.

C Herculis,
(3d and 6-5th Mag.)

l"-208
l"-254

0-4320
0-4482

30-220
36-357

Madler 1847.

Y. Villarceau 1847.

71 Coronae,
(5-5thand6thMag.)

0"-902
1"-012
1"-111

0-2891
0-4744
0-4695

42-500
42-501
66-257

Madler 1847.

Y. Villarceau 1847.
The same, 2d result.

The problem of the period of revolution of tj Coronae admits of two
solutions: of 42-5 and 66-3 years; but the late observations of Otto
Struve give the preference to the second. M. Yvon Villarceau finds
the semi-major axis, eccentricity, and periods of revolution in years

yVirginis 3"-446 0-8699 153-787

^ Cancri 0"-934 0-3662 58-590

a Centauri 12"-128 07187 78-486

The occultation oi one fixed s^ar by another, as was presented by f Her*
culis, I have called apparent (p. 287). M. Faye shows that it is a con-
sequence of the spui'ious diameter of the stars (^Cosmos, vol. iii., p. 66
and 170) seen in our telescopes. The parallax c f 1830, Groombridge,
which I gave (p. 27) as 0"-226, is found by Schlttter and Wichmann,
0"-182, and by Otto Stmve, 0"-034.

COSMOS

VII.

NEBULOUS SPOTS. ARE THESE ONLY REMOTE AND VEf.Y

DENSE CLUSTERS OF STARS ? THE TWO MAGELLANIC

CLOUDS, IN WHICH CROWDED NEBULOUS SPOTS ARE IN-
TERSPERSED WITH NUMEROUS STELLAR SWARMS. THE SO-
CALLED COAL-SACKS OF THE SOUTHERN HEMISPHERE.

Among the visible cosmical bodies occupying the regions
of space, besides those which shine with stellar light (wheth-
er self-luminous, or illumined like planets, stars isolated or
in multiple groups, and revolving round a common center of
gravity), there are also masses which present a faint and
guilder nebidous light. ^ These bodies, which appear at one
time as sharply defined, disk-formed, luminous clouds, at
another as irregularly and variously-shaped masses, widely
diffused over large spaces, seem to the naked eye, at first
sight, to be wholly different from those cosmical bodies of
which we treated fully in the last four sections of the Astrog-
nosy. In the same way that there is an inclination to infer
from the observed and as yet unexplained motion of the vis-
ible cosmical bodies,! the existence of others hitherto invisi-
ble, so the knowledge gained as to the resolvability of a con-
siderable number of nebulous spots has recently led to con-
clusions regarding the non-existence of all nebulae, and, in-
deed, of all cosmical vapor generally. But whether these
well-defined nebulous spots be a self-luminous vapory mat-
ter, or remote, closely-throngc^.d globular clusters of stars, they
must ever remain objects of vast importance in the knowl-
edge of the structure of the universe and of the contents of
space.

The number whose positions have been determined by
right ascension and declination exceeds 3600. Some of the

* Cosmos, vol. i., p. 85-89, 91, and 142; vol. ii., p. 328; vol. iii., p
37-41, 140, 154, and 162. r Cosmos, vol. iii.. p. 785, 186

14, COSMOS,

more irregularly diffused measure eight lunar diameters, Ac
cording to William Herschel's earlier estimate, made in 1811,
these nebulous spots cover at least 2 7 o^^ P^^^ of the whole
visible firmament. As seen through colossal telescopes, the
contemplation of these nebulous masses leads us into regions
.from w^hence a ray of light, according to an assumption not
A^holly improbable, requires millions of years to reach our
»5arth, to distances for whose measurement the dimensions
<the distances of Sirius, or the calculated distances of the bi-
nary stars in Cygnus and the Centaur) of our nearest stra-
tum of fixed stars scarcely suffice. If these nebulous spots
be elliptical or spherical sidereal groups, their very conglom-
eration calls to mind the idea of a mysterious play of gravi-
tative forces by which they are governed. If they be vapory
massfta, having one or more nebulous nuclei, the various de-
crees of their condensation suggest the possibility of a process
of gradual star-formation from inglobate matter. No other
cosroical structure — no other subject of this branch of astron-
omy more contemplative than measuring — is, in like degree,
adapted to excite the imagination, not merely as a symbolic
ima^e of the infinitude of space, but because the investiga-
tion of the different conditions of existing things, and of their
presumed connection of sequences, promises to afford us an in-
sight into the laws oi genetic development.^

The historical development of our knowledge of nebulous
bodies teaches us that here, as in the progress of almost every
other branch of physical science, the same opposite opinions,
which still have numerous adherents, were maintained long
since, although on weaker grounds. Since the general use
of the telescope, we find that Galileo, Dominique Cassini,
and the acute John Michell regarded all nebulse as remote
clusters of stars ; while Halley, Derham, Lacaille, Kant, and
Lambert maintained the existence of starless nebulous mass-
es. Kepler (like Tycho Brahe before the invention of the
telescope) was a zealous adherent of the theory of star-forma-
tion from cosmical vapor — from condensed conglobate celes-
tial nebulous matter. He believed " codi materiam tenuis-
simam (the vapor which shines with a mild stellar light in
the Milky Way) in unum glohum condensatam, stellam ef-
jingere^ and grounded his opinion, not on the process of con-
densation operating in defined roundish nebuloUs spots (for
those were unknown to him), but on the sudden a,ppearance
of new stars on the margin of the galaxy.
♦ Cosmos, vol. i., p. 84.

NEBULiE. 15

If we take into account the number of objects discovered,
the accuracy of their telescopic investigation, and the gener
alization of views, the history of nebulous spots, like that of
double stars, may be said to begin with WilUam Herschel.
Until his time there were not more than 120 unresolved neb-
ulae in both hemispheres whose positions were determined,
including even the results of Messier' s meritorious labors ;
and in 1786 the great astronomer of Slough published the
first catalogue, containing 1000. I have already fully point
ed out, in an earlier portion of this work, that the bodies
named nebulous stars {yecpeXoEidelg) by Hipparchus and
Geminus in the Catasterisms of the pseudo-Eratosthenes
and in the Almagest of Ptolemy, are stellar clusters which
appear to the naked eye with a nebulous luster. =^ This des-
ignation, Latinized nebulosce, passed in the middle of the
thirteenth century into the Alphonsine Tables, probably
through the preponderating influence of the Jewish astrono-
mer, Isaac Aben Sid Hassan, chief Rabbi of the wealthy
synagogue at Toledo. The Alphonsine Tables were first
printed in 1483 at Venice.

The first notice of a remarkable aggregation of innumer-
able true nebulous spots, blended with stellar swarms, dating
from the middle of the tenth century, is in the writings of an
Arabian astronomer, Abdurrahman Sufi, a native of the Per-
sian Irak. The White Ox, which he saw shining with a
milky light far below Canopus, was undoubtedly the larger
Magellanic Cloud, which, witli an apparent breadth of nearly
twelve lunar diameters, extends over a portion of the heav-
ens measuring forty-two square degrees. No mention is made
by European travelers of this phenomenon until the begin-
ning of the sixteenth century, although, 200 years earlier, the
Normans had advanced as far along the western coasts of Af-
rica as Sierra Leone (8° 30' N. Lat.).t It might have been
expected that a nebulous mass of such vast extent, which

* Cosmos, vol. iii., p. 91, and note, and 140, and note.

t Prior to the expedition of Alvaro Becerra. The Portuguese ad'
vanced beyond the equator in 1471. — See Humboldt's Examen Critiqve
de VHist. de la Giographie du Nouveau Continent, torn, i., p. 290-292
In Eastern Africa the Lagides had availed themselves, for purposes of
commerce, of the passage along the Indian Ocean, and, favored by the
southwest monsoon (Hippalus), had passed from Ocelis in the Straits
of Bab-el-Mandeb to the Malabar emporium of Muziris and to Ceylon
(Cosmos, vol. ii., p. 172, and note). Although the Magellanic Clouds
must have been seen in all these voyages, we meet with no record of
their appearance.

16 ^ COSMOS.

was distinctly visible to the naked eye, would have attracted
attention sooner.*

The first isolated nebula which was observed and recog-
nized by the telescope as wholly starless and as an object of
special nature was the nebula near v Andromedae, which, like
that last mentioned, is also visible to the naked eye. Simon
Marius [Mayer], of Gunzenhausen, in Franconia, originally
a musician, and subsequently court mathematician of one of
the Margraves of Colmbach, the same person who saw the sat-
ellites of Jupiter nine days earlier than Galileo, f has also the
merit of having given the first, and, indeed, a very accurate
description of a nebula. In the preface to his Mundus Jovi-
alis,t he relates that, "on the 15th of December, 1612, hp
observed a fixed object difiering in appearance from any he
had ever seen. It was situated near the 3d and northern
star of Andromeda's girdle ; seen with the naked eye, it ap-
peared to him to be a mere cloud, and by the aid of the tel-
escope he could not discover any signs of a stellar nature, a

* Sir John Herscbel, Observations at the Cape, $ 132.

t Op. cit., p. 357, 509 (note 43). Galileo, who endeavored to refer
the difference in the days of discovery (29th of December, 1609, and
7th of Januaiy, 1610) to a difference in the calendar, maintained that he
had seen the satellites of Jupiter one day earlier than Marius, and even
allowed himself to be so far carried away by his indignation at " the
falsehood of the heretical impostor of Gutzenhausen" (bugia del im-
postore eretico GjintzenhusaTio^') as to declare his belief" that very prob-
ably the heretic, Simon Marius, never observed the Medicean planets"
('' che molto probabilmente il eretico, Simon Mario, non ha ossei-vato gi-
ammai i Pianeti Medicei"). — See Operedi Galileo Galilei, Padova, 1744,
tom. ii., p. 235-237 ; and Nelli, Vita e Commercio letterario di Galilei,
1793, vol. i., p. 240-246. The " heretic" had nevertheless expressed
himself very pacifically and modestly in reference to the extent of merit
due to his discovery. " I simply affirm," says Simon Marius, in the
preface to the Mundus Jovialis, ''haec sidera (Brandenburgica) a nullo
mortalium mihi ulla ratione commonstrata, sed propria indagine sub ip-
sissimum fere tempus, vel aliquanto citius quo Galilffius in Italia ea pri-
mum vidit, a me in Germania adinventa et observata fuisse. Merito
7gitur Galilseo tribuitur et manet laus primae inventionis horum side-
rum apud Italos. An autem inter meos Germanos quispiara ante me
ea invenerit et viderit, hactenus intelligere non potui." " I simply af-
firm that I was led to the discovery of these stars, not by any reason-
ings of others, but by the result of my own investigations, and that they
were observed by me in Germany about the very same time, or a lit-
tle sooner, than Galileo first saw them in Italy. To Galileo, among the
Italians, is therefore due the merit of having first discovered these stars.
But whether, among my own countrymen in Germany, any person be«
:.^re me has discovered and seen them, I have not as yet been able to
ascertain."

t Mundu$ Jovialis, anno 1609, delectus ope pertpicilli Belgici. (Nori
^ers^x, 1614.)

NEBULiE. 17

circumstance which distinguished it from the nebulous stars
in Cancer, and from other nebulous clusters. All that could
oe recognized was a whitish glimmering appearance, bright-
er in the center, and fainter toward the margins. With a di-
ameter of one fourth of a degree, the whole resembled a light
seen from a great distance through half-transparent horn
plates {similis fere splendor apparet, si a longinquo cande-
la ar dens per cornu pellucidum de noctu cernatur).''^ Si-
mon Marius hazards a conjecture whether this singular star
be not of recent formation, but will not give a decided opin-
ion, although it strikes him as singular that Tycho Brahe,
who had enumerated all the stars in the girdle of Andromeda,
should have said nothing of this nehulosa. The Mundus Jo-
malis, which first appeared in 1614, indicates, therefore, as I
have already observed elsewhere, =^ the difference between a
nebulous spot unresolvable by the telescopic powers of that
age, and a cluster of stars,t to which the mutual proximity of
its numerous small stars, not visible to the naked eye, imparts
a nebulous luster. Notwithstanding the great improvements
made in optical instruments, the nebula in Andromeda was
considered for nearly two centuries and a half — as at its dis-
covery— to be wholly devoid of stars, until two years since, the
transatlantic observer, George Bond, of Cambridge, in Massa-
chusetts, discovered 1500 small stars within the limits of the
nebula. I have not hesitated to class it among the stellar
clusters, although the nucleus has not hitherto been resolved. $
It is probably only to be ascribed to some singular acci-
dent that Galileo, who, when the Sidereus Nuntius appear-
ed in 1610, had already made frequent observations of the con-
stellation of Orion, should have subsequently mentioned, in
his Saggiatore, no other nebulsB in the firmament but those
which his own weak optical instruments had resolved into
stellar clusters, although he might long before have learned,
through the Mundus Jovialis, of the discovery of the starless
nebula in Andromeda. When he speaks of the nehulose del
Orione e del Prescpe, he understands by the expression merely
"aggregations (coacervazioni) oi innumerable small stars." §
He successively delineates, under the deceptive designations of
nebuloscB capitis, cingidi, et ensis Orionis, clusters of stars,

• Cosmos, vol. ii., p. 320.

t Germ,, Sternhaufen ; French, amas d'etoiles.
X Cosmos, vol. iii., p. 142.

$ Galilei nolo che le Nehulose di Orione nulV altro erano che rnucchi e
coac«rvazioni cC innumerabili Sfelle.'^ — Nelli, Vita di Galilei, i., p. 208

18 COSMOS.

ill whicli he exults in having discovered 400 hitherto unob-
served stars in a space of one or two degrees. He never
makes any reference to unresolved nebulous matter. Yet
how could the great nebulous spot in the sword of Orion have
failed to rivet his attention ? But, although this great ob-
server probably never saw the irregular nebula in Orion, or
the roundish disk of a so-called irresolvable nebula, still his
general views=^ on the intrinsic nature of nebulous spots were
very similar to those to which the greater number of our
astronomers of the present day incline. Like Galileo, Hevel
of Dantzig, who, although a distinguished observer, was not
much inclined to rely upon telescopic observation for aid in
cataloguing the stars,! made no mention in his writings of
the great nebula in Orion. His star catalogue, moreover, did
not contain upward of 1 6 nebulous spots, of which the posi-
tions were accurately determined.

At length, in the year 1656, Huygens discovered the neb-

* '' In primo integram Ononis constellationem pingere decreveram ;
vero, ab ingenti stellarum copia, temporis vero'inopia obrutus, aggres-
sionem hauc in aliam occasionem distuli. Cum non tantum in Galaxia
Lacteus ille candor veluti albicantis nubis spectetur, sed complures con-
similis coloris areolce sparsimper cethera subfulgeant, si in illarum, quam-
libet specillura convertas, stellarum conslipatarum ccetum offendes.
Amplius (quod magis mirabile) stellse, ab astronomis singulis in lianc
usque diem nebulosce appellatae, stellarum mirum in modum consitarura
gregessunt : ex quarum radiorum commixtione, dum uuaquaque ob ex-
iiitatem, sen maximam a nobis remotionem, oculorum aciem fugit, cau.
dor ille consurgit, qui densior pars cceli, stellarum aut solis radios re-
torquere valens, hucusque creditus est." — Opere di Galileo Galilei, Pa-
dova, 1744, torn, ii., p. 14, 15. " At first I had resolved to describe
the whole constellation of Orion ; but the multitude of the stars and the
want of leisure compelled me to postpone the undertaking till another
occasion. Since not only in the Milky Way may be observed that brill-
iancy as of a whitish cloud, but several areoles of a similar color are
scattered through the firmament ; if you direct the glass to any one of
them, you will meet with a host of clustered stars. Moreover, the stars
(still stranger to say) which, by every astronomer, are to this day call-
ed nebulous, are clusters of stars lying close together in a wonderful
manner, from the combination of whose rays (while they can not be
separately distinguished by the eye on account of their minuteness, or
their very great distance from us) arises that whiteness, which, from its
capacity of reflecting the rays of the stars or of the sun, has been hith-
erto supposed to belong to a denser part of the atmosphere." — Side-
reus Nuntius, p. 13, 15 (Nos. 19-21), and 35 (No. 56).

t Compare Cosmos, vol. iii., p. 41. I also remember a vignette at the
close of the introduction to Hevel's Firmamenttim Sobescianum, 1687,
in which three genii are represented, two of whom are making ob
Bervations with Hevel's sextants. The third genius is carrying a tele-
scope which he appears to be worshiping, while those observing ex
claim, PrcEstat nudo oculo !

NEBULiE. 19

ula in the sword of Orion, which is so important fiom its
extent and form, and has become so famous from the num-
ber and celebrity of its subsequent investigators.* Huygens
was the means of inducing Picard (in 1676) to devote himself
diligently to the investigation of this nebulous body. Ed-
mund Halley, during his sojourn in St. Helena in 1677, was
the first to determine any of the nebulous spots belonging to
portions of the southern heavens not visible in Europe, al-
though his observations embraced only a very small number.
The lively interest taken by the great Cassini (Jean Dom-
inique) in all branches of contemplative astronomy, led him,
toward the close of the seventeenth century, to a more care-
ful exploration of the nebulae in Andromeda and Orion. He
thought he could detect alterations in the latter since Huy
gens's observations, and that he " had recognized stars in the
former which could not be seen with telescopes of low pow-
ers." There are reasons for regarding the assertion of an
alteration of figure as a delusion ; not entirely so the exist-
ence of stars in the nebula in Andromeda since the remark-
able observations of George Bond. Cassini, moreover, con-
jectured, on theoretical grounds, the possibility of such a res-
olution of the nebula ; since, in direct opposition to Halley
and Derham, he considered all nebulous spots to be very re-
mote stellar swarms. f The faint mild effulgence in Androm-
eda was indeed, according to his opinion, analogous to the
zodiacal light, which he also conjectured to be composed of a
crowd of densely, thronged, small planetary bodies. $ Lacaille's
residence in the southern hemisphere (at the Cape of Good
Hope, and in the Isle of France and Bourbon, between 1750-
1752), so considerably increased the number of known nebu-
lous spots, that Struve has justly remarked, that from the ob-
servations of this traveler more was known, at that time, of

* Huygens, Systema Saturnhim, in his Opera varia, Lugd. Bat., 1724,
torn, ii., p. .52.3 and 593.

t "Dans les deux n^buleuses d'Andromede et d'Orion, j'ai vu des
^toiles qu'on n'aper^oit pas avec des lunettes communes. Nous ne sa-
vons pas si Ton ne pourrait pas avoir des lunettes assez grandes pour
que toute la nebulosite pAt se resoudre en de plus petites etoiles, comme
il arrive k celle du Cancer et du Sagittaire." " I have seen st£ii-s in the
nebula of Andromeda and Orion," says Dom'nique Cassini, " which can
not be recognized by ordinary insti'uments. We are ignorant whethei
telescopes may not be constructed of sufficient power to resolve the
whole nebula into smaller stars, as has been done in .he case of th^
nobnlae in Cancer and Sagittarius." — Delambre, Hist, de VAttr. Mo
Mrne, com. ii., p. 700 and 744.

t Cosmos, vol. i,, p. 141, note.

20 COSMC.S.

the nebt.lous bodies of the southern hemisphere, than of those
which were visible in Europe. Lacaille, moreover, success-
fully attempted to divide nebulae into classes according to their
apparent configuration ; he also was the first to undertake,
though with little result, the difficult task of analyzing the
heterogeneous contents of the Magellanic Clouds {nubecula
major et rmnor). If we subtract the 14 nebulae, which, even
with instruments of low powers, were perfectly resolved into
true clusters of stars, from the other 42 isolated nebulous spots
which Lacaille observed in the southern heavens, there re-
main only 28, while Sir John Herschel, by the aid of more
powerful instruments, as well as greater skill and superior
powers of observation, succeeded in discovering under the
same zone, and also independently of clusters, as many as
1500 nebulous spots.

Devoid of personal knowledge or experience of the subject,
and originally ignorant of each other's attempts, although
both had very similar aims in view,* Lambert (from 1749)
and Kant (from 1755) speculated with admirable sagacity on
nebulous spots, detached galaxies, and sporadic nebulous and
stellar islands scattered singly through the realms of space.
Both inclined to the nebular hypothesis, and to the idea of a
perpetual development in the regions of space, and even of a
star-formation from cosmical vapor. The great traveler, Le
Gentil (1760—1769), long before his voyages, and his unsuc-
cessful observations of the transit of Venus, had imparted ani-
mation to the study of nebulae by his observations on the con-
stellations of Andromeda, Sagittarius, and Orion. He made
use of an object-glass 'of Campani's, 37 feet in focal length,
which was in the possession of the Paris Observatory. In
entire opposition to the views of Halley, Lacaille, Kant, and
Lambert; the intellectual John Michell declared (as Galileo
and Dominique Cassini had done) that all nebulae were stel-
lar clusters, aggregations of very minute or very remote tel-
escopic stars, whose existence would undoubtedly be some
day revealed by means of more perfect optical instruments.!

* On the commnuity and difTerenco of ideas between Kant and
Lambert, as well as in reference to the period of their publications,
Bee Struve, Etudes d^Astr. Stellaire, p. 11, 13, 21, notes 7, 15, and 33.
Kant's Allgemeine Natur-Geschichte und Theorie des Himmels appear-
ed anonymously, and was dedicated to Frederick the Great, 175.5.
Lambert's Photometria, as already remarked, appeared in 1760; and
his Sammlung kosmologischer Briefe uher die Einrichtung des Welt-
baucM, in 17G1.

t " Those nebulae," says John Michell in 17G7 (Pkilos Transact., vol

NEBULiE. 21

Compared with the slow progress we have hitherto depicted,
the knowledge of nebulous spots received a rich accession of
facts by the persevering industry of Messier. His catalogue
of 1771 contains, after deducting the older nebulae discovered
by Lacaille and Mechain, 66 w'hich had not been previously
observed. He had the merit of doubling the number of the
nebulous spots hitherto enumerated in both hemispheres, al-
though his labors were carried on in the ill-supplied Observa-
toire de la Marine (Hotel de Clugny).=*

To these feeble beginnings succeeded the brilliant epochs
of the discoveries of William Herschel and his son. The for-
mer began, as early as 1779, a regular exploration of the nu-
merous nebulous masses with which the heavens are studded.
These observations were made with a seven-feet reflector.
His colossal forty-feet telescope was completed in 1787; and
in the three catalogues! which he published in 1786, 1789,
and 1802, he indicated the positions of 2500 nebulae and
cluste-^ of stars. Until 1785, or almost as late as 1791,
this great observer appears to have been more disposed, like
Michell, Cassini, and the present Lord Rosse, to regard the
nebulous spots which he was unable to resolve as very remote
clusters of stars ; but a prolonged consideration of the subject
between 1799 and 1802 led him to adopt the nebular theory,
as Halley and Lacaille had done, and even, with Tycho Brahe
and Kepler, the theory of a star-formation through the grad-
ual condensation of cosmical vapor. The two hypotheses,
however, are not necessarily connected. $ The nebulous and
stellar clusters observed by Sir WiUiam Herschel were sub-
jected by his son to a renewed investigation from 1825 to
1833 ; he also enriched the older catalogues with 500 new
objects, and published in the Philosophical Tra7isactions for
1833 (p. 365-481) a complete catalogue of 2307 nebulae and
clusters of stars. This great work contains all that had been
discovered in the heavens of Central Europe ; and in the five
succeeding years (from 1834-1838) we find Sir John Her-

Ivii., for 1767, p. 251), " in which we can discover either none, or only
a few stars, even with the assistance of the best telescopes, are probably
systems that are still more distant than the rest."

* Messier, in the Mim. de VAcadimie des Sciences, 1771, p. 435, and
in the Connaissance des Temps pour 1783 et 1784. The whole catalogue
contains 103 objects.

t Philos. Transact., vols. lxxvi.,lxxix., and xcii.

X " The nebular hypothesis, as it has been termed, and the theory of
sidereal aggregation, stand, in fact, quite independent of each other. "-
Sir John Herschel, Oitiiwes of Astronomy, $ 872, p. 599.

22 COSMOS.

«

schel engaged at the Cape of Good Hope in exploring the
whole of the visible firmament with a colossal twenty-feet
reflector, and adding 1708 determinations of position to his
previous catalogue of 2307 nebulae and clusters of stars !*
Only one third of the southern nebulae and clusters of stars
in Dunlop's catalogue (containing 629 nebulous bodies, ob-
served from 1825-1827, at Paramatta, with a nine-feet re-
flector, having a nine-inch speculumf) were inserted in Sir
John Herschel's work.

A third great epoch in our knowledge of these mysterious
cosmical bodies commenced with the construction of the mar-
velous fifty-three feet telescope^ of the Earl of Rosse, at Par-
sonstown. All that had ever been advanced on either side
of the question, during the long fluctuation of opinions in the
different stages of the development of cosmical contem.plation,
was now made the -subject of keen discussion in the contest
regardmg the nebular hypothesis and its asserted untenabil-
ity. It appears, from all the notices I have been able to col-
lect from the works of distinguished astronomers long accus-
tomed to the observation of nebulous spots, that out of a large
number of nebulae indiscriminately taken from among all the
classes contained in the catalogue of 1833, and regarded as
irresolvable, almost all (Dr. Robinson, the Director of the Ar-
magh Observatory, enumerates more than 40 such) have been
perfectly resolved. § Sir John Herschel maintains the same

* The numbers which I here give include the objects enumerated
from Nos. 1 to 2307 in the European, Northern Catalogue of 1833, and
those from Nos. 2308 to 4015 in the African, Southern Catalogue. — Ob-
servations at the Cape, p. 51-128.

t James Duulop, in the Philos. Transact, for 1828, p. 113-151.

t Compare Cosmos, vol. iii., p. 65, and note.

$ See ^« Account of the Earl of Rosse's great Telescope, -p. 14-17,
which gives a list of the nebulae resolved by Dr. Robinson and Sir James
South in March, 1845. " Dr. Robinson could not leave this part of his
subject without calling attention to the fact that no real nebula seemed
to exist among so many of these objects chosen without any bias : all
appeared to be clusters of stars, and every additional one which shall be
resolved will be an additional argument against the "existence of any
such." — Schumacher, Astr. Nachr., No. 536. In the Notice sur les
grands Telescopes de Lord Oxmantown, aujourd^hui Earl of Rosse {Bib-
Itothdque Universelle de Geneve, tom. Ivii., 1845, p. 342-357), we find the
following passage: " Sir James South rappelle que jamais il n'a vu de
representations sidexdales aussi magnifiques que celles que lui offrait
I'instrument de Parsonstown; qu'une bonne partie des nebuleuses se
presentaient comme des amas ou groupes d'etoiles, tandis que quelques
autres, k ses yeux du moins, n'ofFraient aucune apparence de resolution
en ^toiles." "Sir James South remarks that he never beheld more mag-
nificent representations of the stars than tliose he saw in the Parsoni*.

NEBULA. 23

«riew, as well in his opening address before the British Asso-
ciation at Cambridge in 1845, as in the Outlines ofAstroU'
omyy 1849, where he expresses himself as follows : " The
magnificent reflecting telescope constructed by Lord E-osse,
six feet in aperture, has resolved or rendered resolvable mul-
titudes of nebulas which had resisted all inferior powers. . . .
Although, therefore, nebulae do exist which, even in this pow-
erful telescope, appear as nebulae, without any sign of resolu-
tion, it may very reasonably be doubted whether there be
really any essential physical distinction between nebulae and
clusters of stars*."*

The constructor of the powerful optical apparatus at Par-
sonstown, who always discriminates between the result of act-
ual observation and the promises of a knowledge to which
we hope to attain, expresses himself with much caution re-
garding the nebula in Orion, in a letter to Professor Nichol,
of Glasgow,! dated Parsonstown, 19th of March, 1846 : "In
accordance with my promise of communicating to you the
result qf our examination of Orion, I think I may safely say,
that there can be little, if any, doubt of the resolvability of
the nebula. Since you left us, there was not a single night
when, in absence of the moon, the air was fine enough to ad-
mit of our using more than half the magnifying power the
speculum bears ; still we could plainly see that all about the

town telescope, and that a great number of nebulae appeared like clus-
ters or groups of stars, while others, at least to his sight, presented no
appearance of resolution."

* See Outlines, p. 597, 598; also the Report of the Fifteenth Meeting
of the British Association held at Cambridge in June, 1845, p. xxxvi. :
" By far the major part," says Sir John Herschel, *' probably, at least,
nine tenths of the nebulous contents of the heavens, consist of nebulae
of spherical or elliptical forms, presenting every variety of elongation
and central condensation. Of these a great number have been resolved
into distant stars (by the reflector of the Earl of Rosse), and a vast mul-
titude more have been found to present that mottled appearance which
renders it almost a matter of certainty that an increase of optical pow-
er would show them to be similarly composed. A not unnatural or un-
fair induction would therefore seem to be, that those which resist such
resolution do so only in consequence of the smallness and closeness of
the stars of which they consist; that, in short, they are only optically,
and not physically nebulous. Although nebula? do exist which, even
in this powerful telescope (of Lord Rosse), appear as nebula?, without
any sign of resolution, it may very reasonably be doubted whether there
be really any essentiil physical distinction between nebula) and clus-
ters of 8tar§."

t Dr. Nichol, Professor of Astronomy at Glasgow, published the let-
ter above referred to in his Thoughts of some Important Points relating
to the Syttem of the World, 1846, p. 55.

24 COSMOS.

trapezium is a mass of stars, the rest of the nebulae als'
abounding with stars, and exhibiting the characteristics of re-
solvabiHty strongly marked." At a subsequent period (1848)
Lord Rosse had not announced that his expectations had as
yet been fulfilled, although he cherished the hope of being
able to resolve the remaining portion of the nebula into stars.

When we separate the results of actual observation from
those of mere inductive conclusions in this much-disputed
question of the existence or non-existence of a self-luminous,
vaporous matter in the universe, we find that although the
increasing improvements in telescopic vision may indeed con-
siderably diminish the number of nebulsB, they caniiot by any
means wholly exhaust them. By the application of increas-
ing powers, each new instrument may resolve what the pre-
ceding ones had left unresolved, but it must, at the same time,
in consequence of its greater powers of penetrating space, re-
place (at least partially) the resolved nebulse by others not
previously reached. =^ A resolution of the older, and the dis
covery of new nebulse, would therefore follow one another in
endless succession, as the fruit of increased optical power.
For if we suppose a different result, we must either, accord-
ing to my view, assume the occupied regions of space to be
limited, or that the world-islands, to one of which our system
belongs, are so remote from each other that no telescopic in-
strument can ever be invented of sufficient power to penetrate
to the confines of any other of these worlds, and that our last
or extremest nebulae may resolve themselves into clusters of
stars, which, like the stars in the Milky Way, " are projected
on a black ground entirely free from vapor."t But can we
believe in the probability of a condition of the universe, and
of a degree of perfection in optical instruments, in which the
entire firmament will no longer exhibit any unresolved neb-
ulous spots ?

The hypothetical assumption of a self-luminous fluid, ap-
pearing, when sharply defined, in round or oval nebulous spots,
must not be confounded with the equally hypothetical as-
sumption of a non-luminous ether pervading the universe, and
generating by its unduJatory motion the phenomena of light,
radiant heat, and electro-magnetism.$ The emanations from
cometary nuclei, which, in the form of tails, frequently extend
over enormous tracts of space, disperse the substance of which
they are composed — and with which we are unacquainted —

* Compare Edinburgh Review, vol. Ixxivii., 1848, p. 1 86.

t Cosmos, vol. iii., p. 144, and note. X Ibid., p. 34.

NEBULiE. 25

tmong the planetary orbits of our solar system, which they
intersect. But when separated from the controlling nucleus,
this substance ceases to be perceptibly luminous. Newton
even considered it possible that vapor es ex sole et stellisjixis
et caudis cometarum, " vapors from the sun, the stars, and
the tails of comets," might blend with our terrestrial atmos-
phere.* No telescope has as yet indicated any sidereal char-
acter in the vaporous, rotating, and flattened ring of the zodi-
acal light. Whether the particles of which this ring consists,
and which, according to some, are conceived to rotate upon
themselves in obedience to dynamic conditions, and, accord-
ing to others, merely to revolve round the Sun, are illumined
or self-luminous, like many kinds of terrestrial vapors,! is a
question as yet undecided. Dominique Cassini believed them
to be small planetary bodies. $ It seems as if it were a re-
quirement of the human intellect to seek in all fluid bodies
for discrete molecular particles,^ similar to the full or hollow
vesicles of which clouds are formed ; while the gradations in
the decrease of density in our planetary system, from Mercury
to Saturn and Neptune (from 1-12 to 0*14; the Earth being
= 1), leads the mind to the consideration of comets, through
the external layers of whose nuclei even a faint star contin-
ues visible, and finally to that of discrete particles, so deficient
in density that their solidity, either within large or small di-
mensions, can scarcely be characterized, except by the limits
which bound them. It was by such considerations as to the
constitution of the apparently vaporous zodiacal light that
Cassini, long before the discovery of the so-called smaller plan-
ets between Mars and Jupiter, and prior to all conjectures re-
garding meteor-asteroids, was led to the idea that there exist
cosmical bodies *of all dimensions and all degrees of density.
We here almost involuntarily touch v^^on the old metaphys«
ical controversy regarding matter of primitive fluidity and
that composed of discrete molecular particles, and therefore
more amenable to mathematical treatment. From hence we
turn the more readily to our former consideration of the pure-
ly objective part of the phenomenon.

In the 3926 (2451 + 1475) positions which belong, a. to
the portion of the firmament visible at Slough, and which we
shall here, for the sake of brevity, term the northern heav-
ens, according to the three catalogues of Sir William Herschel

* Newton, PJiilos. Nat. Principia Mathematica, 1760, torn, iii., p. 671
\ Cosmos, vol. i., p. 141. % Ibid., p. 140

$ Observations at the Cape, $ 109-111.

VoT.. IV.— B

26 COSMOS.

from 1786 to 1802, and the above-named great exploration
of the heavens published by his son in the Philos. Transact
of 1833 ; and b. to the portion of the southern heavens visi-
ble at the Cape of Good Hope, according to Sir John Her-
schel's African Catalogues, nebulae and clusters of stars are
set down indiscriminately together, I have, however, deemed
it best, notwithstanding the natural affinity of these objects,
to enumerate them separately, in order to indicate a definite
epoch in the history of their discovery. I find that the Nwth-
em Catalogue^ contains 2299 nebulae and 152 clusters of
stars; the Southern or Cape Catalogue, 1239 nebulae and
236 clusters of stars. We have, therefore, 3538 for. the num-
ber of the nebulae throughout the firmament which were given
in these catalogues as not yet resolved into clusters. This
number may, perhaps, be increased to 4000, if we take into
account 300 or 400 seen by Sir "William Herschel,! but not
again determined, and the 629 observed by Dunlop at Para-

* The data on which these numbers ai-e based require some expla-
nation. The three catalogues of the elder Herscliel contain 2500 objects,
viz., 2303 nebulae and 197 clusters of stars. (Madler, ^s^?-., p. 448.)
These numbers were altered in the subsequent and far more exact ex-
ploration made by Sir John Herschel (Observations of Nebulae and Clus-
ters of Stars made at Slough with a twenty-feet reflector, between the
years 1825 and 1833, in the Philosophical Transactions of the Royal
Society of London for the year 1833, p. 365-481). About 1800 objects
w^ere identical with those of the three earlier catalogues ; but 300 or 400
were temporarily excluded, and more than 500 newly discovered were
determined according to Right Ascension and Declination. (Struve,
Astr. Stellaire, p. 48.) The Northern Catalogue contains 152 clusters
of stars, consequently 2307 — 152:=2155 nebula); but, in reference to
the Southern Catalogue {Observations at the Cape, p. 3, § 6, 7), we have
to subtract from the 4015 — 2307=1708 objects, among which there are
236 clusters of stars (see Op. cit., p. 3, § 6, 7, p. 128), 233, viz., 89-{-
135-f-9, as belonging to the Northern Catalogue, and observed by Sir
William and Sir John Herschel at Slough, and by Messier in Paris.
There remain, therefore, for the Cape observations, 1708 — 233=1475
nebulae and clusters of stars, or 1239 nebulae alone. We have, how-
ever, to add 135-f 9=144 to the 2307 objects of the Northern Slougu
Catalogue, which increase its numbers to 2451 objects, in which, after
subtracting 152 clusters, there remain 2299 nebulae, a number which
is not, however, very strictly limited to the latitude of Slough. When
numerical relations are to be given in the topography of the firmament
of both hemispheres, the author feels that although such data are from
their nature variable, owing to the differences in the epochs and the
advances of observation, he is bound to have regard to their accuracy.
In a sketch of the Cosmos, it must be endeavored to delineate the con-
dition of science appertaining to a definite epoch.

t Sir John Herschel says, in his Observations at the Cape, p. 134,
* There are between 300 and 400 nebulae of Sir William Herschel's Cat
alugue still unobserved by me : for the most part, very faint objects "

NEBULiE. 27

matta, with a nine-inch Newtonian reflector, of which Sir
John Herschel included only 206 in his catalogue.* Simi-
lar results have recently heen published by Bond and Mad-
ler. The number of nebulae, compared with that of double
stars, appears, therefore, according to the present condition
of science, to be in the ratio of 2 : 3 ; although it must not
be forgotten that under the designation of double stars are
included those which are merely optically double, and that
hitherto alterations of position have only been observed in a
ninth, or perhaps but an eighth portion of the whole number. 1

The above numbers — 2299 nebulae, with 152 clusters of
stars, in the Northern, and only 1239 nebulae, with 236 clus-
ters of stars, in the Southern Catalogue — show that the south-
ern hemisphere, with a smaller number of nebulae, possesses
a preponderance of clusters of stars. If we assume that all
nebulae are, from their probable constitution, resolvable, as
merely more remote clusters of stars or stellar groups, com-
posed of smaller and less thronged, self-luminous celestial bod-
ies, this apparent contrast (whose importance has been the
more noticed by Sir John Herschel$ in consequence of his
having employed reflectors of equal powers in both hemi-
spheres) indicates, at least, a striking difference in the nature
and cosmical position of nebulae, that is to say, in reference
to the directions in which they present themselves to the ob-
servation of the inhabitants of the earth in the northern or
southern firmament.

We owe to the same great observer our first accurate knowl-
edge of, and cosmical survey of, the distribution of nebulae and
groups of stars throughout the entire heavens. With a view
of investigating their position, relative local accumulation,
and the probability or improbability of their being arranged
in accordance with certain characteristic features, he classi-
fied between three and four thousand objects graphically, in
divisions, each embracing a space measuring 3° Declination
and 15m. Right Ascension. The greatest accumulation of
nebulous spots occurs in the northern hemisphere, where they
are distributed through Leo Major and Leo Minor ; the body,
tail, and hind feet of the Great Bear ; the nose of Camelo-
pardalus ; the tail of the Dragon ; Canes Yenatici ; Coma
Beisnices (where the north pole of the galaxy is situated); ^

* Op. cit., $ 7. Compare Dunlop's Cat. of Nebulae and Clusters of

the Southern Hemisphere, in the Philos. Transact, for 1828, p. 114-146

t Cosmos, vol. iii., p. 200. X Observations at the Cape, $ 105-107.

% III the Cosmos, vol. iii., p. 144. lines 5 and 6 from the top, by an

28 COSMOS.

the right foot of Bootes ; and more especially through the
head, wings, and shoulder of Virgo. This zone, which has
been termed the nebulous region of Virgo, contains, as al-
ready stated,^ one third of all the nebulous bodies in a space
embracing the eighth part of the surface of the celestial hem-
isphere. It does not stretch far beyond the ecliptic, extend-
ing only from the southern wing of Virgo to the extremity
of Hydra and to the head of the Centaur, without reaching
its feet or the Southern Cross. A less dense accumulation
of nebulae in the northern hemisphere, which extends further
south than the former, has been named by Sir John Herschel
the nebulous region of Pisces. It forms a zone, beginning
with Andromeda, which it almost entirely incloses, stretch-
mg beyond the breast and wings of Pegasus, and the band
uniting the Fishes, and extending toward the southern galac-
tic pole and Fomalhaut. A striking contrast to these accu
mulations presents itself in the barren region lying near Per
ECUS, Aries, Taurus, the head and chest of Orion, around Au
riga, Hercules, Aquila, and the whole constellation of Lyra.1
If we divide all the nebulae and clusters of stars contained
in the Northern Catalogue (of Slough), and classified accord-
ing to Right Ascension (as given in Sir John Herschel's Ob-
servations at the Cape), into six groups of four hours each,
we obtain the following result :

R.Asc. Oh. 4h 311

4 8 .... 179
8 12 .... 606

fl.Asc.l2h. 16h 850

16 20 121

20 0 . . . . 239.

By a more careful separation, according to Northern and
Southern Declination, we find that in the six hours' Right
Ascension from 9h. — 15h., there are accumulated 1111 neb-
ulae and clusters of stars in the northern hemisphere alone,
viz. :X

From 9h. lOh...

.. 90

Froml2h. 13h...

.. 309

10 11 ..

. . 150

13 14 ...

.. 181

11 12 ..

.. 251

14 15 ..

.. 130.

error of the press, the words south pole and north pole have been con-
founded.

* " In this region of Virgo, occupying about one eighth of the whole
surface of the sphere, one third of the entire nebulous contents of the
heavens are congregated." — Outlines, p. 596.

t In reference to this barren region, see Observations at the Cape,
$ 101, p. 135.

X I liave based these numerical data on a computation of the numbers
yielded by the projection of the northern heavens as given in Obtervor
lions at the Cape, pi. xi.

NEBULA. 29

The actual northern maximum lies, therefore, between
12h. and 13h., v«ry near the north galactic pole. Beyond
that point, between 15h. and 16h. toward Hercules, the dim-
inution is so rapid that the number 130 is followed directly
by 40.

The southern hemisphere presents not only a smaller num-
ber, but a far more regular distribution of nebula3. Regions
destitute of nebulse here frequently alternate with sporadic
nebulae. An actual local accumulation, more dense, indeed,
than the nebulous region of Virgo in the northern heavens,
occurs only in the Great Magellanic Cloud, which alone con-
tains as many as 300 nebulse. The immediate polar regions
of both hemispheres are poor in nebulse, and to a distance of
15° the Southern Pole is still more so than the Northern, in
the ratio of 4 to 7. The present North Pole exhibits a small
nebula, only 5 minutes' distance from it, while a similar neb-
ulous body, which Sir John Herschel has aptly named Nebula
polarissima Australis (No. 3176 of his Cape Catalogue, R.
A. 9h. 27m. 56s. ; N. P. D. 179° 34' 14"), is situated at a dis-
tance of 25 minutes from the South Pole. This paucity of
stars in the south polar region, and the absence of any pole-
star visible to the naked eye, were made the subject of bitter
lamentation by Amerigo Vespucci and Vicente Yaiiez Pinzon,
when, at the close of the fifteenth century, they penetrated
far beyond the equator to Cape San Augustin, and when the
former even expressed the erroneous opinion that the fine
passage of Dante, "Jo mi volsi a man destra, e posi mente

" and the four stars described as " non viste mai

fuorcK alia prima gente,"" referred to antarctic polar stars. ^

* Humboldt, Examen Critique de VHist. de la Geographic, torn, iv., p.
319. The Venetian Cadamosto (more properly called Alvise da Ca da
Mosto) first turned his attention to the discovery of the position of a
south polar star when in company with Antoniotto Usodimare, at the
mouth of the Senegal, in 3 454, in the course of one of the many voy-
ages in which the Portuguese engaged, under the auspices of the In-
fante Don Henrique, for the purpose of advancing along the western
shores of Africa, beyond the equator. " While I still see the north
polar star," he writes, being then in about 13° north latitude, " I can
not see the south polar star itself, but the constellation which I perceivt»
toward the south is the Carro del ostro (wagon of the south). (Aloysit
Cadam. Navig., cap. 43, p. 32 ; Ramusio, Ddle Navtgationi et Viaggi,
vol. i., p. 107.) Could he have traced the figure of a wagon among
some of the larger stars of the constellation Argo ? The idea that both
poles had a constellation of the " Wain" or wagon appears to have been
so universal in that age, that there is a drawing of a constellation per-
fectly similar to Ursa Minor, supposed to have been seen by Cadamosto,
both in the Itinerarium Portugallense, 1508, fol. 23, b, and in Grynaeua

30 COSMOS.

We have hitherto considered nebulae in reference to thedi
number and their distribution in what we call the firmament

(Novus Orbis, 1532, p. 58) ; while Ramusio (Navigationi, vol. i., p. 107),
and the new Collecgao de Noticias para a Hist, e Geog. das Nagoes Ultra
marinas (torn, ii., Lisboa, 1812, p. 57, cap. 39), in the place of the for-
mer, give an equally arbitrary drawing of the Southern Cross. (Hum-
boldt, Examen Crit. de VHist. de la G6ogr., torn, v., p. 236.) Since, ia
the Middle Ages, and probably for the sake of replacing the two Dan-
cers, xopevrai, of Hyginus {Poet.Astron., iii., 1), i. e., the Ludentes of the
Scholiast of Germanicus, or the Custodes of Vegetius in the Lesser Wain,
the stars (3 and y of Ursa Minor had been denominated the Guards, le
due guardie, of the neighboring north pole, on account of their rotation
round that point, and as this designation, as well as the habit of determ-
ining polar altitudes by these Guards (Pedro de Medina, Arte de Nave-
gar, 1545, lib. v., caps. 4-7, p. 183-195), was familiar to the European
pilots of all nations in the northern seas, so erroneous conclusions led
men to believe from analogy that they could recognize in the southern
horizon the polar star which had so long been sought for. It was not
until Amerigo Vespucci's second voyage (from May, 1499, to Septem-
ber, 1500), when he and Vicente Yanez Pinzon (both voyages are per-
haps one and the same) advanced as far in the southern hemisphere
as Cape San Augustin, that they devoted themselves diligently, but to
no purpose, to the search for a visible star in the immediate vicinity of
the South Pole. (Bandini, Vita e Lettere di Amerigo Vespucci, 1745, p.
70; Anghiera, Oceanica, 1510, dec. i., lib. ix., p. 96; Humboldt, Exa-
men. Crit., torn, iv., p. 205, 319, 325.) The South Pole was then situ-
ated within the constellation Octans, so that f3 of Hydrus, if we follow
the reduction of Brisbane's Catalogue, had still a southern declination
of fully 80° 5'. *' While I was engaged in observing the wonders of the
southern heavens, and in vainly seeking for a pole-star, I was remind-
ed," says Vespucci, in his letter to Pietro Francesco de' Medici, "of an
expression made use of by our Dante, when, in the first chapter of the
Purgatorio, he depicts a presumed passage from one hemisphere to the
other, and in describing the Antarctic Pole, says, lo mi volsi a man des-
tra In my opinion, the author intended in these verses to in-
dicate the pole of the other firmament by his four stars {non viste mai
fuorcK alia prima gents'). I am the more certain of this, because I act-
ually saw four stars, which together formed a lozenge, and had a slight
(?) movement." Vespucci refers to the Southern Cross, la croce mara-
vigliosa of Andrea Corsali (Letter from Cochin, dated January 6, 1515,
in Ramusio, vol. i., p. 177), whose name he did not then know; but
which subsequently served to mark to all pilots the position of the South
Pole (as/3 and y Urs. Min. indicated the North Pole. {Mim. de VAcad.
des Sciences, 1666-1699, tom. vii., part 2. Paris, 1729, p. 58.) This
constellation also served for determinations of latitude. (Pedro de Me-
dina, Arte de Navegar, 1545, lib. v., cap. x.i., p. 204.) Compare my in-
vestigation of the celebrated passage of Dante in the Examen Crit,
de VHist. de la Geogr., tom. iv., p. 319-334. I there drew attention to
the fact that a of the Southern Cross, which was carefully observed in
modern times by Dunlop (1826), and by RUmker (1836) at Paramatta,
is one of those stars whose multiple nature was first recognized in 1681
and 1687 by the Jesuits Fontaney, No6l, and Richaud. {Hist, de VAcad.
dep. 1686-1699, tom. ii.. Par., 1733, p. 19; M&mde VAcad. dep. 1666-
1699, tom. vii., 2, Par., 1729, p. 206 ; Lettres idijiantes, recueil vii., 1703i

nebula:. 31

—an apparent distribution which must not, however, be con-
founded with their actual distribution through the region? of
Bpace. "We now, therefore, proceed to the consideration of
the remarkable differences presented by their individual forms,
which are either regular (globular, more or less elliptical, an-
nular, planetary, or resembling the photosphere surrounding
a star) or irregular, and almost as difficult to classify as those
of the aggregated aqueous vapor of our atmosphere — the
clouds. The elliptical (spheroidal) form^ has been regarded
as the normal type of nebulse ; this form is most readily re-
solved into clusters of stars when it assumes a globular shape
in the telescope ; but when, on the other hand, with instru-
ments of equal powers, it appears much flattened, elongated
in one dimension, and discoidal, it is less easy of resolution.!
Gradual transitions of form from the round to the elongated,
elliptical, or awl-shaped form, are of frequent occurrence in
the heavens. (Fhilos. Transact., 1833, p. 494, pi. ix., figs.
19-24.) The nebula is always condensed around one or more
central points (nuclei). It is only by a discrimination between
round and oval nebulce that we recognize double nebulce ; for
as no relative motion is perceptible among the individual neb-
ulous bodies, either in consequence of its absence or its ex-
treme slowness, we are deficient in a criterion by which to

p. 79.) This early recognition of binary systems, long before that of ^
Ursae Maj. {Cosmos, vol. iii., p. 185), is the more remarkable, as Lacaille,
seventy years later, did not describe a Crucis as a double star; perhaps
(as RUmker conjectures), because the main star and the companion were
then not sufficiently distant from each other. (Compare Sir John Her-
Bchel, Observations at the Cape, $ 183-185.) Richaud also discovered
the binary character of a Centauri almost simultaneously with that of a
Crucis, and fully nineteen years before the voyage of Feuillee, to whom
Henderson erroneously attributed the discoveiy. Richaud remarks
" that, at the time of the comet of 1689, the two stars which form the
double star a Crucis were at a considerable distance from each other;
but that in a twelve-feet refractor both parts of a Centauri could be dis«
tinctly recognized, and appeared to be nearly in contact.

* Observations at the Cape, $ 44, 104.

t Cosmos, vol. iii., p. 140, and note. As we have already remarked in
reference to clusters of stars {Ibid., p. 143), Mr. Bond, of the United
States, succeeded, by means of the great space-penetrating power of
his refractor, in completely resolving the very elongated, elliptical neb-
ula of Andromeda, which, according to Bouillaud, had been already
described before the time of Simon Marius in 985 and 1428. It has a
reddish light. Near this celebrated nebula lies the still unresolved,
but very similarly shaped nebula, discovered on the 27th of August,
1783, by my honored friend, Miss Caroline Herschel, who died at an
advanced age, universally esteemed. (Philos. Transact., 1833, No. 61
of the Catalogue of Nebulae, fig. 52.)

32 COSMOS.

prove the existence of a mutual relation between the two, as
in distinguishing loetween physicallij and merely optically
double stars. Figures of double nebulae are given in the
Philos. Transact, for the year 1833, figs. 68-71. Compare
also Herschel, Outlines of Astr., § 878 ; Observ. at the Cape
of Good Hope,h 120.

Annular nebulae aire of the rarest occurrence. According
to Lord Rosse, we are acquainted with seven of these bodies
in the northern hemisphere ; the most celebrated of these is
situated between /3 and y Lyrae (No. 57, Messier ; No. 3023
of Sir John Herschel' s Catalogue), and was discovered in
1779 by Darquier at Toulouse, when Bode's Comet passed
near it. Its apparent size is nearly equal to that of Jupiter's
disk, and its form is an ellipse, whose greater and lesser axes
are in the ratio of 5 to 4. The interior of the ring is not
black, but somewhat illumined. Sir William Herschel dis-
covered some stars in the ring, which has since been entirely
resolved by Lord Rosse and Mr. Bond.^ The splendid an-
nular nebulae of the southern hemisphere, numbered 3680 and
3686, appear, on the contrary, perfectly black in the interior
of the rings. The last-named of the two is not elliptical, but
perfectly round ;t all are probably annular clusters of stars.
The increasing power of optical instruments appears, more-
over, generally to render the contour of both elliptical and
annular nebulae less defined ; thus, for instance, Lord E-osse's
colossal telescope exhibits the annular nebula of Lyra in the
form of a simple elHpse, with remarkable divergent, thread-
like nebulous appendages. The transformation effected in a
nebulous spot — Lord Rosse's Crab nebula — which appears in
instruments of inferior power to be a simple elliptical body,
is particularly striking.

The so-called planetary nebulae, which were first observed
by the elder Herschel, and which rank among the most re-
markable phenomena of the heavens, although of less rare
occurrence than annular nebulae, do not number, according
to Sir John Herschel, more than 25, of which nearly three
fourths lie within the southern hemisphere. These bodies
present the most striking resemblance to planetary disks ; the

* " Annular Nebulce.''^ — Ohservations at the Cape, p. 53 ; Outlines of
Astr., p. 602. " Nebulcuse perfor^e.'^ — Arago, in the Annuaire for 1842,
p. 423; Bond, in Schum., Asiron. Nachr., No. 611.

t Ohservations at the Cape, p. 114, pi. vi., figs. 3 and 4. Compare
also No. 2072 in the Philos. Transact, for 1833, j). 466. See Nichol,
Thoughts on the System of the World, p. 21, pi. iv., and p. 22, pi. L
fig 5.

NEBULiE. 33

greater number are round, or somewhat oval, and either
sharply defined, or indistinct and vaporous at the margins.
The disks of many of these nebulee present a very uniform
light, w^hile others appear mottled, or of a pecuhar texture
as if curdled. No trace of condensation round a central point
has ever been observed. Lord E-osse has recognized five plan-
etary nebulous spots to be annular nebulsB, having one or two
central stars. The largest of these planetary nebulae is sit-
uated in the Great Bear (near (i Ursse Maj.), and was discov-
ered by.Mechain in 1781. The diameter of the disk''^ is 2'
40". The planetary nebula in the Southern Cross (No. 3365,
Observations at the Cape, p. 100), with a disk having a di-
ameter scarcely equal to 12", exhibits the brightness of a star
of the 6- 7th magnitude. Its hght is indigo-blue, and the
same color, which is very remarkable in nebulae, is observed
in three other objects of the same form, although in the lat-
ter the blue is less intense.! The blue color of some plan-
etary nebulae does not militate against the possibility of their
being composed of small stars ; for we find blue stars not only
as the individual members of a pair of double stars, but even
stellar clusters composed entirely of blue stars, or of the lat-
ter interspersed with small red and yellow stars. $

The question whether planetary nebulae are very remote
nebulous stars, in which our telescopic vision is unable io rec-
ognize the difference between a luminous central star and the
vaporous envelope surrounding it, has already been considered
in the beginning of my Delineation of Nature. k Would that
Lord Rosse's colossal telescope might finally be the means of

* If we consider the planetary nebula in the Great Bear to be a
sphere having an apparent diameter of 2' 40", " and assume its distance
to be equal to the known distance of 61 Cygni, we shall obtain an act-
ual diameter for the sphere, which is seven times greater than the orbit
described by Neptune." — Outlines, ^ 876.

t Outlines, p. 603 ; Observations at the Cape, $ A7. There is an or-
ange-red star of the eighth magnitude in the vicinity of No. 3365 ; but
the planetary iiebul^ retains its deep indigo-blue color when the red
star is not in the field of the telescope. The color is, therefore, not the
effect of contrast.

X Cosmos, vol. iii,, p. 136, 208, and note. The companion and the
main star are blue, or bluish, in more than 63 double stars. Indigo-
blue stars are intermixed in the splendid, many-colored clusters of stars,
No. 3435 of the Cape Catalogue (Dunlop's Catalogue, No. 301). An en-
tirely uniform blue cluster of stars is observed in the southern heavens
(No. 573 of Dunlop ; No. 3770 of Sir John Herschel). This cluster has
a diameter of 3^', with prolongations measuring 8' in length ; the stars
are of the 14th and 16th magnitude. {Observations at the Cape, p. 119.)

^ Cosmos, vol i., p. 85, and note. Compare Outlines, ^ 877.

B2

34

COSMOS.

elucidating the nature of these remarkable planetary vapor
ous disks ! Although there is considerable difficulty in ac-
quiring a clear conception of the complicated dynamic condi-
tions under which, in a globular or spheroidally flattened stel-
lar cluster, the rotating crowded suns, whose specific density
is greater toward the center, constitute a system of equilibri-
um ;* this difficulty increases still more in those circular,
well-defined, planetary nebulous disks which exhibit a per-
fectly uniform brightness, without any increase of intensity to-
ward the center. Such a condition seems to depend less upon
sphericity of form (the state of aggregation of many thousand
small stars) than on the existence of a gaseous photosphere,
which is supposed, as in our Sun, to be covered with a thin,
untransparent, or very faintly illuminated stratum of vapor.
Does the light in the planetary nebulous disk appear to be
thus uniformly diffused simply in consequence of the great
distance, which causes the difference between the center and
the margins to disappear ?

The fourth and last order of regular nebulae comprises Sir
"William Herschel's nebulous stars, i. e., true stars surround-
ed by a milky nebula, which is very probably connected with,
and dependent upon, the central star. Very different opin-
ions exist as to M^hether the nebula, which, according to Lord
Rosse and Mr. Stoney, appears to be perfectly annular in some
of these groups (Philos. Transact, for 1850, pi. xxxviii., figs.
15 and '16), is self-luminous, forming a photosphere like our
Sun, or whether (which, however, is less probable) it is sim-
ply illumined by the central Sun. It was the opinion of Ber-
ham, and to some extent also of Lacaille, who discovered
many nebulous stars at the Cape of Good Hope, that the stars
'iv^ere situated far from the nebulae on which they were pro-
jected. Mairan appears (1731) first to have expressed the
view that nebulous stars are surrounded by an atmosphere of
light appertaining to them.f We even find that some of the
larger stars (of the 7th magnitude, for instance, as No. 675

* On the development of the dynamic relations manifested in the
partial attractions in the interior of a globular cluster of stars, which ap-
pears in a telescope of weak power as a round nebula increasing in
density toward the center, see Sir John Herschel, in Outlines of As-
tronomy, $ 866 and 872; Observations at the Cape, § 44, 111 to 113;
Philoa. Transact, for 1833, p. 501 ; Address of the Preside7it in the
Report of the Fifteenth Meeting of the British Association, 1845, p.
xxxvii.

t Mairan, Traiti de VAurore BorSale, p. 263 ; Arago, in the Annuaire
for 1842, p. 403-413.

NEBULiE. 35

of the Catalogue of 1833) have a photosphere, whose diam.
eter measures from 2' to 3'.^

The large nebulous masses of irregular configuration com-
pose a class of nebulae differing entirely from those we have
described as regular, and which are, at all events, faintly de-
fined. They are characterized by the most variously un sym-
metrical forms, having indefinite and confused outlines. These
bodies, which constitute mysterious phenomena sui ge?ieris,
have mainly given occasion to the opinions advanced in ref
erence to the existence of cosmical clouds and self-luminous
nebulce, supposed to be distributed through the regions of
space, and to resemble the substratuni of the zodiacal light.
These irregular nebulae, which cover a portion of the firma-
ment several square degrees in extent, present a striking con-
trast with the smallest of all the regular isolated and oval
nebulous disks, which is equal in luminous intensity to a tel-
escopic star of the 14th magnitude, and is situated between
the constellations Ara and Apus, in the southern hemisphere.!
No two of the unsymmetrical, diffused nebulous masses re-
semble one another ;$ but, adds Sir John Herschel, from the
experience of many years' observation, one thing observed in
reference to them, and which gives them a peculiar charac-
ter, is, that all are situated within or very near to the mar-
gins of the Milky Way, and may be regarded as offshoots from
it. On the contrary, the regularly shaped and well-defined
small nebulous spots are partly scattered over the whole heav-
ens, and partly compressed together in special regions, far
from the Milky Way, as, for instance, in the northern hemi-
sphere, in the regions of Virgo and Pisces. Although the large
irregular nebulous mass in the sword of Orion is certainly sit-
uated at a considerable distance from the visible margin of

* In other instances these nebulous stars are only of the eighth to the
ninth magnitude ; as Nos. 311 and 450 of the Catalogue of 1833, fig. 31
having photospheres of 1' 30". {Outlines, § 879.)

t Observations at the Cape, p. 117, No. 3727, pi. vi., fig. 16.

X We meet with remarkable forms of irregular nebulse, as, for in-
stance, the omega-shaped {Observations at the Cape, pi. ii.,fig- 1, No.
2008), which has been investigated and described by Lamont, and by
a meritorious North American astronomer, Mr. Mason, whose early loss
is much to be lamented {Mem. of the Amer. Philos. Society, vol. vii., p
117) ; a nebula having from 6 to 8 nuclei {Observations at the Cape, p
19, pi. iii., fig. 4) ; the cometary tuft-like form in which the nebulous
rays seem occasionally to expand, as from a star of the ninth magni-
tude (pi. vi., fig. 18, Nos. 2534 and 3688) ; a silhouette profile, or bust-
like outline (pi. iv., fig. 4, No. 3075) ; a fissure-like opening, inclosing
a filiform nebula (No. 3501, pi. iv., fig. 2 ; Outlines, $ 883 ; Observationt
ttihe Cape, $ 121).

36 COSMOS.

the Galaxy (fully 15°), still even it may perhaps helong to
that prolongation of its branch which appears to lose itself
from a and e Persei toward Aldebaran and the Hyades, and
to which we have already referred at p. 147. The brilliant
stars which gave early celebrity to the constellation of Orion,
are, moreover, reckoned to belong to that zone of very large
and probably less remote stars, whose prolonged direction in-
dicates the vast circle of the Southern Galaxy, passing through
e Orionis and a Crucis.=^

The opinion which at one time prevailed so extensivelyf
of the existence of a galaxy of nehulcB intersecting the stellar
Milky Way almost at right angles, has not been confirmed by
more recent and accurate observations in reference to the dis-
tribution of symmetrical nebulse in the firmament 4 There
certainly are, as has already been observed, very great ac;cu-
mulations at the northern pole, of the Galaxy, while a very
considerable abundance of nebulous matter is also observed
at the south galactic pole near Pisces ; but in consequence of
the many interruptions which break the zone, we are unable
to indicate any large circle connecting these poles together,
and formed by a continued line of nebulae. William Her-
schel, in advancing this view in 1784, at the close of his first
treatise on the structure of the heavens, developed it with a
caution worthy of such an observer, and from which doubt
was not entirely excluded.

Some of the irregular, or, rather, unsymmetrical nebulae
(as those in the sword of Orion, near r] Argus in Sagittarius
and in Cygnus), are remarkable for their extraordinary size ;
others (as Nos. 27 and 51 of Messier's Catalogue) for their
singular forms.

It has already been noticed in reference to the large nebula
in the sword of Orion, that Galileo never mentioned it, al-
though he devoted so much attention to the stars between the
girdle and the sword, § and even sketched a map of this re-

* Cosmos, vol. iii., p. 147. Outlines, $ 785.

t Cosmos, vol. i., p. 150, and note ; Sir John Herschel's first edition
of his Treatise on Astronomy, 1833, in Lardner's Cabinet Cyclopedia,
$ 616; Littrow, Theoretische Astronomic, 1834, th. ii., § 234.

X See Edinburgh Review, January, 1848, p. 187, and Observations at
the Cape, § 96, 107. " The distribution of the nebulae is not like that
of the Milky Way," says Sir John Herschel, " in a zone or band en-
circling the heavens ; or if such a zone can bo at all traced out, it is
with so many interruptions., and so faintly marked out through by far
the greater part of its circumference, that its existence as such can be
hardly more than suspected."

$ " There can be no doubt," writes Dr. Galle, " that the drawing''

NEBULiE. 3^

gion of the heavens. That which he names Nebulosa Ori
mis, and dehneates in the vicinity oi NebidosaPr^sepe, hi.
expressly declares to be an accumulation of small stars (s^e^
larum consiipatarum) in the head of Orion. In the draw-
ing which he gives in the Siderius Nuncius, § 20, extend-
inl from the girdle to the beginning of the right leg {a On-
onis), I recognize the multiple star d above the star i. ihe
instruments employed by Galileo did not magnify more than
from eight to thirty times. It is probable that as the nebula
in the sword is not isolated, but appears, when seen through
imperfect instruments or a hazy atmosphere, like a halo round
the star d, its individual existence and configuration may have
escaped the notice of the great Florentine observer He was
moreover, little inclined to assume the existence of nebulae^*
It was not until fourteen years after Gahleo s death, m the
vear 1656, that Huygens first observed the great nebula ol
Orion, of which he gave a rough sketch in the Systeina Satur-
nium, which appeared in 1659. "While,'' says this great
man, " I was observing, with a refractor of twenty-five leet
focal length, the variable belts of Jupiter, a dark central belt
in Mars, and some faint phases of this planet, my attention
was attracted by an appearance among the fixed stars, which,
as far as I know, has not been observed by any one else, and
which, indeed, could not be recognized, except by such pow-
erful instruments as I employ. Astronomers enumerate three
stars in the sword of Orion, lying very near one another. On
one occasion, when, in 1656, 1 was accidentally observing the
middle one of these stars through my telescope, I saw twelve
stars instead of a single one, which, indeed, not unfrequentiy

(Opere di Galilei, PaJova, 1744, toni. ii., p. 14, No. 20) "which you
lav^e me inclades the girdle and sword o Orion and consequently alo
fhe star 6: but it is difficult, owing to the striking inaccuracy of the
draw n- to recognize the three small stars in the sword (the middle
oS of wWch is e\ and which appear to the unaided eye to be placed
?n a strli^ht line. I conjecture that you have correctly designated the
B?a? fand that the bright star to the right and below, or the one imme-
dfateiy above it, is 0^ Galileo expressly says, " In P^-o m\eg^^^^^^
Orionis Constellationem pingere decreveram: vervim. ^^ mgenti stel-
larum copia, temporis vero inopia obrutus, aggressionem banc m aliara
occaTionem distuli." Considedng Galileo's observation of the constel-
latirof Orion, we are the more°struck by the circumstance that he
40rtars wh?ch he thought he had counted between the ginl^e and^he
Bword of Orion in a space often square degrees (Neni,F»^a dt Gahet
vol ' , p. 208), should subsequently (accordmg to Lambert, Com.Z.|
Briefe 1760, p. 155) have led himto the erroneous estimate of l,6o0,00a
fgL L w^hole Ornament. (Struve, ^-r^^^X^^';^^^^
lb.)

38 COSMOS.

happens in using the telescope. Three of this number were
almost in contact with one another, and four of them shone
as if through a mist, so that the space around them, having
the form drawn in the appended figure, appeared much bright-
er than the rest of the sky, which was perfectly clear, and
looked almost black. This appearance looked, therefoie, al-
most as if there were a hiatus or interruption. I have fre-
quently observed this phenomenon, and up to the present time
as always unchanged in form ; whence it would appear that
this marvelous object, be its nature what it may, is very
probably permanently situated at this spot. I never observed
any thing similar to this appearance in the other fixed stars."
(The nebulous spot in Andromeda, described fifty-four years
earlier by Simon Marius, must therefore either have been un
known to him, or did not attract his attention.) That which
has usually been regarded as nebulous matter, adds Huygens,
" even the Milky Way, when seen through telescopes, exhib-
its nothing nebulous, and is nothing more than a multitude
of stars, thronged together in clusters."* The animation of

* " Ex his autem tres ilhe pene inter se contiguee stellae, cumque his
aliae quatuor, velut trans nebulara lucebant : ita ut spatium circa ip-
sas, qua forma hie conspicitur, multo illustrius appareret rehquo omni
cceIo ; quod cum apprime serenum esset ac cerneretur nigerrimum, ve-
lut hiatu quodam interruptum videbatur, per quem in plagam magis hi-
cidam esset prospectus. Idem vero in hanc usque diem nihil immutata
facie saepius atque eodem loco conspexi ; adeo ut perpetuam illic sedem
habere credibile sit hoc quidquid est portenti : cui certe simile aliud
nusquam apud reliquas fixas potui animadvertere. Nam caeterte nebu-
losae olim existimatae, atque ipsa via lactea, perspicillo inspectae, nullas
nebulas habere comperiuntur, neque aliud esse quam plurium stellarum
congeries et frequentia." — Christiani Hugenii, Opera varia, Lugd. Bat.,
1724, p. 540-541. " Of these, however, those three almost contiguous
stars, and, with these, four others, shone, as it were, through a nebula,
BO that the space around them, as is shown in this figure, is much more
brilliant than all the rest of the sky ; and when this is very serene and
appears quite dark, it seemed broken by a sort of gap, through which
one looked upon a brighter region behind. The same thing I have
since beheld over and over again, without any change in its appeamnce
and in the same position, so that one might almost believe that this
marvelous object, whatever it is, is permanently fixed there ; it is cer-
tain I have nowhere else noticed any thing similar to this in the other
fixed stars ; for those which have generally been considered as nebulte,
and even the Milky Way itself, when seen through a telescope, arc found
to have nothing nebulous about them, but are nothing more than a mul-
titude of several stars clustered together." Huygens himself estimated
the powers ho employed in his twenty-five feet refractor as equal to a
hundred diameters (p. 538). Are the " quatuor stellae trans nebulam
lucentes" the stars of the trapezium ? The small and very rough sketch
(Tab. xlvii., fig. 4, Phenomenon in Orione Novum) represents only a group

NEBULJE. 39

Jn.ia first description testifies the freshness and depth of the
impressions produced on his mind ; but how great is the dis-
tance from this first sketch, made in the middle of the sev-
enteenth century, and the somewhat less imperfect descrip-
tions of Picard, Le Gentil, and Messier, to the admirable de-
lineations of Sir John Herschel (1837), and of William C. Bond
(1848), the Director of the Observatory at Cambridge, U. S. \^
The former of these two astronomers had the great ad-
vantage! of observing the nebula in Orion since 1834, at the
Cape of Good Hope, at an altitude of 60°, and with a twen-
ty-feet reflector, by which means he was enabled to render
his earlier delineations of 1824-1826 more perfect 4 The
positions of 150 stars, mostly of from the fifteenth to the
eighteenth magnitudes, in the vicinity of 6 Orionis, were de-
termined. The celebrated trapezium, which is not surround-
ed by a nebula, is formed of four stars of the fourth, sixth,
seventh, and eighth magnitudes. The fourth star was dis-
covered (in 1666 ?) by Dominique Cassini, at Bologna ;^ the
fifth (y') in 1826, by Struve ; and the sixth (a), M^hich is
of the thirteenth magnitude, in the year 1832, by Sir John
Herschel. De Yico, the Director of the Observatory at the
Collegio Romano, announced in the beginning of the year
1839 that he had discovered three other stars in the trapezi-
um with his great Cauchoix refractor. These have not been
observed either by Sir John Herschel or Mr. Bond. That
portion of the nebula nearest the almost unnebulous trapezi-
um, and forming, as it were, the anterior part of the head
above the throat, the regio Huygeniana, is speckled, and of
a granular texture, and has been resolved into clusters of
stars both by Lord Rosse's colossal telescope and by the large

of three stars, near an indentation which one might certainly regard as
the Sinus Magmis. Perhaps the drawing gives only the three stars in
the trapezium, which range from the fom-th to the seventh magnitude.
Dominique Cassini, moreover, boasts that he was the first who observed
the fourth star.

* William Cranch Bond, in the Transactions of the American Academy
of Arts and Sciences, New Series, vol. iii., p. 87-96.

t Observations at the Cape, $ 54-69, pi. viii. ; Outlines, $ 837 and
885, pi. iv., fig. 1.

X Sir John Herschel, in the Memoirs of the Astronomical Society, vol.
ii., 1824, p. 487-495, pi. vii., viii. The latter of these gives the nomen-
clature of the separate regions of the nebula in Orion, which have been
explored by so many astronomers.

^ Delambre, Hist, de V Astron. Modeme, torn, ii., p. 700. Cassini
reckoned the appearance of this fourth star (" aggiunta della quarta
Btella alle tre contigue") among the changes which had taken place in
the nebula of Orion in his time.

40 COSMOS,

Cambridge (U. S.) refractor.* Man} positions of the smaller
stars have been determined by accurate observers of the pres-
ent day ; as, for instance, Lamont at Munich, and Cooper and
Lassell in England. The first named of these employed a
1200-fold magnifying power. Sir William Herschel was of
opinion, from a comparison of his own observations made
with the same instruments, from 1783 to 1811, that altera-
tions had taken place in the relative brilliancy and in the
outlines of the great nebula of Orion.f Bouilland and Le
Gentil had maintained the same opinion in reference to the
nebula in Andromeda ; but the thorough investigations of Sir
John Herschel have rendered the occurrence of any such cos-
mical changes, although formerly considered to be well estab-
lished, exceedingly doubtful, to say the least.

The large tiehula round t] Argus is situated in that por-
tion of the Milky Way which extends from the feet of the
Centaur, through the Southern Cross, toward the middle part
of Argo, and is so distinguished by the intensity of its mag-
nificent effulgence. The light emanating from this region is
so extraordinary, that Captain Jacob, an accurate observer,
and a resident in the tropical parts of India, remarks, entirely
in harmony with my prolonged experience, " Such is the gen-
eral blaze from that part of the sky, that a person is imme
diately made aware of its having risen above the horizon,
though he should not be at the time looking at the heavens,
by the increase of general illumination of the atmosphere, re-
sembling the effect of the young Moon."$

* " It is remarkable, however, that within the area of the trapezium
no nebula exists. The general aspect of the less luminous and cirrous
portion is simply nebulous and irresolvable, but the brighter portion,
immediately adjacent to the trapezium, forming the square front of the
head, is-shown with the eighteen-inch reflector broken up into masses
(very imperfectly represented in the figure), whose mottled and cur-
dling light evidently indicates, by a sort of granular texture, its consist-
ing of stars, and when examined under the great light of Lord Rosse'a
reflector, or the exquisite defining power of the great achromatic at
Cambridge, U. S., is evidently perceived to consist of clustering stars.
There can, therefore, be little doubt as to the whole consisting of stars,
too minute to be discerned individually even with these powerful aids
but which become visible as points of light when closely adjacent in the
more crowded parts." — Outlines, p. 609. William C Bond, who made
use of a twenty-five feet refractor, having a fourteen-inch objectglass,
says, " There is a great diminution of light in the interior of the trapezi
um, but no suspicion of a star." {Memoirs of the American Academy,
New Series, vol. iii., p. 93.)

+ Philoa. Transact, for the year 1811, vol. ci., p. 324.

t Trans, of the Roy. Soc. of Edinb., vol. xvi., 1849, part iv., p. 4 15.

NEBULA. 41

The nebula, in the midst of which lies the star 77 Argus,
which has become so celebrated for the alterations observed
in the intensity of its light, covers a space of more than four
sevenths of a square degree.^ The nebula itself, which is
divided into many unsymmetrical masses of unequal lumin-
ous intensity, nowhere exhibits the speckled, granular ap-
pearance which admits of the assumption of its resolvability.
It incloses a singularly shaped, oval vacancy, covered with a
faint glimmer of light. A fine delineation of the entire ap-
pearance, the result of two months' measurements, is given
in Sir John Herschel's Observations at the Cape.\ This
observer determined no less than 1216 positions of stars,
mostly from the fourteenth to the sixteenth magnitudes, in
the nebula of 77 Argus. These extend far beyond the nebula
into the Milky Way, where they stand clearly forth on the
deep black ground of the sky, and they are probably, there-
fore, unconnected with, and far removed from, the nebula it-
self. The whole contiguous portion of the Milky Way is,
moreover, so rich in stars (not clusters), that by means of the
telescopic star-gauges 3138 stars have been found for every
mean square degree between R. A. 9h. 50m. and llh. 34m.
These numbers even increase to 5093 in the sweeps for R. A.
llh. 24m., that is to ^ay, for one square degree of the firma-
ment, a number of stars greater than those which are visible
to the naked eye in the horizon of Paris or Alexandria, from
the first to the sixth magnitude. :j:

The nebula in Sagittarius, which is of considerable size,
appears as if composed of four separate masses (R. Asc. 17h.
53m. ; N. P. Decl. 114° 21'), one of which is again three-
membered. All are interrupted by spots free from nebulous
matter, and the whole was imperfectly observed by Messier. §

The nebulce in Cygnus are several irregular masses, one
of which forms a very narrow divided band, passing through
the double star ?/ Cygni. Mason was the first to recognize
the connection of these masses, so widely different, by means
of a singular cellular tissue. ||

The nebula in Vulpes was imperfectly seen by Messier (No

* Cosmos, vol. iii., p. 177-179.

+ Observ. at the Cape, § 70-90, pi. ix. Outlines, $ 887, pi. iv., fig. 2

% Cosmos, vol. iii., p. 107.

$ Observ. at the Cape, $ 24, pi. i., fig. 1, No. 3721 of the Catalogue
Outlines, § 888.

II The nebula iu Cygnus, partly in R. Asc. 20h. 49m. ; N. P. Decl
58^ 27'. {Outlines, $ 891.) Compare Catalogue of 1833, No. 2092
pi. xi., fig. 34.

42 COSMOS.

17 of his Catjilogue) when he was making an observation of
Bode's Comet in 1779. Sir John Herschel was the first who
delineated and accurately determined its position (R. Asc. 19°
52' ; N. P. Decl. 67° 43'). This nebula, which is not of an
irregular form, first received the name of the "Dumb-bell"
on the application of a reflector with an eighteen-inch aper
ture. (Philos. Transact, for 1833, No. 2060, fig. 26 ; Out
lines, § 881.) This similarity to a dumb-bell entirely disap-
peared in Lord Rosse's reflector of three-feet aperture.* (See
his recent important delineation, Philos. Transact, for 1850,
pi. xxxviii., fig. 17.) It was also successfully resolved into
numerous stars, which, however, continued mixed with neb-
ulous matter.

The spiral nehula in the more northern of the Canes
Venatici was discovered by Messier on the 13th of Octo-
ber, 1773 (on the occasion of his discovery of the Comet), in
the left ear of Asterion, very near rj (Benetnasch) in the tail
of the Great Bear (No. 51 of Messier, and No. 1622 of the
great Catalogue published in the Philos. Transact, for 1833,
p. 496, fig. 25). This is one of the most remarkable phenom-
ena in the firmament, both on account of its singular config-
uration, and of the unexpected transformative efiect produced
on its appearance by Lord E-osse's six-feet speculum. In Sir
John Herschel's eighteen-inch reflector, the nebula presented
the appearance of a spherical body, surrounded by a far-dis-
tant ring, so that it exhibited, as it were, an image of our
starry stratum with its galactic ring.f But in the spring of
1845, the large Parsonstown telescope transformed the whole
into a helicine twisted coil — a luminous spiral, whose convo-
lutions appear unequal, and are prolonged at both extremi-
ties, both in the center and outward, into dense, granular,
globular nodules. Dr. Nichol made a drawing of this object,
which was laid before the meeting of the British Association
at Cambridge in 1845 by Lord Ilosse4 But the most per-

* Compare pi. ii., fig. 2, with pi. v. in Thoughts on some important
Points relating to the System of the World, 1846 (by Dr. Nichol, Pro-
fessor of Astronomy at Glasgow), p. 22. " Lord Rosse," says Sir John
Herschel, Outlines, p. 607, "describes and figures it as resolved into
numerous stars with much intermixed nebula."

t Cosmos, vol. i., p. 150, and note, where the nebula, No. 1622. is
lermed a " brother-system."

X Report of the Fifteenth Meeting of the British Association for the
Advancement of Science, Notices, p. 4 ; Nichol, Thoughts, p. 23. (Com-

f)are pi. ii., lig. 1, with pi. vi.) In the Outlines, $ 882, we find the fol-
owing passage : " The whole, if not clearly resolved into stars, has a
resolvable charactei*, which evidently indicates its composition."

MAGELLANIC CLOUDS. 43

feet delineation of this nebula has been given by Mr. John-
stone Stoney. {Philos. Transact., 1850, part i., pi. xxxv.,
fig. 1.) A similar spiral form is observed in No. 99 of Mes-
sier's Catalogue, which presents also a single central nucleus,
and in other northern nebulae.

It still remains for us to notice, more circumstantially than
could be done in " the general delineation of Nature,"* an ob-
ject vi^hich is unparalleled in the world of forms exhibited
throughout the firmament, and by which the picturesque
effect of the southern hemisphere — if I may be permitted to
use the expression — is heightened. The two Magellanic
Clouds, which were probably first named Cape Clouds by Port-
uguese, and subsequently by Dutch and Danish pilots,! most
strongly rivet the attention of travelers, as I can testify from
personal experience, by the intensity of their light, their in-
dividual isolation, and their common rotation round the South
Pole, although at different distances from it. We learn, from
the express mention and definite description of these circling
clouds of fight by the Florentine, Andrea Corsali, in his trav-
els to Cochin, and by the Secretary of Ferdinand the Catho-
lic, Petrus Martyr de Anghiera, in his work De rebus O^ean-
ids et Orbe Novo (dec. i., lib. ix., p. 96), that the designa-
tion which refers to Magellan's circumnavigation is not the
older name ;$ for the notices here indicated are both of the
year 1515, while Pigafetta, the companion of Magellan, does
not mention the nebbiette in his journal earlier than January,
1521, when the ship " Victoria" passed through the Patago-
nian Straits into the South Sea. The very old designation of
" Cape Clouds" did not, moreover, arise from the vicinity of
the more southern constellation of " Table Mount," since the
latter was first introduced by Lacaille. The name would
more probably seem to refer to the actual Table Mountain,
and to the appearance of a small cloud on its summit, which
was dreaded by mariners as portending the coming of a storm.
We shall presently see that both the nubecul(^, which had
been long observed in the southern hemisphere, although not
definitely named, acquired with the spread of navigation, and
the increasing animation of certain commercial routes, desig-
nations which were derived from these very routes themselves.

* Cosmos, vol. i., p. 85, and note.

t Lacaille, iu the M6m. de VAcad., annee 1755, p. 195. This is an
unfortunate confusion of terminology, in the same manner as Horner
and Littrow call the Coal-bags Magellanic Spots, or Cape Clouds.

t Cosmos, vol. ii., p. 287, and note.

44 ' COSMOS.

The constant navigation of the Indian Ocean, washing the
shores of Eastern Africa, was the earUest means — especially
since the time of the Lagides and the Monsun-navigation — of
making mariners acquainted with the stars near the Southern
Pole. As early as the middle of the tenth century, we find,
as already observed, that the Arabs had given a name to the
larger of the Magellanic Clouds. This designation is, accord-
ing to Ideler's researches, identical with that of the Wliite
Ox, elrbakar, of the celebrated astronomer Derwisch Abdur-
rahman Sufi of E-ai, a city in the Persian province of Irak.
In his Introduction to the Knoivledge of the Starry Heav-
ens, which he composed at the court of the sultans of the dy-
nasty of the Buyides, he says that "below the feet of the Suhel
(by which he expressly means the Suhel of Ptolemy, Canopus,
although the Arabian astronomers named many other large
stars of Argo, el-sefna, Suhel) there is a ' white spot,' which
is invisible both in Irak (in the district of Bagdad and in
JSTedsch, ' Nedjed') and in the more northern and mountain-
ous part of Arabia, but may be seen in the Southern Tehama,
between Mecca and the extremity of Yemen, along the coast
of the Red Sea."* The relative position of the White Ox to
Canopus is here indicated with sufficient accuracy for the
naked eye ; for the Right Ascension of Canopus is 6h. 20m.,
and the eastern margin of the larger Magellanic Clouds lies
in Right Ascension 6h. The visibility of the Nubecula ma-
jor in northern latitudes can not have been appreciably af-
fected by the precession of the equinoxes since the tenth cen-
tury, for the maximum distance from the north had already
been attained long before that period. If we follow the re-
cent determination of position for th« larger cloud by Sir John
Herschel, we shall find that it was perfectly visible as far
north as 17° in the time of Abdurrahman Sufi ; at the pres-
ent time it is seen in about 18° north latitude. The south-
ern clouds must therefore have been visible throughout the
whole of southwestern Arabia, in Hadhramaut (noted for its
frankincense) as well as in Yemen, the ancient seat of civil-
ization of Saba, and the long-established colony of the Joctan-
ides. The southernmost extremity of Arabia, at Aden, on

* Ideler, Untersuchitngen uher den Ursprung vnd die Bcdeutung der
Stemnamen, 1809, p. xlix., 262. The name Abdurrahman Sufi was
contracted by Uiugh Beg from Abdurrahman Ebn-Omar Ebn- Moham-
med Ebn-Sahl Abu'l-Hassan el-Sufi el-Razi. Ukigh Beg. who, like
Nassir-eddin, amended the Ptolemaic star-positions from his own ob-
servations (1437), admits that he boiTowed from Abdurrahman Sufi's
work the positions of 27 southern stai's, not visible at Samarcand.

MAGELLANIC CLOUDS. 45

the Sfc-aits of Bab-el-Mandeb, is situated in 12° 45', and Lo-
heia in 15° 44' north latitude. The settlement of many Ara-
bian colonies on the eastern coast of Africa, between the trop-
ics, north and south of the equator, naturally led to a more
special knowledge of the southern stars.

The western coasts of x*L£nca beyond the line were first
visited by some of the more cultivated European pilots (espe-
cially Catalanians and Portuguese). Undoubted documents,
such as the Map of the World of Marino Sanuto Torsello, of
the year 1306, the Genoese Portulano Mediceo (1351), the
Planisferio de la Palatifia (1417), and the Mappa-mondo
di Fra Mauro Camaldolese (between 1457 and 1459), prove
that the triangular configuration of the southern extremity of
the African Continent was known 178 years before the so-
called ^rs^ discovery of the Cabo Tormentoso (Cape of Good
Hope) by Bartholomseus Diaz, in the month of May, 1487.*
The importance of such a commercial route, rapidly increas
ing from the time of Gama's expedition, was, on account of
the common aim of all West- African voyages, the occasion of
the two Southern Clouds being designated by the pilots Capft
Clouds, as remarkable celestial phenomena seen during voy-
ages to the Cape.

The constant endeavors made to advance along the eastern
shores of America, beyond the equator, and even to the south-
ern extremity of the continent, directed the attention of mar-
iners uninterruptedly to the southern stars, from the period of
Alonso de Hojeda's expedition, in which Amerigo Vespucci
took part (in 1499), to that of Magellan and Sebastian del
Cano in 1521, and of Garcia de Loaysa,t with Francisco de

* See my geographical investigations on the discovery of the south-
ern extremity of Africa, and on the stntements of Cardinal Zurla and
Count Baldelli in the Examen Crit. de VHist. de la Giographie aux quin-
zieme et seizieme siecles, tom. i., p. 229-348. The discovery of the Cape
of Good Hope, which Martin Behaim calls the Terra Fragosa, and not
Cabo Tormentosa, was made, singularly enough, when Diaz CB.me from
the east (from the Bay of Algoa, 33° 47' south latitude, and more than
7° 18' east of Table Bay). — Lichtenstein, in Das Vaterlu7idi$che Mtise-
urn, Hamburgh, 1810, $ 372-389.

t The merit of the discovery of the southernmost extremity of the
new continent in 55"^ south latitude (whose importance has not been
sufficiently estimated), is due to Francis de Hoces, who commanded
one of the ships of the expedition of Loaysa in 1525. It is very char-
acteristically described in Urdaneta's Journal by the words acabamiento
de tierra, " the ceasing of land." De Hoces probably saw a portion of
Terra del Fuego west of Staten Island, for Cape Horn is situated, ao
cording to Fitzroy, in 55"^ 58' 41". — See Navarette, Viages y descubrim.
de los Espanolesy tom. v., p. 28, 404.

46 COSMOS.

Hoces in 1525. It would appear from the journals still ex-
tant, and from the historical testimony of Anghiera, that the
southern stars were made the special objects of attention dur-
ing the voyage in which Amerigo Vespucci and Vicente Yanez
Pinzon discovered Cape San Augustin in 8° 20' south lati-
tude. Vespucci boasts on this occasion of having seen three
Canopi (one dark, Canopofosco; and two bright stars, Cano-
pi risplendenti). We find from an attempt made by Ideler,
the ingenious author of works on the " Names of the Stars"
and on " Chronology," to explain Vespucci's very confused
description of the southern heavens, in his letter to Lorenzo
Pierfrancesco de' Medici, of the party of the " Popolani," that
Vespucci used the name in nearly as indefinite a manner as
the Arabian astronomers had used the word Suhel. Ideler
shows that the '' canopo fosco nella via lattea'' must have
been the black spot, or large coal-sack in the Southern Cross ;
while the position of three stars, in which are supposed to be
recognized a, (i, and y of Hydrus, renders it very probable
that the " canopo risplendente di notabile grandezza" (of
considerable extent) is the Nubecula Major, and the second
risplende7ite the Nubecula Minor.^ It is very singular that
Vespucci should not have compared these recently-noticed
celestial objects to clouds, as « all other observers had done.
One would have thought the comparison irresistible. Peter
Martyr Anghiera, who was personally acquainted with all
the discoverers, and whose letters were written under the
vivid impression excited in his mind by their narratives, de-
scribes, with striking truthfulness, the mild but unequal efful-
gence of the nubecula3. He says, " Assecuti sunt Portugallen
ses alterius poli gradum quinquagesimum araplius, ubi punc-
tum (polum ?) circumeuntes quasdam nubeculas licet intueri,
veluti in lactea via sparsos fulgores per universi cobH globum
intra ejus spatii latitudinem."t The exceeding fame, and

* Humboldt, Examen Crit. de la Giogr., torn, iv., p. 205, 295-316
torn, v., p. 225-229, 235. Ideler, Sternnamen, ^ 346.

t Petrus Martyr Angh., Oceanica, dec. iii., lib. i., p. 217. I can
prove from the numerical data in dec. ii., lib. x., p. 204, and dec. iii.,
lib X., p. 232, that the portion of the Oceanica, in which the Magellanic?
Clouds are referred to, was written between 1514 and 1516, and there
fore immediately after the expedition of Juan Diaz de Solis to the Rio
de la Plata (then known as the Rio de Solis, una mar dulce). The lati-
tudes are much exaggerated.

f ** The Portuguese extended their discoveries to within less than 50
degrees of the South Pole, where they plainly observed certain nebulre
moving round the point (pole?), like the luminous spots scattered ia

MAGELLANIC CLOUDS. 47

the long duration of Magellan's circumnavigation (from Au-
gust, 1519, to September, 1522), and the long sojourn of a
numeJ-ous crew under the southern sky, obHterated the re-
membrance of all earher observations, and spread the name
of the Magellanic Clouds among all the sea-faring nations
of the Mediterranean.

We have thus shown by a single example how the exten-
sion of the geographical horizon southward opened a new
field to contemplative astronomy. There were four objects
to which the attention of pilots was especially directed in the
new hemisphere, viz., the search for a southern polar star, the
form of the Southern Cross, which assumes a vertical position
when it passes through the meridian of the place of observ-
ation, the Coal-sacks, and the circling clouds of light. We
learn from the treatise on the art of navigation [Arte de Nav-
egar, lib. v., cap. 11), by Pedro de Medina, which has been
translated into many languages, and first appeared in 1545,
that the meridian altitudes of the " Cruzero" were used as
early as the first half of the sixteenth century for the determ-
inations of latitude. Measurement soon succeeded the mere-
ly contemplative observation. The first work on the position
of stars contiguous to the antarctic pole was based on the dis-
tances of known stars of the Rudolphine Tables, as calcula-
ted by Tycho Brahe. This work, as I have already observed,*
was composed by Petrus Theodori of Embden, and Friedrich
Houtman of Holland, who navigated the Indian Seas about the
year 1594. The results of their measurements were speedi-
ly embodied in the Star- Catalogues and celestial globes of
Blaeuw (1601), of Bayer (1603), and of Paul Morula (1605).
Such were the materials for the foundation of the topography
of the southern heavens before Halley (1677), and before the
meritorious astronomical researches of the Jesuits Jean de
Fontaney, Richaud, and Noel. The intimate connection be-
tween the history of astronomy and that of geography thus
indicates those memorable epochs in which (scarcely two
hundred and fifty years ago) men first acquired the knowl-
edge necessary for the completion of the cosmical image of
the firmament and of the configuration of continents.

The Magellanic Clouds, the larger of which covers a ce-
lestial space of forty-two, and the smaller a space of ten
square degrees, certainly produce, at first sight, the same

the Milky Way throughout the arch of heaven within tho breadth of
that space."]

* Cosmos, vol. ii., p. 287; vol. iii., p. 112, 138.

48 COSMOS.

impression on tlie unaided eye as might be excited by two
bright portions of the Milky Way, equal in size and isolated
in position. The smaller cloud entirely disappears in clear
moonlight, while the larger one only loses a considerable por-
tion of its brightness. Sir John Herschel's delineation of
these objects is admirable, and accurately corresponds with
the vivid impressions excited in my own mind during my so-
journ in Peru. Astronomy is indebted to the laborious re-
searches of this observer at the Cape of Good Hope in 1837,
for the first accurate analysis of this most wondrous aggrega-
tion of heterogeneous elements. =^ He found a large number
of individual and scattered stars, stellar swarms and globular
clusters of stars, and both oval regular and irregular nebulae
more closely thronged together than in the nebulous zone of
Virgo and Coma Berenices. The nubecula can not, there-
fore, from this condition of complicated aggregation, be re-
garded, as has too often been done, either as exceedingly
large nebulae, or as detached portions of the Milky Way ;
for, with the exception of a small zone lying between the
constellation Ara and the tail of the Scorpion, globular stel-
lar clusters and oval nebulae are of rare occurrence in the
Galaxy, t

The Magellanic Clouds are not connected with one anoth-

* Cosmos, vol. i., p. 85, and note. See Observ. at the Cape, p. 143-
164; pi. vii. gives a representation of the Magellanic Clouds as tliey ap-
pear to the naked eye ; pi. x. the telescopic analysis of the Nubecula
Major, and pi. xi., fig. 4 ($ 20-23), affords a special view of the nebula
Doradfis. — Outlines, $ 892-896, pi. v., fig. 1, and James Dunlop in the
Philos. Transact, for 1828, parti., p. 147-151. So erroneous w^ere the
views of the earlier observers, that the Jesuit Fontaney, who was great-
ly esteemed by Dominique Cassini, and to whom we are indebted for
many valuable astronomical observations in India and China^ wrote as
follows so recently as 1685 : " Le grand et le petit nuages sont deux
choses singulieres. lis ne paraissent aucunement un amas d'etoiles
comme Praesepe Cancri, ni meme une lueur sombre, comme la nebu-
leuse d'Andromede. On n'y voit presque rieu avec de tres grandes
lunettes, quoique sans ce secours on les voie fort blancs, particuliere-
ment le grand nuage." " The lai-ge and the small cloud are both very
remarkable objects. They do not appear a mere mass of stars, like
Praesepe in Cancer, nor are they a faint light, like the nebula in An-
dromeda. Very little is to be seen within these bodies even with large
instruments, although when observed without such optical aid they ap
pear very white, and this is especially the case with the large cloud."
— Lettre du Pere de Fontaney an Pere de la Chaize, Confesseur du Roi,
in the Lettres Edijiantes, Recueil vii., 1703, p. 78; and Hist, de VAcad.
de$ Sciences dep. 1686-1699 (tom. ii., Paris, 1733), p. 19. In my de-
Bcription of the Magellanic Clouds, in the text, I have excli^sively fol.
lowed Sir John Herschel's work.

t Cosmos, voL iii., p. 145, and note.

MAGELLANIC CLOUDS. 49

er or with the Milky Way by any appreciable nebulous vapor.
If we except the cluster of stars in the constellation Toucan,*
Nubecula Minor is situated in a portion of the heavens bar-
ren of stars, and Nubecula Major in a less starless region.
The form and internal structure of the latter are so involved
that it presents many separate masses (as seen in No. 2878
of Herschel's Catalogue), which present an accurate image
of the aggregate condition of the whole clouds. The con-
jecture advanced by the meritorious observer Horner, that
the clouds were once parts of the Milky Way, in which we
can, as it were, recognize their original place, is a myth, and
quite as unfounded as the assertion that they have exhibit-
ed, since Lacaille's time, a progressive movement — an altera-,
tion of position. Their position was incorrectly given in con-
sequence of the indistinctness of their margins, when seen
through the older telescope having smaller apertures than
our more recently constructed instruments ; and Sir John
Herschel states that the lesser cloud is inserted about Ih.
Rt. Asc. out of its true position, in all celestial globes and
star-maps. According to him, Nubecula Minor lies between
the meridians of Oh. 28m. and Ih. 15m., N. P. Decl. 162^
and 165° ; Nubecula Major in E,t. Asc. 4h. 40m.— 6h. Om.,
and N. P. Decl. 156° and 162°. In the former he has cata-
logued according to right ascension and declination no less
than 919 stars, nebulse, and clusters, and in the latter 244.
With a view of separating the three classes, I have counted
the objects in the catalogue, which I find gives for

Stars. Nebulas. Clusters.

Nubecula Major 582 291 46

Nubecula Minor 200 37 7

The inconsiderable number of nebulsB contained in Nubecula
Minor is very striking, for we find that, compared to the neb-
ulae in Nubecula Major, they are only as 1 : 8, while the ra-
tio of the isolated stars is about 1:3. The catalogued stars,
almost 800 in number, are for the most part of the 7th and
8th magnitudes ; some few belong even to the 9th and 10th
magnitudes. There is in the middle of the larger cloud a
nebula, noticed by Lacaille (30 Doradus, Bode, No. 2941 of
Sir John Herschel's Catalogue), which is said to resemble no
other nebulous body in form. Although it occupies scarcely
ji gth of the area of the whole cloud. Sir John Herschel has
determined the position of 105 stars of from the 14th to the

* Cosmos, vol. ill., p. 142, and note.
Vol. IV.— C

60 COSMOS.

16th magnitude in this space. These stars are projected on
the wholly unresolved, uniformly bright and unspeckled neb-
ula.=^

The Black Specks which attracted the attention of Portu-
guese and Spanish pilots as early as the close of the fifteenth
and the beginning of the sixteenth centuries, circle round the
southern pole opposite to the Magellanic Light-clouds, al-
though at a greater distance from it. They are probably, as
already remarked, the Ca7iopo fosco of the "three Canopi,"
described by Amerigo Vespucci in his third voyage. I find
the first definite notice of these spots in the first Decade of
Anghiera's work, ''De Rebus Oceanicis"" (Dec. i., lib. 9, ed.
1533, p. 20, b). "Interrogati a me nautas qui Vicentium Ag-
nem Pinzonum fuerant comitati (1499), an antarcticum vide-
rint polum : stellam se nullam huic Arcticse similem, quso
discerni circa punctum (polum ?) possit, cognovisse inquiunt.
Stellarum tamen aliam, ajunt, se prospexisse faciem den-
samque quandam ab horizonte vaporosam caliginem, qusB
oculos fere obtenebraret."! The word Stella is used here for
a celestial constellation, and the narrators may not have ex-
plained themselves very distinctly in reference to a caligo
which obscured their sight. Father Joseph Acosta, of Me-
dina del Campo, gives a more satisfactory account of the
Black Specks and the cause of this phenomenon. He com-
pares them, in his Historia Natural de las Indias (lib. i.,
cap. 2), to the echpsed portion of the Moon's disk in respect
to color and form. " As the Milky "Way," he says, "is more
brilliant because it is composed of denser celestial matter, and
hence gives forth more light, so likewise the Black Specks,
which are not visible in Europe, are entirely devoid of light,
because they constitute a portion of the heavens which is
barren, i. e., composed of very attenuated and transparent
matter." The error of a distinguished astronomer in sup-
posing that this description referred to the spots of the Sun, J
seems scarcely less singular than that the missionary Richaud

* See Observ. at the Cape, § 20-23 and 133, the beautiful drawing, pi.
ii., fig. 4, and a special map of the graphical analysis.— PL x., as well
as Outlines, $ 896, pi. v., fig. 1.

t " I asked some mariners who had accompanied Vicentius Agnes
Pinzo (1499) whether they saw the antarctic pole, and they told me
that they did not observe any star like our North Star, which may be
Been about the arctic pole, but that they noticed stars in another forna,
having the appearance of a dense and dark vapor rising frcxn the hori-
«on, which almost obscured their vision.

X Cosmos, vol. ii., p. 287, and note.

THE COAL-SACKS. 51

(1689) should have mistaken Acosta's ''manchas negras'' for
the luminous Magellanic Clouds.*

Richaud, moreover, like the earliest pilots, speaks of the
Coal-sacks in the plural, mentioning two, of which the large
one was situated in the constellation of the Cross, and an-
other in Charles's Oak ; the latter, according to other descrip-
tions, was subdivided into two distinct specks. These were
described by Feuillee in the early part of the eighteenth
century, and by Horner (in a letter to Olbers, written from
Brazil in 1804), as undefined, and having confused outlines.!
I was unable, during my residence in Peru, to discover any
thing definite as to the Coal-sacks in Charles's Oak ; and as
I was disposed to ascribe this to the low position of the con-
stellation, I applied for information to Sir John Herschel and
to Riimker, the director of the Observatory at Hamburgh,
who had been in far more southern latitudes than myself.
Notwithstanding their endeavors, they were equally unsuc-
cessful in discovering any thing that could be compared for
definiteness of outline and intensity of blackness with the
Coal-sack in the Cross. Sir John Herschel is of opinion that
we can not speak of a plurality of Coal-sacks, unless we would
include under that head every ill-defined and darker portion
of the heavens, as the regions between a Centauri and fS and
y Trianguli,$ between rj and 6 Argus, and more especially
the barren portion of the Milky Way in the Northern heav-
ens, between e, a, and y Cygni.^

The longest known Black Speck in the Southern Cross,
and the one which is also the most striking as seen by the
naked eye, is of a pear-like shape, and lies on the eastern
side of that constellation, in 8° long, and 5° lat. This large
space presents one visible star of the 6th to the 7th magni
tude, together with a large number of telescopic stars, vary
ing from the 11th to the 13th magnitudes. A small group
of 40 stars lies nearly in the center. ll The paucity of stars,
and the contrast with the magnificent effulgence of the neigh-

* M^m. de V Acad, des Sciences dep. 1666 jusqu'a 1699, t. vii., partie 2
(Paris, 1729), p. 206.

t Letter to Olbers from St. Catharina (January, 1804), in Zach's
Monatl. Correspondenz zur Beford. der Erd- nnd Himmels-Kunde, bd.
X., p. 240. See, on Feuillee's observation and rough sketch of the black
spot in the Southern Cross, Zach, Op. cit., bd. xv., 1807, p. 388-391.

% Observ. at the Cape, pi. xiii. § Outlines of Astronomy, p. 531,

II Observ. at the Cape, p. 384, No. 3407, of the catalogue of nebulae
and clusters. (Compare Dunlop in the Philos. Transact, for 1828, p.
149, and No. 272 of his Catalogue.)

52 COSMOS.

boring heavens, are assigned as the causes of the remarkable
blackness of this portion of the firmament. This opinion,
which has been generally maintained since Lacaille's time,*
has been especially confirmed by the " gauges" and " sweeps"
made round the region where the Milky Way appears as if
covered by a black cloud. The Coal-bag yielded from seven
to nine telescopic stars for every sweep, but never an entirely
blank field ; while in a field of equal size the margins pre-
sented from 120 to 200 stars. This mode of explanation,
which ascribes the darkness to contrast alone, did not, al-
though perhaps incorrectly, appear quite satisfactory to me
while I was in a tropical region, and remained under the
vivid impression produced on my mind by the aspect of the
southern heavens. "William Herschel's considerations on
wholly starless regions in Scorpio and Serpentarius, and
which he has termed "openings in the heavens," led me to
the idea that the starry strata lying behind one another in
such regions may be less dense, or even wholly interrupted,
and that our instruments being insufficient to penetrate to
these last strata, "we look into the remote regions of space,
as through tubes." I have already elsewhere noticed these
openings,! and the effects of perspective on such interruptions
in the starry strata have again been lately made the subject
of earnest consideration. $

The extreme and most remote strata of self-luminous cos-
mical bodies — the distances of nebulae — all that has been
considered in the last seven sidereal or astrognostic portions
of this work, fill the imagination and the speculative mind
of man with images of time and space surpassing his powers
of comprehension.

* " Cette apparence d'un noir fonc§ dans la partie Orientale de la
Croix du Sud, qui frappe la vue de tous ceux qui regardent le cie
austral, est causee par la vivacite de la blancheur de la voie lactee qui
renferme I'espace noir et I'entoure de tous cotes." " The appearance
of deep black in the eastern portion of the Southern Cross, which
strikes all who observe the heavens in those regions, is owing to the
intensity of the whiteness of the Milky Way surrounding the black
space on every side." — Lacaille, in the M6m. de V Acad, des Sciencea,
annee 1755 (Paris, 1761), p. 199.

t Cosmos, vol. i., p. 152, and note.

I " When we see," says Sir John Herschel, " in the Coal-sack (near
a Crucis) a sharply-defined oval space free from stars, it would seem
much less probable that a conical or tubular hollow traverses the whole
of a starry stratum, continuously extended from the eye outward, than
that a distant mass of comparatively moderate thickness should be sim
ply perforated from side to side." — Outlines, $ 702, p. 532.

THE SOIiAR REGION. 55

However wonderful are the improvements made in optical
instruments within scarcely sixty years, we are at the same
time too well acquainted with the difficulties of their con-
struction to indulge in the bold and even unlicensed antici
pations so ardently cherished by the intellectual Hooke from
1663 to 1665."^ Moderation in the expectations entertained
will be the most likely to lead to their fulfillment. Each
succeeding generation has reaped the noblest and most ex
alted results from the triumphs of free intellect in the differ-
ent stages to which art has gradually exalted itself. Without
attempting to express in definite numbers the distances to
which the space-penetrating powers of telescopic vision may
already reach, and without attaching much confidence to
such numbers, the knowledge of the velocity of light yet pro-
claims that the appearance of the remotest star — the light-
generating process on its surface — is the " most ancient sens-
uous evidence of the existence of matter."!

(3. The Solar Region.

planets and their satellites. comets. ring op the

zodiacal light. swarms of meteor-asteroids.

On passing, in the Uranological portion of the physical
description of the universe, from the heaven of the fixed stars
to our solar and planetary system, we descend from the great
and universal to the relatively small and special. The do-
main of the Sun is the domain of one individual fixed star
among the millions revealed to us in the firmament by tel-
escopic aid — the limited space in which very various cosmical
bodies, in obedience to the direct attraction of a central body,
revolve around it in more or less extended orbits, whether
they are isolated or encircled by other bodies similar to them-
selves. Among the stellar bodies whose arrangement we
have endeavored to consider in the sidereal portion of the
Uranology, there is, indeed, a class of those millions of tele-
scopic fixed stars — double stars — which exhibit special, bi
nary, or multiple systems ; but notwithstanding the analogy
presented by the forces by which they are impelled, they yet
differ in their natural character from our solar system. In

* Lettre de Mr. Hooke k M. Auzout, in the M4m. de VAcadimie,
1666-1699, torn, vii., partie ii., p. 30, 73. t Cosmos, vol. i , p. 154

54 • COSMOS.

them, self-luminous fixed stars revolve round one common
center of gravity, which is not filled with visible matter ;
while in our solar system dark cosmical bodies rotate around
a self-luminous body, or, to speak more definitely, around one
common center of gravity, which lies at different times either
within or without the central body. " The great ellipse
which the Earth describes round the Sun is reflected in a
small perfectly similar one, in which the central point of the
Sun moves round its own and the Earth's common center of
gravity." In general notices like the present, we need hard-
ly enter into any special consideration of the question as to
whether the planetary bodies, among which we must class
interior and exterior comets, may not be capable, at least in
part, of generating some special light of their own, in addition
to that which they receive from the central body.

We have hitherto acquired no direct evidence of the exist-
ence of dark planetary bodies revolving round other fixed
stars. The faintness of the reflected light would prevent
their ever being visible to us, if, as Kepler conjectured (long
before Lambert), such bodies actually revolve round every
fixed star. If the nearest fixed star, a Centauri, be 226,000
times the Earth's distance, or 7523 times the distance of Nep-
tune ; if a very distant comet, that of 1680 (to which has been
ascribed, although on very uncertain data, a revolution of
8800 years), is twenty-eight times the distance of Neptune
from our solar system when in its aphelion, then the distance
of the fixed star a Centauri is still 270 times greater than
the distance of our solar system from the aphelion of the most
remote comet. The light of Neptune is reflected to us from
a distance thirty times greater than our distance from the
Sun. If, by the future construction of more powerful tele-
scopes, three additional planets should be recognized, each
situated at about 100 times the Earth's distance from the
other, even this would not amount to the eighth part of the
distance int'ervening to the aphelion of the comet referred to,
or to the 2200th part of the distance^ which the reflected

* See Cosmos, vol. i., p. 109, 148, where I based my calculations on
the distance of Uranus, which then constituted the extreme known
boundary of the planetaiy system. If we assume the distance of Nep-
tune from the Sun to be 3004 times that of the Earth, the distance of
a Centauri from the Sun would still be 7523 times that of Neptune, the
parallax being assumed as 0' -9128 {Cosmos, vol. iii., p. 191),. yet the
distance of 61 Cygni is nearly two and a half, and that of Sirius (with
a parallax of 2"-230) four times that of a Centauri. The distance of
Neptune from the Sun is about 2484 millions of geographical miles, and

THE SOLAR REGION. 55

light of a satellite revolving round a Centauri would have
to traverse in order to reach our telescopic vision. But is it
absolutely necessary that we should assume the existence of
ratellites around the fixed stars ? For when we cast a glance
at the subordinate particular systems within our large plan-
etary system, we find that, notwithstanding the analogies
which may present themselves in planets attended by many
satellites, there are others, such as Mercury, Venus, and Mars,
which have no attendant moons. If we disregard that which
is merely possible, and limit ourselves to the consideration of
that which is actually explored, we shall be vividly impressed
with the idea that the solar system, especially in the great
mutual connection revealed to us during the last ten years,
yields the richest image of the evident and direct relations
borne by many cosmical bodies to a special one.

The more limited sphere of the planetary system afibrds
by its very limitation undoubted advantages, both as to the
certainty and correctness of the facts ascertained by measuring
and calculating astronomy, over the results of a contempla-
tion of the heaven of the fixed stars. Many of these results
are only connected with contemplative astronomy, through the
medium of stellar swarms and nebulous groups, as well as of
the insecurely-based photometric arrangement of the stars.
The most certain and brilliant portion of astrognosy is the
determination of positions by right ascension and declination
— a department of astronomical science that has been very
extensively improved and increased in our own day, in refer-
ence to isolated fixed stars, double stars, stellar masses, and
nebulae. Equally difficult, although more or less accurately
measurable relations likewise present themselves in the prop-
er motion of the stars — the elements from which their paral-
laxes are determined — telescopic star-gauging, which leads

that of Uranus, according to Hansen, about 1586 millions. The dis-
tance of Sirius amounts, according to Galle (assuming the parallax
computed by Henderson), to 896,800 radii of the Earth's orbit, or
74,188,000 millions of geographical miles, a distance which gives four-
teen years for the passage of light. The aphelion of the comet of 1680
is forty-four times the distance of Uranus, and therefore twenty-eight
times that of Neptune from the Sun. According to these assumptions,
the Sun's distance from the star a Centauri is nearly 270 times that of
this comet in its aphelion, which we regard as the minimum of the very
bold estimates of the radius of the solar system (see p. 204). The es.
timate of such numerical relations has, at all events, this merit, not-
withstanding other defects, that the assumption of a very high standard
of measurement of space leads to results which may be expressed in
•mailer numbers

5G COSMOS.

us to the distribution in space of cosmical bodies — ^the pericdfc
of variable stars — and the slow revolution of double stars.
That which, from its very nature, is not amenable to meas-
urement, such as the relative position and configuration of
starry strata or rings of stars, the arrangement of the uni-
verse, and the effects of powerfully metamorphic physical
forces=^ in the sudden appearance or extinction of the so-called
new stars, excite the mind the more deeply and vividly, its
touching on the confines of the graceful domain of fancy.

We purposely abstain in the following pages from entering
on the consideration of the connection existing between our
solar system and the systems of other fixed stars, nor shall we
revert to the question of that subordination and annexation
of cosmical systems which might almost be said to force it-
self on our notice from intellectual necessity ; nor yet will
we consider whether our central body, the Sun, may not it-
self stand in some planetary dependence on a higher system
— not even, perhaps, as a main planet, but merely as a plan-
etary satellite, like Jupiter's moons. Limited within the
more familiar sphere of our solar region, we, however, enjoy
this advantage, that with the exception of what refers to the
signification of the surface-appearance or gaseous envelopes
of the revolving cosmical bodies, the simple or divided tails
of comets, the ring of the zodiacal light, or the mysterious ap-
pearance of meteoric asteroids, almost all the results of ob-
servation admit of being referred to numerical relations, as
the deductions of strictly-tested presuppositions. It does not,
however, belong to the sketch of a physical description of the
universe to test the accuracy of such presuppositions, its prov-
ince being simply to give a methodical arrangement of numer-
ical results. They constitute the important heritage whicli,
ever augmenting, is bequeathed by one century to another.
A table, comprising the numerical elements of the planets
(that is to say, their mean distances from the Sun, sidereal
periods of revolution, the eccentricity of their orbits, their in-
clination toward the ecliptic, their diameter, mass, and dens-
ity), would now embrace within very narrow limits the rec-
ord of the great intellectual conquests of the present age. Let
us for a moment transport ourselves in imagination to the
times of the ancients, and fancy Philolaiis the Pythagorean,
the instructor of Plato, Aristarchus of Samos, or Hipparchus,
in possession of such a numerical table, or of a graphic rep-

• On the appearance of new stars, and their subsequent disappear
ance, see p. 151-164.

THE SOLAR REGION. 57

resentation of the orbits of the planets, such as is given in
our most epitomized manuals, there is scarcely any thing to
which we could compare the admiration and surprise of these
men — the heroes of the early and limited knowledge of that
age — excepting, perhaps, that which might have been expe-
rienced by Eratosthenes, Strabo, and Claudius Ptolemy, could
they have seen one of our maps of the world, on Mercator's
projection, not above a few inches in length and breadth.

The return of comets in closed elliptical orbits, as a conse-
quence of the attractive force of the central body, indicates
the limits of the solar region. As, however, we are as yet
ignorant whether comets may not some day appear in which
the major axis may prove to be larger than any that have as
yet been observed and calculated, these bodies must be re-
garded as indicating, in their aphelia, merely the limits to
which the solar regions must at least extend. Hence we may
characterize the solar system by the visible arM measurable
results of peculiar operating central forces, and by the cos-
mical bodies (planets and comets) which rotate round the Sun
in closed orbits, and are intimately connected with it. The
considerations which at present engage our attention do not
embrace a notice of the attraction which the Sun may exert
on other suns (or fixed stars) lying beyond the limits of these
reappearing cosmical bodies.

According to the state of our knowledge at the close of
this half of the nineteenth century, the solar region includes
the following bodies, arranging the planets according to theii
respective distances from the central body :

22 Principal Planets (Mercury, Venus, the Earth,
Mars ; Flora, Victoria, Vesta, Iris, Metis, Hebe, Parthen-
ope, Irene, Astrcea, Egeria, Juno, Ceres, Pallas, Hygiea ,
Jupiter, Saturn, Uranus, Neptune) ;

21 Satellites (1 belonging to the Earth, 4 to Jupiter,
8 to Saturn, 6 to Uranus, 2 to Neptune) ;

197 Comets, whose orbits have been calculated. Of
these, 6 are interior ; i.e., such as have their aphelia in-
closed within the outermost of the planetary orbits, viz., that
of Neptune : we may very probably add to these

The Rino of the Zodiacal Light, which probably
lies between the orbits of Venus and Mars ; and likewise,
according to the opinion of numerous observers,

The Swarms of the Meteor.-Asteroids which more
especially intersect the Earth's orbit at certain points
C 2

58 COSMOS.

In the enumeration of the 22 principal p anets, of which
6 only were known before the 13th of March, 1781, the 14
small planets, which are sometimes termed co-planets or as-
teroids, and describe intersecting orbits between Mars and
Jupiter, have been distinguished from the 8 larger 2^lci'nets
by the use of smaller type.

The following occurrences constitute main epochs in the
more recent history of planetary discoveries. The discovery
cf Uranus, as the first planet beyond Saturn's orbit, by Will-
iam Herschel, at Bath, on the 13th of March 1781, who rec-
ognized it by its motion and disk-like form ; the discovery of
Ceres — the first observed of the smaller planets — on the 1st
of January, 1801, by Piazzi, at Palermo ; the recognition of
the first interior comet, by Encke, at Gotha, in August, 1819,
and the prediction of the existence of Neptune by Leverrier,
at Paris, in August, 1846, by the calculation of planetary dis-
turbances, sM well as the discovery of Neptune by Galle, at
Berlin, on the 23d of September, 1846. These important
discoveries have not only tended directly to extend and en-
rich our knowledge of the solar system, but have further led
to numerous other discoveries of a similar nature ; as, for in-
stance, to the knowledge of five other interior comets (of Bi-
ela, Faye, De Vico, -Brorsen, and D'Arrest, between 1826 and
1851), and of thirteen small planets, three of which, Pallas,
Juno, and Vesta, were discovered from 1801 to 1807, and aft-
er an interval of fully thirty-eight years, since Hencke's for-
tunate and preconceived discovery of Astrsea, on the 8th of
December, 1845, the nine others were discovered, in rapid suc-
cession, by Hencke, Hind, Graham, and De Gasparis, from
1845 to the middle of 1851. The attention of observers has
of late been so extensively directed to the cometary world, that
the orbits of thirty-three newly-discovered comets have been
calculated during the last eleven years ; hence, nearly as
many as had oeen determined during the previous forty yearg
of this century .

THE SUN. 59

THE SUN CONSIDERED AS THE CENTRAL BODY.

The lantern of the world {lucerna Mundi), as Copernicub
names the Sun,=^ enthroned in the center, is, according to
Theon of Smyrna, the all- vivifying, pulsating heart of the
Universe ;t the primary source of light and of radiating heat,
and the generator of numerous terrestrial, electro-magnetic
processes, and, indeed, of the greater part of the organic vital
activity upon our planet, more especially that of the vegetable
kingdom. In considering the expression of solar force in its
widest generality, we find that it gives rise to alterations on
the surface of the Earth — partly by gravitative attraction —
as in the ebb and flow of the ocean (if we except the share
taken in the phenomenon by lunar attraction) — partly by light
and heat-generating transverse vibrations of ether, as in the
fructifying admixture of the aerial and aqueous envelopes of
our planet, from the contact of the atmosphere with the vap-
orizing fluid element in seas, lakes, and rivers. The solar
action operates, moreover, by differences of heat, in exciting
atmospheric and oceanic currents, the latter of which have
continued for thousands of years (though in an inconsiderable
degree) to accumulate or wash away alluvial strata, and thus
change the surface of the inundated land ; it operates in the
generation and maintenance of the electro-magnetic activity
of the Earth's crust, and that of the oxygen contained in the
atmosphere ; at one time calling forth calm and gentle forces
of chemical attraction, and variously determining organic life
in the endosmoee of cell-walls and in the tissue of muscular
and nervous fibres ; at another time evoking light-processes
in the atmosphere, such as the colored coruscations of the polar
light, the thunder and lightning, hurricanes, and water-spouts.

Our object in endeavoring to compress in one picture the

* I have already, :n an earlier part of this work (vol. ii., p. 308, and
note *), given the passage imitated from the Somnium Scipionis, in ch.
X. of the first book De Revolut.

t "The Sun is the heart of the Universe." — Theonis Smymcei, Pla-
tonici Liber de Astronomia, ed. H. Martin, 1849, p. 182, 298: t^? e/z^'u-
XtciQ fiiaov TO nepi tov tjIlov, olovel Kapdcav ovra tov Travrdf , bdev (pepov-
civ avTov Kul TTiv 'ipvxvv dp^afiivTjv 6ia Travrof ^kecv tov au/xuTOc tstc-
uevTjv and tuv nepuTuv. (This new edition is worthy of notice, since it
completes the peripatetic views of Adrastus, and many of the Platonic
dogmas of Dercyllides.) '

60 COSMOS.

influences of solar action, in as far as they are independent
of the orbit and the position of the axis of our globe, has been
clearly to demonstrate, by an exposition of the connection ex-
isting between great, and, at first sight, heterogeneous phe-
nomena, how physical nature may be depicted in the History
of the Cosmos as a whole, moved and animated by internal
and frequently self-adjusting forces. But the waves of light
not only exert a decomposing and recombining action on the
corporeal world — they not or iy call forth the tender germs of
plants from the earth, generate the green coloring matter
(chlorophyll) within the leaf, and give color to the fragrant
blossom — they not only produce myriads of reflected images
of the Sun in the graceful play of the waves, as in the moving
grass of the field, but the rays of celestial light, in the varied
gradations of their intensity and duration, are also mysteri-
ously connected with the inner life of man, his intellectual
susceptibilities, and the melancholy or cheerful tone of his
feelings. " Cccli tristitiam discutit Sol et humani 7iubila
animi serenat^ (Phn., Hist. Nat., ii., 6.)

In the description of each of the cosmical bodies, I shall
precede whatever consideration of their physical constitution
may (except in the case of the Earth) be necessary by their
respective numerical data. The numerical arrangement of
these results is nearly identical with that which was adopted
by Hansen,^ in his admirable Review of the Solar System,
although I have necessarily made some alterations and addi-
tions in the data, from the fact that 1 1 planets and 3 satel
lites have been discovered since 1837, the year in which Han-
sen wrote.

The mean distance of the center of the Sun from the Earth
is, according to Encke's supplementary correction of the
Sun's parallax {Ahhandlung der Berl. Akad., 1835, p. 309),
82,728,000 geographical miles, of which 60 go to an equa-
torial degree, and of which each one, according to Bessel's
investigation often measurements of degrees {Cosmos, vol. i.,
p. 165), contains exactly 951,807 toises, or 5710-8405 Paris
feet, or 6086-76 English feet.

Light requires for its passage from the Sun to the Earth,
i. e., to traverse the radius of the Earth's orbit, according to
Struve's observations of aberration, 8' 17"'78 {Cosmos, vol.
iii., p. 83) ; whence it follows that the Sun's true position ia
about 20"-445 in alvance of its apparent place.

• Hansen, in Schumacher's Jahrbuch for 1837, p. 65-141.

THE sun's spots. 61

The apparent diameter of the Sun, at its mean distance
from the Earth, is 32' l"-8, and therefore only 54"' 8 greater
than the Moon's disk at its mean distance from us. In the
perihelion, when in winter we are nearest to the Sun, the
apparent diameter of the latter increases to 32' 34"*6 ; in the
aphelion, when in summer we are farthest from the Sun, its
apparent diameter is diminished to 31' 30"' 1.

The Sun's true diameter is 770,800 geographical miles, oi
more than 112 times greater than that of the Earth.

The mass of the Sun is, according to Encke's calculation of
Sahine's pendulum formula, 359,551 times that of the Earth,
or 355,499 times that of the Earth and Moon together ( Vierte
Abhandlung uber den Cometen von Pons in den Schr. der
Bed. Akad., 1842, p. 5) ; whence the density of the Sun is
only about one fourth (or, more accurately, 0-252) that of the
Earth.

The volume of the Sun is 600 times greater, and its mass
(according to Galle) 738 times greater than that of all the
planets combined. It may assist the mind in conceiving a
sensuous image of the magnitude of the Sun, if we remem-
ber that if the solar sphere were entirely hollowed out, and
the Earth placed in its center, there would still be room
enough for the Moon to describe its orbit, even if the radius
of the latter were increased 160,000 geographical miles.

The Sun rotates on its axis in 25^ days. The equator in-
clines about 7° 30' toward the ecliptic. According to Lau-
gier's very careful observations {Comptes Rendus de V Acad,
des Sciences, tom. xv., 1842, p. 941), the period of rotation
is 25yW days (or 25d. 8h. 9m.), and the inclination of the-
equator 7° 9'.

The conjectures gradually adopted in modern astronomy re-
garding the physical character of the Sun's surface are based
on long and careful observations of the alterations which take
place in the self-luminous disk. The order of succession, and
the connection of these alterations (the formation of the Sun-
spots, the relation of the deep black nuclei to the surround-
ing ash-gray penumbras), have led to the assumption that the
body of the Sun itself is almost entirely dark, but surrounded
at a considerable distance by a luminous envelope ; that fun-
nel-shaped openings are formed in this en> elope, in conse-
quence of the passage of currents from below upward, and
that the black nucleus of the spot is a portion of the dark
body of the Sun which is visible through the opening. In oi
der to render this explanation, of which we here only briefly

62 COSMOS.

give the most general features, sufficiently applicable to the
Aotails of the phenomena upon the surface of the Sun, science
at present assumes the existence of three envelopes round the
dark solar sphere ; viz., one interior cloud-like va'poroits en-
velope, next a luminous investment (photosphere), and above
these, as appears to have been especially shown by the solar
echpse of the 8th of July, 1842, an external cloudy envelope ^
which is either dark or slightly luminous.*

As felicitous presentiments and sports of fancy — such sub-
sequently realized speculations as abound in Grecian antiqui-
ty— sometimes contain the germ of correct views long prior
to any actual observation, so we find in the writings of Car-
dinal Nicolaus de Cusa (in the second book De docta Igno-
rantid), which belong to the middle of the fifteenth century,
the clearly expressed opinion that the body of the Sun itself
is only " an earth-like nucleus, surrounded by a circle of light
as by a delicate envelope ; that in the center (between the
dark nucleus and the luminous covering?) there is a mixture
of water-charged clouds and clear air, similar to our atmos-

* "D'apres I'etat actuel de nos connaissances astronomiques le Soleil
Be compose, 1. d'un globe central £l peu pres obscur; 2. d'une immense
couche de nuages qui est suspendue k une certaine distance de ce globe
etl'enveloppe de toutes parts ; 3. d'une photosphere ; en d'autres termes,
d'une sphere resplendissante qui enveloppe la couche nuageuse, comme
celle-ci, k son tour, enveloppe le noyau obscur. L'eclipse totale du 8
Juillet, 1842, nous a mis sur la trace d'une troisieme enveloppe, situee
au-dessus de la photosphere et formee de nuages obscurs ou faiblement
lumineux. Ce sent les nuages Ae la troisieme enveloppe solaire, situes
en apparence, pendant l'eclipse totale, sur le contour de I'astre ou un
peu en dehors, qui ont donne lieu k ces singulieres preeminences rou-
ge^tres qui en 1842 ont si vivement excite I'altention du monde savant."
"According to the present condition of our astronomical knowledge,
the Sun is composed, 1st. of a central sphere which is nearly dark ; 2d.
of a vast stratum of clouds, suspended at a certain distance from the
central body, which it surrounds on all sides; 3d. of a photosphere, or,
in other words, a luminous sphere inclosing the cloudy stratum, which
in its turn envelops the dark nucleus. The total eclipse of the 8th of
July, 1842, afforded indications of a third envelope, situated above the
photosphere, and formed of dark or faintly illumined clouds. These
clouds of the third solar envelope, apparently situated during the total
eclipse on the margin ol' the Sun, or even a little beyond it, gave rise
to those singular, rose-c( lored protuberances, which so powerfully ex-
cited the attention of the scientific world in 1842." — Arago, in the An-
nuaire du Bureau des Longitudes pour Van 1846, p. 464, 471. Sir John
Herschel, in his Outlines of Astronomy, p. 234, § 395 (edition of 1849),
thus expresses himself: "Above the luminous surface of the Sun, and
the region in which the spots reside, there are strong indications of the
existence of a gaseous atmosphere, having a somewhat imperfect trans-
parency."

THE sun's spots. 63

phere ; and that the power of radiating light to vivify the
vegetation of our Earth does not appertain to the earthy nu-
cleus of the Sun's body, but to the luminous covering by which
it is enveloped." This view of the physical condition of the
Sun's body, which has hitherto been but little regarded in the
history of astronomy, presents considerable similarity with the
opinions maintained in the present day.=^

* I would, in the first place, give in the original the passages to which
I refer in the text, and to which my attention was directed by a learned
work of Clemens. {Giordano Bruno nndNicoIaus von Ctt«ar,1847,$101.)
Cardinal Nicolaus de Cusa (whose family name was KhrypfFs, i. e., Crab)
was born at Cues, on the Moselle. He thus writes in the twelfth chap-
ter of the second book of the Treatise De docta Ignorantia (Nicolai de
Cusa Opera, ed. Basil, 1565, p. 39), a work that was much esteemed
at that age : " Neque color nigrediuis est argumentum vilitatis Terrae ;
nam in Sole si quis esset, non appareret ilia claritas qure nobis : consid
erato enim corpore Solis, tunc habet quandam quasi terram centrali-
oi-em, et quandam luciditatem quasi ignilem circumferentialem, et in
medio quasi aqueam nubem et a^rem clariorem, quemadmodum terra
ista sua elementa." " Blackness of color is no proof of the inferiority
of the Earth's substance ; for to an inhabitant of the Sun, if such there
be, the same brilliancy of appearance would not be presented as to us:
if we consider the Sun's body, we shall conclude that it consists of a
certain earthy substance in the center, surrounded by a luminous mat-
ter, partaking, perhaps, of the nature of fire, and in the midst a sort of
aqueous clouds and brighter atmosphere, resembling the elements of
which the Earth consists." To this are appended the words Paradoxa
and Hypni; by the last of which, he probably understands {hvvnvLa)
certain speculations, vague and bold hypotheses. In the long Treatise,
Exercitationes ex Sermonibus Cardinalis {Opera, p. 579), I again find
the following comparison : " Sicut in Sole considerari potest natura cor-
poralis, et ilia de se non est magnse virtutis" (notwithstanding the at-
traction of masses or gravitation!) " et non potest virtutem suam aliis
corporibus communicare, quia non est radiosa ; et alia natura lucida ilia
anita, ita quod Sol ex unione utriusque naturae habet virtutem quae suf-
ficit huic sensibili mundo, ad vitam innovandam in vegetabilibus et an-
iraalibus, in elementis et mineralibus per suam influentiam radiosam.
Sic de Christo, qui est Sol justitiae . . . ." "As in the Sun may be
supposed to exist a corporeal nature, which of itself is of no great effi-
cacy, and can not communicate its virtues to other bodies, because it is
not radiant, and another nature united with this ; so that the Sun, from
the union of the two natures, has a virtue which suffices for this sensi-
ble world, to renew life in vegetables and animals, in elements and
minerals, by its own radiant influence. So from Christ, the Sun of Jus-
tice . . . ." Dr. Clemens thinks that all this must be more than a
mere felicitous presentiment. It appears to him unlikely that Cusa, in
the expressions " Considerato corpore Solis ;^^ "in Sole considerari po-
' test . . . ." " could have appealed to experience, without a tolerably
accurate observation of the Sun's spots, both their darker portions and
the penumbrae." He also conjectures " that the penetration of the phi-
losopher may have been in advance of the results of the science of his
age, and that his views may have been influenced by discoveries which

o4 COSMOS.

The spots on the Sun, as I have already shown in the
Historical Epochs of the Physical Contemplation of the
Universe,* were not first observed by Gahleo, Scheiner, or
Harriot, but by John Fabricius of East Friesland, who also
was the first to describe, in a printed work, the phenomenon
he had seen. Both this discoverer and Gralileo, as may be
se3n by his letter to the Principe Cesi (25th of May, 1612),
were aware that the spots belonged to the body of the Sun
itself; but ten or twenty years later, Jean Tarde, a canon of
Sarlat, and a Belgian Jesuit, maintained almost simultane-
ously that the Sun's spots were the transits of small planets.
The one named them Sidera Borbonia, the other Sidera
Austriaca.i Scheiner was the first who employed blue and

have usually been ascribed to later observers." It is, indeed, not only
possible, but even highly probable, that in districts w^here the Sun is
obscured for many months, as on the coast of Peru, during the garua,
even uncivilized nations may have seen Sun-spots with the naked eye ;
but no traveler has, as yet, afforded any evidence of such appearances
having attracted attention, or having been incorporated among the re-
ligious myths of their system of Sun-worship. The mere observation
of the rare phenomenon of a Sun-spot, when seen by the naked eye, in
the low, or faintly obscured, white, red, or perhaps greenish disk of the
Sun, would scarcely have led even experienced observers to conjecture
the existence of several envelopes around the dark body of the Sun.
Had Cardinal de Cusa known any thing of the spots of the Sun, he
would assuredly not have failed to refer to these macules Solis in the
many comparisons of physical and spiritual things in which he was too
much inclined to indulge. We need only recall the excitement and
bitter contention with which the discovenesof Joh. Fabricius and Gal-
ileo were received, soon after the invention of the telescope in the
beginning of the seventeenth century. 1 have already referred {Cos'
mos, vol. ii., p. 311) to the obscurely expressed astronomical views of
the cardinal, who died in 1464, and therefore nine years before the
birth of Copernicus. The remarkable passage, "Jam nobis manifest-
um est Terram in veritate moveri;" "Now it is evident that the Earth
really moves," occurs in lib. ii., cap. 12, De docta Ignorantia. Accord
ing to Cusa, motion pervades every portion of the celestial regions; we
do not even find a star that does not describe a circle. " Terra non
potest esse fixa, sed movetur ut aliae stellae;" "The Earth can not be
fixed, but moves like other stars." The Earth, however, does not re-
volve round the Sun, but the Earth and the Sun rotate " around the
ever-changing pole of the universe." Cusa did not, therefore, hold the
Copernican views, as has been so successfully shown by Dr. Clemens's
discovery, in the hospital at Cues, of the fragmentary notice written in
the cardinal's own hand in 1444. * Cosmos, vol. ii., p. 324-326.

t Borbonia Sidera, id est, planetoe qui Solis luraina circumvolitant
motu proprio et regulari, false hactenus ab helioscopis maculae Solis
nuncupati, ex novis observationibus Joannis Tarde, 1620. Austriaca
Sidera heliocyclica astronomicis hypothesibus illigata opera Caroli Mai-
apertii Belgae Montensis e Societate Jesu, 1633. The latter work has
at all events the merit of affording observations of a succession of spots

THE SUN S SPOTS. 65

green stained glasses in solar observations, "which had been
jproposed seventy years earlier by Apian (Bienewitz), in the
Astronomicum Ccesareum, and had also been long in use
among Belgian pilots.* The neglect of this precaution con-
tributed much to Galileo's blindness.

As far as I am aware, the most definite expression of the
necessity for assuming the existence of a dark solar sphere,
surrounded by a photosphere, grounded upon direct observa-
tion after the discovery of the Sun's spots, is first to be met
with in the writings of the great Dominique Cassini,t and
belongs probably to about the year 1671. According to his
views, the solar disk which we see is " an ocean of light sur-
rounding the solid and dark nucleus of the Sun ; the violent
movements (up-wellings) which occur in this luminous en-
velope enable us from time to time to see the mountain sum-
mits of the non-luminous body of the Sun. These constitute
the black nuclei in the center of the Sun's spots." The ash-
colored penumbrae surrounding these nuclei had not then been
explained.

between 1618 and 1626. This period includes the years for which
Scheiner published his own observations at Rome in his Rosa Ursina.
The Canon Tarde beUeves those appearances to be the transits of small
planets, because " Toeil du monde ne peut avoir des ophthalmies," " the
eye of the universe can not experience ophthalmia." It must justly
excite surprise that the meritorious observer, Gascoigne (see Cosmos,
vol. iii., p. 61), should, twenty years after Tarde's notice of the Bor-
bonic satellites, still have ascribed the Sun's spots to a conjunction of
numerous planetary bodies revolving round the Sun in close proximity
to it and in almost intersecting orbits. Several of these bodies, placed,
as it were, one over another, were supposed to occasion the black shad-
ows. (Philos. Transact., vol. xxvii., 1710-1712, p. 282-290, from a let-
ter of William Crabtree, August, 1640.)

* Arago, Sur les may ens d' Observer les taches Solaires, in the Annu-
aire pour Van 1842, p. 476-479 ; Delarabre, Hist, de V Astronomic dtt
Moyen Age, p. 394 ; and his Hist, de V Astronomie Moderne, torn, i., p.
681.

t Mimoires pour servir a VHistoire des Sciences, par M. le Comte de
Cassini, 1810, p. 242 ; Delambre, Hist, de VAstr. Mod., tom. iii., p. 694.
Although Cassini in 1671, and La Hire in 1700, had declared the Sun's
body to be dark, otherwise trustworthy and valuable text-books on as-
tronomy still continue to ascribe the first idea of this hypothesis to the
meritorious Lalande. Lalande, in the edition of 1792, of his Astronomie,
torn, iii., $ 3240, as in the first edition of 1764, tom. ii., $ 2515, merely
adopts the older view of La Hire, according to which " les taches sont
les eminences de la masse solide et opaque du Soleil, recouverte com-
munement (en entier) par le fluide igne ;" " the spots are the elevations
of the solid and op'aque mass of the Sun, covered by an igneous fluid."
Alexander Wilson, between the years 1769 and 1774, conceived the firwt
correct view of a funnel-shaped opening in the photosphere.

i56 COSMOS.

An ingenious observation, which has subsequently been
fully confirmed, made by the astronomer, Alexander Wilson
of Glasgow, of a large solar spot, on the 22d of Novembe,
1769, led him to an elucidation of the penumbree. "Wilson
discovered that as a spot mo'\ied toward the Sun's margin,
the penumbra became gradually more and more narrow on
the side turned toward the center of the Sun, compared with
the opposite side. The observer, in 1774, very correctly con-
cluded,^ from these relations of dimension, that the nucleus
of the spot (the portion of the dark solar body visible through
the funnel-shaped excavation in the luminous envelope) was
situated at a greater depth than the penumbra, and that the
latter was formed by the shelving lateral walls of the funnel.
This mode of explanation did not, however, solve the ques-
tion why the penumbrse were the lightest near the nuclei.

The Berlin astronomer, Bode, in his work entitled " Thoughts
on the Nature of the Sun, and the Formation of its Spots"
( Gedanken iiber die Natur der Sonne iind die Entstehung
Hirer Flecken), developed very similar views with his usual
perspicuity, although he was unacquainted with Wilson's ear-
lier treatise. He, moreover, had the merit of having facili
tated the explanation of the penumbrae, by assuming, very
much in accordance with the conjectures of Cardinal Nicolaus
de Cusa, the existence of another cloudy stratum of vapor be-
tween the photosphere and the dark solar body. This hy-
pothesis of two strata leads to the following conclusions : If
there occur in less frequent cases an opening in the photo-
sphere alone, and not, at the same time, in the less transpar-
ent lower vaporous stratmn, which is but faintly illumined by
the photosphere, it must reflect a very inconsiderable degree
of light toward the inhabitants of the Earth, and a gray pe-
numbra will be formed — a mere halo without a nucleus ; but
when, owing to tumultuous meteorological processes on the
surface of the Sun, the opening extends simultaneously through
both the luminous and the cloudy envelopes, a nucleoid spot
will appear in the ash-gray penumbra, " which will exhibit

* Alexander Wilson, Observations on the Solar Spots, writes as fol-
lows in the Philos. Transact., vol. Ixiv., 1774, part i., p. 6-13, tab. i. :
" I found that the umbra, which before was equally broad all round the
nucleus, appeared much contracted on that part which lay toward the
center of the dish, while the other parts of it remained nearly of the
former dimensions. I perceived that the shady zone or umbra, which
surrounded the nucleus, might be nothing else but the shelving sides
of the luminous matter of the Sun." Compare also Arago, in the Annu-
aire for 1842, p. 506.

THE SUN S SPOTS. 67

more or less hlackness, according as the opening occurs op-
posite to a sandy, rocky, or aqueous portion of the surface of
the Sun's disk.*= The halo surrounding the nucleus is fur-
ther a portion of the outer surface of the vaporous stratum ;
and as this is less opened than the photosphere, owing to tht
funnel-shaped form of the whole excavation, the direction of
the passage of the rays of light, impinging on both sides on
the margins of the interrupted envelope, and reaching the
eyes of the observer, occasions the difference, first noticed by
Wilson, in the breadth of the opposite sides of the penumbra,
which appears after the nucleoid spot has moved away from
the center of the Sun's disk. If, as Laugier has frequently
remarked, the penumbra passes over the black nucleus, caus-
ing it wholly to disappear, this obscuration must depend on
the closing of the opening — not of the photosphere, but of the
vaporous stratum below it.

A solar spot, which was visible to the naked eye in the year
1779, fortunately directed William Herschel's superior pow-
ers of observation and induction to the subj ect which we have
been considering. We possess the results of his great work,
which treats of the minutest particulars of the question in a
very definite manner, and in a nomenclature established by
himself. His observations appeared in the Philosophical
Transactions for 1795 and for 1801. As usual, this great
observer pursued his own course independently of others, re-
ferring only in one instance to Alexander Wilson. In their
general character, his views may be regarded as identical
with those of Bode, and he bases the visibility and dimensions
of the nucleus and the penumbra (Philos. Transact., 1801,
p. 270, 318, tab. xviii., fig. 2) on the assumption of an open-
ing in two envelopes, while he assumes the existence of a
clear and transparent aerial atmosphere (p. 302) between the
vaporous envelope and the dark body of the Sun, in which
clouds that are either wholly dark, or only faintly illumined
by reflection, are suspended at a height of about 280 to 320
geographical miles. William Herschel seems, in fact, also
disposed to regard the photosphere as a mere stratum of
unconnected phosphorescent clouds of very unequal surface.
According to his view, " an elastic fluid of unknown nature
rises from the crust or surface of the dark solar body, gener-
ating only small luminous pores in the higher regions Avhere
the action is weak, and large openings, with nuclei, sur-

* Bode, in the Beschdftigungen der Berlyiischen Gesellschaft NcUur*
forschender Fi-eunde,hd. ii., 1776, p. 237-241, 249.

68 COSMOS. A

rounded by shallows or penumbrse, where the action is more
tumultuous."

The black spots, which are seldom round, almost always
angularly hroken, and characterized by entering angles, are
frequently surrounded by halos or penumbrse, which exhibit
the same figure on a larger scale. There is no appearance
of a transition of the color of the spot into the penumbra, or
of the latter, which is sometimes filamentous, into that of the
photosphere. Capocci and Pastorff" (of Buchholz, in Bran-
denburg)— most diligent observers — have both given very
accurate representations of the angular form of the nuclei.
(Schum., Astr. Nachr., No. 115, p. 316 ; No. 133, p. 291 ;
No. 144, p. 471.) William Herschel and Schwabe saw the
nucleoid spots divided by bright veins or luminous bridges —
phenomena of a cloud-like nature generated within the second
stratum where the penumbrsB originate. These singular con-
figurations, which probably owe their origin to ascending cur-
rents, the tumultuous formation of spots, solar faculae, furrows,
and projecting stripes {crests of luminous waves), indicate,
according to Sir William Herschel, an intense evolution of
light ; while, on the other hand, according to the same great
authority, " the absence of solar spots find their concomitant
phenomena seems to indicate a low degree of combustion, and,
consequently, a less beneficial action on the temperature of
our planet, and the development of vegetation." These con-
jectures led Sir William Herschel to institute a series of com-
parisons between the prices of corn and the complaints of poor
crops,^ and the absence of solar spots, between the years 1676
and 1684 (according to Flamstead), from 1686 to 1688 (ac-
cording to Dominique Cassini), from 1695 to 1700, and from
1795 to 1800. Unfortunately, however, we can never attain
a knowledge of the numerical elements on which to found
even a conjectural solution of such a problem ; not only, as
this circumspect astronomer has himself observed, because the
price of corn in one part of Europe can not be taken as a cri-
terion of the state of vegetation over the whole Continent, but
more especially because a diminution of the mean annual
temperature, even if it affected the whole of Europe, would
afford no evidence that the Earth had derived a smaller
quantity of solar heat throughout that year. It appears from
Dove's investigations of the irregular variations of tempera-
ture, that extremes of meteorological conditions always lie

* WiUiam Herschel, iudthe Philosophical Transactions of the Royal
Society for 1801, part ii., p. 310-316.

1«£; SUN S SPOTS. G9

laterally hy one another, i. e., in almost equal degrees of lat-
itude. Our own continent, and the temperate parts of North
America, generally present such contrasts of temperature.
When our winters are severe, the season there is mild, and
conversely. These compensations in the local distribution of
heat, when associated with vicinity to the ocean, are attend-
ed by the most beneficial results to mankind, owing to the
indubitable influence exercised by the mean quantity of sum-
mer heat on the development of vegetation, and consequently
on the ripening of the cereals.

While William Herschel attributed an increase of heat on
the Earth to the activity of the central body — a process from
which result spots on the Sun — Batista Baliani, almost two
and a half centuries earlier, in a letter to Galileo, described
solar spots as cooling agents.* .This opinion coincides with
the experiment made by the zealous astronomer Gautierf at
Geneva, in comparing four periods characterized by numer-
ous and by few spots on the Sun's disk (from 1827 to 1843),
with the mean temperatures presented by thirty- three Euro-
pean and twenty-nine American stations of similar latitude.
This comparison proves, by positive and negative differences,
the contrasts exhibited by opposite Atlantic coasts. The final
results, however, scarcely give 0*76° Fahr. as the cooling
force ascribed to the Sun's spots, and this might with equal
propriety be attributed to errors of observation and the direc-
tion of the winds at the localities indicated.

It still remains for us to notice the third envelope of the
Sun, to which we have already referred. This is the most
external of the three, inclosing the photosphere, is cloudy, and
of imperfect transparency. The remarkable phenomena of

• We find a reference in the historical fragments of the elder Cato to
an oflBcial notice of the high price of corn, and an obscuration of the
"Sun's disk, which continued for many months. The '' luminis caligo'^
and " defectus Solis^^ of Roman authors does not invariably indicate an
echpse of the Sun; as, for instance, in the account of the long-continued
diminution of the Sun's light after the death of Caesar. Thus, for in-
stance, we read in Aulus Gellius, Noct. Att., ii., 28, " Verba Catonis in
Originum quarto haec sunt: non libet scribere, quod in tabula apad
Pontificem maximum est, quotiens anona cara, quotiens Luna? an Soils
lumini caligo, aut quid obstiterit." " The words of Cato in the fourth
book of his Origines are these : I may not write what is frequently en-
tered in the tables of the priests, that corn was dear whenever there
was any decrease in the light of the Sun and Moon, or when any thing
obscured them."

t Gautier. Reckerches relatives a V Influence que le nombre des tacket
SoLaires exerce sur les temperatures Terrestres, in the Bibliotkique Uni'
verselle dc Gentve, Nouv. Serie, torn, li., 1844, p. 327-335.

70 COSMOS.

red, mountain, or flame-like elevations, which, if not seen for
the first time, were at all events more distinctly visible during
the eclipse of the Sun of the 8th of July, 1842, when they
were simultaneously noticed by several of the most experi-
enced observers, have led astronomers to assume the existence
of a third envelope of this kind, Arago, in a treatise devoted
to the subject,^ has with much ingenuity tested the several
observations, and enumerated the grounds which necessitated
the adoption of this view. He has at the same time shown
that since 1706 similar red marginal protuberances have been
eight times described on the occasion of total or annular so-
lar eclipses. t On the 8th of July, 1842, when the apparently
larger disk of the Moon entirely covered the Sun, the Moon's
disk was observed to be surrounded not only by a whitish
light, $ encircling it like a crown or luminous wreath, but two
or three protuberances were also seen, as if originating at its
margin, and were compared by some observers to red jagged
mountains, by others to reddened masses of ice, and again by
others to fixed indented red flames. Arago, Laugier, and
Mauvais at Perpignan, Petit at Montpelier, Airy on the Su-
perga, Schumacher at Vienna, and numerous other astrono-
mers, agreed perfectly in the main features of the final re-
sults, notwithstanding the great difierences in the instruments
they employed. The elevations did not always appear simul-
taneously ; in some places they were even seen by the naked
eye. The estimates of the angles of altitude certainly differ-
ed ; the most reliable is probably that of Petit, the directoi
of the Observatory at Toulouse. He fixed it at 1' 45", which,
if these phenomena were true sun-mountains, would give an
elevation of 40,000 geographical miles ; that is to say, nearly
seven times the Earth's diameter, which is only 112th part
of the diameter of the Sun. The consideration of these phe-
nomena has led to the very probable hypothesis that these
red figures are emanations within the third envelope — masses
of clouds which illumine and color the photosphere. § Ara-

* Arago, in the Annuaire for 1846, p. 271-438.

t Id., Ibid., p. 440-447.

X This is the white appearance which was also observed in the solar
eclipse of the 15th of May, 1836, and which the great astronomer of
Konigsberg very correctly described at the time by observing " that
although the Moon's disk entirely covered the Sun, a luminous corona
still encircled it, which was a portion of the Sun's atmosphere." (Bes-
Bel, in Schum., Astr. Nachr., No. 320.)

$ " Si nous examinions de plus pres I'explication d'apres laquelle lea
protuberances rougeitres seraient assimilees k des nuages (de la troi-
Bieme enveloppe), nous ne trouvcrious aucun principe de physique qui

THE SUN*S SPOTS. 71

go, in putting forward this hypothesis, expresses the conjec-
ture that the intense blue color of the sky, which I have my-
self measured upon the loftiest part of the Cordilleras, though
with instruments which are certainly " still very imperfect,
may afford a convenient opportunity for frequently observing
these mountain-like clouds in the outermost atmosphere of
the Sun.^

When we consider the zone in which solar spots are most
commonly observed (it is only on the 8th of June and the 9th
of December, that the spots describe straight lines on the Sun's
disk, which at the same time are parallel with one another
and the Sun's equator, and not concave or convex), we are
struck by the fact that they have rarely been seen in the

nous empechdt d'admettre que des masses nuageuses de 25,000 k
30,000 lieues de long flottent dans I'atmosphere du Soleil; que ces
masses, comme certains nuages de I'atmosphere terrestre, ont des con-
tours arretes, qu'elles afFectent, qa. et lei, des formes tres tourmentees,
m^me des forms en surplomb ; que la lumiere solaire (la photosphere)
les colore en rouge. Si cette troisieme enveloppe existe, elle donnera
peut-etre la clef de quelques-unes des grandes et deplorables anomalies
que Ton remarque dans le cours des saisons." "On examining more
closely the grounds on which these rose-colored protuberances are com-
pared to clouds (of the third atmosphere), we do not find any principle
in physics which would oppose the assumption that masses of clouds
extending from 25,000 to 30,000 leagues, float in the Sun's atmosphere ;
that these masses, like some clouds in our terrestrial atmosphere, as-
sume contours exhibiting here and there much-involved forms, appear-
ing sometimes even sloping or inverted, as it were ; and that they are
colored red by the light of the Sun (the photosphere). If this third
atmosphere actually exist, it may, perhaps, tend to solve some of those
vast and deplorable anomalies which we observe in the course of the
seasons." — Arago, in the Annuaire for 1846, p. 460, 467.

* " Tout ce qui afFaiblira sensiblement I'intensite eclairante de la
portion de I'atmosphdre terrestre qui parait entourer et toucher le con-
tour circulaire du Soleil, pourra contribuer k rendre les preeminences
rouge&tres visibles. II est done permis d'esperer qu'un astronome ex-
erce, etabli au sommet d'une tres haute montagne, pourrait y observer
regulierement les nuages de la troisieme enveloppe solaire, situes, en ap-
parence, sur le contour de I'astre ou un pen en dihors, determiner ce
qu'ils ont de permanent et de variable, noter les periodes de disparition

et de reapparition " Whatever will perceptibly diminish the

briUiant intensity of that portion of the terrestrial atmosphere which
appears to inclose and touch the circumference of the Sun, may con
tribute to render the rose-colored protuberances visible. We may
therefore, hope that an experienced astronomer may succeed, on the
summit of some high mountain, ia making systematic and regular ob
servations of the clouds of the third solar envelope, whicn appear to ba
situated on the margin of the Sun, or a little beyond it, and thus determ
ine the permanence or variability of their character, and note th
epochs of their disappearance and reappearance . . . ." — Arago, Ibid,
p. 471

72 COSMOS.

equatorial region l>etween 3^ north and 3° south latitude,
and that they do not occur at all in the polar regions. They
are, on the whole, most frequent in the region between 11*^
and 15° north of the equator, and generally of more common
occurrence in the northern hemisphere) or, as Sommering
maintains, may be seen there at a greater distance from the
equatorial regions than in the southern hemisphere. [Out-
lines, § 393 ; Observations at the Cape, p. 433.) Galileo
even estimated the extreme limits of northern and southern
heliocentric latitude at 29°. Sir John Herschel extends them
to 35°, as has also been done by Schwabe. (Schum. Astr.
Nachr., No. 473.) Laugier found some spots as high as 41°
(Comptes Kendus, tom. xv., p. 944), and Schwabe even in
50°. The spot observed by La Hire in 70° north latitude,
must be regarded as a very rare phenomenon.

This distribution of spots on the Sun's disk, their rarity
under the equator and in the polar regions, and their paral-
lel position in reference to the equator, led Sir John Herschel
to the conjecture that the obstructions which the third vapor-
ous external atmosphere may present at some points to the
liberation of heat, generates currents in the Sun's atmosphere
from the poles toward the equator similar to those which upon
the Earth occasion the trade- winds and calms near the equa-
tor, owing to differences of velocity in each of the parallel
zones. Some spots are of so permanent a character that they
have continued to appear for fully six months, as was the case
with the large spot visible in 1779. Schwabe was enabled
to follow the same group eight times in the year 1840. A
black nucleoid spot, deUneated in Sir John Herschel's Ob-
servations at the Cape (to which I have made such constant
reference), was found, by accurate measurement, to be so large,
that supposing the whole of our Earth to be propelled through
the opening of the photosphere, there would still have re-
mained a free space on either side of more than 920 geograph-
ical miles. Sommering directs attention to the fact that there
are certain meridian belts on the Sun's disk in which he had
never observed a solar spot for many years together. ( TJiilo.
de Soils maculis a Sa^mmeringio observatis, 1828, p. 22.)
The great differences presented in the data given for the pe-
riod of revolution of the Sun are not, by any means, to be as-
cribed solely to want of accuracy in the observations ; thoy
depend upon the property exhibited by some spots, of chang-
ing their position on the disk. Laugier has devoted special
attention to this subject, and has observed spots which would

THE sun's spots. • 73

give separate rotations of 24d. 28m. and 26d. 46m. Our
knowledge of the actual period of the rotation of the Sun can
therefore only be regarded as the mean of a large number of
observations of those maculae, which, from their permanence
of form, and invariability of position in reference to other co-
existent spots, may form the basis of reliable observations

Although solar maculae may be more frequently seen by the
naked eye than is generally supposed, if the Sun's disk be at-
tentively observed, there yet occur not more than two or three
notices of this phenomenon between the beginning of the ninth
and of the seventeenth centuries, on the accuracy of which we
can rely. Among these I would reckon the supposed reten-
tion of Mercury within the Sun's disk for eight days, m the
year 807, as recorded in the annals of the Frankish kings,
first ascribed to an astronomer of the Benedictine order, and
subsequently to Eginhard ; the 91-days transit of Venus over
the Sun, under the Calif Al-Motassem, in the year 840 ; and
the Signa in Sole of the year 1096, as noticed in the Stain-
delii Chronicon. I have, during several years, made the
epochs of the mysterious obscurations of the Sun which have
been recorded in history — or, to use a more correct expression,
the periods of the more or less prolonged diminution of bright
daylight — the subject of special investigation, both in a mete-
orological and a cosmical point of view.*= Since large num-

* Although it can not be doubted that individual Greeks and Romans
may have seen large Sun-spots with the naked eye, it is at all events
certain that such observations have never been referred to in any of the
works of Greek and Roman authors that have come down to us. The
passages of Theophrastus, De Signis, iv., 1, p. 7^7 ; of Aratus, Diosem.,
v., 90-92 ; and of Proclus, Paraphr., 11, 14, in which the younger Ideler
{Meteorol. Veterum,p. 201, and in the Commentary to Aristotle, Meteor.,
torn, i., p. 374) thought he could discover references to the Sun's spots,
merely imply that the Sun's disk, which indicates fine weather, exhib-
its no difference on its surface, nothing remarkable (fxrjde ti a^fia ^ipoi),
but, on the contrary, perfect uniformity. The aiifia, the dappled sur-
face, is expressly ascribed to light clouds, the atmosphere (the scholiast
of Aratus says, to the thickness of the air) ; hence we always hear of
the morning and evening Sun, because their disk, independently of all
Sun-spots, are supposed, even in the present day, according to an old
belief, not wholly unworthy of regard, to give notice to the farmer and
the mariner, as diapho,nomeiera, of coming changes of weather. The
Sun's disk, on the horizon, gives an indication of the condition of the
lower atmospheric strata which are nearer the Earth. The first of the
Sun-spots noticed in the text as visible to the naked eye, and falsely re-
garded in the years 807 and 840 as transits of Mercury and Venus, is
recorded in the great historical collection of Justus Reuberus, Veterta
Scriptores (1726), in the section Annales Regum Francarum Piptni,
Karoli Magni et Ludovici, a quodavi ejus eelatis Astronomo, Ludovici re-

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16 COSMOS.

obscurations during which stars were partly visible, as in to«
tal solar eclipses.

626 A.D. According also to Abu'l-Farag. {Hist. Dynast., p. 94, 99),
half of the Sun's disk continued obscured for ei^ht months.

733 A.D. One year after the Arabs had been driven back across the
Pyrenees after the battle of Tours, the Sun was so much darkened
on the ]9tb of August as to excite universal terror. — Schnurrer,
Chron., theil i., p. 164.

807 A.D. A Sun-spot was observed, which was believed to be the
planet Mercury. — Reuber, Vet. Script., p. 58 (see p. 70).

840 A.D. From the 28th of May to the 26th of August (Assemani
singularly euougii gives the date of May, 839), the so-called transit
of Venus across the Sun's disk was observed. (See above, p. 73-
74.) The Calif Al-Motassem reigned from 834 to 841, when he was
succeeded by Harun-el-Vatek, the ninth Calif.

934 A.D. In the valuable work Historia de Portugal, by Faria y
Souza, 1730, p. 147, I find the following passage: " En Portugal se
vio sin luz la tierra por dos meses. Avia el Sol perdido su splendor."
The Earth was without light for two months in 'Portugal, for the
Sun had lost its brightness. The heavens were then opened in fis-
sures " por fractura," by strong flashes of lightning, when there was
suddenly bright sun-light.

1091 A.D. On the 21st of September, the Sun was darkened for three
hours, and when the obscuration had ceased, the Sun's disk still re
tained a peculiar color. "" Fuit eclipsis Solis, 11 Kal. Octob. fere tres
horas : Sol circa meridiem dire nigrescebat." — Martin Crusius, An-
nales Suevici, Francof., 1595, torn, i., p. 279 ; Schnurrer, th. i., p. 219,

1096 A.D. Sun-spots were seen by the naked eye on the 3d of March.
'' Signum in Sole apparuit V., Nono Marcii feria secunda incipientis
quadragesimae. Joh. Staindelii, Presbyteri Pataviensis, Chronicon
Generate, in Oefelii Rerum Boicarum Scriptores, tom. i., 1763, p. 485.

1206 A.D. On the last day of February there was, according to Joa-
quin de Villalba (Epidemiologia Espanola, Madr., 1803, tom. i., p.
30), complete darkness for six hours, turning the day into night.
This phenomenon was succeeded by long-continued and abundant
rains. " El dia ultimo del mes de Febrero hubo un eclipse de Sol
que dur6 seis horas con tanto obscuridad como si fuera media noche.
Siguieron k este fenomeno abundantes y contiuuas Uuvias." A very
similar phenomenon is recorded for June, 1191, by Schnurrer, th. i.,
p. 258, 265.

1241 A.D. Five months after the Mongolian battle at Liegnitz, the
Sun was darkened (in some places?), and such darkness caused that
the stars could be seen in the heavens at three o'clock on Michael-
mas day. " Obscuratus est Sol (in quibusdam locis?), et factae sunt
tenebrai, ita ut stella? viderentur in ccelo, circa festum S. Michaelis
hora nona." — Chronicon Claustro-Neoburgense (of the Monastery of
Neuberg, at Vienna : this chronicle comprises the annals of the pe-
riod from the year 218 A.D. to 1348) ; Pez, Scriptores Rerum Avs-
triacarum. Lips., 1721, tom. i., p. 458.

1547 A.D. The 23d, 24th, and 25th of April, consequently the days
preceding and immediately succeeding the battle of Mtlhlbach, in
which the Elector John Frederick was taken prisoner. Kepler says
in Paralipom. ad Vitellium, quihus Astronomice pars Optica traditur,
16P4, p. 259, " The elder and younger Gemma record that in the year

THE SUN S SPOTS. 77

f

As, according to Du Sejour's calculation, the longest possi-
ble duration of a total eclipse of the Sun can not be more than
7m. 58s. at the equator, nor more than 6m. 10s. for the lati-
tude of Paris, the decrease of daylight which is recorded by
the annalists may, on account of its duration for many hours,
possibly be referred to one or other of the three following and
very different causes : 1 . A disturbance in the process of the
evolution of light, as it were a diminution of intensity in the
photosphere ; 2. Obstructions (such as a greater and denser
formation of clouds) in the outermost opaque vaporous en-
velope investing the photosphere, by which the radiation of
solar light and heat is impeded ; 3. The impure condition of
our atmosphere, arising, for instance, from the obscuring (most-
ly organic) meteoric dust, rain, or sand-rain, such as is de-
scribed by Macgowan to have continued for several days to-
gether in China. The second and third of these causes do
not require the occurrence of a diminution of the electro-mag-
netic light process, perhaps (of the perpetual polar light=^), in
the solar atmosphere, but the last-named cause excludes the
visibility of stars at noon, of which such frequent mention is
made in these mysterious and vaguely-described obscurations.

Arago's discovery of chromatic polarization has not only
confirmed the existence of the third and outermost envelope

1547, before the battle between Charles V. and the Duke of Saxony,
the Sun appeared for three days as if it were suSused by blood, while
at the same time many stars were visible at noon." " Refert Gemma^
pater et filius, anno 1547, ante conflictum Caroli V. cum Saxoniai
Duce, Solem per tres dies ceu sanguine perfusum comparuisse, ut
etiam stellce plereque in meridie conspicerentur." Kepler (in Stella
Nova in Serpentario, p. 113) further expresses his uncertainty as to
the cause of the phenomenon ; he asks whether the diminution of the
Sun's light be owing to some celestial causes: *' Soils lumen ob cau-

sas quasdam sublimes hebetari " whether it be owing to the

•\vide diffusion of some cometary substance, " materia cometica latins
sparsa," for the cause can not have originated in our atmosphere,
since the stars were visible at noon. Schnurrer ( Chronik der Seu-
chen, th. ii., p. 93) thinks, notwithstanding the visibility of the stars,
that the phenomenon must have been the same as the so-called
" HShenrauch," for Charles V. complained before the battle " that
the Sun was always obscured when he was about to engage with the
enemy." " Semper se nebula? densitate infestari, quoties sibi cum
hoste pugnandum sit." (Lambert, Hortens. de bello German., lib
vi., p. 182.)

* Horrebow (Basis Astronomies, 1735, $ 226) makes use of the same
expression. Solar light, according to him, is "a perpetual Northern
light ioithin the Sun's atmosphere, produced by the agency of powerful
magnetic forces^ (See Hanow, in Joh. Dan. Titius's OemoinnHtzig^
Abhandlungen iiber naturliche Dinge, 1768, p. 102.)

78 COSMOS.

of the Sun, but has likewise added considerable weight to the
conjectures advanced in reference to the whole physical con-
stitution of the central body of our planetary system. " A
ray of light which reaches our eyes, after traversing many
millions of miles, from the remotest regions of heaven, an-
nounces, as it were of itself, in the polariscope, whether it is
reflected or refracted, whether it emanates from a solid, or
fluid, or gaseous body, it announces even the degree of its in-
tensity. {Cosmos, vol. i., p. 52, and vol. ii., p. 332.) It is
essential to distinguish between natural light, as it emanates
directly from the Sun, the fixed stars, or flames of gas, and is
polarized by reflection from a glass plate at an angle of 35°
25', and that polarized light which is radiated as such from
certain substances (as ignited bodies, whether of a solid or
liquid nature). The polarized light which emanates from
the above-named class of bodies very probably proceeds from
their interior. As the light thus emanates from a denser body
into the surrounding attenuated atmospheric strata, it is re-
fracted on the surface, and in this process a part of the re-
fracted ray is reflected back to the interior, and is converted
by reflection into polarized light, while the other portion ex-
hibits the properties of light polarized by refraction. The
chromatic polariscope distinguishes the two by the opposite
position of the colored complementary images. Arago has
shown, by careful experiments extending beyond the year
1820, that an ignited solid body (for instance, a red-hot iron
ball), or a luminous, fused metal, yield only ordinary light, in
rays issuing in a perpendicular direction, while the rays which
reach our eyes from the margins, under very small angles, are
polarized. When this optical instrument, by which the two
kinds of light could be distinguished, was applied to gas flames,
there was no indication of polarization, however small were
the angles at which the rays emanated. If even the light be
generated in the interior of gaseous bodies, the length of way
does not appear to lessen the number and intensity of the very
oblique rays in their passage through the rare media of the
gas, nor does their emergence at the surface and their transi-
tion into a different medium cause polarization by refraction.
Now, since the Sun does not either exhibit any trace of polar-
ization when the hght is suffered to reach the polariscope in
a very oblique direction, and at small angles from the margin,
it follows from this important comparison that the light shin-
ing in the Sun can not emanate from the solid solar body, nor
from any liquid substance, but must be derived from a gase*

THE SUN S SPOTS. 79

(ms, self-luminous envelope. We thus possess a material phys-
ical analysis of the photosphere.

The same instrument has, however, also led to the conclu-
sion that the intensity of the light of the Sun is not greater
in the center of the disk than at its margins. When the
two complementary colored images of the Sun — the red and
blue — are so arranged that the margin of the one image falls
on the center of the other, perfect white will be produced.
If the intensity of the light were not the same in the different
parts of the Sun's disk — if, for example, the center were more
luminous than the margin, then the partial covering of the
images in the common segments of the blue and red disk
would not exhibit a pure white, but a pale red, because the
blue rays would only be able to neutralize a portion of the
more numerous red rays. If, moreover, we remember that
in the gaseous photosphere of the Sun, in opposition to that
which occurs in solid or liquid bodies, the smallness of the
angle at which the rays of light emanate does not cause their
number to diminish at the margins, and as the same angle
of vision embraces a larger number of luminous points at the
margins than in the center of the disk, we could not here
reckon upon that compensation which, were the Sun a lu-
minous iron globe, and consequently a solid body, would take
place between the opposite effects of the smallness of the an-
gle of radiation and the comprehension of a larger number
of luminous points at the same visual angle. The self-lumin-
ous gaseous envelope, i. e., the solar disk visible to us, must
therefore (in opposition to the indications of the polariscope,
which shows the margin and the center to be of equal intens-
ity) appear more luminous in the center than at the margin.
The cause of this discrepancy has been ascribed to the outer-
most and less transparent vaporous envelope surrounding the
photosphere, which diminishes the light from the center less
than that of the marginal rays on its long passage through
the vaporous envelope. =^ Bouguer, Laplace, Airy, and Sir

* Arago, in the Mimoires des Sciences MatMm. et Phys. de i Institut
de France, annee 1811, partie i., p. 118; Matthieu, in Delambre, Hist,
de VAstr. au dix-huitieme siecle, p. 351, 652 ; Fourrier, Eloge de William
Herschel, in the Mim. de V Institut, torn, vi., annee 1823 (Par., 1827),
p. Ixxii. It is alike remarkable and corroborative of the great uniform-
ity of character in the light of the Sun, whether emanating from its cen-
ter or its margins, that, according to an ingenious experiment made by
Forbes, during a solar eclipse in 1836, a spectrum formed from the cir-
cumferential rays alone was identical both in reference to the number
amd position of the dark lines or stripes intersecting it. with the spec-

80 ' COSMOS.

John Herschel, are all opposed to these views of my friend,
and consider the intensity of the light weaker at the margin

trum arising from the entire solar light. When, therefore, rays of cer>
tain refrangibility are wanting in solar light, they have probably not
passed into the Sun's atmosphere, as Sir David Brewster conjectures,
since the circumferential rays produce the same dark lines when they
shine through a much thicker medium. — Forbes, in the Comptes Rendus,
torn, ii., 1836, p. 576. I will append to this note all the facts that I col
lected in the year 1847, from Arago's MSS. :

'* Des phenomenes de la polarisation color6e donnent la certitude que
lo bord du Soleil a la meme intensite de lumiere que le centre ; car en
pla9ant dans la polariscope un segment du bord sur un segment du cen
tre, j'obtiens (comme efi'et complemenlaire du rouge et du bleu) un
blanc pur. Dans un corps solide (dans une boule de fer chauffee au
rouge) le meme angle de vision embrasse une plus grande etendue au
bord qu'au centre, selon la proportion du cosinus de I'angle : mais dans
la meme proportion aussi, le plus grand nombre de points materiels
emettent une lumiere plus faible, en raison de leur obliquiti. Le rap-
port de I'angle est naturellement le meme pour une sphere gazeuse,
mais I'obli quite ne produisant pas dans les gazes le meme eflfet de dimi-
nution que dans les corps solides, le bord de la sphere gazeuse serait
plus lumineux que le centre. Ce que nous appelons le disque lumi-
ueux du Soleil, est la photosphere gazeuse, comme je I'ai prouve par le
manque absolu de traces de polarisation sur le bord du disque. Pour
expliquer done VigaliU dHntensiU du bord et du centre indiquee par
le polariscope, il faut admettre une enveloppe exterieure, qui diminue
(eteint) moins la lumiere qui vient du centre que les rayons qui vien-
iient sur le long trajet du bord k I'oeil. Cette enveloppe exterieure
forme le couronne blanchatre dans les eclipses totales du Soleil. La
lumiere qui emane des corps solides et liquides incandescens, est par-
tiellement polarisee quand les rayons observes forment, avec la surface
de sortie, un angle d'un petit nombre de degres ; mais il n'y a aucune
trace sensible de polarisation lorsqu'on regarde de la m6me maniere
dans le polariscope des gazes enflammes. Cette experience demontre
que la lumiere solaire ne sort pas d'une masse solide ou liquide incan-
descente. La lumiere ne s'engendre pas uuiquement k la surface des
corps; une portion nalt dans leur substance meme, cette substance fAt-
elle du platine. Ce n'est done pas la decomposition de I'oxygene am-
biant qui donne la lumiere. L'emission de lumiere polarisee par le fer
liquide est un effet de refraction au passage vers un moyen d'une moindre
densite. Partout ou il y a refraction, il y a production d'un peu de lu-
miere polarisee. Les gazes n'en donnent pas, parceque leurs couches
n'ont pas assez de densite. La Lune, suivie pendant le cours d'une lu-
naison entiere, ofFre des effets de polarisation, excepte k I'epoque de la
pleine Lune et des jours qui en approchent beaucoup. La lumiere sol-
aire trouve, surtout dans les premiers et derniers quartiers, k la surface,
in6gale (montagneuse) de notre satellite, des inclinaisons, de plans con-
venables pour produire la polarisation par reflexion."

'' The phenomena of chromatic polarization afford evidence that the
margin of the Sun has the same intensity of light as the center ; for by
placing in the polariscope a segment of the margin upon a-central seg-
ment, I obtain a pure white as the complementary effect of red and
blue. In a solid body (as in an iron ball heated red-hot), the same
visual angle embraces a larger extent of the margin than of the center

THE sun's spots. 81

than in the center. The last named of these distinguished
physicists and astronomers expresses himself as follows, in
reference to this question.* " Now, granting the existence
of such an atmosphere, its form, in obedience to the laws of
equilibrium, must be that of an oblate spheroid, the elliptic-
ities of whose strata differ from each other and from that of
the nucleus. Consequently, the equatorial portions of this

according to the ratio of the cosine of the angle ; but in the same ratio^
the greater number of the material points emit a feebler light, in con'
sequence of their obliquity. The ratio of the angles is naturally the same
for a gaseous sphere ; but since the obliquity does not produce the same
amount of diminution in gases as in solid bodies, the margin of the gas-
eous sphere would be more luminous than its center. That which we
term the luminous disk of the Sun is the gaseous photosphere, as I have
proved by the entire absence of every trace of polarization on the mar-
gin of the disk. To explain the eqtiality of intensity indicated by the
polariscope for the margin and the center, we must admit the existence
of an outer envelope, which diminishes (extinguishes) less of the light
which comes from the center than from the marginal rays having a
longer way to traverse before they reach the eye. This outer envel-
ope forms the whitish corona of light observed in total eclipses of the
Sun. The light which emanates from solid and liquid incandescent
bodies is partially polarized when' the rays observed form an angle of
a few degrees with the surface from whence they emerge ; but there
is no sensible evidence of polarization when incandescent gases are
seen in the polariscope. This experiment proves, therefore, that solar
light does not emanate from a solid mass or an incandescent liquid.
Light is not engendered solely on the surface of bodies ; but a portion
originates within the substance itself, even when the experiment is
made with platinum. Light, therefore, is not produced by the decom-
position of the ambient oxygen. The emission of polarized light from
liquid iron is an effect of refraction during its passage toward a medium
of lesser density. Wherever there is refraction, a small amount of po-
larized light must be produced : gases do not emit polarized light, be-
cause their strata do not possess the requisite amount of density. When
the Moon is followed through all its phases, it will be found to afford
evidences of polarization, excepting at the full moon, and the days im-
mediately preceding and following it. It is more especially during
the first and last quarters that the unequal (mountainous) surface of
our satellite presents suitable inclinations for the polarization of solar
light by reflection."

* Sir John Herschel, Astron. Observ. made at the Cape of Good Hope,
$ 425, p. 434; Outlines of Astr., $ 395, p. '234. Compare Fizeau and
Foucault, in the Comptes Rendus de V Acad, des Sciences, t. xviii., 1844,
p. 860. It is remarkable enough that Giordano Bruno, who was burned
eight years before the invention of the telescope, and eleven years be-
fore the discovery of the spots of the Sun, should have believed in the
rotation of the Sun upon its axis. He considered, on the other hand,
that the center of the Sun was less luminous than the edges. Owing
to an optical deception, he believed that he saw the disk turn round,
and the whirling edges expand and contract. (Jordauo Bruno, par
Christian Bartholmess, tom. ii., 1847, p. 367.)

D 2

82 COSMOS.

envelope must be of a thickness difierent from that of the
polar, density for density, so that a difierent obstacle must
be thereby opposed to the escape of heat from the equatorial
and the polar regions of the Sun." Arago is engaged at the
present moment in a series of experiments, by which he pur-
poses to test not only his own views, but also to reduce the
results of observation to accurate numerical relations.

A comparison between solar light and the two most intense
kinds of artificial light which man has hitherto been able to
produce, yields, according to the present imperfect condition
of photometry, the following numerical results : Fizeau and
Foucault found, by their ingenious experiments, that Drum-
mond's light (produced by the flame of the oxyhydrogen lamp
directed against a surface of chalk) was to the light of the
Sun's disk as 1 to 146. The luminous current, which in Da-
vy's experiment was generated between two charcoal points
by means of a Bunsen's battery, having forty-six small plates,
was to the light of the Sun as 1 to 4*2 ; but when very large
plates were used, the ratio was as 1 to 2 5, and this light was,
therefore, not quite three times less intense than solar light.*
When we consider the surprise still experienced at the cir-
cumstance of Drummond's dazzling light forming a black spot
when projected on the Sun's disk, we are doubly struck by the
felicity with which Galileo, by a series of conclusions as early
as 1612,t on the smallness of the distance from the Sun at
which the disk of Venus was no longer visible to the naked
eye, arrived at the result that the blackest nucleus of the
Sun's spots was more luminous than the brightest portions
of the full Moon.

William Herschel, assuming the intensity of the whole
light of the Sun at 1000, estimated the average light of the
penumbrae at 469, and the black nuclei at 7. According to
this estimate, which is certainly very conjectural, a black nu-
cleus would yet possess 2000 times more light than the full

* Fizeau and Foucault, RecJierch.es sur VIntensiti de la Lumiere imise
par le Charbon dans V Experience de Davy, in the Comptes Rendus, torn.
xviii., 1844, p. 753. " The most intensely ignited solid (ignited quick-
lime in Lieutenant Drummond's oxyhydrogen lamp) appear only as
black spots on the disk of the Sun when held between it and the eye."
—Outlines, p. 36 (Cosmos, vol. ii., p. 325-326).

t Compare Arago's commentary on Galileo's letter to Marcus Welser,
as well as his optical explanation of the influence of the diffuse reflected
solar light of the atmospheric strata which covers the object seen in the
sky upon the field of a telescope, as it were, with a luminous vail,m the
Annuaire du Bureau des Long, for 1842, p. 482-487.

SOLAR LIGHT. 83

Moon, since the latter, according to Bouguer, is 300,000 less
bright than the Sun. The degree of illumination of the nu-
clei visible to us, i, e., of the dark body of the Sun illumined
by reflection from the walls of the opened photosphere, the
interior atmosphere from which the penumhrse are generated,
and by the light of the strata of our terrestrial atmosphere
through which we see it, has been strikingly manifested on
the occasion of several transits of Mercury. When compared
with the planet, whose dark side was turned toward us, tho
near and darkest nuclei presented a light brownish-gray ap-
pearance.*" The admirable observer, Counselor Schwabe, of
Dessau, was particularly struck by this difference of blackness
between the planet and the nuclei, in the transit of Mercury
on the 5th of May, 1832. On the occasion of my observing
the transit of this planet in Peru, on the 9th of November,
1802, in consequence of being engaged in measuring the dis-
tances from the threads, I was unfortunately unable to make
any comparison between the different intensities of the light,
although Mercury's disk almost touched the nearest dark
spot. Professor Henry, of Princeton, North America, had al-
ready shown, by his experiments in 1815, that the Sun's spots
radiate a perceptibly less heat than those portions on which
there were no spots. The images of the Sun and of a large
spot were projected on a screen, and the differences of heat
measured by means of a thermo-electrical apparatus.!

Whether rays of heat differ from rays of light by a differ-
ence in the lengths of the transversal vibrations of ether, or
whether they are identical with rays of light, but that a cer-
tain velocity in the vibrations which generates very high tem-
peratures is requisite to excite the impression of light in our
organs, the Sun, as the main source of light and heat, must
nevertheless be able to call forth and animate magnetic forces
on our planet, and more especially in the gaseous strata of
our atmosphere. The early knowledge of thermo-electrical
phenomena in crystallized bodies (such as tourmaline, bora-
cite, and topaz), and Oersted's great discovery (1820) that
every conducting body charged with electricity exerts a defin-
ite action on the magnetic needle during the continuation of
the electrical current, afforded practical evidence of the cor-
relation of heat, electricity, and magnetism. Basing his de-
ductions on the idea of such an affinity, Ampere, who ascribed

* Madler, Astr., p. 81.

t Philos. Mag., ser. iii., vol. xxviii., p. 230 ; and Poggend., Afmalen,
bd. Ixviii., p. 101.

84 COSMOS.

all magnetism to electrical currents which lie in a plane at
right angles to the axes of the magnet, advanced the in-
genious hypothesis that terrestrial magnetism (the magnetic
charge of the Earth) was generated by electrical currents,
circulating round the planet from east to west ; and that the
horar}' variations of the magnetic declination are on this ac-
count consequences of the fluctuations of heat, varying with
the position of the Sun, by whose action these currents are
excited. These views of Ampere have been confirmed by
Seebeck's thermo-magnetic experiments, in which differences
of temperature of the points of contact of a circle composed
of bismuth and copper, or other heterogeneous metals, affect
the magnetic needle.

Another recent and brilliant discovery of Faraday's, the
notice of which has been of almost simultaneous occurrence
with the printing of these pages, throws an unexpected light
on the same important subject. While the earlier researches
of this great physicist showed that all gases are diamagnetic,
i. e., assume a direction from east to west, as bismuth and
phosphorus, but that this property is most feebly exhibited in
oxygen, it has been shown by his latest researches, which
were begun in 1847, that oxygen alone, of all gases, like iron,
assumes a position from north to south, and that oxygen gas
loses a portion of its paramagnetic force by expansion and by
elevation of the temperature. Since the diamagnetic activity
of the other constituents of the atmosphere, such as the nitro-
gen and carbonic acid, are not modified by expansion or by
an elevation of temperature, it only remains for us to consid-
er the oxygen, " which surrounds the whole Earth, as it were,
like a large sphere of sheet tin, and receives magnetism from
it." The half of this sphere which is turned toward the Sun
is less paramagnetic than the opposite half ; and as the bound-
aries of these halves are constantly altered by their rotation
and revolution round the Sun, Faraday is inclined to refer a
portion of the variations of terrestrial magnetism on the
Earth's surface to these thermic relations. The assimilation
thus shown by experiment to exist between a single gas (oxy-
gen) and iron, is an important discovery of our ow,i age,*
which derives additional value from the fact that oxygen
probably constitutes the half of all the ponderable matters

* Faraday upon atmospheric magnetism, in the Exper. Researcket
on Electricity, series xxv. and xxvi. (Philos. Trantact. for 1851, part i.)^
§ 2774, 2780, 2881, 2892, 2968, and for the history of the investigation,
$ 2847. .

THE SUN S SPOTS. 85

ihat occur in accessible portions of our Earth. Without as-
suming magnetic poles in the Sun's body, or any special mag-
netic forces in the solar rays, the central body may, as a pow-
erful source of heat, excite magnetic activity on our planet.

The attempts that have been made to prove, by means of
meteorological observations prosecuted ibr many years at m-
dividual spots, that one side of the Sun (for instance, the side
which was turned toward the Earth on the 1st of January,
1846) possesses a more intsnse heating power than the oppo-
site one,* have not led to more reliable results than the older
Greenwich observations of Maskeleyne, which were supposed
to prove that the Sun had decreased in diameter.

The observations made by Counselor Schwabe, of Dessau,
for reducing the periodicity of the Sun's spots to definite nu-
merical relations, appear to have a surer foundation. No as-
tronomer of the present day, however admirable may have
been his instruments, could have devoted his attention more
continuously to this subject than Schwabe, who, during the
long period of twenty-four years, frequently examined the
Sun's disk upward of 300 days in the year. As his observa-
tions of the Sun's spots from 1844 to 1850 have not yet been
published, I have presumed so far on our friendship as to re-
quest that he would communicate them to me, and at the
same time answer a number of questions which I proposed
to him. I will close this section of the Physical Constitu-
tion of our Central Body with the observations with which
this observer has allowed me to enrich the astronomical por-
tion of my work.

" The numbers contained in the following table leave no
doubt that, at least from the year 1826 to 1850, the occur-
rence of spots has been so far characterized by periods of ten
years, that its maxima have fallen in the years 1828, 1837,
and 1848, and its minima in the years 1833 and 1843. I
have had no opportunity," says Schwabe, " of acquainting
myself with the older observations in a continued series, but
I willingly concur in the opinion that this period may itself
be further characterized by variability. "f

* Compare Nerviinder of Helsingfors, in the Bulletin de la Ctasse
Physico-MatMm. de V Acad, de St. Pitersbourg, torn, iii., 1845, p. 30-32 ;
and Buys-Ballot, of Utrecht, in Poggend., Annalen der Physik, vol
Ixviii., 1846, p. 205-213.

t I have distinguished by inverted commas the quotations from
Schwabe's manuscript communications from p. 85-87. Only the ob
servations of the years 1826 to 1843 have already been published in
Schumacher's Astron. Nachr., No. 495 (bd. xxi., 1844), p. 235".

fi6

COSMOS.

Year.

Groups.

Days shov/ing
no Spots.

Days of Ob-
servation.

1826

118

22

277

1827

161

2

273

1828

225

0

282

1829

199

0

244

1830

190

1

217

1831

149

3

239

1832

84

49

270

1833

33

139

267

1834

51

120

273

1835

173

18

244

1836

272

0

200

1837

333

0

168

1838

282

0

202

1839

162

0

205

1840

152

3

263

1841

102

15

283

1842

68

64

307

1843

34

149

312

1844

52

111

321

1845

114

29

332

1846

157

1

314

1847

257

0

276

1848

330

0

278

1849

238

0

285

1850

186

2

308

" I observed large spots visible to the naked eye in almost
%11 the years not characterized by the minimum ; the largest
appeared in 1828, 1829, 1831, 1836, 1837, 1838, 1839, 1847,
1848. I regard all spots whose diameter exceeds 50" as
large, and it is only when of such a size that they begin to
be visible to even the keenest unaided sight.

" The spots are undoubtedly closely connected with the
formation of faculee, for I have often observed faculaB or shal-
lows formed at the same points from whence the spots had
disappeared, while new solar spots were also developed with-
in the faculge. Every spot is surrounded with a more or less
bright luminous cloud. I do not think that the spots exert
any influence on the annual temperature. I register the
height of the barometer and thermometer three times in the
course of each day, but the annual mean numbers deduced
from these observations have not hitherto Indicated any ap-
preciable connection between the temperature and the num-
ber of the spots. Nor, indeed, would any importance be due
to the apparent indication of such a connection in individual
cases, unless the results were found to correspond with others
derived from many difierent parts of the Earth. If the solar

THE SUN S SPOTS. S7

•pots exert any slight miluence on our atmosphere, my tables
would; perhaps, rathei tend to show that the years which
exhibit a larger number of spots had a smaller number of
fine days than those exhibiting few spots." (Schum., Astron.
Nachr., No. 638, h 221.)

"William Herschel named the brighter streaks of light
which are seen only toward the Sun's circumference, /ac«^Z^,
and the vein-like streaks visible only toward the center of the
Sun's disk, shallows {Astr. Nachr., No. 350, p. 243). I am
of opinion that the faculce and shallows are both derived
from the same conglobate luminous clouds, which appear
more intensely bright at the circumference, but, being less
luminous in the center of the Sun's disk than the surface,
exhibit the appearance of shallows. I think it preferable to
designate all the brighter portions of the Sun as lu7ninous
clouds, dividing them, according to their form, into globate
and vein-like. These luminous clouds are irregularly dis-
tributed over the Sun, and when more strongly manifested
occasionally impart a mottled or marbled appearance to the
disk. This is often distinctly visible over the entire circum-
ference of the Sun, and sometimes even to its poles, but yet
always most decidedly manifested in the two proper zones
of the spots, even when no spots are visible in those regions.
At such times these bright zones of Sun-spots vividly remind
one of Jupiter's belts.

" The fainter portions lying between the vein-like lumin
ous clouds on vthe general surface of the Sun are deeper in-
dentations, and always present a shagreen-like gray, sand-
like appearance, reminding the observer of a mass of uni-
formly-sized grains of sand. On this shagreen-like surface
we may occasionally notice exceedingly small faint gray (not
black) pores, which are further intersected by very delicate
dark veins. {Astr. Nachr., No. 473, p. 286.) These pores,
when present in large masses, form gray nebulous groups,
constituting the penumbrse of the Sun-spots. Here the pores
and black points may be seen spreading from the nucleus to the
circumference of the penumbra, generally in a radiating form,
which occasions the identity of configuration so frequently ob-
served to exist between the penumbra and the nucleus."

The signification and connection of these varying phenom-
ena can never be manifested in their entire importance to
the inquiring physicist until an uninterrupted series of repie-
sentations of the Sun's spots* can be obtained by the aid of
* Sir John Herschel, Observations at the Cape, p. 434.

88 COSMOS.

mechanical clock-work and photographic apparatus, as the
result of prolonged observations during the many months of
serene weather enjoyed in a tropical climate. The meteor-
ological processes at work in the gaseous envelopes of the
dark body of the Sun are the causes which produce the phe-
nomena termed Sun-spots and conglobate luminous clouds.
It is probable that there, as in the meteorology of our own
planet, the disturbances of very multifarious and complicated
character depend upon such general and local causes, that it
can only be by means of prolonged observations, character-
ized by completeness, that we can hope to solve even a por-
tion of this still obscure problem.

' II.

THE PLANETS.

General comparative considerations of a whole class of
cosmical bodies must here precede their individual descrip-
tion. These considerations refer to the 22 principal planets
and 21 moons [satellites, or secondary planets'] which have
been discovered up to the present time, not to the planetary
bodies in general, among which the comets whose orbits have
been calculated are alone ten-fold more numerous. The
planets possess, upon the whole, a feeble scintillation, inas-
much as they shine by the reflected light of the Sun, and
their planetary light emanates from disks. {Cosmos, vol. iii.,
p. 76.) In the ash-colored light of the Moon, as well as in
the red light of its obscured disk, which is seen with great in-
tensity between the tropics, the Sun's light undergoes, in
reference to the observer upon the Earth, a twice repeated
change in its direction. Attention has been already directed
elsewhere* to the fact that the Earth and other planets pos-
sess in themselves a feeble power of emitting light, as is
specially proved by some remarkable phenomena upon that
portion of Venus which is turned away from the Sun.

We shall consider the planets according to their nimiber,
the sequence of their discovery, their volumes compared either
with each other or with their distances from the sun ; ac-
cording to their relative densities, masses, periods of rotation,
degrees of eccentricity, the inclinations of their axes, and
characteristic differences ivithin and beyond the zone of the

• Co»mo$, vol. i., p. 201, and note p. 202.

THE PLANETS. <59

small planets. In the comparative contemplation ol these
suhjects, it is consistent with the nature of this work to be-
stow especial attention upon the selection of the numerical
relations, which, at the period in which these pages appear,
are considered to be the most accurate, i. e., the results of
the most recent and reliable investigations.

a. PRINCIPAL PLANETS.

] . Number and Epoch of Discovery. — Of the seven cos-
mical bodies which, firom the most remote antiquity, have
been distinguished by their constantly varying relative po-
sition toward each other from those which apparently main-
tain the same positions and distances — the scintillating stars
of the region of fixed stars [orbis inerrans] — there are only five
which appear star-like, " quinque stellce errantes ;" they are
Mercury, Venus, Mars, Jupiter, and Saturn. The Sun and
the Moon remained almost separated from the others, since
they form large disks, and also on account of the greater
importance attached to them in accordance with religious
myths. ^ Thus, according to Diodorus (ii., 30), the Chaldeans
were acquainted with only five planets. Plato also says
distinctly in the Timceus, where he only once mentions the
planets, " Round the Earth, fixed in the center of the Cosmos,
move the Moon, the Sun, and jive other stars, which have
received the name oi planets ; the whole, therefore, in seven
revolutions."! In the old Pythagorean representation of the
celestial system, according to Philolaus, the five planets were
mentioned in a similar manner among the ten deified bod-
ies which revolve round the central fire (the focus of the
universe, karia) " immediately beneath the region of fixed
stars ;"$ these were succeeded by the Sun, Moon, Earth, and
the avrixOiiiv (the anti-Earth). Even Ptolemy always speaks
of only five planets. The enumeration of the planets in sys-
tems of seven, as JuHus Firmicus distributed them among the
decani,^ as they are represented in the zodiacal circle of Bi-

* Gesenius, in the Hallischen Litter atur-Zeitung, 1822, Nos. 101 and
102 (Supplement, p. 801-812). Among the Chaldeans, the Sun aud
Moon were held to be the two principal deities ; the five planets mere
iy represented genii.

t Plato, in the Timceits, p. 38, Steph. ; Davis's translation, ed. Bohn,
p. 342.

X B6ckh, De Platonico systemate Caslestmm glolorum et de vera iw
dole astronomies Philolaicce, p. xvii., and the same in Philolaus, 1819,
p. 99.

$ Jul. Fii-micus Maternus, Astr-:n., libri viii. (ed. Pruckner, Basil
1551), lib. ii., cap. 4, of the time of IJonstantine the Great.

90 COSMOS.

anchini (probally of the third century after Christ), exam
med by myself elsewhere,* and as they are met with in the
Egyptian monuments of the time of the Csesars, does not be-
long to the ancient astronomy, but to the subsequent epochs,
in which astrological chimeras had become universally dif-
fused.! We must not be surprised that the Moon was in-
cluded in the series of the seven planets, since, with the ex-
ception of a memorable theory of attraction put forward by
Anaxagoras [Cosmos, vol. ii., p. 309, and note), its more
intimate connection with the Earth was scarcely ever sus-
pected by the ancients. On the contrary, according to an
opinion respecting the system of the world which VitruviusJ
and Martianus Capella§ quote, without stating its originator,
Mercury and Venus, which we call planets, are represented
as satellites of the Sun, which itself revolves round the Earth,

* Humboldt, Monumens des Peuples Indigenes de VAm^rique, vol. ii.,
p. 42-49. I have already directed attention in 1812 to the analogy be«
tween the zodiac of Bianchini and that of Dendera. Compare Letronne,
Observations Critiques sur les Reprdscntations Zodiacales, p. 97 ; and
Lepsius, Chronologie der j^gypter, 1849, p. 80.

t Letronne, Sur VOrigine du Zodiaque Grec, p. 29. Lepsius, Chro-
'nol. der ^gypt., p. 83. Letronne opposes the old Chaldean origin of
the planetary week on account of the number seven.

X Vitruv., De Archit., ix., 4 (ed. Rode, 1800, p. 209). Neither Vitru-
vius nor Martianus Capella mention the Egyptians as the originators of
a system, according to which Mercury and Venus are considered as sliI-
ellites of the planetary Sun. The former says, " Mercurii autem et Ve-
neris stellae circum Soils radios, solem ipsum, uti centrum, itineribua
coronantes, i-egi*essus retrorsum et retardationes faciunt." " But Mer
cury and Venus, which encircle in their orbits the Sun itself as a center
retrogress and proceed slowly round its rays."

§ Martianus Mineus Felix Capella, De Nuptiis Philos. et Mercurii, lib.
viii. (ed. Grotii, 1599, p. 289) : "For though Venus and Mercury appear
to rise and set daily, yet their orbits do not, however, go round the
Earth, but revolve round the Sun in a wider orbit. In fact, the center
of their orbits is in the Sun, so that they are sometimes above it . . . ."
"Nam Venus Mercuriusque licet ortus occasusque quotidianos osten-
dant, tamen eorum circuli Terras omnino non ambiunt, sed circa Solem
laxiore ambitu circulantur. Denique circulorum suorum centrum in

Sole constituunt, ita ut supra ipsum aliquando " As this place is

written over, " Quod Tellus non sit centrum omnibus planetis," " Be-
cause the Earth is not the center of all the planets," it may certainly, as
Gassendi asserts, have had an influence upon the first views of Coper-
nicus, more than the passages attributed to the great geometer, Apol-
lonius of Perga. However, Copernicus only says, " Minime contem-
nendum arbitror, quod Martianus Capella scripsit, existimans quod Ve-
nus et Mercurius circumerrant Solem in medio existentem." " I by no
means think that we should despise what Martianus Capella has writ-
ten, who supposes that Venus and Mercury revolve round the Sun,
which is fixed in the center " Compare Cosmos, vol. ii., p. 312, and
note.

THE PLANETS. 91

There is as little foundation for considering such a system as
this to be Egyptian,^ as there is for confounding it with the
Ptolemaic epicycles or the system of Tycho.

The names by which the star-like planets of the ancients
were represented are of two kinds : names of deities, and
ugnificantly descriptive names derived from physical char-
acters. Which part of them originally belonged to the Chal-
deans, and which to the Egyptians, is so much the more dif-
ficult to determine from the sources which have hitherto been
made use of, as the Greek writers present us, not with the
original names employed by other nations, but only transla-
tions of these into Greek equivalents, which were more or
less modified by the individuality of those writers' opinions.
What knowledge the Egyptians possessed anterior to the Chal-
deans, whether these latter are to be considered merely as gift-
ed disciples of the former,! is a question which infringes upon
the important but obscure problem of primitive civilization
of the human race, and the commencement of the develop-

* Henry Martin, in his Commentary to the Timceus (Etudes sur le
TimSe de Platon, torn, ii., p. 129-133), appears to me to have explain-
ed very happily the passage in Macrobius respecting the ratio Ckaldceo
rum, which led the praiseworthy Ideler into error (in WoltF's and Butt
mann's Museum der Alterthums- Wissenschaft, bd. ii., s. 443, and in his
Treatise upon Eudoxus, p. 48). Macrobius (in Somn. Scipionis, lib. i.,
cap. 19 ; lib. ii., cap. 3, ed. 1634, p. 64 and 90) says nothing of the sys-
tem mentioned by Vitruvius and Martianus Capella, according to which
Mercury and Venus are satellites of the Sun, which, however, itself re-
volves with the other planets round the Earth, which is fixed in the
center. He enumerates only the differences in the succession of the
orbits of the Sun, Venus, Mercury, and the Moon, according to the
eiews of Cicero. He says, '• Ciceroni, Archimedes et Chaldseorum ra-
tio consentit ; Plato iEgyptios secutus est." " Archimedes and the sys-
tem of the Chaldajans agree; Plato followed that of the Egyptians."
When Cicero exclaims, in the eloquent description of the whole plan-
etary system (Somn. Scip., cap. 4, Edmond's translation, ed. Bohn, p.
294), " Hunc (Solem) ut comites consequuntur Veneris alter, alter Mer-
curii cursus ;" " The motions of Venus and Mercury follow it (the Sun)
as companions," he refers only to the proximity of the Sun's orbit and
those of the two inferior planets, after he had previously enumerated
the three cursus of Saturn, Jupiter, and Mars, all revolving round the
immovable Earth. The orbit of a secondary planet can not surround
that of a principal planet, and yet Macrobius says distinctly, " ^gyp-
tiorum ratio talis est : circulus, per quem Sol discurrit, a Mercurii cir-
culo ut inferior ambitur, ilium quoque superior circulus Veneris inclu-
dit" "The following is the system of the Egyptians: the circle in
which the Sun moves is encompassed by the circle of Mercury, which
m its turn is encircled by the larger one of Venus." The orbits are aU
permanently parallel to each other mutually surrounding.

f liCpsius, Chronologie der yEgypter, th. i., p. 207.

92 COSMOS.

ment of scientific ideas upon the Nile or the Euphrates. The
Egyptian names of the 36 Decans are known ; but the Egyp-
tian names of the planets, with the exception of one or two,
have not been transmitted to us.^

It is remarkable that Plato and Aristotle employed only
the names of deities for the planets which Diodorus also
mentions ; while at a later period, for example, in the book
De Mundo, erroneously attributed to Aristotle, a combina-
tion of both kinds of names are met with, those of deities, and
the descriptive (expressive) names : (paCvcjv for Saturn, ariX-
6g)v for Mercury, rrvpoEig for Mars.f Although the name

* The name of the planet Mars, mutilated by Vettius Valeus and
Cedrenus, must, in all probability, correspond to the name Her-tosch,
as Seb does to Saturn. (Lepsius, Chronol. der ^gypt., p. 90 and 93.)

t The most striking differences are met with on comparing Aristot.,
Metaph., xii., cap. 8, p. 1073, ed, Bekker, with Pseudo-Aristot., De Mun-
do, cap. 2, p. 392. The planet names Phaethon, Pyrois, Hercules, Stil-
bon, and Juno, appear in the latter work, which points to the times of
Apuleius and the Antonines, in which Chaldean astrology was already
diffused, over the whole Roman empire, and the terms of different na-
tions mixed with each other. (Compare Cosmos, vol. ii., p. 29, and
note). Diodorus Siculus says positively that the Chaldeans first named
the planets after their Babylonian deities, and that these names were
thus transferred, to the Greeks. Ideler {Eudoxus, p. 48), on the con-
traiy, ascribes these names to the Egyptians, and grounds his argument
upon the old existence on the Nile of a seven-day planetary week\Hand-
buck der Chronologic, bd. i., p. 180): an hypothesis which Lepsius has
completely disproved (Ckronologie der u^g., th. i., p. 131). I will
here collate from Eratosthenes, from the editor of Epinomis (Philippua
Opuntius?), from Geminius, Pliny, Theon of Smyrna, Cleomedes, Achil-
les Tatius, Julius Firmicus, and Simplicius, the synonyms of the five
oldest planets, as they have been transmitted to us ^chiefly through pre-
dilection for astrology :

Saturn: cpaivuv, Nemesis, also called a sun by five authors (Theon.
Smyrna, p. 87 and 105, Martin) ;

Jupiter: (paeOov, Osiris;

Mars : nvpostg, Hercules ;

Venus : iua^opo^, (^uaclibpo^, Lucifer ; ^aTvepog, Vesper ; Juno, Isis ;

Mercury : arlMuv, Apollo.
Achilles Tatius {Isag. in Phaen. Arati, cap. 17) considers it strange
" that the Egyptians, as well as the Greeks, should call the least lumin-
ous of the planets the shining" (perhaps only because it brought pros-
perity).^ According to Diodorus, the name refers to the opinion "that
Saturn was that planet which principally and most clearly foretold the
future." — Letronne, Sur VOrigine du Zodiaque Grec, p. 33, and in the
Journal des Savants, 1836, p. 17. Compare also Carteron, Analyse des
Recherches Zodiacales, p. 97. Names which are transmitted as equiv-
alents from one people to another, certainly depend in many cases, in
addition to their oingin, upon accidental circumstances, which can not
be investigated ; however, it is necessaiy to remark here, that etymo-
logically, ^alveiv expresses a mere shining, a fainter evolution of light,

THE PLANETS. 93

of Sun was strangely enough applied to Saturn, the outer-
most of the then known planets, as is proved by several pas-

which is continuous or constant in intensity, while (yTc2.6eiv refers lo an
intermittent scintillating light of greater brilliancy. The descriptive
names : ^aivuv for the remote Saturn, gtiMov for the nearer planet
Mercury, appear the more appropriate, as I have befoi'e pointed out
(Cosmos, vol. iii. p. 72), from the circumstance that, as seen by day
in the great refractor of Frauenhofer, Saturn and Jupiter appear feebly
luminous in comparison with the scintillating Mercury. There is,
therefore, as Professor Franz remarks, a succession of increasing brill-
iancy, indicated from Saturn {(paivuv) to Jupiter, from Jupiter {^aeduv)
to the colored glowing Mars {jTvpoEig), to Venus (^ua<j>6pog), and to Mer
cury (ariMtjv).

My acquaintance with the Indian name of Saturn ('sanaistsckara),
the slowly wandering, induced me to ask my celebrated friend Bopp
whether, upon the whole, a distinction between names of deities and
descriptive names was also to be made in the Indian planetary names,
as in those of the Greeks, and probably the Chaldeans. I here insert
the opinion, for which I am indebted to this great philologist, arrang-
ing the planets, however, according to their actual distances from the
Sun, as in the above table (commencing with the greatest distance),
not as they stand in Amarakoscha (by Colebrooke, p. 17 and 18). There
are, in fact, among the five Sanscrit names three descriptive ones : Sat-
urn, Mars, and Venus.

" Saturn : 'sanaistschara, from 'sanais, slow, and tschara, going ; also
'sauri, a name of Vishnu (derived as a patronymic from 'sfira. Grand-
father of \\.\) and 'sani. The planet name 'sani-vdrafor, ' dies Saturn!,'
is radically related to the adverb 'sanais, slow. The names of the week-
days derived from planets appears, however, not to have been known
to Amarasinha. They are, indeed, of later introduction.

" Jupiter : Vrihaspati ; or, according to an older Vedic mode of writ-
ing which Lassen follows, Brihaspati : the Lord of increase, a Vedic
deity: from vrih (brih), to grow, and pati, lord.

"Mars: angaraka (from angara, burning coal); also lohitdnga, the
red body : from lohita, red, and anga, body.

" Venus: a male planet, which is called suki-a, i. e., the brilliant. An-
other name of this planet is daitya-guru: Teacher, guru, the Titans,
Daityas.

" Mercury : Budha, not to be confounded as a planet name with
Buddha, the founder of the religious sect; also Rauhineya, the son of
the nymph Rohinl, wife of the Moon (soma), on which account the plan-
et is sometimes called saumya, a patronymic of the Sanscrit word mond.
The etymological root of budha, the planet name, and buddha, the name
of the saint, is budh, to know. It seems to me improbable that Wuotan
(Wotan, Odin) are connected with Budha. This conjecture is found-
ed, indeed, principally upon the external similarity of form, and upon
the correspondence of the name of the day of the week, * dies Mercu-
rii,' with the old Saxon Wodanes-dag, and the Indian Budha-vfira, i. e.,
Budha's day. The primitive signification of v6ra is repetition, for ex-
ample, in bahuv&rdn, many times, often ; it subsequently occurs at the
end of a compound w^ord with the signification day. Jacob Grimm
derives the German Wuotan from the verb watan,vuot (the German
waten), which signifies meare, transmeare, cum impetu ferri, and ortho-
graphically corresponds to the Li tin vadere. (Deutsche Myihologie, p.

94 COSMOS.

sages in the Commentary of Simplicius (p. 122), to the eighth
book of the De Codo of Aristotle, in Hyginus, Diodorus, and
Theon of Smyrna, it certainly was only its position, and the
length of its orbit, which raised it above the other planets.
The descriptive names, however old and Chaldean they may
be, were not very frequently employed by the Greek and Ro-
man writers until the time of the Caesars. Their diffusion
is connected with the influence of astrology. The planetary
signs are, with the exception of the disk of the Sun and the
Moon's crescent upon Egyptian monuments, of very recent
origin ; according to Letronne's researches, =^ they would not

120.) Wuotan, Odinn, is, according to Jacob Grimm, the all-powerful,
all-penetrating being : * qui omnia permeat,' as Lucan says of Jupiter." —
Compare, with reference to the Indian names of the days of the week
Budha and Buddha, and the week-days in general, the observations of
my brother, in his work Ueber die Verbindungen zwischen Java vnd In.'
dien (Kawi Sprache, bd. i., p. 187-190).

* Compare Letronne, Sur VAmulette de Jules Cisar et les Signes Plan
6taires, in the Revue ArcMologiqtie, Ann6e III., 1846, p. 261. Salmasius
considered the oldest planetary sign for Jupiter to be the initial letter
of Zevf, that of Mars a contraction of the cognomen -dovpLog. The sun-
disk was rendered almost unrecognizable by an oblique and triangular
bundle of rays issuing from it. As the Earth was not included among
the planets in any of the ancient systems, except, perhaps, the Philo-
Pythagorean, Letronne considers the planetary sign of the Earth " to
have come into use after the time of Copernicus." The remarkable
passage in Olympiodorus, on the consecration of the metals to individ-
ual planets, is taken from Proclus, and was traced by Boekh (it is in
p. 14 of the Basil edition, and at p. 30 of Schneider's edition^. — Com
pare, for Olympiodorus, Aristot., MeteoroL, ed. Ideler, tom. ii., p. 163.
The scholium to Pindar {Isthm.), in which the metals are compared
with the planets, also belongs to the new Platonic school. — Lobeck
( Aglaophamus in OrpTi., tom. ii., p. 936). In accordance with the samo
connection of ideas, planetary signs by-and-by became signs of the met
als; indeed, some (as Mercurius, for quicksilver, the argentum vivum
and hydrargyrus of Pliny) became names of metals. In the valuable
collection of Greek manuscripts of the Paris Library are two manu-
scripts on the cabalistic, or so-called sacred art, of which one (No. 2250)
mentions the metals consecrated to the planets without planetary signs;
the other, however (No. 2329), which, according to the writing, is of
the fifteenth century (a kind of chemical dictionary), combines the
names of the metals with a small number of planetary signs. (H6rer,
Histoire de la Ckimie, tom. i., p. 250.) In the Paris manuscript No.
2250, quicksilver is attributed to Mercury, and silver to the Moon,
while, on the contrary, in No. 2329, quicksilver belongs to the Moon,
and tin to Jupiter. Olympiodorus has ascribed the latter metal to Mer-
cury. Thus indefinite were the mystic relations of the cosmical bodies
to the metaUic powers.

This is also the appropriate place to mention the planetary hours and
the planetary days in the small seven-day period (the week), concern*
ing the antiquity and diffusion of which among i-emote nations more

THE PLANETS. 95

date further back than the tenth century. Even upon stones
with Gnostic inscriptions they are not met with. Subsequent

correct views have only recently been established. The Egyptians had
originally no short periods of seven days, but periods ot ten days, simi-
lar to the week, as has been proved by Lepsius {Chronologic der ^g-,
p. 132), and as is also testified by monuments which date back to the
most remote times of the erection of the large pyramids. Three such
decades formed one of the twelve months of the solar year. On read-
ing the passage in Dio Cassius (lib. xxxvii., cap. 18), " That the custom
of naming the days after the seven planets was first adopted by the
Egyptians, and had, in no very long time, been communicated by them
to all other nations, especially the Romans, with whom it was then al-
ready quite familiarized," it must not be forgotten that this writer lived
in the later period of Alexander Severus, and that, since the first irrup-
tion of the Oriental astrology under the Caesars, and in consequence of
the early and extensive commerce of so many races of people in Alex-
andria, it was the fashion among Western nations to call every thing
Egyptian which appeared ancient. The seven-day week was undoubt-
edly the earliest and most diffused among the Semitic nations ; not only
among the Hebrews, but even among the nomadic Arabians long be-
fore the time of Mohammed. I have submitted to a learned investiga-
tor of Semitic antiquities, the Oriental traveler Professor Tischeudorf,
at Leipsic, the question whether, besides the Sabbath, there occur in
the Old Testament any names for the individual days of the week (other
than the second and the third of the achebua) 1 Whether no planetary
name for any one day of the seven-day period occurred any where in
the New Testament at a period in which it was certain that the foreign
inhabitants of Palestine already pursued planetary astrology ? The an-
swer was, " There is an entire absence, not only in the Old and New
Testaments, but also in the Mischna and Talmud, of any traces of
names of week-days taken from the planets. Neither is the expression
the second or third day of the schebua employed ; and time is general-
ly reckoned by the days of the month ; the day before the Sabbath is
also called the sixth day, without any further addition. The word Sab-
bath was also transferred to the week throughout (Ideler, Handbuch
der ChronoL, bd. i., p. 780); consequently, the first, second, and third
day of the Sabbath stand for the days of the week in the Talmud as
well. The word i68o[j.dq for schebua is not in the New Testament.
The Talmud, which certainly extends from the second to the third cen-
tury, has descriptive Hebrew names for a few planets, for the brilliant
Venus and the red-colored Mars. Among these, the name of Sabbatai
(literally Sabbath-star) for Saturn is especially remarkable, as among
the Pharisaic names of the stars which Epiphanius enumerates, the name
Hochab Sabbath is employed for Saturn." Has not this had an influ-
ence upon the conversion of Sabbath day into Saturn day, the " Satumi
sacra dies" of Tibullus {Eleg., i., 3, 18)? Another passage in Tacitus
extends the range of these relations to Saturn as a planet and as a tra-
ditional historical personage. (Compare also Ftirst, Kultur- und Litte-
raturgeschichte der Juden in Asien, 1849, p. 40.)

The different luminous forms of the Moon certainly attracted the ob-
servation of hunters and herdsmen earlier than astrological phantasms.
It may therefore be assumed, with Ideler, that the week has origin-
ated from the length of the synodic months, the fourth part of which
jimouQts, on the average, to 7§ days ; that, on the contrary, r *fereuces

\)G COSMOS.

transcribers have, however, added them to Gnostic and al-
chemistic manuscripts ; scarcely, in any case, to the oldest

to the planetary series (the sequence of their distances from each oth-
er), together with the planetary hours and days, belongs to an entirely
different period of advanced and speculative culture.

With reference to the naming of the individual week-days after plan-
ets, and the arrangement and succession of the planets —
Saturn, Venus,

Jupiter, Mercury, and

Mars, Moon,

Sun,
situated, according to the most ancient and widely-diffused belief (Gem-
inus. Element. Astr., p. 4; Cicero, Somn. Scip., cap. 4; Firmicus, ii., 4,
Edmond's translation, ed. Bohn, p, 294-298), between the sphere of
fixed stars and the immovable earth as a central body, there have been
three views put forward : one derived from musical intervals ; another
from the astrological names of the planetary hours ; a third from the
distribution of each three decans, or three planets, which are the rulers
{domini) of these decans among the twelve signs of the zodiac. The
first two hypotheses are met with in the remarkable passage of Dio
Cassius, in which he endeavors to explain (lib. xxxvii., cap. 17) why
the Jews, according to their laws, celebrated the day of Saturn (our
Saturday). " If," says he, " the musical interval which is called 6ia
Tsaadpuv, the fourth, is applied to the seven planets according to their
times of revolution, and Saturn, the outermost of all, taken as the start-
ing-point, the next which occurs is the fourth (the Sun), then the sev-
enth (the Moon), and in this way the planets are encountered in the
same order of succession in which their names have been applied to
the week-days." A commentary upon this passage is given by Vincent,
Snr les Manuscrits Grecs relative a la Musique, 1847, p. 138. Compare
also Lobeck, Aglaophamus, in Orph., p. 941-946. The second expla-
nation of Dio Cassius is borrowed from the periodical series of the plan
etary hours. " If," he adds, " the hours of the day and the night are
counted from the first (hour of the day), and this ascribed to Saturn,
the following to Jupiter, the third to Mars, the fourth to the Sun, the
fifth to Venus, the sixth to Mercury, the seventh to the Moon, always
recommencing from the beginning, it will be found, if all the twenty-
four hours are gone through, that the first hour of the following day
coincides with the Sun, the first of the third with the Moon; in short,
the first hour of any one day coincides with the planet after which the
day is named." In the same way, Paulus Alexandrinus, an astronomic-
al mathematician of the fourth century, calls the ruler of each week
day that planet whose name agrees with the first hour of the particular
day.

These modes of explaining the names of week-days have hitherto
been very generally considered as the more correct; but Letronne en-
tertains a third explanation — the distribution of any three planets over
B sign of the zodiac — which he considers to be the most adequate, upon
the evidence of the long-neglected zodiacal circle of Bianchini, pre-
served in the Louvre, to which I myself directed the attention of ar-
chfeologists in 1812, on account of the remarkable combination of a
Greek and Kirgisch-Tartar zodiac. (Letronne, Observ. Crit. et ArchM.
$ur VOhjet. des Representations ZodiacaUf, 1824, p. 97-99.) This dis
tribution of pknets among the 36 decaiis of the Dodecatomeria is pre

THE PLANETS 97

manuscripts of Greek astronomers ; of Ptolemy, of Theon, or
of Cleomedes. The earliest planetary signs, some of which

cisely that which Julius Firmicus Maternus (ii., 4) describes as " sig-
norum decani eorumque domini." If those planets are separated which
in each of the signs are the first of the three, the succession of the plan-
etary days in the week is obtained (Virgo: Sun, Venus, Mercury;
Libra: Moon, Saturn, Jupiter; Scorpio: Mars, Sun, Venus ; Sagittarius:

Mercury which may here serve as an example for the first four

days of the week : Dies Soils, Lunce, Martis, Mercurii). As, according
to Diodorus, among the Chaldeans, the number of the planets (star-
like) originally amounted only to five, and not seven, all the here-men-
tioned combinations in which more than five planets form periodical
series appear to be not of old Chaldean origin, but much rather to date
from a subsequent astrological period. (Letronne, Sur VOrigine du
Zodiaque Grec, 1840, p. 29.)

With respect to the concordance of the arrangement of the planets
as days of the week with their arrangement and distribution among
the decans in the zodiacal circle of Bianchini, a brief explanation will,
perhaps, be acceptable to some readers. If a letter is assigned to each
cosmical body in the order of succession adopted in antiquity (Saturn
a, Jupiter b, Mars c, Sun d, Venus e, Mercury /, Moon g), and with
these seven members the following periodical series are formed—

ab cdefg, abed....
there is obtained, 1st, by passing over two members of the distribution
among the decans, each of which comprises three planets (the zodiacal
sign of the first one giving, in each case, its name to the week-day), the
new periodical series

adgefbe, adgc....
that is. Dies Saturm, Solis, Lunce, Martis, and so on ; 2dly, the same
new series,

adgc....
obtained by the method of Dio Cassius, according to which the sue
cessive week-days take their names from the planet which rules the
first hour of the day, so that alternately a member of the periodical
seveu-membered planet-series is to be taken, and twenty-three mem-
bers to be passed over. Now it is immaterial, in the case of a period-
ical series, whether it is a certain number of members which is passed
over, or whether it is this number increased by any multiple of the
number of members (in this case seven) of the period. By passing
over twenty-three (=3.7-|-2) members, according to the second meth-
od, that of the planetary hours, the same result is obtained as when the
first method, that of the decans, is adopted, in which only two members
are to be passed over.

Attention has already been directed (page 92, note +) to the remark-
able resemblance between the fourth day of the week, dies Mercm-ii,
of the Indian Budha-vdra, and the old Saxon Wodanes-dag. (Jacob
Grimm, Deutsche Mythologie, 1844, bd. i., p. 844.) The identity af-
firmed by William Jones to exist between the founder of the Buddhist
religion and the race of Odin or Wuotan, and Wotan, famous in North-
ern heroic tales, as well as in the history of Northern civilization, will,
perhaps, gain more interest when it is called to mind that the name of
Wotan is met with in a part of the new continent as belonging to a half-
mythical, ha.f-historical personage concerning whom I have collected
Vol. IV.— E

98 COSMOS.

(Jupiter and Mars) originated, as Salmasius has shown, with
his ordinary acuteness, from letters, and were very different
from ours ; the present form reaches scarcely beyond the fif-

a great number of notes in my work on the monuments an d myths of
the natives of America (Vv.es des Cordilleres et Monumens des Pe2iple$
Indigenes de VAmirique, tom. i., p. 208, and 382-384 ; tom. ii., p. 356).
This American Wotan is, according to the ti-aditions of the natives of
Chiapa and Soconusco, the gi-andson of the man vv^ho saved his life in
a boat during the great dehige, and renewred the human race ; he com-
menced the erection of large buildings, during which time ensued a
confusion of languages, war, and dispersion of races, as in the erection
of the Mexican pyramids of Cholula. His name was also transferred
to the calendar of the natives of Chiapa, as was the name of Odin in
the north of Germany. One of the five-day periods — four of which
formed the month of the people of Chiapa and the Aztecs — was named
after him. While the names and signs of the days among the Aztecs
were taken from animals and plants, the natives of Chiapa (properly
Teochiapan) assigned to the days of the month the names of twenty
chieftains who, coming from the north, had led them so far southward.
The names of the four most heroic, Wotan or Wodan, Lambat, Been,
and Chinax, commenced the small periods of five-day weeks, as did the
symbols of the four elements among the Aztecs. Wotan and the other
chieftains indisputably belonged to the race of the Tolteks, who invaded
the country in the seventh century. Ixtlilxochitl (his Christian name
was Fernando de Alva), the first historian of his people (the Aztecs),
says distinctly, in the manuscripts which he completed as early as the
beginning of the sixteenth century, that the province of Teochiapan
and the whole of Guatemala were peopled by Tolteks from one coast
to the other ; indeed, in the beginning of the conquest of the Spaniards,
a family was still living in the village Teopixca who boasted of being
descended from Wotan. The Bishop of Chiapa, Francisco Nunez de la
Vega, who presided over a provincial council in Guatemala, has, in his
Preambulo de las Constituciones Diocesanas, collected a great deal of
information respecting the American tradition of Wotan. It is also still
very undecided whether the tradition of the first Scandinavian Odin
(Odinn, Othinus) or Wuotan, who is said to have emigrated from the
banks of the Don, has an historical foundation. (Jacob Grimm,
Deutsche Mythologie, bd. i., p. 120-150.) The identity of the Ameri-
can and Scandinavian Wotan, certainly not founded on mere resem-
blance of sound, is still quite as doubtful as the identity of Wuotan
(Odinn) and Buddha, or that of the names of the founder of the Bud
dhist religion and the planet Budha.

The assumption of the existence of a seven-day Peruvian week, which
is 80 often brought forward as a Semitic resemblance in the division of
time in both continents, is founded upon a mere error, as has been al
ready proved by Father Acosta {Hist. Natural y Moral de las India$
1591, lib. vi., cap. 3), who visited Peru soon after the Spanish conquest
and the Inca, Garcilaso de la Vega, himself coi-rects his previous state
ment (parte i., lib. ii., c. 35) by distinctly saying there were three fes
tivals in each of the months which were reckoned after the moon, and
that the people should work eight days and rest upon the ninth (parte
i., lib. vi., cap. 23). The so-called Peruvian weeks, therefore, con
disted of nine days. (See my Vues det CordilUn§, tom. i., p. 341-343

THE PLANETS. 90

teenth century. The symbolizing habit of consecrating cer-
tain metals to the planets belongs, undoubtedly, to the new
Platonic doctrines of the Alexandrian school in the fifth cen-
tury, as is ascertained from passages in Proclus {ad Tim., ed.
Basil, p, 14), from Olympiodorus, as well as by a late scholium
to Pindar {Isthm., vol. ii.). (Compare Olympiod., Comment,
m Aristot., Meteorol.., cap. 7, 3 in Ideler's edition of the Me-
ieorol., tom. ii., p. 163 ; also tom. i., p. 199 and 251 .)

Although the number of the visible planets amounted, ac-
cording to the earliest limitation, to five, and subsequently,
by the addition of the large disks of the Sun and Moon, in-
creased to seven, conjectures were prevalent; even in antiqui-
ty, that beyond these visible planets there were yet other less
luminous, unseen planets. This opinion is stated by Simpli-
cius to be Aristotelean. " It is probable that such dark cos-
mic al bodies which revolve round the common center some-
times give rise to eclipses of the moon as well as the earth."
Artemidorus of Ephesus, whom Strabo often mentions as a
geographer, believed in the existence of an unlimited number
of such dark, revolving cosmical bodies. The old ideal body,
the anti-earth (dvrcxOcov) of the Pythagoreans, does not be-
long to this class of conjectures. The earth and the anti-
earth have a parallel concentric motion ; and the anti-earth,
conceived in order to avoid the assumption of the rotatory
motion of the eaYth, moving in a planetary manner round .
the central fire in twenty-four hours, can scarcely be any
thing else than the opposite hemisphere — the antipodean
portion of our planet. =^

When from the 43 principal and secondary planets now
known (a number six times greater than that of the planet-
ary bodies known to the ancients), the 36 objects which have
been discovered since the invention of the telescope are chro-
nologically separated according to the succession of their dis-
covery, there is obtained for the seventeenth century nine,
for the eighteenth century also nine, and for the half of the
nineteenth century eighteen newly-discovered planet*.

* Bockh Ueber Philolaut, p. 102 and 117.

100 COSMOS.

Sequence of the Planetary Discoveries {of principal and
secondary planets) since the Invention of the Telescope
in the Year 1608.

(A.) The Seventeenth Century.

Four satelUtes of Jupiter : Simon Marius, at Anshach, De-
cember 29, 1609 ; Galileo, January 7, 1610, at Padua.

Triple configuration of Saturn : Galileo, November, 1610 ,
Hevelius, hypothesis of two lateral bars, 1656 ; Huygens,
final discovery of the true form of the ring, December 7,
1657.

The sixth satellite of Saturn (Titan) : Huygens, March 25,
1655.

The eighth satellite of Saturn (the outermost, Japetus) : Do-
min. Cassini, October, 1671.

The fifth satellite of Saturn (Rhea) : Cassini, December 23,
1672.

The third and fourth satellites of Saturn (Tethys and Dione) :
Cassini, end of March, 1684.

(B.) The Eighteenth Century.

Uranus : WilHam Herschel, May 13, 1781, at Bath.

The second and fourth satellitss of Uranus : "William Her-
schel, January 11, 1787.

The first satellite of Saturn (Mimas) : "William Herschel,
August 28, 1789.

The second satellite of Saturn (Enceladus) : William Her-
schel, September 17, 1789.

The first satellite of Uranus : William Herschel, January 18,
1790.

The fifth satellite of Uranus : William Herschel, February
9, 1790.

The sixth satellite of Uranus : William Herschel, February
28, 1794.

The third satellite of Uranus : William Herschel, March 26,
1794.

(C.) The Nineteenth Century.
Ceres*= : Piazzi, at Palermo, January 1, 1801.
Pallas^ : Olbers, at Bremen, March 28, 1802.
Juno*: Harding, at Lilienthal, September 1, 1804.
Vesta*= : Olbers, at Bremen, March 29, 1807.

(During 38 years no planetary discoveries w^ere made).
AsTREA*^ : Hencke, at Dresden, December 8, 1845.

THE PLANETS. IQI

Neftune : Galle, at Berlin, September 23, 1846.

The first satellite of Neptune : W. Lassell, at Starfield, near
Liverpool, November, 1846 ; Bond, at Cambridge (U. S.).

Hebe*': Hencke, at Dresden, July 1, 1847.

Iris=^ : Hind, in London, August 13, 1847.

Flora* : Hind, in London, October 18, 1847.

Metis*: Graham, at Markree Castle, April 25, 1848.

The seventh satellite of Saturn (Hyperion) : Bond, at Cam
bridge (U. S.),' September, 16-19 ; Lassell, at Liverpool,
September 19-20, 1848.

Hygeia*= : De Gasparis, at Naples, April 12, 1849.

Parthenope* : De Gasparis, at Naples, May 11, 1850.

The second satellite of Neptune : Lassell, at Liverpool, Au-
gust 14, 1850.

Victoria* : Hind, in London, September 13, 1850.

Egeria* : De Gasparis, at Naples, November 2, 1860.

Irene* : Hind, in London, May 19, 1851 ; and De Gasparis,
at Naples, May 23, 1851.

In this chronological summary* the principal planets are
distinguished from the secondary planets or satellites by a dif-
ferent type. Some bodies are included in the class of princi-
pal planets, which form a peculiar and very extended group,
forming, as it were, a ring of 132 millions of geographical
miles, situated between Mars and Jupiter, and are generally
called small planets, as well as telescopic planets, co-planets,
asteroids, or planetoids. Of these, four were discovered in the
first seven years of this century, and ten during the last six
years ; which latter circumstance is to be attributed less to
the perfection of the telescopes, than the industry and dex-
terity of the investigators, and especially the improved charts
enlarged by additions of fixed stars of the ninth and tenth
magnitudes. It is now more easy to distinguish between

* In the history of the discoveries, it is necessary to distinguish be-
tween the epoch at which the discovery was made, and the time of its
first announcement. In consequence of a neglect of this distinction,
dissimilar and erroneous dates have been inti'oduced into astronomical
manuals. So, for example, Huygens discovered the sixth satellite of
Saturn (Titan) on March 25, 1655 {Huy genii Opera vaHa, 1724, p. 523;,
and did not announce it until March 5, 1656) Systema Saturnium, 1659,
p. 2). Huygens, who devoted himself uninterruptedly from March,
1655, to the study of Saturn, had already obtained the full and indubi
table view of the open ring on December 17, 1657 {Systema Satuminm,
p. 21), but did not publish his scientific explanation of all the phenom-
ena until the year 1659. (Galileo had thought that he saw, on each
eide of the planet, only two projecting circular disks.)

i02 COSMOS.

moving 3osmica- bodies and fixed. See CosmoSy vol. iii., p.
115.)

The number of the principal planets has been exactly doub-
led since the first volume of Cosmos appeared, =^ so excessive-
ly rapid is the succession of discoveries, the extension and per-
fection of the topography of the planetary system.

2. Classification of the Planets in tivo Groups. — If the
region of small planets situated in the solar system between
the orbits of Mars and Jupiter, but, on the whole, nearer to
the former, is considered as a separating zone — as it were, an
intermediate group — then, as has already been remarked, those
planets which are nearest to the sun, the interior (Mercury,
Venus, the Earth, and Mars), present several resemblances
among each other, and contrasts with the exterior planets
(Jupiter, Saturn, Uranus, and Neptune), or those which are
more remote from the sun, beyond this separating zone. Of
these three groups, the intermediate one occupies a space
scarcely equal to half the distance of the orbit of Mars from
that of Jupiter. Of the space between the two great princi-
pal planets, Mars and Jupiter, that part which is nearest to
Mars is, as far as has hitherto been observed, the most close-
ly filled ; for if, in the zone which the asteroids occupy, the
two outermost, Flora and Hygeia, are examined, it will be
found that Jupiter is more than three times further from Hy-
geia than Flora is from Mars. The most distinctive features
of this intermediate group of planets are the great inclination
and eccentricity of their interlacing orbits, and the extreme
smallness of the planets. The inclination of the orbits to-
ward the ecliptic increases in that of Juno to 13° 3', in that
of Hebe even to 14° 47', of Egeria to 16° 33', of Pallas even
to 34° 37' ; while in the same intermediate group it falls as
low, in the orbit of Astrea, as 5° 19', in that of Parthenope
to 4° 37', and that of Hygeia to 3° 47'. The whole of the
orbits of the small planets having inclinations smaller than
7° are, to go from the large to the small, those of Flora, Me-
tis, Iris, Astrea, Parthenope, and Hygeia. Nevertheless, none
of these orbits attain such a small degree of inclination as
those of Venus, Saturn, Mars, Neptune, Jupiter, and Uranus.
The eccentricities partly exceed even that of Mercury (0 206) ;
for Juno, Pallas, Iris, and Victoria have 0255, 0239, 0232,
and 0-218, while Ceres (0-076), Egeria (0-086), and Vesta
(0089) have orbits less eccentric than Mars (0*093), without,

* Cosmos, vol, i., p. 92. Compare also Encke, in Schumacher' s Astron
Nachr., vol. xxvi., 1848, No 622, p. 347.

THE PLANETS. 103

/lowever, attaining to the approximative circular orbits of the
other planets (Jupiter, Saturn, and Uranus). The diameter
of the telescopic planets is immeasurably small ; and accord-
ing to observations made by Lament in Munich, and Madler
with the Dorpat refractor, it is probable that the largest of
the small planets is at the utmost only 145 geographical
miles in diameter ; that is, one fifth of that of Mercury, one
twelfth of that of the Earth.

If the four planets nearest to the Sun, situated between the
ring of the asteroids (the small planets) and the central body,
are called interior planets, they will all agree in presenting
a moderate size, a greater density, less flattened at the poles,
and, at the same time, rotating slowly round their axes (in
periods of rotation of nearly 24 hours), and, with the excep-
tion of one (the Earth), without moons. On the contrary, the
four exterior planets, those which are more remote from the
Sun, situated between the ring of asteroids, and the, to us, un-
known limits of the solar system (Jupiter, Saturn, Uranus,
and Neptune), are considerably larger, five times less dense,
their axial rotation more than twice as rapid, and their num-
ber of moons greater in the proportion of 20 to 1. The in-
terior planets are all smaller than the Earth (Mercury and
Mars \ and \ smaller in diameter) ; the exterior planets, on
the contrary, are from 4*2 to 11*2 larger than the Earth.
The density of the Earth being taken as ==1, the densities
of Yenus and Mars are the same to within less than J^ ; the
density of Mercury is also but very httle more, according to
Encke's determination of his mass. On the contrary, none
of the exterior planets exceed in density \ ; Saturn, indeed,
is only |, almost only half the density of the other exterior
planets and the Sun. The exterior planets present the soli-
tary phenomenon of the whole solar system, the wonderful
circumstance of one of its principal planets being surrounded
by an unattached ring ; also atmospheres which, in conse-
quence of the peculiarity of their condensation, appear to us
variable ; in Saturn, indeed, sometimes as interrupted bands.

Although in the important classification of the planets into
two groups oi interior and exterior planets, the general char-
acters oif absolute magnitude, density, flattening at the poles,
velocity of rotation, absence of moons, present themselves as
dependent upon the distances, i. e., from their semi-orbital
axes, this dependence can not be affirmed of each one of these
groups Up to the present time we are ignorant, as I have
already remarked^ of *iay internal necessity, any mechanical

104 COSMOS.

law of nature, which (like the beautiful law which connects
the square of the periods of revolution with the cube of the
major axes) represents the above-named elements of the order
of succession of the individual planetary bodies of each group
in their dependence upon the distances. Although the planet
which is nearest to the Sun (Mercury) is the densest, even
six or eight times denser than some of the exterior planets,
Jupiter, Saturn, Uranus, and Neptune, the order of succes-
sion, in the case of Yenus,' the Earth, and Mars," or Jupiter,
Saturn, and Uranus, is very irregular. The absolute mag-
nitudes do generally, as Kepler has already observed (Har-
monice Mundi, vol. iv., p. 194 ; Cosmos, vol. i., p. 93-97),
increase with the distances; but this does not hold good
when the planets are considered individually. Mars is small-
er than the Earth, Uranus smaller than Saturn, Saturn small-
er than Jupiter, and succeeds immediately to a host of plan-
ets, which, on account of their smallness, are almost im-
measurable. It is true the period of rotation generally in-
creases with the distance from the Sun ; but it is, in the case
of Mars, slower than in that of the Earth, slower in Saturn
than in Jupiter.

The external world of forms, I again repeat it, can only
be represented in the enumeration of relations of space, as
something actually existing in nature, and not as the subject
of intellectual deductions of previously known causal rela-
tions. No universal law for the cosmical regions is here
traced, any more than for terrestrial regions in the culmina-
ting points of mountain chains, or. in the configuration of con-
tinents. These are natural facts which have resulted from
the conflict of numerous attractive and repulsive forces, un-
der conditions which are unknown to us. We here enter with
eager and unsatisfied curiosity upon the obscure domain of
incipient foTTnation. It is to t;hese phenomena that the so-
frequently misused term of natural facts may be applied in
its strictest sense, cosmical processes which have taken place
during spaces of time of, to us, immeasurable extent. If the
planets have been formed from revolving rings of nebulous
matter, it must, after having commenced to aggregate into
globes, according to the preponderating influence of individ-
ual centers of attraction, have passed through an intermina-
ble series of conditions in order to have formed sometimes
simple, sometimes interwoven orbits, planets of such diflerent
magnitudes, flattening, and density, with and without moons,
and even, in one case, to blend the satellites into a solid ring.

THE PLANETS.

105

The present form of things, and the exact numerical determ-
inations of their relations, has not hitherto been able to lead
us to a knowledge of the past states, or a clear insight into
the conditions under which they originated. These condi-
tions must not, however, on that account, be called accident-
al, as men call every thing whose genetic organ they are not
able to explain.

3. Absolute and apparent Magnitude; Configuration.
— The diameter of the largest of all the planets (Jupiter) is
30 times as great as the diameter of the smallest of those
which have been determined with certainty (Mercury) ; near-
ly 11 times as great as the diameter of the Earth. Very
nearly the same relations obtain between Jupiter and the
Sun. Their diameters are nearly as 1 to 10. It has been
asserted, perhaps erroneously, that the distance of the me-
teoric stones, which there is a tendency to consider as small
planetary bodies, from Vesta, which, according to a measure-
ment-by Madler, is 66 geographical miles in diameter, there-
fore 80 miles less than the diameter of Pallas according to
Lament, is not greater than the distance of Vesta from the
Sun. According to these relations, there must be meteoric
stones of 517 feet in diameter. Fire-balls certainly have,
while they retain a disk-like appearance, a diameter amount-
ing to 2600 feet.

The dependence of the flattening at the poles upon the ve-
locity of rotation appears most strikingly in the comparison
of the Earth as a planet of the interior group (Rot., 23''- 56';
Flattening, ^^g) with the exterior planet Jupiter (Rot., Q*"- 55'',
Flattening, according to Arago, y^ ; according to John Her-
gchel, yV). and Saturn (Rot., 10^- 29'; Flattening, yV)- But
Mars, whose rotation is still 41 minutes slower than the ro-
tation of the Earth, has, even when a much smaller result is
assumed than that of William Herschel, very probably a much
greater flattening. Does the reason of this anomaly, inas-
.much as the figure of the surface of an elliptical spheroid
ought to correspond with the velocity of rotation, consist in
the difference of the law of the increasing density toward the
center of the superincumbent strata? or in the circumstance
that the liquid gurface of some planets was solidified before
they could assume the figure appertaining to their velocity
of rotation ? The important phenomena of the backward
motion of the equinoctial points or the apparent advance ot
the stars (precession), that of nutation (oscillation of the
Earth's axis), and the variation of the inclination of the
E 2

106 COSMOS.

ecliptic, depen 1, as theoretical astronomy proves, upon the
configuration.

The absolute magnitudes of the planets, and their distance
from the Earth, determine their apparent diameter. We
have, therefore, to arrange the planets according to their ab-
solute (actual) magnitudes, proceeding from the larger to
the smaller :

The small planets with involved orbits, of which the larg-
est appsars to be Pallas and Vesta :

Mercury, Neptune,

Mars, Uranus,

Venus, Saturn,

Earth, Jupiter.

The apparent equatorial diameter of Jupiter, at a mean
distance from the Earth, is 38"'4, while that of Venus, which
is nearly equal in magnitude to the Earth, is only 16-9";
that of Mars, 5''-8. But the apparent diameter of the disk
of Venus increases in the inferior conjunction to 62", while
that of Jupiter attains only an increase to 46". It is neces-
sary to call to mind in this place that the point of the orbit
of Venus at which it appears to us with the brightest light,
falls between the inferior conjunction and her greatest digres-
sion from the Sun, because in that position the small lumin-
ous crescent gives the most intense light, on account of its
greatest proximity to the Earth, Upon the average, Venus
appears the most beautifully luminous, even casting shadows
in the absence of the Sun, when at a distance of 40° east or
west from the Sun ; the apparent diameter then amounts to
only 40", and the greatest width of the illuminated phase is
scarcely 10".

Apparent Diameter of Seven Planets.

Mercury at a mean distance 6"'7 (oscillates from 4"'4 to 12")

Venus

((

16"

•9 ( " 9"-5 to 62")

Mars

"

5"-8 ( *' 3"-3 to 23")

Jupiter

((

38"-4 ( " 30" to 46")

Saturn

C(

17"-1 ( '* 15" to 20")

Uranus

((

3"- 9

Neptune

((

2"-7

The volumes of the

planets in relation to the Earth are ;

Mercury

as

1 :

16-7

Jupiter as 1414 : 1

Venus

((

1 :

1-05

Saturn " 735 : 1

Earth

((

1 :

1

Uranus " 82 : 1

Mars

<<

1 :

7-14

Neptune " 108 : 1

THE PLANETS. 107

while the volume of the Sun is to that of the Earths 1407124.
Small alterations in the measurements of the diameters in-
crease the data of volumes in the ratio of their cubes.

The moving planets which agreeably enliven the aspect of
the heavens, influence us simultaneously by the magnitudes
of their disks and their proximity, by the color of their light,
by scintillation — which is not entirely wanting to some plan-
ets, in certain positions — and by the peculiarity wiih which
their different surfaces reflect the Sun's light. Whether a
feeble evolution of light from the planets themselves modifies
the intensity and properties of their light, is a problem which
still remains to be solved.

4. Arrangement of the Planets and their Distances from
the Sun. — In order to form a general conception of the plan-
etary system as a whole, so far as it is yet known, and to rep-
resent it in its mean distances from the central body, the Sun,
the following table is given, in which, as has always been the
custom in astronomy, the mean distance of the Earth from
the Sun (20,682,000 geographical miles) is taken as unity.
The greatest and smallest distances of the individual planets
from the Sun in aphelion and perihelion — according as the
planet is situated in the ellipse whose focus is occupied by
the Sun, at that point of the major axis (line of apsides) which
is the farthest from or nearest to the focus — will be added
afterward, when treating of the planets individually. By the
mean distance from the Sun, of which alone mention will be
made in this place, is to be understood the mean of the great-
est and smallest distance, or the half major axis of the plan-
et's orbit. It must also be observed, that the numerical data
employed, both previously and hereafter, are for the most part
taken from Hausen's careful classification of the planetary
elements in Schumacher's Jahrbuch for 1837. Where .the
data refer to time, they are, in the case of the older and larger
planets, for the year 1800 ; but in the case of Neptune, for
the year 1851, by the aid of the Berlin astronomischen Jahr-
buch of 1853. The comparison of the small planets occur-
ring afterward, and for which I am indebted to Dr. Galle,
refers exclusively to more recent epochs.

Distances of the Planets from the Sun.

Mercury 0-38709 ( Earth 1-00000

Venus. 0-72333 Mars 1-52369

108 COSMOS.

Small Planets.

Egeria 2'579

Juno 2-669

Ceres 2768

Flora 2-202

Victoria 2-335

Vesta 2-362

Iris 2-385

Metis 2-386

Hebe 2-425

Parthlnope 2.448

Irene 2553

Astrea 2-577

Pallas 1-773

Hygeia 3-151

Jupiter 5-20277

"Saturn 9-53885

Uranus 19*18239

Neptune 30-03628

The simple observation of rapidly diminishing periods of
revolution, from those of Saturn and Jupiter to Mars and
Venus, led, at a very early time, under the assumption that
the planets were attached to movable spheres, to conjectures
as to the distances of these spheres from each other. As
there are no traces of methodically-instituted observations
and measurements to be found among the Greeks before the
time of Aristarchus of Samos, and the establishment of the
Alexandrinian Museum, a great difference arose in the hypoth-
esis as to the arrangement of the planets and their relative
distances ; whether according to the most prevailing system,
with reference to their distances from the Earth as the fixed
center, or, as among the Pythagoreans, with reference to the
distances from the focus of the universe. The principal sub-
ject on which there was a discrepancy of opinion was the
position of the Sun, that is, its relative situation in reference
to the inferior planets and the Moon.^ The Pythagoreans,
who considered number to be the source of all knowledge, the
real essence of all existing things, applied their theory of num-
bers, the all-blending doctrine of numerical relations, to the
geometrical consideration of the five regular bodies, to the
musical intervals of tone which determine, accord, and form
different kinds of sound, and even to the system of the uni-
verse itself, supposing that the moving, and, as it were, vi-
brating planets, exciting sound-waves, must produce a spher-
al music, according to the harmonic relations of their inter-
vals of space. • " This music," they add, "would be perceived

* BOckh, De Platonico Syst., p. xxiv., and in Philolaos, p. 100. The
succession of the planets, which, as we have just seen (page 94, note),
gave rise to the naming of the week-days after the planetary deities,
that of Geminus is distinctly called the oldest by Ptolema)us. (Almag.,
xi., cap. i.) He blames the motives from which ** the moderns haM^
placed Venus and Mercury beyond the Sun."

THE PLANETS. 109

by tho human ear if it was rendered insensible by extreme
familiarity, as it is perpetual, and men are accustomed to it
from childhood."* The harmonic part of the Pythagorean
doctrine of numbers thus became connected with the figura-
tive representation of the Cosmos precisely in the Platonic
Timseus ; for " cosmogony is to Plato the work of the union
of opposite first causes, brought about by harmony."! Ho
attempted, moreover, to illustrate the tones of the universe in
an agreeable picture, by attributing to each of the planetary
spheres a syren, who, supported by the stern daughters of Ne-
cessity, the three Fates, maintain the eternal revolution of the
world's axis." J Such a representation of the Syrens, in whose
place the Muses are sometimes substituted as the choir of
heaven, has been, in many cases, handed down to us in an-
tique monuments, especially in carved stones. Mention is
constantly made of the harmony of the spheres, although gen
erally reproachfully, throughout the writings of Christian an-
tiquity, and all those of the Middle Ages, from Basil the Great
to Thomas Aquinas and Petrus Alliacus.§

* The Pythagoreans affirm, in order to justify the reality of the tones
produced by the revolution of the spheres, that hearing takes place only
where there is an alternation of sound and silence. — Aristot., De Ccelo,
ii., 9, p. 290, No. 24-30, Bekker. The inaudibility of the spheral music
is also accounted for by its overpowering the senses. — Cicero, De Rep.,
vi., 18. Aristotle himself calls the Pythagorean tone-myth pleasing
and ingenious {KOfitpug koI nepiTTug), but untrue (1. c. No. 12-15).

t Bockh, in Philolaus, p. 90.

X Plato, De Republica, x., p. 617 {Davis's translation, Bohn's Class.
Lib., p. 307). He estimates the planetary distances according to two
entirely difterent progressions, one by doubling, the other by tripling,
from which results the series 1. 2. 3. 4. 9. 8. 27. It is the same series
which is found in the Timseus, where the subject of the arithmetical
division of the woi-ld — spirit (p. 35, Steph., Davis's trans., Bohn's Class.
Lib.), which Demiurgus propounds, is treated of. Plato had, indeed,
considered the two geometrical progressions 1. 2. 4. Sand 1. 3. 9. 27
together, and thus alternately taken each successive number from one
of the two series, whence resulted the above-mentioned succession 1.

2. 3. 4. 9 Compare Bockh in the Studien von Daub und Creu-

zer, bd. iii., p. 34-43 ; Martin, Etudes sur le Tim6e, tom. i., p. 384, and
tom. ii., p. 64. (Compare also Prevost, Sur VAme d'apres Platon, in the
M6m. del' Acad, de Berlin for 1802, p. 90 and 97 ; the same in the Bibli-
oth^que Britannique, Sciences et Arts, tom. xxxvii..ll08, p. 153.)

$ See the acute woi-k of Professor Ferdinand Piper, Von der Harmo'
nie der Sphdren, 1850, p. 12-18. The supposed relation of the seven
vowels of the old Egyptian language to the seven planets, and Gustav
Seyftarth's conception, already disproved by Zoega's and Tdlken's in-
vestigations, of the astrological hymns, rich m vowels, of the Egyptian
priests, according to passages of Pseudo-Demetrius Fhalaereus (perhaps*
Demetrius of Alexandria), an epigram of Eusebius, and a Gnostic maa

110 COSMOS.

At ini vlose of the sixteenth century, all the Pythagoiean
and Platonic views of the system of the universe were again
reajiimated in the person of the imaginative Kepler. He, in
the first instance, constructed the planetary system in the
Mysterium Cosmographicum, in accordance with the prin-
ciple of the five regular solids, which may be imagined as
situated between the planetary spheres, then in the Harmo-
nice Mundi, according to the intervals of tone.* Convinced
of the regularity of the relative distances of the planets, he
believed that he had solved the problem by a happy combi-
nation of his earlier and later views. It is extremely re-
markable that Tycho Brahe, who in other respects is found
to be so strictly attached to actual observation, had already
expressed the opinion (controverted by Rothmann) that the
revolving cosmical bodies were capable of vibrating the ce-
lestial air (what we now call resisting medium) so as to pro-
duce tones, t But the analogies between the relations of tone
and the distances of the planets, which Kepler so long and
laboriously endeavored to trace out, remained, in his opinion,
as it appears to me, entirely with the domain of abstract
speculation. He congratulated himself upon having, to the
greater glorification of the Creator, discovered musical rela-
tions of number in the relations of cosmical space ; as if, in
poetic enthusiasm, he makes "Venus, together with the
Earth, sound sharp in aphelion and flat in perihelion; the
highest tone of Jupiter and that of Yenus must coincide in
flat accord." In spite of these merely symbolical expres-
sions, so frequently employed, Kepler says positively, "Jam
soni in coelo nuUi existunt, nee tam turbulentus est motus, ut
ex attritu aurcB codestis eliciatur stridor. $ {Harmonice
Mundi, lib. v., cap. 4.) The thin and clear celestial air
(aura'coBlestis) is also mentioned here again.

The comparative consideration of the planetary intervals
with the regular bodies which would fill these intervals, en-

uscript in Leyden, have been minutely treated of with critical erudition
by the younger Ideler (Hermapion, 1841, pars i., p. 198-214). Com-
pare also Ijoheck, A glaoph., torn, ii., p. 932.

* On the gradual development of the musical ideas of Kepler, vide
Apelt's Commentary of the Harmonice Mundi, in his work ; Johann
Kepler's Weltansicht, 1849, p. 76-116. (Compare also Delambre,
Hist, de VAstronom. Mod., tom. i., p. 352-360.)

t Cosmos, vol. ii., p. 316.

X [Now there are no such things as sounds among the heavenly
bodies, nor is their motion so turbulent as to elicit noise from the at
trition of the celestial air.]

THE PLANETS. Ill

couraged Kepi jr to extend his hypothesis even so far as the
region of fixed stars.* The circumstance which, on the oc-
casion of the discovery of Ceres, and the other so-called small
planets, first forcibly recalled to mind Kepler's Pythagorean
arguments, was his almost forgotten conjecture as to the prob-
able existence of a yet unseen planet in the great planetless
chasm between Mars and Jupiter. ('* Motus semper distan-
tiam pone sequi videtur ; atque ubi magnus hiatus erat inter
orbes, erat et inter motus. "f) " I have become more daring,"
he says, in the introduction to the Mysterium Cosmography
icum, " and place a new planet between Jupiter and Mars,
as also (a conjecture which was less fortunate, and remained
long unnoticed^) another planet between Venus and Mercu-
ry ; neither of these have been seen, probably on account of
their extreme smallness.§ Kepler subsequently found that

* Tycho had denied the existence of the crystalline spheres, in which
the planets were supposed to be fixed. Kepler praised the undertak-
ing, but he still adhered to the opinion that the sphere of fixed stars
was a solid globular shell of two German miles in thickness, upon which
are the twelve fixed stars, which are all situated at equal distances from
us, and have a peculiar relation to the corners of an icosahedron. The
fixed stars " lumina sua ab intus emittunt;" " emit light from their own
bodies ;" he also considered for a long time that the planets were self-
luminous, until Galileo taught him better! Although he, like many
other of the ancients and Giordano Bruno, considered the fixed stars to
be suns like our own, still he was not much inclined to entertain the
opinion, which he had well considered, that all fixed stars are sur-
rounded by planets, as I had formerly stated them to be. ( Cosmos, vol.
ii., p. 328.) Compare Apelt, Commentary to the Harmonice, p. 21-24.

t [" There seems to be always a close relation between the motion
and the distance [of the planets]; that is to say, where there is a great
interval between their orbs, the same exists also between their mo-
tions."]

X It was not until the year 1821 that Delambre, in the Hist, de VAs-
iron. Mod., torn, i., p. 314, directed attention to the planets which Kep-
ler conjectured to lie between Mercury and Venus, in the extracts
which are complete with regard to astronomy, but not with regard to
astrology, from Kepler's collected works (p. 314-615). "On n'a fait
aucune attention k cette supposition de Kepler, quand on a forme des
projets de decouvrir la planete qui (selon une autre de ces predic-
tions) devait circuler entre Mars et Jupiter." " No attention was paid
to that supposition of Kepler's when projects were formed for discover-
ing the planet, which (according to another of his predictions) ought to
revolve between Mars and Jupiter."

§ The remarkable passage respecting a space to be filled up between
Mars and Jupiter [hiatus] is in KeTpXcv' s Prodromus Dissertaiionum Cos-
mographicarum, coniinens Mysterium. Cosmo grapkictim de admirabili
proportione Orbium Coelestium, 1596, p. 7: <' Cum igitur hac non succe-
deret, alia via, mirum quam audaci, tentavi aditum. Inter Jovem et
Martem interposui novum planetam, itemque alium inter Venerem et

113 COSMOS.

he did not require these new planets for hi« solar system
founded upon the properties of the regular solids ; it was only
necessary to modify the distances of the old planets a little
arbitrarily. ('' Non reperies novos et incognitos planetas, ut
paulo antea, interpositos, non ea mihi probatur audacia ; sed
illos veteres parum admodum luocatos''^ — Myst. Cosmogr.,
p. 10.) The ideal tendencies of Kepler were so analogous
to those of the Pythagorean school, and still more to those of
Plato expressed in the Timceus,^ that in the same way as
Plato [Cratyl., p. 409) assumed, in addition to the difier-
ences of tone in the planetary spheres, those of color, Kepler
likewise instituted some experiments [Astron. Opt., cap. 6,
p. 261) for the purpose of detecting the colors of the planets.
Even the great Newton, always so precise in his conclusions,
was inclined, as Prevost has already remarked (^Mem. de
VAcad. de Berlin for 1802, p. 77 and 93), to reduce the di-

Mercurium, quos duos forte ob exilitatem non videamus, iisque sua
tempora periodica ascripsi. Sic enim existimabam me aliquam aequal-
itatem proportioniim effecturum, quae proportiones inter biuos versus
Solem ordine minuerentur, versus fixas augescerent ; ut propior est
Terra Veneri quantitate ori)is terrestris, quara Mars Terrse, in quanti-
tate orbis Martis. Verum hoc pacto neque unius planetiB interpositio
sufBciebat ingenti hiatu, Jovem inter et Martem: manebat enim major
Jovis ad ilium novum proportio, quam est Saturni ad Jovem. Rursus
alio modo exploravi." '' When this plan therefore failed, I tried to
reach my aim in another way, of, I must confess, singular boldness.
Between Jupiter and Mars I interposed a new planet, and another also
between Venus and Mercury, both which it is possible are not visible
on account of their minuteness, and I assigned to them their respective
periods. For in this way I thought that I might in some degree equal-
ize their ratios, which ratios regularly diminished toward the Sun, and
enlarged toward the fixed stars, as the Earth is nearer to Venus than
Mars is to the Earth. , But even in this way the interposition of one
planet did not supply the great chasm between Jupiter and Mars, for
the ratio between Jupiter and the supposed new planet still remained
greater than between Saturn and Jupiter. Again. I tried in another
way." Kepler was twenty-five years of age when he wrote this. It
may be seen how his restless mind formed hypotheses, and again quick-
ly forsook them, to deceive himself with others. He always retained
a hopeful faith in being able to discover numerical laws where matter
had aggregated under the manifold disturbances of attractive forces
(disturbances whose combinations are incalculable, as are so many past
events and formations on account of our ignorance of the accompanying
conditions), aggregated into globes, revolving in orbits, sometimes sim
pie and almost parallel, sometimes grouped together and surprisingly
complicated.

* [" You will not find new and unknown planets, as I said before ;
that boldness I do not approve of; but you will find the old ones a little
altered in position."]

t {Plato's Wo'ks translated, vol. ii., Bohn'e Classical Libraiy."]

THE PLAN.ETS. 113

mensions of the seven colors of the spectrum to the diatonio
scale.*

The hypothesis of yet unknown merahers of the planetary
series calls to mind the opinion of Hellenic antiquity, that
there were far more than five planets ; these were, indeed,
all that had been observed, but many others might remain
unseen, on account of the feebleness of their light and. their
position. Such a doctrine was especially attributed to Arte-
midorus of Ephesus.f Another old Hallenic, and perhaps
even Egyptian belief, appears to have teen, that " the celes-
tial bodies which we now see were not all visible in earlier
times." Connected with such a physical, or, much rather,
historical myth, is the remarkable form of the praise of a
high antiquity which some races ascribed to themselves.

Thus the pre-Hellenic Pelasgian inhabitants of Arcadia
called themselves Proselenes, because they boasted that they
came into the country before the Moon accompanied the
Earth. i?re-Hellenic and pre-lunarian were synonymous.
The appearance of a star was represented as a celestial event,
as the Deucalionic flood was a terrestrial event. Apuleius
(Apologia, vol. ii., p. 494, ed. Oudendorp ; Cosmos, vol. ii.,
p. 189, note) extends the flood as far as the Gatulean mount-
ains of Northern Africa. Apollonius Rhodius, who, accord-
ing to Alexandrian custom, was fond of imitating old models,
speaks of the early colonization of the Egyptians in the val-

* Newtoni Opuscula Mathematica, Philosophica et Philologica, 17 M,
torn, ii., Opusc. xviii., p. 246: "Chordatn musice divisam potius adhi-
bui, non tantum quod cum phaenominis (hicis) optime couvenit, sed
quod fortasse, aliquid circa colorum harmonias (quarum pictores non
penitus ignari sunt), sonorum concordantiis fortasse analogas, involvat.
Quemadmodum verisimilius videbitur animadvertenti affitiitatem, qu®
est inter extimam Purpuram (Violarura colorem) ac Rubedinem, colo-
rum extremitates, qualis inter octavae terminos (qui pro unisonis quo-
dammodo haberi possunt) reperitur." " I preferred employing the di-
visions of the musical chord, not only because they harmonize best with
the phenomena [of light], but because it is possible there may be some
latent analogy between the harmonies of .colors (with which painters
are not altogether unacquainted) and the concords of sounds. This
will appear more probable to any one who shall notice the similarity
of relations between violet and red, the extreme colors [on the spec-
trum], and the highest and lowest notes of the octave, which somehow
may be considered as in unison." — Compare also Prevost in the MSm.
de VAcad, de Berlin for 1802, p. 77 and 93.

t Seneca, Nat. Qucest. VII., 13 : " Non has tantum Stellas quinque
discurrere, sed solas observatas esse : ceterum innumerabiles ferri per
occultum." " Not that these five stars only moved, but that they only
had been observed, for a countless number are borne along beyond the
reach of vision."

114 rosMos.

'ey of the Nile : " the stars did not yet revolve in the heavens ;
nor ha(?. the Danaides yet appeared, or the race of Deucalion."^

* Since the explanations which Heyne has given of the origin of the
astronomical myth of the Proselenes, so widely diffused in antiquity (Pg
Arcadibus Luna Antiquioribus, in Opusc. Acad., vol. ii., p. 332), were
msatisfactory to me, I was greatly rejoiced to receive from my acute
philological friend, Professor Johannes Franz, a new and very happy
dolution of this much-debated problem, by simple combinations of ideas.
This solution is unconnected with either the arrangement of the calen*
dar by the Arcadians, or their worship of the Moon. I restrict myself
here to an extract from an unpublished and more extended work. This
explanation will not be unwelcome to some of my readers in a work
hi which I have made a rule frequently to trace back the whole of our
present knowledge to the knowledge of the ancients, and even to tra-
iitions believed generally or by very many.

" We shall commence with a few of the principal passages from the
undents which treat of the Proselenes. Stephanus of Byzantium (v.
Ap/cdf) mentions the logographs of Hippys of Rhegium, a cotemporary
of Darius and Xerxes, as the first who called the Arcadians ■Kpoailr]'
■fovg. The scholiasts {ad Apollon. Rhod. IV., 264, and ad Aristoph.,
Nub., 397) agree in saying, the remote antiquity of the Arcadians be-
comes most clear from the fact of their being called npoaeXrivoi. They
appear to have been there before the Moon, as Eudoxus and Theodorus
■ilso say ; the latter adds that it was shortly before the labors of Her-
cules that the Moon appeared. In the government of the Tegeates,
Aristotle states that the barbarians who inhabited Arcadia were driven
jut by the later Arcadians before the Moon appeared, and therefore
:hey were called -Kpoailrivoi. Others say, Endymion discovered the
revolution of the Moon ; but, as he was an Arcadian, his countrymen
ivere called after him irpoceXTjvoi. Lucian expresses himself slighting-
ly. (Astrolog., 26.) According to him, it was from stupidity and folly
that the Arcadians said they were there before the Moon. In the Schol.
udj^lschyl., Prom., 436, it is observed, that TrpoaeXovfxevov is called v6pi-
\6fiEvov, whence, therefore, the Arcadians were called TrpoaeTirjvoi, be-
cause they are arrogant. The passages in Ovid as to the existence of
the Arcadians before the Moon are universally known. Recently, in-
deed, the idea has sprung up that all the ancients were deceived by
ahe form TrpoaeTiijvoi, and that the word (properly irpoiXXijvoi) meant
only pre-Hellenic, as Arcadia certainly was a Pelasgian country.

"If, now, it can be proved," continues Professor Franz, " that an-
other people connected their origin with another cosmical body, the
irouble of taking refuge in deceptive etymological explanations will
be obviated. This kind of testimony exists in the njost suitable form.
The learned rhetorician Menander says literally in his work, De Econ-
omOs (sec. ii., cap. 3, ed. Heeren), as follows: 'A third motive for the
^iraise of objects is the time ; this is the case in all the most ancient na-
tions : when we say of a town or of a country it was founded before
this or that star, or with those stars, before the flood or after the flood
•—as the Athenians affirm they originated at the same time as the Sun,
Ike Arcadians before the Moon, the Delphiahs immediately after the
3ood-^— these are epochs, and, as it were, starting-points in time.'

" Therefore Delphi, the connection of which with the flood of Deu-
oalion is otherwise prove 1 (Pausan., x., 6), is surpassed by Arcadia,
tnd Arcadia by Athens. ApcUonius Rhodius, who was so fond of imi

THE PLANETS. 115

This important passage explains the praise of the Pelasgian
Arcadia.

I conclude these considerations respecting the distances of
the planets, and their arrangement in space, with a law,
which, however, scarcely deserves this name, and which is
called by Lalande and Delambre a play of numbers; by oth-
ers, a help for the memory. It has greatly occupied our la-
borious Bode, especially at the time that Piazzi discovered
Oeres : a circumstance, however, which was in no way occa-
sioned by that so-called law, but rather by a misprint in Wol-
iiston's Catalogue of the Stars. If any one is inclined to
consider that discovery as the fulfillment of a prediction, it
must not be forgotten that the latter, as we have already
pointed out, extends back as far as Kepler, or more than a
century and a half beyond Titius and Bode. Although the
Berlin astronomer had already distinctly declared, in the sec-
ond edition of his popular and extremely useful Anleitung

tating old models, expresses himself quite in accordance with this pas-
sage where he says (iv., 261), Egypt is said to have been inhabited be-
fore all other countries ; ' the stars did not yet all revolve in the heavens;
the Danaides had not yet appeared, nor the race of Deucalion ; the Ar-
cadians alone existed ; those of whom it is said that they lived before
the Moon, eating acorns upon the mountains.' In the same manner,
Nonnus (xli.) says of the Syrian Bero6 that it was inhabited before the
time of the Sun.

" Such a habit of deriving determinations of time from epochs in the
formation of the world is an offspring of the speculative period, in which
all objects have still more vitality, and is most closely allied to the gen-
ealogical local poetry ; so that it is not improbable that the tradition sung
by an Arcadian poet of the battle of the giants in Arcadia, to which the
above-quoted words of old Theodorus (whom some consider to be a
Samothracian, and whose work must have been very comprehensive"*
refer, may have given occasion to the general application of the epitnet
TT-poaiTirjvoi to the Arcadians." With regard to the double names 'Ar-
kades Pelasgoi,' and the opposition of a more ancient or recent peopling
of Arcadia, compare the excellent work Der Peloponnesos, by Ernst
Curtius, 1851, p. 160 and 180. In the New Continent, also, there is,
as I have already shown in another place (see my Kleinen Schrifien,
bd. i., p. 115), upon the elevated plain of Bogota, the race of JVIuyscas
or Mozcas, who in their historical myths boast of a proselenic antiquity.
The origin of the Moon is connected with the tradition of a great flood,
which a woman who accompanied the miracle-worker Botschika had
caused by her magical arts. Botschika drove away the woman (called
Huythaca or Schia). She left the Earth, and became the Moon, " which
until then had never shone upon the Muyscas." Botschika, pitying the
human race, opened a steep rocky wall near Canoas, where the Rio de
Tunzha now ruslies down, forming the famous waterfall Tequendama.
The valley, filled with water, was then laid dry— a geognostic romance
which occurs repeatedly : for example, in the closed Alpine valley of
Cashmir, where the mighty drainer is called Kasyapa.

116 COSMOS.

ZUT Kenntniss des gestirnten Himmels, that " he had taken
the law of the distances from a translation of Bonnet's Con-
templation de la Nature, prepared by Professor Titius at
"Wittenberg," still it has generally borne his name, and sel-
dom that of Professor Titius. In a note which the latter add-
ed to the chapter on the System of the Universe,*" he says,
*' When the distances of the planets are examined, it is found
that they are almost all removed from each other by distances
which are in the same proportion as their magnitudes in-
crease. If the distance from Saturn to the Sun is taken as
100 parts, the distance of Mercury from the Sun is 4 such
parts, that of Venus 4 + 3 = 7 such parts, the Earth 4 + 6 = 10,
Mars 4+12 = 16. But from Mars to Jupiter there is a de-
viation from this accurate (!) progression. Mars is foUowM
by a space of 4 + 24 = 28 such parts, in which neither a prin-
cipal planet nor a subordinate planet has yet been seen. Is
it possible that the Creator should have left this space empty ?
It can not be doubted that this space belongs to yet undis-
covered satellites of Mars ; or that perhaps even Jupiter has
further satellites around him, which have not hitherto been
seen by any telescope. In this space (unknown to us as re-
gards its contents) Jupiter's circle of action extends to 4 + 48
= 52. Then follows Saturn in 4 + 96 = 100 parts — an ad-
mirable proportion." Titius was therefore inclined to consid-
er the space between Mars and Jupiter as containing, not
one, but, as is actually the case, several cosmical bodies ; how-
ever, he conjectured that they were more likely to be subor^
dinate than principal planets.

Hov/ the translator and commentator of Bonnet obtained
the number 4 for the orbit of Mercury, is nowhere stated.
Perhaps he selected it only in order to have in combination
with the easily divisible numbers 96, 48, 24, &c., exactly 100
for Saturn, at that time the most distant planet known, whose
distance is 9-5, thus very nearly =100. It is less probable
that he constructed the order of succession by commencing
from the nearer planets. ' A sufficient correspondence of the
law of duplication, setting out, not from the Sun, but from
Mercury, with the true planetary distances, could not have
been affirmed in the last century, as the latter were known

* Karl Bonnet, Betrachtnng uber die Natur, translated by Titius, sec-
ond edition, 1772, p. vii., note 2 (the first edition appeared in 1766). In
Bonnet's original work no such law is noticed. (Compare also Bode,
Anleit. zur Kenntniss des gsslirnten Himmels, second edition, 1772, p
462.)

THE PLANETS.

117

at that time with sufficient accuracy for this purpose. In
reahty, the distances between Jupiter, Saturn, and Uranus ap-
proximate very closely to the duplication ; nevertheless, since
the discovery of Neptune, v/hich is much too near to Uranus,
the defectiveness in the progression has become strikingly ev-
ident.*

"What is called the law of Wurm of Leonberg, and some-
times distinguished from the law of Titius and Bode, is mere-
ly a correction' which Wurm made as to the distance of Mer-
cury from the Sun, and the difference between the distances
of Mercury and Venus. Approximating nearer to the fact,
he fixes the former as 387, the latter 680, and the distance
of the Earth 1000. f Gauss had already, on the occasion of

* Since, according to Titius, the distance from the Sun to Saturn,
then the outermost planet, is taken as =100, the individual distances
should be,

Mercury, Venus, Earth, Mars, Small planets, Jupiter,

4 7 10 _1_6_ _2 8 _5 2

107 iWo 100 100 iFO" loir

according to the so-called progression : 4, 4+3, 4+6, 4+12, 4+24,

4+48 ; consequently, when the distance of Saturn from the Sun is taken

as 789-2 million geographical miles, those of the other planets, expressed

in the 'same measure, are.:

Distances, according to Titius, in Geographical
Miles.

Actual Distance in

Geographical Miles.

32-0 millions.

600

82-8

126-0

220-8

430-0

789-2

1586-8

2484-8

Mercury 31'6 millions.

Venus 55-2

Earth 78-8

Mars 126-0

Smallplanets 2208 "

Jupiter 410 4 "

Saturn 789-2

Uranus 1586-8 "

Neptune. ..3062-0

t Wurm, in Bode^s Astron. Jakrbnch for the year 1790, 'p. 168; and
Bode, Von dem neuen zwischen Mars und Jupiter entdeckten achten
Hauptplaneten des Sonnensystems, 1802, p. 45. With the numerical cor-
rection of Wurm, the series, according to the distances from the Sun, is :

Mercury 387 Parts.

Venus 387+ 293= 680.

Earth 387+ 2-293= 973.

Mars 387-f 4-293= 1559.

Smallplanets 387-1- 8-293= 2731.

Jupiter 387+ 16-293= 5075.

Saturn 387-f 32-293= 9763.

Uranus 387+ 64293=19139.

Neptune 387+128-293=37891.

In order' that the degree of accuracy of these results may be tested,
the actual mean distances of the planets are given in the next table, as
they are acknowledged at the present time with the addition of the

118

COSMOS.

the discovery of Pallas by Olbers, aptly criticised the so-
called law of distances in a letter to Zach (October, 1802).
** The statement of Titius," says he, " contrary to the nature
of all truths which merit the name of laws, agrees only ap-
proximatively with observed facts in the case of most plan-
ets, and, what does not appear to have been once observed, not
at all in the case of Mercury. It is evident that the series

4, 4+3, 4 + 6, 4+12, 4+48, 4+96, 4+192,

with which the distances should correspond, is not a continu
ous series at all. The member which precedes 4 + 3 should
not be 4 ; i. e., 4+0, but 4 + 1|-. Therefore, between 4 and
4 + 3, there should be an infinite number ; or, as "Wurm ex-
presses it, for ^=1, there is obtained from 4 + 2"~^.3, not 4,
but 5i. Otherwise, the attempt to discover such approxi-
mative similarities in nature is by no means to be censured."
5. Masses of the Planets. — These elements are determined
by satellites when there are any, by the mutual disturbances
of the principal planets among each other, or by the influence
of a comet of brief revolution. In this way the hitherto un-
known mass of Mercury was determined by Encke in 1841,
by the disturbances which his comet suffered. The same
comet offers a prospect of a future improvement in the esti-
mation of the mass of Venus. The disturbances of Vesta aie
applied to Jupiter. The mass of the Sun being taken as
unity, those of the planets are (according to Encke, vierte
Abhandlung uher den.Cometen von Pons in den Schriften
der Berliner Akademie der Wissenschaften for 1842, p. 5) :

Mercury TJe Kit

Venus 47T8 3 9

Earth 3 5 9S5T

numbers which Kepler considered, in accordance with the Tychonio
system, to be the true ones. I quote the latter from Newton's work
l)e Mundi Systemate (Opuscula Math. Philos. et Philol., 1744, torn, ii.,
p22):

Planets.

Actual Distances.

Kepler's Results.

Mercury . ... -..-.

0-38709
0-72333
1-00000
1-52369
2-66870
5-20277
9-53885
19-18239
30-03628

0-38806
0-72400
1-00000
1-52350

5-19650
9-51000

Venus ............ .

Earth

Mars ... .... .... .... ....

Juno ................

Jupiter .. ........ ....

Saturn .. ................

Uranus . ...............

Neptune ... ... .....

THE PLANETS.

119

(Earth and Moon together

Mars ;

Jupiter and his satellites .

Saturn ,.

Uranus

Neptune

311*99)

2680

33^

ToTT

•87^

35^

TF

24|

OS

The mass

which Le Yerrier found, by means of his

sagacious calculations, before the actual discovery of Neptune
by Galle, is greater, although remarkably near to the truth.
The arrangement of the principal planets, according to their
increasing masses, is, when leaving out the small ones, the
following :

Mercury, Mars, Venus, Earth, Uranus, Neptune, Saturn,
Jupiter ;
thus, like the volumes and densities, entirely different from the
order of succession of the distances from the central body.

6. Densities of the Planets. — By applying the above quot-
ed volumes and masses, the following numerical relations are
obtained for the densities of the planets (according as the
eirth or water is taken as unity) :

Planets.

Relation to the

Relation to the

Earth.

density of Water.

1-234

6-71

0-940

5-11

1-000

5-44

0-958

5-21

0-243

1-32

0-140

0-76

0-178

0-97

0-230

1-25

Mercury.
Venus . . .
Earth . . .

Mars

Jupiter . .
Saturn ..
Uranus . .
Neptune .

In the comparison of the density of the planets with water,
the density of the Earth serves as a basis. Reich's experi-
ments, made in Freiberg with the torsion balance, gave
5-4383 : very nearly the same as the analogous experiments
of Cavendish, which, according to the more accurate calcula-
tions of Francis Baily, gave 5448. The result of Baily's
own experiments is 5*660. It will be seen from the above
table that Mercury, according to Encke's determination of
mass, comes very near to the other planets of medium mag-
nitude.

This table calls to mind forcibly the classification, several
times mentioned by me, of the planets into two groups, which
are separated from each other by the zone of the small plan

120 COSMOS.

ets. The differences of density which are presented by Mars,
Venus, the Earth, and even Mercury, are very slight ; almost
equally similar among each other, but from 4 to 7 times less
dense than the former group, are the planets more distant
from the Sun — Jupiter, Neptune, Uranus, and Saturn. The
density of the Sun (0-252, if the Earth is taken as I'OOO ;
therefore, in reference to water, 1'37) is but little more than
the densities of Jupiter and Neptune. Consequently, the
planets and the Sun^ must be arranged, according to their
increasing density, in the following order :

Saturn, Uranus, Neptune, Jupiter, Sun, Venus, Mars, Earth,
Mercury.

Although, upon the whole, the densest planets are nearer to
the Sun, still, when they are considered individually, their
density is by no means proportional to the distances, as New-
ton was inclined to assume. f

7. Periods of Sidereal Revolution and Axial Rotation.
— We shall confine ourselves here to giving the sidereal, or
true periods of revolution of the planets in reference to the
fixed stars, or a fixed point of the heavens. ■ During such a
revolution, a planet passes through exactly 360 degrees in its
course round the Sun. The sidereal revolutions of the plan-
ets must be clearly distinguished from the tropical and synodic,
the former of which refer to the return to the spring equinox,
the latter to the difference of time between two consecutive
conjunctions or oppositions.

* The Sun (which Kepler considered to be magnetic, probably from
3nthusiastic admiration for the divina inventa of his justly famous co
temporary, William Gilbert, and whose rotation in the same direction
as the planets he maintained long before the Sun-spots were discovered)
Kepler declares, in his Comment, de moiibzis Stellce Martia (cap. 23), and
in Astronomice pars Optica (cap. 6), to be " the densest of all cosmical
bodies, because it moves all the others which belong to his system."

t Newton, De Mundi Systemate, in Opusculis, tom. ii., p. 17 : " Cor-
pora Veneris et Merturii majore Solis calore magis concocta et coagu-
lata sunt. Planetae ulteriores, defectu caloris, carent substantiis illis
metallicis Qt mineris ponderosis quibus Terra referta est. Densiora cor-
pora qu8B Soli propiora : ea ratione constabit optime pondera Planeta-
rum omnium esse inter se ut vires." " The bodies of Venus and Mer-
cuiy are more ripened and condensed on account of the greater heat
of the Sun. The more remote planets, by want of heat, are deficient
in those metallic substances and weighty minerals with which the Earth
abounds. Bodies are denser in proportion to their nearness to the Sun ,
from which reason it will easily appear that the weight c fall planets is
in proportion to their forces."

THE PLANETS.

121

Planets.

Periods of sidereal
Revolutions,

Rotation.

87'i-96928

224-70078

365-25637

686-97964

4332-58480

10759-21981

30686-82051

60126-70000

d. h. m. 8.

0 23 56 4

1 0 37 20
0 9 55 27
0 10 29 17

Earth

Mars

Jupiter ..............

Saturn ...............

Uranus ... .... .... ....

Neptune ... ........

lyh.

30">

41

20

2

7

23

16

32

19

41

36

17

0

0

In another more perspicuous form the two periods of revo-
lution are :

Mercuiy 87'^- 23'^- 15"^ 47"-

Venus 224 16 49 7

Earth 365 ' 6 9 10 -7496

whence it follows that the period of the tropical revolution,
or the length of the solar year, is 365''-24222, or 365d. 5h.
48m. 47"* 80 91 ; the length of the solar year is shortened
0"'595 in 100 years' on account of the precession of the equi-
noxes :

Mars 1 year, 321'^-

Jupiter 11 years, 314

Saturn 29 years, 166

Uranus 84 years, 5

Neptune 164 years, 225

The rotation is most rapid in the case of the exterior planets,
which have, at the same time, a longer period of revolution ;
slower in the case of the smaller interior planets, which are
nearer to the Sun. The periods of revolution of the asteroids
between Mars and Jupiter are very various, and will be spoken
of in the enumeration of the individual planets. It is there-
fore sufficient, in this place, to give a comparative result, and
to observe that among the small planets Hygeia has the lon-
gest, and Flora the shortest period of revolution.

8. Inclination of the Planetary Orbits and Axes of Ro-
tation.— Next to the masses of the planets, the inclination
and eccentricity of their orbits are among the most important
elements upon which the disturbances depend. The compar-
ison of these, in the order of succession of the interior, small
intermediate and exterior planets (from Mercury to Mars, from
Flora to Hygeia, from Jupiter to Neptune), presents manifold
similarities and contrasts, which lead to considerations as to
the formation of these cosmical bodies, and their changes dur

Vol. IV.— F

122

COSMOS.

ing long periods of time. The planets revolving in such va-
rious elliptical orbits are also all situated in diflerent planes.
In order to render a numerical comparison possible, they are
reduced to a fundamental plane, either fixed or movable, ac-
cording to certain laws. As such, the most convenient is the
ecliptic — the course which the Earth actually traverses — or
the equator of the terrestrial spheroid. "We add to the same
table the inclinations of the axes of rotation of the planets
toward their own orbits, so far as they are determined with
any certainty.

Planets.

Inclination of the
Planetary Orbits
to the Ecliptic.

Inclination of the
Planetary Orbits
to the Earth's
Equator.

Inclination of the
axes of the Plan-
ets to their Orb-
its.

Mercury

Venus ......

7° 0' 5"-9
3° 23' 28"'5
0° 0' 0"
1° 51' 6"-2
1° 18' 51"-6
2° 29' 35"-9
0° 46' 28"'0
lo 47/ 0"

28° 45' 8"
24° 33' 21"
230 27' 54"-8
240 44' 24"
23° 18' 28"
22° 38' 14"
23° 41' 24"
22° 21' 0"

66° 32'
61° 18'
86° 54'

Earth

Mars

Jupiter .

Saturn

Uranus

Neptune

The small planets are omitted here, because they will be
treated of further on as a separate distinct group. If thd
planet Mercury, situated near the Sun, and the inclination
of whose axis toward the ecliptic (7° 0' 5"* 9) approaches
very near to that of the solar equator (7° 30'), the inclinations
of the other seven planets will be seen to oscillate between
0|° and 3|-°. Jupiter exhibits, in the position of the axis of
rotation with reference to its own orbit, the closest approxi-
mation to the extreme of perpendicularity. On the contrary,
the axis of rotation of Uranus, to conclude from the inclina-
tion of the orbits of its satellites, very nearly coincides with
the plane of the planet's orbit.

Since the division and duration of the seasons, the solar al-
titudes under various latitudes, and the length of the days,
depend upon the amount of the inclination of the Earth's axis
toward the plane of its orbit, as well as upon the obliquity of
the ecliptic {i.e., upon the angle which the apparent course
of the Sun makes with the equator at their point of intersec-
tion), this element is of the most extreme importance as re-
gards the astronomical climate, i.e., the temperature of the
Earth, in as far as this is a function of the meridian altitude
attained by the Sun and the duration of its continuance above
the horizon. If the obliquity of the ecliptic were great, or

THE PLANETS. 123

if, indeed, the Earth's equator were perpendicular to the
Earth's orbit, at each part of its surface, even under the
poles, the Sun would be in the zenith once in the year, and
for a greater or less time, neither rise nor set. The differ-
ences of summer and winter under each latitude (as well as
the length of the day) would obtain the maximum of opposi-
tion. The climates in each part of the Earth would belong,
in the highest degree, to those which are called extreme, and
which an interminably complicated series of rapidly-changing
currents of air could only slightly equalize. If the reverse
were the case, or the obliquity of the ecliptic null, if the
Earth's equator coincided with the ecliptic, the differences of
the seasons and in the length of the days would cease every
where, because the Sun would continually appear to move in
the equator. The inhabitants of the poles would see it per-
petually at the horizon. " The mean annual temperature of
each point of the Earth's surface would also be that of each
individual day."^ This condition has been called an eternal
spring, although, however, only on account of the universally
equal length of the days and nights. As the growth of
plants would be deprived of the stimulating action of the
Sun's heat, a great part of those districts which we now call
temperate zones would be reduced to the almost always uni-
form and not very agreeable spring climate, from which I
suffered much under the equator, upon the barren mountain
plains (Paramosf) between 10,659 and 12,837 feet above the
level of the sea, situated near the boundary of perpetual snow
in the Andes chain. The temperature of the air during the
day oscillates there between 4^° and 9° Reaum. (42° and
520-25 Fahr.).

Grecian antiquity was much occupied with the obliquity
of the ecliptic, with rough measurements, conjectures as to its
variability, and the influence of the inclination of the Earth's
axis upon climate, and the luxuriance of organic development.
These speculations belonged especially to Anaxagoras, the
Pythagorean school, and to (Enopides of Chios. The pas-
sages which give us any information on this point are scanty
and indecisive ; however, they show that the development of
organic life and the origin of animals were considered to have
been simultaneous with the epoch in which the axis of the
Earth first commenced to be inclined, which also altered thg

* Madler, Astronomic, § 193.

t Humboldt, De Distributione GeograpTiica Plantarum,^. 104. ( View$
cf Nature, p. 220 to 223, Bohn's edition.)

124 COSMOS.

inhabitability of the planet in particular zones. According
to Plutarch, De Plac. Philos., ii., 8, Anaxagoras believed
•' that the world, after it had come into existence and pro*
duced from its womb living beings, had of itself inclined to-
ward the south." In the same regard, Diogenes Laertius
says of the Clazomenier, " the stars had originally projected
themselves in a dome-like layer, so that the pole appearing
at any time was vertically over the Earth ; but that after-
ward they assumed an oblique direction." The origin of the
obliquity of the ecliptic was considered as a cosmical event.
There was no question respecting a subsequent progressive
alteration.

The description of the two extreme, therefore opposite, con
ditions to which the planets Uranus and Jupiter approximate
most closely, is suited to call to mind the variations which the
increasing or decreasing obliquity of the ecliptic would pro-
duce in the meteorological relations of our planet, if these va-
riations were not comprised within very narrow limits. The
knowledge of these limits, the subject of the great works of
Leonhard Euler, Lagrange, and Laplace, may be called one
of the most brilliant achievements of modern times in theo-
retical astronomy and the perfected higher analysis. These
limits are so narrow, that Laplace {Expos, du Systeme du
Monde, ed. 1824, p. 303) puts forward the opinion that the
obhquity of the ecliptic oscillates about its mean position only
1^° toward both sides. According to this statement,^ the
tropical zone (the tropic of Cancer, as its northernmost and
outermost boundary) would approach only so much nearer to
us. The result would therefore be, if the numerous other
meteorological perturbations are omitted, as if Berlin were
gradually displaced from it present isothermal line to that
of Prague. The elevation of the mean annual temperature
would scarcely amount to more than one degree of the cen-
tigrade {j\ of a degree of Fahrenheit's) thermometer.! Biot,

* " L'etendue entiere de cette variation serait d'environ 12 dcgres,
mais I'action du Soleil et de la Lune la reduit k peu pres k trois degr^s
(ceut^simaux)." " The entire extent of that variation would be about
12^, but the action of the Sun and Moon reduce it to very nearly 3*^
(centesimal)." — Laplace, Expos, du Syst. du Monde, p. 303.

t I have shown in another place, by comparison of numerous mean
annual temperatures, that in Europe, from the North Cape to Palermo,
the difference of one degree of geographical latitude very nearly cor-
responds to 0-5° of the centigrade thermometer, but in the western
temperature-system of America (between Boston and Charlestown) to
0-9O. {Asie Centrale, tom. iii., p. 229.)

THE PLANETS. 125

indeed, also assumes only narrow limits for the alternating
variation in the obliquity of the ecliptic, but considers it
more advisable not to assign to it a determinate number.
" La diminution lente et seculaire de I'obliquite de I'eclip-
tique," says he, " ofire des etats alternatifs qui produisent
une oscillation eternelle, comprise entre dea limites fixes. La
theorie n'a pas encore pu parvenir a determiner cea limites ;
inais d'apres la constitution du systeme planetaire, elle a de-
montre qu'elles existent et qu'elles sent tres 2^€U etendues
Ainsi, a ne considerer que le seul effet des causes constantes
qui agissent actuellement sur le systeme du monde, on peut
affirmer que le plan de I'ecliptique n^ a jamais coincide et ne
coincidera jamais avec le plan de I'equateur, phenomene qui,
s'il arrivait, produirait sur le Terre le (pretendu !) printemps
perpetuel."=^ — Biot, Traite d' Astronomic Physique, 3d ed.,
1847, tom. iv., p. 91.

While the nutation of the Earth's axis discovered by Brad-
ley depends merely upon the influence of the Sun and the
Earth's satellite upon the oblate figure of our planet, the in-
crease and decrease in the obliquity of the ecliptic is the con-
sequence of the variable position of all the planets. At the
present time, these are so situated that their united influence
upon the Earth's orbit produces a diminution in the obliquity
of the ecliptic. This obliquity amounts, according to Bessel,
to 0"-457 annually. At the end of many thousand years, the
situation of the planetary orbits and their nodes (their points
of intersection with the ecliptic) will be so different, that the
advance of the equinoxes will be converted into a retrogres-
sion, and consequently an increase in the obliquity of the eclip-
tic. Theory teaches us that these increases and diminutions
occupy periods of very unequal duration. The most ancient
astronomical observations which have come down to us, with
accurate numerical data, reach back to the year 1104 before
Christ, and testify to the extreme antiquity of Chinese civil-
ization. The literary remains are scarcely a century more

* "The slight and secular variation of the obliqaity of the ecliptic
presents alternating states, which produce an eternal oscillation com-
prised within fixed limits. Theory has not been able to determine
those limits ; but, according to the constitution of the planetary system,
it has been proved that they exist, and that they are of very slight ex*
tent. Thus, to consider only the effect of the permanent causes which
act upon the system of the world, it may be affirmed that the plane of
the ecliptic never has and never icill coincide with the plane of the
equator, a phenomenon which, if it took place, would produce upon the
Earth the (pretended !) eternal spring.

12C COSMOS.

recent, and a regulated calculation of time extends (accord-
ing to Edward Biot) as far back as 2700 years before Christ.*
Under the reign of Tscheu-Kung, the brother of Wu-Wang,
the meridian shadows were measured in two solstices, upon
an eight-foot gnomon, in the town of Layang, south of the
Yellow River (the town is now called Ho-nan-fu, and is in
the province of Ho-nan), in a latitude of 34° 46'. f These
measurements gave the obliquity of the ecliptic as 23° 54' ;
that is, 27' greater than it was in 1850. The observations
of Pytheas and Eratosthenes at Marseilles and Alexandria are
six and seven centuries later. We possess the results of four
observations of the obliquity of the ecliptic previous to our era,
and seven subsequent, up to Ulugh Beg's observations at the
observatory of Samarcand. The theory of Laplace corresponds
sometimes in plus, sometimes in minus, in an admirable man-
ner with the observations made during a period of nearly 3000
years. The knowledge transmitted to us of Tscheu-Kung's
measurement cf the shadow-length is so much the more for-
tunate, as the manuscript which mentions it escaped, from
some unknown cause, the fanatical destruction of books com-
manded by the Emperor Schi-hoang-ti of the Tsin dynasty, in
the year 246 before Christ. Since the commencement of the
fourth Egyptian dynasty with the Kings Chufu, Schafra, and
Menkera — the builders of the Pyramids — falls, according to
Lepsius, twenty-three centuries before the solstitial observa-
tion at Layang, it is indeed very probable, from the high de-
gree of civilization of the Egyptian people and their early
regulation of a calendar, that even at that time the length
of shadows had been measured in the valley of the Nile ; but
no knowledge of this has come down to us. Even the Peru-
vians, although less advanced in the perfection of calendars
and intercalations than the Muyscas (mountain inhabitants
of New Granada) and the Mexicans were, possessed gno-
mons, surrounded by a circle marked upon a very level sur-
face. They stood in several parts of the empire, as well as
in the great temple of the Sun at Cuzco ; the gnomon at
Q/Uito, situated almost under the equator, was held in great-
er veneration than the others, and crowned with flowers upon
the equinoctial feasts. $

* Cosmos, vol. ii., p. 114, 115, and notes.

t Laplace, Expos, du Systeme du Monde, 5th ed., p. 303, 345, 403,
406, and 408 ; the same in the Connaissance des Temps for 1811, p. 386
Biot, Traits Elem. d'Astron. Physique, torn, i., p. 61 ; torn, iv., p. 90-99
and 614-623.

X Garcilaso, Comment. Reales, part i. lib. ii., cap. 22-25 ; Prescott

THE PLANETS. 127

9. Eccentricity of the Planetary Orbits. — The form of
the elliptical orbits is determined by the greater or less dis-
tance of the two foci from the center of the ellipse. This
distance, or the eccentricity of the planetary orbits expressed
in fractional parts of their half major axes, varies from 0006
in the orbit of Venus (consequently very near the circular
form), and 0-076 in that of Ceres, to 0205 and 0255 in
those of Mercury and Juno. Next in succession to the least
eccentric orbits of Venus and Neptune follows that of the
Earth, whose eccentricity is now decreasing at the rate of
about 0-00004299 in 100 years, while the minor axis in-
creases ; then come the orbits of Uranus, Jupiter, Saturn,
Ceres, Egeria, Vesta, and Mars. The most eccentric orbits
are those of Juno (0-255), Pallas (0-239), Iris (0-232), Vic-
toria (0-217), Mercury (0-205), and Hebe (0-202). The ec-
centricity is on the increase in the orbits of some planets, as
Mercury, Mars, and Jupiter ; on the decrease in those of
others, as Venus, the Earth, Saturn, and Uranus. The fol
lowing table gives the eccentricities of the large planets for
the year 1800, according to Hansen. The eccentricities of
the fourteen small planets will be given subsequently, to-
gether with other elements of their orbits for the middle of
the nineteenth century.

Hist, of the Conquest of Peru, vol, i., p. 126. The Mexicans possessed
among their twenty hieroglyphical signs of the days, one held in espe-
cial veneration, called OllintonatiuTi, that of the four movements of the
Sun, which governed the great cycle, renewed every 52=:r4 X 13 years,
and referred to the course of the Sun intersecting the solstices and equi-
noxes, and hieroglyphically expressed hy foot-steps. In the beautiful-
ly-painted illuminated Aztec manuscript, which was formerly preserved
in the villa of Cardinal Borgia at Veletri, and from which I derived
much important information, there is the remarkable astrological sign
of a cross. The day-signs, which are written on the margin by its side,
would perfectly represent the passage of the Sun through the zenith of
the town of Mexico (Tenochtitlan), the equator, and the solstitial points,
if the points (round disks), added to the day-signs on account of the
periodic series, were equally complete in all three passages of the Sun.
(Humboldt, Vues des Cordiliires, pi. xxxvii., No. 8, p. 164, 189, and 237.)
The King of Tezcuco, Nezahualpilli (called a fast child, because his fa-
ther fasted for a long time previously to the birth of the wished-for
son), who was passionately given to astronomical observations, erected
a building which Torquemada rather ventui'ously calls an observatory,
and the ruins of which he saw. (Monarquia Indiana, lib. ii., cap, 64.)
In the Raccolta di Mendoza, we find a priest represented ( Vuet de»
Cordilleres, pi. Iviii., No. 8, p. 289), who is watching the stars, which
is expressed by a dotted line which passes from the observed star to hia
eye.

12S COSMOS.

Mercury 0-2056163

Venus 0-0068618

Earth 0-0167922

Mars 0-0932166

Jupitei 0-0481621

Saturn 0-0561505

Uranus 0-0466108

Neptune 0-00871946

The motion of the major axis {line of apsides) of the
planetary orbits, by which the place of the perihelion is
changed, is a motion which goes on perpetually in one di-
rection, and proportionally to the time. It is a change in
the position of the major axis, which requires more than a
hundred thousand years to complete its cycle, and is to be
distinguished as essentially different from those alterations
which the planetary orbits undergo in their ybrm — their el-
lipticity. The question has been raised as to whether the
increasing value of this ellipticity is capable, during thou-
sands of years, of modifying, to any considerable extent, the
temperature of the Earth, in reference to the daily and an-
nual quantity and distribution of heat ? Whether a partial
solution of the great geological problem of the imbedding of
tropical vegetable and animal remains in the now cold zones
may not be found, in these astronomical causes, proceeding
regularly in accordance with eternal laws ? The same
mathematical arguments which excite apprehensions as to
the position of the apsides, the form of the elliptical planet
ary orbits (according as these approach the circular form oi
a cometary eccentricity), as to the inclination of the planet-
ary axes, changes in the obliquity of the ecliptic, the influ-
ence of precession upon the length of the year, also afford,
in their higher analytical development, cosmical grounds for
reassurance. The major axes and the masses are constant.
Periodic recurrence hinders the unlimited augmentation
of certain perturbations. In consequence of the mutual, and,
at the same time, compensating influence of Jupiter and Sat-
urn, the eccentricities of their orbits, in themselves slight,
are alternately in a state of increase and decrease, and are
also comprised within fixed, and, for the most part, narrow
limits.

The point in which the Earth is nearest to the Sun falls in
very different periods of the year, in consequence of the al-
teration in the position of the major axis.=^ If the perihelion
falls at the present time on the first day of January, and the

* John Herschol, on the Astronomical Causes which may injluenc9
Geological Phenomena, iu the Transact, of the Gcolog. Soc. of London
2d series, vol. iii., pi. i., p. 298; the same in lii? Treatise on Astnmomy
1833. (Cab. Cyclop., vol. xliii., $ SIS.')

THE PLANETS. 129

aphelion six months afterward, upon the first day of July, it
may happen, on account of the advance (turm7ig) of the
major axis of the Earth's orbit, that the minimum may oc-
cur m summer and the maximum in winter, so that in Jan-
uary the Earth would be farther from the Sun than in the
summer by about 2,800,000 geographical miles {i. e., about
3'^th of the mean distance of the Earth from the Sun). It
might, at the first glance, be supposed that the occurrence
of the perihelion at an opposite time of the year (instead of
the winter, as is now the case, in summer) must necessarily
produce great climatic variations ; but, on the above suppo-
sition, the Sun will no longer remain seven days longer in
the northern hemisphere ; no longer, as is now the case,
traverse that part of the ecliptic from the autumnal equinox
to the vernal equinox, in a space of time which is one week
shorter than that in which it traverses the other half of its
orbit from the vernal to the autumnal equinox. The differ-
ence of temperature which is considered as the consequence
to be apprehended from the turning of the major axis (and
we refer here merely to the astronomical climates, excluding
all considerations as to the relations of the solid and liquid
portion of ihe many-formed surface of the Earth) will, on the
whole, disappear,^ principally from the circumstance that
the point of our planet's orbit in which it is nearest to the
Sun is at the same time always that over which it passes
with the greatest velocity. The reassuring solution of this
problem is to a certain extent contained in the beautiful law
first pointed out by Lambert,! according to which the quan-
tity of heat which the Earth receives from the Sun in each
part of the year is proportional to the angle which the radius
vector of the Sun describes during the same period.

* Arago, in the Annuaire for 1834, p. 199.

t " II s'ensuit (du theoreme dA k Lambert) que la quantite de cha
leur envoyee par le Soleil k la Terre est la merae en allant de r6qui
noxe du prin temps k I'equinoxe d'automne qu'en revenant de celui-ci au
premier. Le temps plus long que le Soleil emploie dans le premier
trajet, est exactement compense par son eloignementaussiplus grand;
et les qnantites de chaleur qu'il envoie k la Terre, sont les m^mes pen
dant qu'il se trouv»dans I'un ou I'autre hemisphere, boreal ou austral."
— Poisson, Sur la StabiliiS du Systeme Planitaire, Connaissance des
2'emps for 1836, p. 54. " It follows, from the theorem of Lambert, that
tl:3 quantity of heat which is conveyed by the Sun to the Earth is the
same during the passage from the vernal to the autumnal equinox as in
returning from the latter to the former. The much longer time which
the Sun takes in the first part of its course is exactly compensated by
its proportionately greater distance, and the quantities of heat which

F 2

130 COSMOS.

As the altered position of the major axis is capable of ex-
erting only a very slight influence upon the temperature of
the Earth, so likewise the limits of the probable changes in
the elliptical form of the Earth's orbit are, according to Arago
and Poisson,* so narrow that these changes could only very
slightly modify the climates of the individual zones, and that
in very long periods. Although the analyses which determ-
ine these limits accurately is not yet quite completed, still so
much, at least, follows from it, that the eccentricity of the
Earth's orbit will never equal those of the orbits of Juno,
Pallas, and Victoria.

10. hitensity of the Light of the Sun upon the Planets.
— If the intensity of light upon the Earth is taken as =1,
it will be found to be upon the other planets as follows •

Mercury .... 6-674

Venus 1-911

Mars 0-431

Pallas 0-130

Jupiter 0-036

Saturn 0-011

Uranus 0 003

Neptune . . . 0-001

In consequence of the very great eccentricity of their orb-
its, the intensity of light on the following planets varies in

Mercury, in perihelion, 10-58 ; in aphelion, 4-59 ;

Mars " " 0-52; " " 0-36;

Juno " " 0-25; " " 009;

while the Earth, owing to the slight eccentricity of its orbits,
has in perihelion 1-034, and in aphelion 0-967. If the sun
light upon Mercury is seven times more intense than upon the
Earth, it must also be 368 times more feeble upon Uranus.
The relations of heat have not been mentioned here, because
they are complicated phenomena, dependent upon the exist-
ence or non-existence of an atmosphere surrounding the plan-
it conveys to the Earth are the same while in the one hemisphere or
the other, north or south."

* Arago, op. cit., p. 300-204. " L'excentricite," says Poisson {op.
cit., p. 38 and 52), "ayant toujours ete et devant toujours demeurer
tres petite, I'influence des variations seculaires de la quantite de chaleur
solaire re^ue par la'Terre sur la temperature moyenne parait aussi de-
voir dtre tres limitee. On ne saurait admettre que l'excentricite de la
Terre, qui est actuellement environ un soixantieme, ait jamais et6 ou
devienne jamais un quart, comme celle de Junon ou de Pallas." "As
the eccentricity alw^ays has been, and always will be, very small, the
influence of the secular variations of the quantity of solar heat received
by the Earth upon the mean temperature would appear also to be very
limited. It can not be admitted that the eccentricity of the Earth,
which is actually about ^^, has ever been, or ever will be \, as that
of Juno or Pallas."

THE PLANETS. 131^

ets, its constitution, and height. I will merely call to mind
here the conjecture of Sir John Herschel, as to the temper-
ature of the Moon's surface, " which must necessarily be very
much heated — possibly to a degree much exceeding that cf
boiling water." ^

b. SECONDARY PLANETS.

The general cmnparative considerations relating to the
secondary planets have already been 'given with some com-
pleteness in the delineations of nature {Cosmos, vol. i., p.
94-98). At that time (March, 1845) there were only 11
principal and 18 secondary planets known. Of the asteroids
so called telescopic, or small planets, only four were discov
ered : Ceres, Pallas, Juno, and Yesta. At the present time
(August, 18-51), the number oi the principal planets exceeds
that of the satellites. We are acquainted with 22 of the for
mer and 21 of the latter. After an intermission of thirty-
eight years in planetary discoveries (from 1807, to December,
1845), commenced a long series of ten new small planets,
with Astrea, discovered by Hencke. Of these, two (Astrea
and Hebe) were first detected by Hencke at Dries©n, four
(Iris, Flora, Victoria, and Irene) by Hind in London, one (Me-
tis) by Graham at Markree Castle, and three (Hygeia, Par-
thenope, and Egeria) by De Gasparis at Naples. The dis-
covery of the outermost of all the large planets, Neptune, an-
nounced by Leverrier, and fpund by Galle at Berlin, followed
ten months after Astrea. The discoveries now accumulate
with such rapidity, that the topography of the solar regions
appears, after the lapse of a few years, quite as antiquated as
statistical descriptions of countries.

Of the 21 satellites now known, one belongs to the Earth,
four to Jupiter, eight to Saturn (the last discovered of these
eight is, according to distance, the seventh, Hyperion ; discov-
ered in two different places at the same time by Bond and
Lassell), six to Uranus (of which the second and fourth are
most positively determined), and two to JNTeptune.

The satellites revolving round the principal planets con-
stitute subordinate systems, in which the principal planets
take the place of central bodies, forming individual regions
of very different dimensions, in which the great solar region
is, as it were, repeated in miniature. According to our pres-
ent knowledge, the region of Jupiter is 208,000 geographical
miles in diameter, and that of Saturn 4,200,000. In Galileo's
* Outlines, $ 432.

Jil32 COSMOS.

time, when the expression of a small Jovial world {Mundus
Jovialis) was frequently made use of, these analogies between
the subordinate systems and the solar system contributed
much to the more rapid and general diffusion of the Coper-
nican system of the world. They suggest the repetitions of
form and position which is so frequently presented by organic
nature in subordinate spheres.

The distribution of the satellites in the solar regions is so
unequal, that while the proportion of the moonless principal
planets to those which ,are accompanied by Moons is as 3 to
5, the latter belong, with the single exception of one, the
Earth, to the exterior planetary groups, situated beyond the
ring of the asteroids with interlacing orbits. The only satel
lite which has been formed in the group of interior planets
between the Sun and the asteroids, the Earth's Moon, has
a remarkably large diameter in proportion to that of its pri-
mary. This proportion is g'.g- ; while the largest of Saturn's
satellites (the sixth. Titan) is perhaps only y^.j , and the larg-
est of Jupiter's satellites, the third, ^ j.-g of the diameter of
their primaries. A wide distinction must be drawn between
this consideration of a relative magnitude and that of an ab-
solute magnitude. The Earth's Moon, relatively so large
(1816 miles in diameter), is absolutely smaller than all four
of Jupiter's satellites (3104, 2654, 2116, and 1900 miles in
diameter). The sixth satellite of Saturn differs very little in
magnitude from Mars (3568 miles).* If the problem of tel-
escopic visibility depended only upon the diameter, and was
not, at the same time, determined by the proximity of the
disks of the primaries, the great distance and the nature of
the reflecting surfaces, it would be necessary to consider as
the smallest of the secondary planets the first and second of
Saturn's satellites (Mimas and Enceladus), and the two satel-
lites of Uranus ; but it is safer to represent them merely as
the smallest luminous points. It has hitherto appeared more
certain fhat, upon the whole, the smallest of all planetary
bodies (primaries and satellites) are to be found among the
small planets. t

The density of the satellites is by no means always less
than that of their primaries, as is the case with the Earth's
Moon (whose density is only 0619 of that of our Earth) and

* Outlines, $ 548.

t See Madler's attempt to estimate the diameter ofVesta (264 geo
graphical miles) with a thousand-fold magnifying power in His Attrc
wmie, p. 218.

THE PLANETS.

13^

the third satellite of Jupiter. The densest of this group of
satellites, the second, is even denser than Jupiter himself,
while the third and largest appears to be oi equal density
with the primary. The masses also do not increase in at all
the same ratio as the distances. ' If the planets have been
formed from revolving rings, then the greater or less dense
aggregation round a nucleus must have been caused by pe-
cuUar causes, which may, perhaps, always remain unknown
to us.

The orbits of the secondary planets which belong to the
same group have very different degrees of eccentricity. In
the Jovial system, the orbits of the first and second satellites
are nearly circular, while the eccentricities of those of the
third and fourth satellites amount to 0*0013 and 00072. In
the Saturnian system, the orbit of the satellite nearest to the
primary (Mimas) is considerably more eccentric than the orb-
its of Enceladus and Titan, the largest and first discovered,
whose orbit was so accurately determined by Bessel. The
eccentricity of the orbit of the sixth satellite of Saturn is only
0-02922. According to all these data, which are among those
that may be relied upon, Mimas only is more eccentric than
the Earth's Moon (0-05484) ; the latter possesses the pecul-
iarity that its orbit round the Earth has a greater eccentric-
ity, in comparison with that of its primary, than any other
satellite. Mimas revolves round Saturn in an orbit whose
eccentricity is 0-068, while that of the orbit of its primary is
0-056 ; but the orbit of our Moon has an eccentricity of 0-054.
while the eccentricity of that of the Earth is only 0-016. With
regard to the distances of the satellites from their primaries,
compare Cosmos, vol. i., p. 94-98. The distance of the sat-
ellite nearest to Saturn (Mimas) is now no longer taken as
80,088 geographical miles, but as 102,400 ; whence its dis-
tance from the ring, this being calculated as 24,188 miles
broad, and at a distance of 18,376 miles from the surface of
the planet, will be 28,000 miles. ^ Remarkable anomalies,
together with a certain correspondence, are also presented in
the position of the orbits of the satellites in the Jovial sys-
tem, in which very nearly all the satellites move in the plane
of the equator of their primary. In the group of Saturnian
satellites, seven of them revolve almost in the plane of the
ring, while the outermost (the eighth, Japetus) is inclined to-
ward their plane 12° 14'.

* In the earlier data (Cosmos, vol. i., p . 97) the equatorial rliametei
was taken as a basis.

^34 COSMOS.

In this general consideration of the planetary revolutions
in the universe, we have descended from the higher — though
probably not the highest* system — from that of the Sun to
the subordinate partial systems of Jupiter, Saturn, Uranus,
and Neptune. In the same way that, from the striving to-
ward generalization of views, which is innate in thoughtful,
and, at the same time, imaginative men, the unsatisfied cos-
mical presentiment of a translatory motionf of our solar sys-
tem through space appears to suggest the idea of a higher
relation and subordination, so the possibility has been con-
ceived that the satellites of Jupiter may be again central
bodies to other secondary ones, which, on account of their
smallness, are unseen. In that case, the individual mem
bers of the partial systems, which are chiefly situated among
the group of exterior principal planets, would have other and
similar partial systems subordinate to them. Repetitions of
form in recurring organizations, as well as the self-created
images of the fancy, are certainly pleasing to a systematic
mind ; but in every serious investigation, it is imperatively
necessary to distinguish between the ideal and the actual
Cosmos — between the possible, and that which has been dis-
covered by actual observation.

SPECIAL ENUMERATION OF THE PLANETS AND THEIR MOONS, AS
PARTS OF THE SOLAR SYSTEM.

It is, as I have already often remarked, the especial object
of a physical description of the ivorld to bring together all
the important and well-established numerical results which
have been obtained in the domain either of sidereal or ter
restrial phenomena up to the middle of the nineteenth cen
tury. All that has form and motion should here be repre
sented as something already created, existing, and definite
The grounds upon which the obtained numerical results ai
founded ; the cosmological conjectures respecting genetic de
velopment, which during thousands of years have been called
into existence by the ever-changing conditions of mechanical
and physical knowledge — these do not, in the strictest sense
of the word, come within the range of empirical investiga-
tion. {Cosmos, vol. i., p. 47-49, 71, and 83.)

* Compare Cosmos, vol. iii., p. 196.

t I have fully treated of the translatory motion of the Sun in the de-
lineation of nature. {Cosmos, vol. i., p. 145-149. Compare also voL
iii., p. 184.)

THE SUN.

The Sun.

13#

Whatever relates to the dimensions, or to the present views
as to the physical constitution of the central body, has been
already given, [Cosmos, vol. iv., p. 59-88.) It only re-
mains to add in this place some remarks, according to the
most recent observations, upon the red figures and masses
of red clouds, which were specially treated of at page 70.
The important phenomena which the total eclipse of the Sun
of July 28, 1851, presented in Eastern Europe, have still
more strengthened the opinion put forward by Arago in 1842,
that the red mountain, or cloud-like 'projectio7is upon the edge
of the eclipsed Sun, belong to the outermost gaseous envelope
of the central body.^ These projections became visible on the
Moon's western edge as it proceeded in its motion toward the
east {Annuaire du Bureau des Longitudes for 1842, p. 457),
and disappeared again when they were covered on the oppo-
site by the eastern edge of the Moon.

On a subsequent occasion, the intensity of the light of these
projections became so considerable, that they could be per-
ceived within the corona through telescopes, when veiled by
^heir clouds, and even with the naked eye.

The form of some of the projections, which were mostly
Yuby or peach-colored, changed with perceptible rapidity dur-
ing the total obscuration ; one of these projections appeared to
be curved at its summit, and presented to many observers the
appearance of a freely-suspended detached cloud\ near the
point, and resembling a column of smoke curved back at the
top. The height of most of these projections was estimated
at from 1' to 2' ; at one point it is said to have been more
Besides these tap-formed projections, from three to five of
which were counted, there were also observed ribbon-like
streaks of a carmine color, extended lengthways, which ap-
peared to rest upon the Moon, and were often serrated 4

* Cosmos, vol. iv,, p. 70, note % and $, and p. 79.

t Compare the observations of the Swedish mathematician, Bigerus
Vassenius, at Gottenburg, during the total eclipse of May 2, 1733, and
the commentary upon them by Arago, in the Annuaire du Bureau des
Longitudes for 1846, p. 441 and 462. Dr. Galle, v^rho observed on the
28th of July at Frauenburg, saw " the freely-suspended cloud connect-
ed with the curved, hook-formed gibbosity by three or more threads."

t Compare what a very expert observer. Captain Berard, saw at Tou-
lon upon the 8th of July, 1842. " II vit une bande rouge tres mince
dentelee irr^guli^rement." {Annuaire du Bureau des Longitudes, p
416.) " He saw a very narrow red band irregularly serrated."

^136 COSMOS.

That part of the Moon's edge which was not projected
upon the Sun's disk again . became perceptibxe, especially
during the egress.*

A group of Sun-spots was visible, though some minutes
distant from the edge of the Sun, where the largest red,
hook-formed projection was developed. On the opposite side,
not far from the feeble eastern projection, there was also a
Sun-spot near the edge. It is scarcely possible that these
funnel-shaped depressions can have furnished the material
constituting the red gaseous exhalations, on account of the
distance above mentioned ; but as the whole surface of the
Sun appears to be covered with pores, perhaps the most
probable conjecture is, that the same emanation of vapor and
gas, which, rising from the body of the Sun, forms the fun-
nels,! pours through these, which appear to us as Sun-spots

* This outline of the Moon, clearly perceived by four observers dur
ing the total eclipse of the Sun on the 8th of July, 1842, was never pre-
viously described as having been seen during similar eclipses. The
possibility of seeing an exterior outline appears to depend upon the
light which is given by the third outermost envelope of the Sun and
the ring of light (corona). " La Lune se projette en partie sur I'atmo-
sphere du Soleil. Dans la portion de la lunette ou I'image de la Lune
se forme, il n'y a que la lumiere provenant de I'atmosphere terrestre.
La Lune ue fournit I'ien de sensible, et, semblable k un ecran, elle ar-
rete tout ce qui provient de plus loin et lui correspond. En dehors de
cette image, et preeisement k partir de son bord, le champ est eclaire
a la fois par la lumidre de I'atmosphere terrestre et par la lumiire de
V atmosphere solaire. Supposons que ces deux lumieres reunies ferment
un total plus fort de ^ que la lumiere atmospherique terrestre, et, des
ce moment, le bord de la Lune sera visible. Ce genre de vision pent
prendre le nom de vision negative; c'est en effet par une moindre intensity
de la portion du champ de la lunette ou existe I'image de la Lune, que le
contour de cette image est aper9U. Si I'image etait plus intense que le
reste du champ, la vision serait positive." — Arago, Annuaire du Bureau
des Longitudes, p. 384. " The Moon is projected partially upon the at-
mosphere of the Sun. In that portion of the telescope where the image
of the Moon is formed, no other light enters except that of the terres-
trial atmosphere. The Moon gives no sensible light, and, like a screen,
it stops all that which comes frortj^ beyond and corresponds with it.
Outside the image, and immediately round its edge, the field is lighted
simultaneously by the light of the terrestrial atmosphere and by that of
the solar atmosphere. If we suppose that these two lights collectively
are -^-^ stronger than the light of the terrestrial atmosphere, the Moon's
edge will be directly visible. This kind of vision may be designated
a negative vision, for it is, in fact, by the less intensity of that portion of
the field of the telescope in which is the image of the Moon, that the
outline of this image is perceptible. If this image were more intense
than the remaining part of the field, tje vision would be positive."
(Compare also, on this subject, Cosmos, vol. iii., p. 56, note *.)

* Cosmos, vol. iv., p. 63-67

MERDURY.

13f^

or smaller pores, and, when illuminated, present the appear^
ance of red columns of vapor, and clouds of various forms in
the third envelope of the Sun.

Mercury.

When it is rememhered how much the Egyptians^ occu-
pied themselves with the plan3t Mercury (Set-Horus), and
the Indians with their Buddha,t since the earliest tinics ;
how, under the clear heaven of Western Arabia, the star-
worship of the race of the AseditesJ was exclusively directed
to Mercury ; and, moreover, that Ptolemy was able, in the
19th book of the Almagest, to make use of fourteen observa-
tions of this planet, which reach back to 261 years before
our era, and partly belong to the Chaldeans, § it is certainly
astonishing that Copernicus, who had reached his seventieth
year, should have lamented, when on his death-bed, that with
all his endeavors, he had never seen Mercury. Still the
Greeksll justly characterized this planet by the name of
{oriXtGiv) the sparkling, on account of its occasionally very
intense light. It presents phases (variable form of the illu-
minated part of the disk) the same as Venus, and, like the
latter, appears to us as a morning and evening star.

Mercury is, in his mean distance, little more than 32 mill-
ions of geographical miles from the Sun, exactly 0-3870938
parts of the mean distance of the Earth from the Sun. On
account of the great eccentricity of its orbit (0-2056163), the
distance of Mercury from the Sun in perihelion is 25 millions,
in aphelion 40 millions of miles. He completes his revolu-
tion round the Sun in 87 mean terrestrial days and 23h.
15m. 46s. Schroter and Harding have estimated the rota-
tion at 24h. 5m. from the uncertain observation of the form
of the southern cusp of the crescent, and from the discovery
of a dark streak, which was darkest toward the east.

According to Bessel's determination on the occasion of the
transit of Mercury on May 5, 1832, the true diameter amounts
to 2684 geographical miles,1[ i. e., 0-391 parts of the Earth's
diameter.

* Lepsius, Chronologie der ^gypter, th. i., p. 92-96.

t Cosmos, vol. iv., p. 93, note t, p. 92. X Ibid., vol. ii., p. 221.

^ Lalande, in the Mim. de VAcad. des Sciences for 1766, p. 498 ; De-
tambre, Hisioire de VAstron. Ancienne, torn, ii., p. 320.

II Cosmos, vol. iv., p. 93.

11 On the occasion of the transit of Mercury on the 4th of May, 1832,
Madler and William Beer (Beitrdge zur Phys. Kenniniss der kimtn-
Uschtn Kor^tr, 1841, p. 145) found the diameter of Mercury 2332 miles,

i[38 COSMOS.

The mass of Mercury was determined by Lagrange upon
very bold assumptions as to the reciprocity of the relations of
distances and densities. A means of improving this element
was first afforded by Encke's Cornet of short period of rev-
olution. The mass of this planet was fixed by Encke at
4765TST of the Sun's mass, or about yi.Tj- of the Earth's. La-
place^ gave the mass of Mercury as 2 025 sTo according to La-
grange ; but the true mass is only -^-^ of that assigned by La-
grange. By this correction, also, the previous hypothesis of
the rapid increase of density in the planets, in proportion as
they were nearer to the Sun, was disproved. When, with
Hansen, the material contents of Mercury are assumed to be
yI^ those of the Earth, the resulting density of Mercury is
1-22. " These determinations," adds my friend, the author
of them, " are to be considered only as first attempts, which,
nevertheless, come much nearer the truth than the numbers
assumed by Laplace." Ten years ago the density of Mer-
cury was taken as nearly three times greater than the dens-
ity of the Earth— as 2-56 or 294, when the Earth =1-00.

Venus.

The mean distance of this planet from the Sun, expressed
in fractional parts of the Earth's distance from the Sun, i. e.,
60 million geographical miles, is 0-7233317. The period of
its sidereal, or true revolution, is 224 days, 16h. 49m. 7s.
No principal planet comes so near the Earth as Venus. She
can approach the Earth to within a distance of 21,000,000
miles, but can also recede from it to a distance of 144,000,000
miles. This is the reason of the great variability of her ap-

but in the edition of the Astronomie of 1849, Madlerhas given the pref-
erence to Bessel's result.

* Laplace, Exposition du Syst. du Monde, 1824, p. 209. The cele-
brated author admits, however, that in the determination of the mass
of Mercury, he founded his opinion upon the " hypoth^se tr^s precaire
qui suppose les densit6s de Mercure et de la Terre reciproques k leur
moyenue distance du Soleil." " The very precarious hypothesis which
supposes the densities of Mercury and the Earth reciprocal to their mean
distance from the Sun." I have not considered it necessary to mention
either the chain of mountains, 61,826 feet in height, which SchrSter
states that he saw upon the disk of Mercuiy and measured, and which
Kaiser {Sternenhimmel, 1850, $ 57) doubts the existence of, or the vis
ibility of an atmosphere round Mercury during his transit over the Sun,
asserted by Lemonnier and Messier (Delambre, Hisi. de V Astronomie
au dixhuitieme siicle, p. 222), or the temporary darkening of the surface
of the planet. On the occasion of the transit which I observed in Peru
on the 8th of November, 1802, I very closely examined the outline of
the planet during the egress, but observed no indications of an envelop©

VENUS. 139

parent diameter, which by no means alone determines the
degree of brilliancy.* The eccentricity of the orbit of Venus
expressed, as in all cases, in fractional parts of half the major
axes, is only 0-00686182. The diameter of this planet is
6776 geographical miles; the mass ^-otVso' *^^ material
contents 0-957, and the density 0*94 in comparison to the
Earth.

Of the transits of the two hiferior planets first announced
by Kepler after the appearance of his E-udolphine tables,
that of Yenus is of most importance for the theory of the
whole planetary system, on account of the determination of
the Suns parallax, and the distance of the Earth from the
Sun deduced from the latter. According to Encke's thor-
ough investigation of the transit of Yenus in 1769, the Sun's
parallax is 8"-57ll6. (Berliner Jahrbuch for 1852, p. 323.)
A. new examination of the Sun's parallax has been under-
taken since 1849, by command of the government of the
United States, at the suggestion of Professor Gerling of Mar-
burg. The parallax is to be obtained by means of observa-
tions of Yenus near the eastern and western stationary points,
as well as by micrometer measurements of the differences in
the right ascension and declination of well-determined fixed
stars in very different latitudes and longitudes. (Schum.,
Astr. Nachr., No. 599, p. 363, and No. 613, p. 193.) The
astronomical expedition, under the command of the learned
Lieutenant Gilliss, has proceeded to Santiago in Chili.

The rotation of Yenus was long subject to great doubt
Dominique Cassini, 1669, and Jacques Cassini, 1732, found

* " That point of the orbit of Venus in which she can appear to us
with the brightest light, so that she may be seen at noon even with the
naked eye, lies between the inferior conjunction and the greatest di-
gression, near the latter, and near the distance of 40° from the Sun, or
from the place of the inferior conjunction. On the average, Venus ap-
pears with the finest light when distant 40° east or west from the Sun,
in which case her apparent diameter (which in the inferior conjunction
can increase to 66") is only 40", and the greatest breadth of her ilki-
minated phase measures scarcely 10". The degree of proximity to the
Earth then gives the small luminous crescent such an intense light, that
it throws shadows in the absence of the Sun." — Littrow, Theoretische
Asiranomie, 1834, th. ii., p. 68. Whether Copernicus predicted the ne
cessity of a future discovery of the phases of Venus, as is asserted in
Smith's Optics, sec. 1050, and repeatedly in many other works, has re-
cently become altogether doubtful, from Professor de Morgan's strict
examination of the woik De Revolutionibus, as it has come down to us.
— See the letter from Adams to the Rev. R. Main, on the 7th of Sep-
tember, 1846, in the Report of the Royal Astronomical Society, vol. vil..
No. 9, p. 142. (Compare also Cosmos, vol. ii., p. 325.)

140 COSMOS.

it 231i. 20m., while Bianchini* of Rome, 1726, assmne^ the
slow rotation of 24^ days. More accurate observations by De
Vice, from 1840 to 1842, afford, by means of a great number
of spots upon Venus, as the mean value of her period of ro-
tation, 23h. 2V 21"-93.

These spots are not very distinct, and are mostly variable ;
they seldom appear at the boundary of the separation be-
tween light and shadow in the crescent-shaped phase of the
planet, and both the Herschels, father and son, are conse-
quently of opinion that they do not belong to the solid sur-
face of the planet, but more probably to an atmosphere.!
The changeable form of the horns of the crescent, especially
the southern, has been taken advantage of by La Hire,
Schroter, and Madler, partly for the estimation of the height
of mountains, partly and more especially for the determina-
tion of the rotation. The phenomena of this changeability
are of such a nature that they do not require for their ex-
planation the assumption of the existence of mountain-
peaks, twenty geographical miles in height (121,520 feet),
as Schroter of Lilienthal stated, but merely elevations like
those which our planet presents in both continents. $ With
the little that we know with certainty of the appearance of
the surfaces of the planets near the Sun, Mercury, and Ve-
nus, and their physical constitution, the phenomenon of an
ash-colored light, sometimes observed in the dark parts, and

* Delambre, Hisi. de VAstron. au dixhuitieme siecle, p. 256-258. The
result obtained by Bianchini was supported by Hussey and Flaugergues;
Hansen also, whose authority is justly so great, considered it to be the
more probable until 1836. (Schumacher's Jahrbuch for 1837, p. 90.)

t Arago, on the remarkable observation at Lilienthal on the 12th of
August, 1700, in the Annuaire for 1842, p. 539. "Ce qui favorise aussi
la probabilite de I'existence d'une atmosphere qui enveloppe Venus
e'est le resultat optique obtenu par I'emploi d'une lunette prismatique.
L'intensite de la lumiere de I'interieur du croissant est sensiblement
plus faible que celle des points situes dans la partie circulaire du disque
de la planete." — Arago, Manuscripts of 1847. "That circumstance
which also favors the probability of the existence of an atmosphere
sun-ounding Venus is the optical result obtained by employing a pris-
matic telescope. The intensity of the light of the interior of the cres-
cent is sensibly weaker than that of the points situated in the circular
part of the planet's disk."

X Wilhelm Beer and Miidlerj Beitrdge zur Physiscken Kenntniss der
Himmlischen Korper, p. 148. The so-called moon of Venus, which
Fontana, Dominique Cassini, and Short declared that they had seen, fbr
which Lambert calculated tables, and which was said to have been
seen in the center of the Sun's disk, full three hours after the egress of
VenuS; belongs to the astronomical myths of an uncritical age.

THE MOON. 141

mentioned by Christian Mayer, William Herschel,* and
Harding, also remains exceedingly mysterious. It is not
probable that at so great a distance the reflected light of the
Earth should produce an ash-colored illumination upon Ve-
nus as upon our Moori. Hitherto there has been no flatten-
ing observed in the disks of the two inferior planets, Mercu-
ry and Venus.

The Earth.

The mean distance of the Earth from the Sun is 12,032
times greater than the diameter of the Earth ; therefore,
82,728,000 geographical miles, uncertain as to about
360,000 miles (o-yo)- The period of the sidereal revolution
of the Earth round the Sun is 365d. 6h. 9' 10"-7496. The
eccentricity of the Earth's orbit amounts to 0-01679226 ; its
mass is 3 j^Vjt > i^^ density in relation to water, 5-44. Bes-
sel's investigation of ten measurements of degrees gave for
the flattening of the Earth 29 9"'t5 3- The length of a geo-
graphical mile, sixty of which are contained in one equato-
rial degree, 951,807 toises, and the equatorial and polar di-
ameters, 6875*6 and 6852-4 geographical miles. {Cosmos,
vol. i., p. 65, note.) We restrict ourselves here to numerical
data referring to the Earth's figure and motions : all that
refers to its physical constitution is deferred until the con-
cluding terrestrial portion of the Cosmos.

The Moon of the Earth.

The mean distance of the Moon from the Earth is 207,200
geographical miles ; the period of sidereal revolution is 27d.
7h. 43' ll"-5 ; the eccentricity of her orbit, 0-0548442 ; her
diameter is 1816 geographical miles, nearly one fourth of
the Earth's diameter; her material contents j\ those of the
Earth ; the mass of the Moon is, according to Lindeman,
■Q-^}j-ri (according to Peters and Schidloffsky, j\) of the mass
of the Earth ; her density, 0619, therefore nearly three fifths
of the density of the Earth. The moon has no perceptible
flattening, but an extremely slight prolongation on the side
toward the Earth, estimated 'theoretically. The rotation of
the Moon upon its axis is completed exactly in the same time
in which it revolves round the Earth, and this is probably the
case with all other secondary planets.

Tlie sunlight reflected from the Moon is in all zones mora

Philos. Transact., 1795, vol. htxxvi., p. 214.

142 COSMOS.

feeble than the sunlight which is reflected by a white cloud
in the daytime. When, in determining geographical longi-
tudes, it is often necessary to take the distance of the Moon
from the Sun, it is not unfrequently difficult to distinguish the
Moon between the more intensely luminous masses of cloud.
Upon mountain-heights, which lie between 12,791 and 17,057
feet above the level of the sea, and where, in the clear mount-
ain air, only feathery cirri are to be seen in the sky, I found
the detection of the Moon's disk was much more easy, be-
cause the cirrus reflects less sunlight on account of its loose
texture, and the moonhght is less weakened by its passage
through the rarer strata of air. The relative degree of in-
tensity of the Sun's light to that of the full Moon deserves a
new investigation, as Bouguer's universally received determ-
ination, -go oVo 0' differs so widely from the certainly less prob-
able one of Wollaston, -g ooVo o •*

The yellow moonlight appears white by day, because the
blue strata of air through which we see it presents the com-
plementary color to yellow. t According to the numerous ob-
servations which Arago made with his polariscope, the moon-
light contains polarized light ; it is most perceptible during
the first quarter and in the gray spots of the Moon's surface ;
for example, in the great, dark, sometimes rather greenish ele-
vated plains, the so-called Mare Crhium. Such elevated
plains are generally intersected by metallic veins, in whose
polyhedric figure the surfaces are inclined at that angle
which is necessary for the polarization of the reflected sun-
light. The dark tint of the surrounding space appears, in
addition, to make the phenomenon still more obvious. With
regard to the luminous central mountain of the group Arh-
tarchus, upon which it has been frequently erroneously sup-
posed that volcanic action has been seen, it did not present
any greater polarization of light than other parts of the Moon.
In the full Moon no admixture of polarized light was observ*

* Cosmos, vol. iii., p. 95, and note t.

i " La lumiere de la Lime est jaune, tandis que celle de V§nus est
blanche. Pendant le jour la Lune parait blanche, parcequ'^ la lumiere
du disque lunaire se mele la lumiere bleue de cette partie de I'atmo-
sphere que la lumiere jaune de la Lune traverse." — Arago, in Handschr.
of 1847. " The light of the Moon is yellow, while that of Venus is white
The Moon appears white during the day, because the blue light of thai
part of the atmosphere which the yellow light of the Moon traverses,
mixes with the light of the lunar disk." The most refrangible rays of
the spectrum, from blue to violet, unite with the less refrangible, from
red to green, to form white. (Cosmos, vol. iii., p. 208, note *.)

THE moon's light. 143

able ; but during a total eclipse of the Moon (31st of May,
1848), Arago detected indubitable signs of polarization in the
reddened disk of the Moon, the latter being a phenomenon of
which we shall speak further on. (Comptes Ile?idus, torn,
xviii., p. 119.)

That the moonlight is capable of2oroducing heat, is a dis-
covery which belongs, like so many others of my celebrated
friend Melloni, to the most important and surprising of our
century. After many fruitless attempts, from those of La
Hire to the sagacious Forbes,*^ Melloni was fortunate enough
to observe, by means of a lens (lentille a echellons) of three
feet jn diameter, which was destined for the meteorological
station on Vesuvius, the most satisfactory indications of an el-
evation of temperature during difierent changes of the Moon.
Mosotti-Lavagna and Belli, professors of the Universities of
Pisa and Pavia, were witnesses of these experiments, which
gave results differing in proportion to the age and altitude
of the Moon. It had not at that time (Summer, 1848) been
determined what the elevation of temperature produced by
Melloni's thermoscope, expressed in fractional parts of the
centigrade thermometer, amounted to.f

* Forbes, On the Refraction and Polarization of Heat, in the Trans'
act. of the Royal Society of Edinburgh, vol. xiii., 1836, p. 131.

t Lettre de M. Melloni a M. Arago sur la Puissance calorifique de la
Lumiire de la Lune, in the Comptes Rendus, tom. xxii., 1846, p. 541-544
Compare also, on account of tlie historical data, the Jahresbericht der
Physicalischen Gesellschaft zu Berlin, bd. ii., p. 272. It had always
appeared sufficiently remarkable to me, that, from the earliest times,
when heat was determined only by the sense of feehng, the Moon had
first excited the idea that light and heat might be separated. Among
the Indians the Moon was called, in Sanscrit, the King of the stars of
cold {^dtala, hima), also the cold-radiating Qiimdn^su), while the Sun
was called a creator of heat {niddghakara). The spots upon the Moon,
in which Western nations supposed they discerned ^.face, represent,
according to the Indian notion, a roebuck or a hare ; thence the San-
scrit name of the Moon {mrigadhara), roebuck-bearer, or {^sd'sabhrif),
hare-bearer. (Scbtitz, Five Hymns of the Bhatti-Kdvya, 1837, p. 19-23.)
Among the Greeks it was complained " that the sunlight reflected from
the Moon should lose all heat, so that only feeble remains of it were
transmitted by her." (Plutarch, in the dialogue " De Facia qucs in
OrbeLunce apparel, Moralia,^^ ed. Wyttenbach, tom. iv., Oxon., 1797, p.
793.) In Maci'obius (Comm. in Somnium Scip., i., 19, ed. Lud. Janus,
1848, p. 105) it is said, " Luna speculi instar lumen quo illustratur . . .
rursus emittit, nullum tamen ad nos preferentem sensum caloris : quia
lucis radius, cum ad nos de origine sua, id est de Sole, pervenit, natu-
ram secum ignis de quo nascitur devehit ; cum vero in LunjB corpus ii>
funditur et inde resplendet, solam refundit claritatem, non calorem. '
The same iu Macrobius, SatvmaL, lib. vii , cap. 16, ed. Bipont, tom
ii., p. 277.

144 C03M0S.

The ash-gray light \vi:h which a part of tne Moon's disk
shines when, some days before oi after the new Moon, she
presents only a narrow crescent, illuminated by the Sun, is
earth-light in the Moon, " the reflection of a reflection." The
less the Moon appears illuminated for the Earth, so much the
more is the Earth luminous for the Moon. But our planet
shines upon the Moon with an intensity 13i times greater
than the Moon upon the Earth ; and this light is sufficiently
bright to become again perceptible to us by a second jeflec
tion. By means of the telescope, mountain-peaks are distin-
guished in the ash-gray light of the larger spots and isolated
brightly-shining points, even when the disk is already more
than half illuminated. =^ These phenomena become particu-
larly striking between the tropics and upon the high mount-
ain-plains of Cluito and Mexico. Since the time of Lambert
and Schroter, the opinion has become prevalent that the ex-
tremely variable intensity of the ash-gray light of the Moon
depends upon the greater or less degree of reflection of the
sunlight which falls upon the Earth, according as it is reflect-
ed from continuous continental masses, full of sandy deserts,
grassy steppes, tropical forests, and barren rocky ground, or
from large ocean surfaces. Lambert made the remarkable
observation (14th of February, 1774) of a change of the ash-
colored moonlight into an olive green color, bordering upon
yellow. " The Moon, which then stood vertically over the
Atlantic Ocean, received upon its night side the green terres-
trial light, which is reflected toward her when the sky is clear
by the forest districts of South America."!

The meteorological condition of our atmosphere modifies
the intensity of the earth-light, which has to traverse the

* Madler, Astron., $ 112.

t See Lambert, Siir la Lumiere Cendrie de la Lune, in the Mim. de
VAcad. de Berlin, annie 1773, p. 46 : " La Terre, vue des planetes, pour-
ra paraitre d'une lumiere verddtre, a peu pres corame Mars nous paralt
d'une couleur rougedtre." " The Earth, seen from the planets, may-
appear of a green color, much the same as Mars affords to us of a
reddish color." We will not, however, on that account, conjecture
with this acute man that the planet Mars may be covered with a red
vegetation, such as tlje rose-red bushes of Bougainvillaea. (Hum-
boldt, Views of Nature, \*. 334.) " When in Central Europe the Moon,
shortly before the new Moon, stands in the eastern heavens during the
morning hour, she receives the earth-light principally from the large
plateau surfaces of Asia and Africa. But if, after the new Moon, it stands
during the evening in the west, it can only receive the reflection in less
quantities from the narrower American continent, and principally from
the wide ocean." — Wilhelm Beer and Madler, Der Mond nach seinen
Cosmischen Verhdltnissen, ^ 106, p. 152.

THE MOON S LIGHT. 145

double course from tlje Earth to the Moon, and from thence
to our eye. " Thus, when we have better photometric in-
struments at our command, we may be able," as Arago re-
marks,*= '' to read in the Moon the history of the mean con-
dition of the diaphaneity of our atmosphere." The first cor-
rect explanation of the nature of the ash-colored light of the
Moon is ascribed by Kepler {ad Vitellionem Paralipomena,
quibus AstronomicB pars Optica traditur, 1604, p. 254) to
his highly venerated teacher Mastlin, who had made it known
in a thesis pubHcly defended at Tiibingen in 1596. Galileo
spoke (Sidereus Nuncius, p. 26) of the reflected terrestrial
light as a phenomenon which he had discovered several years
previously ; but a century before Kepler and Galileo, the ex-
planation of terrestrial light visible to us in the Moon had not
escaped the all-embracing genius of Leonardo da Vinci. His
long-forgotten manuscripts furnished a proof of this. f

In the total eclipse of the Moon, the disk very rarely dis-
appears entirely ; it did so, according to Kepler's earliest ob-
servation,:}: on the 9th of December, 1601, and more recently,
on the 10th of June, 1816 ; in the latter instance so as not
to be visible from London, even by the aid of telescopes. The
cause of this rare and extraordinary phenomenon must be a

* Siance de VAcadimie des Sciences, le 5 Aout, 1833, " M. Arago sig-
nale la comparaison de I'intensite lumineuse de la portion de la Luue
que les rayons solaires ^clairent directement, avec celle de la partie du
m^me astre qui re^oit seulement les rayons r^flecliis par la Terre. II
croit d'apres les experiences qu'il a dej^ tentees k cet egard, qu'on

{)ourra, avec des instrumens perfectionnes, saisir dans la himiere cendrie
es differences de I'eclat plus on moins nuageux de I'atmosphere de
notre globe. 11 n'est done pas impossible, malgre tout ce qu'un pareil
resultat exciterait de surprise au premier coup d'oeil, qu'un jour les me-
teorologistes aillent puiser dans I'aspect de la Lune des notions pre-
cieuses sur Vitat moyen de diaphanite de I'atmosphere terrestre, dans les
hemispheres qui successivement concourrent k la production de la lu-
miere cendree." " M. Arago pointed out the comparison between the
luminous intensity of that portion of the Moon which is illuminated di-
rectly by the solar rays, and that portion of the same body which re-
ceives only the rays reflected by the Earth. After the experiments
which he has already made in reference to this subject, he is of opinion
that with improved instruments it will be possible to detect in the ashy
lieht indications of the differences in bi'ightness, more or less cloudy,
of the atmosphere of our globe. It is not, therefore, impossible, not-
withstanding the surprise which such a result may excite on the first
view, that one day meteorologists will derive valuable ideas as to the
mean state of the diaphaneity of our atmosphere in the hemispheres
which successively contribute to the production of the ashy light."

t Venturi, Essai sur les Ouorages de Leonard de Vinci, 1797, p. 11.

t Kepler, Paralip. vcl Astronomuz pars Optica, 1604, p. 297.
Vol. IV.— G

146 COSMOS.

peculiar and not sufficiently investigated diaphanic conditioq
of individual strata of our atmosphere. Hevelius states dis-
tinctly that, during a total eclipse on the 25th of April, 1642,
the sky vras covered with brilliant stars, the atmosphere per-
fectly clear, and yet, with the difierent magnifying powers
which he employed, not a vestige of the Moon could be seen.
In other cases, likewise very rare, only separate parts of the
Moon are feebly visible. During a total eclipse, the disk gen-
erally appears red ; and, indeed, in all degrees of intensity of
color, even passing, when the Moon is far distant from the
Earth, into a fiery and glowing red. While lying at anchor
off the island of Baru, not far from Carthagena de Indias,
half a century ago (29th of March, 1801), I observed a total
eclipse, and was extremely struck w^ith the greater luminous
intensity of the Moon's disk under a tropicalsky than in my
native north.* The whole phenomenon is known to be a
consequence of refraction, since, as Kepler very correctly ex-
presses himself [Paralip Astron. 'pars Optica, p. 893), the
Sun's rays are inflectedf by their passage through the at-

* " On congoit que la vivacite de la lumiere rouge lie depend paj
uniquement de I'etat de I'atraosphere, qui refracte, plus ou moins affai
blis, les rayons solaires, en les enflecliissant dans le cone d'ombre, niais
qu'elle est modifiee surtout par la transparence variable de la partie de
I'atmosphere k travel's laquelle nous apercevons la Lune eclipsee. Sous
les tropiques, une grande sereiiite du ciel, une dissemination uniforme
des vapeurs diminuent I'extinction de la lumiere que le disque lunaire
nous renvoie." — Humboldt, Voyage aux H^gians Eqitinoxiales, torn, iii.,
p. 544 ; and Recueil d'Observ. Astronomiqnes, vol. ii., p. 145. " It may
easily be understood that the intensity of the red light does not depend
solely upon the state of the atmosphere, which refracts more or less
feebly the solar rays by inflecting them into the shadow cone, but that
it is especially modified by the variable transparency of that part of
the atmosphere across which we perceive the eclipsed Moon. Under
the tropics a great serenity of sky, a uniform dissemination of vapors,
diminish the extinction of the light which the lunar disk sends toward
us." Arago observes : " Les rayons solaires arrivent k notre satellite
par I'effet d'une refraction et k la suite d'une absorption dans les couches
les plus bases de I'atmosphere terrestre ; pourraient-ils avoir une autre
teiute que le rouge?" — Annuaire for 1842, p. 528. "The solar rays
reach our planet by the effect of a refraction, and subsequently to an
absorption (partial) in the lower strata of the Earth's atmosphere. How
can they have any other colors than red ?"

t Babinet declares the reddening to be a consequence of diffraction,
in a memoir as to the different share of the white, blue, and red lights
which are produced by the inflection. See his Reflections upon the
Total Eclipse of the Moon on the 19th of March, 1848, in Moigno's RS-
pertoire d^Optique Moderne, 1850, tom. iv., p. 1656. " La lumiere dif.
fract^e qui penetre dans I'ombre de la Terre, predomine toujours et
m^mo a ^t6 seule sensible. Elle est d'autant plus rouge ou orangfee

THE MOON. 147

mosphere, and thrown into the shadow cone. The reddened
or glowing disk is moreover never uniformly colored. Some
places always appear darker, and are, at the same time, con;
tinually changing color. The Greeks had formed a peculiar
and curious theory with respect to the different colors which
the eclipsed Moon was said to present according to the hour
at which the eclipse took place.*

During the long dispute as to the probability or improba-
bility of an atmospheric envelope round the Moon, accurate
occult observations have proved that no refraction takes
place on the surface of the Moon, and that, consequently, the
assumption made by Schroterf of the existence of a lunar
atmosphere and a lunar tivilight are disproved. " The
comparison of the two values of the Moon's diameter which
may be respectively deduced from direct measurement, oi
from the length of time that it remains before a fixed stai
during the occultation, teaches us that the light of a fixed
star is not perceptibly deflected from its rectilinear course at

qu'elle se trouve plus pres du centre de I'orabre geom^trique ; car se
Bout les rayous les moins refrangibles qui se propagent le plus abou
damment par diflfraction, k mesure qu'on s'eloigne de la propagation en
ligne droite." " The ditFracted light which penetrates into the Earth's
shadow always predominated, and was, indeed, alone sensible. It was
tlie more red or orange in proportion as it was nearer to the geomet-
rical center of the shadow ; for those rays which are least refrangible
are those which are propagated most abundantly by diflfraction, in pro
portion as they differ from a rectilinear course." The phenomena of
diffraction take place as well in a vacuum, according to the acute in
vestigations of Magnus (on the occasion of a discussion between Aii-j
and Faraday). Compare, in reference to the explanations by diffrac
tion in general, Arago in the Annuaire for 1846, p. 452-455.

* Plutarch {De Facie in Orhe Lunce), Moral., ed. Wytten., torn, iv .
p. 780-783 : " The fiery, charcoal-like, glimmering {dvOpaKoeidng) coloi
of the eclipsed Moon (about the midnight hour) is, as the mathemati-
cians affirm, owing to the change from black into red and bluish, and
is by no means to be considered as a character peculiar to the earthy
surface of the planet." Also Dio Cassius (Ix., 26, ed. Sturz, p. iii., p
779), who occupied himself especially with eclipses of the Moon, and
the remarkable edicts of the Emperor Claudius, which predicted the di'
mensions of the eclipsed portion, directs attention to the very different
colors which the Moon assumed during the conjunction. He says (Ixv.,
11, torn, iv., p. 185, Sturtz), "Great was the excitement in the camp
of Vitellius in consequence of the eclipse which took place that night.
The mind was filled with melancholy apprehensions, not so much at
the eclipse itself, although that might appear to predict misfortune to
an unquiet mind, but much more from the circumstance that the Moon
displayed blood-red, black, and other gloomy colors."

t SchrSter, Selenotopographische Fragmente, th. i., 1791, p. 668; th.
ii., 1802, p. 52.

148 COSMOS.

that moment in which it touches the Moon's edge. If a re-
fraction took place at the edge of the Moon, the second de-
termination of her diameter must give a value smaller by
tw^ice the amount of the refraction than the former ; but, on
the contrary, both determinations correspond so closely in
repeated determinations, that no appreciable difference has
ever been detected."=^ The ingress of stars, which may be
particularly well observed at the dark edge, takes place
suddenly, and without gradual diminution of the star's brill-
iancy ; just so the egress or reappearance of the star. In
the case of the few exceptions which have been described,
the cause may have consisted in accidental changes of oui
atmosphere.

If, however, the Earth's Moon is destitute of a gaseous
envelope, the stars must appear then, in the absence of all
diffuse ' light, to rise upon a black sky ;t no air- wave can
there convey sound, music, or language. To our imagina-
tion, so apt presumptuously to stray into the unfathomable,
the Moon is a voiceless wilderness.

The phenomenon of apparent adherence on and within the
Moon's edge,$ sometimes observed in the occultation of stars,
can scarcely be considered as a consequence of irradiation,
which, in the narrow crescent of the Moon, on account of
the very different intensity of the light in the ash-colored
part of the Moon, and in that which is immediately illumin-
ated by the Sun, certainly makes the latter appear as if sur-
rounding the former. Arago saw, during a total eclipse of the
Moon, a star distinctly adhere to the slightly luminous disk
of the Moon during the conjunction. It still continues to be

* Bessel, TJeher eine angenommene Atmosphdre des Mondes in Schu-
macher's Asiron. Nachr., No. 263, p. 416-420. Compare also Beer and
Madler, Der Monde, § 83 and 107, p. 133 and 153; also Arago, in the
Annuaire for 1846, p. 346-353. The frequently mentioned proof of the
existence of an atmosphere round the Moon, derived from the greater or
less perceptibility of small superficial configurations and "the Moon-
clouds moving round in the valleys," is the most untenable of all, on
account of the continually-varying condition (darkening and bi'ighten-
ing) of the upper strata of our own atmosphere. Considerations as to
the form of one of the Moon's horns qn the occasion of the solar eclipso
on the 5th of Septepber, 1793, induced William Herschel to decide
against the assumption of a lunar atmosphere. (Pkilos. Transact., vol.
ixxxiv., p. 167.)

t Madler, in Schumacher's Jahrbuch for 1840, p. 188.

j Sir John Herschel (Outlines, p. 247) directs attention to the ingress
of such double stars as can not be seen separately by the telescope, on
account of the too great proximity of the individual stars of which they
consist.

THE MOON. 149

a subject of discussion between Arago and Plateau whether
the phenomenon here mentioned depends upon deceptive per-
ception and physiological causes,*^ or upon the aberration of
sphericity and refrangibility of the eye.f Those cases in
which it has been asserted that a disappearance and reap-
pearance, and then a repeated disappearance, have been ob-
served during an occultation, may probably indicate the in-
gress to have taken place at a part of the Moon's edge which
happened to be deformed by mountain declivities and deep
chasms.

The great differences in the reflected light from particular
regions of the illuminated disk of the Moon, and especially
the absence of any sharp boundary between the inner edge
of the illuminated and ash-colored parts in the Moon's phases,
led to the formation of several very rational theories as to
the inequalities of the surface of our satellite, even at a very
emote period. Plutarch says distinctly, in the small but
very remarkable work On the Face in the Moon, that we
may suppose the spots to be partly deep chasms and valleys,
partly mountain peaks, " which cast long shadows, like Mount
Athos, whose shadow reaches Lemnos."$ The spots cover
about two fifths of the whole disk. In a clear atmosphere,
and under favorable circumstances in the position of the

* Plateau, Sur V Irradiation, in the Mim. de V Acad. Royale des Sci
ences et Belles-Leitres de Bruxelles, torn, xi., p. 142, aud the supplement-
ary vokime of PoggendorfF's Annalen, 1842, p. 79-128, 193-232, and
405 and 443. " The probable cause of the irradiation is an irritation
produced by the light upon the -retina, and spreads a little beyond the
outline of the image."

t Arago, in the Comptes Rendus, torn, viii., 1839, p. 713 and 883.
" Les phenomenes d'irradiation signales par M. Plateau sont regarcl6a
par M. Arago comme les effets des aberrations de refrangibilit6 et de
sphericite de I'oeil, combines avec I'indistinction de la vision, conse-
quence des circonstances dans lesquelles les observateurs se sont places.
Des mesures exactes prises sur des disques noirs k fond blanc et des
disques blancs k fond noir, qui 6taient places au Palais du Luxembourg
visibles k I'observatoire, n'ont pas indique les effets de I'irradiation.'
" The phenomena of irradiation pointed out by M. Plateau are regarded
Dy M. Arago as the effects of the aberration of sphericity and refrangi-
bility of the eye, combined with the indistinctness of vision consequent
upon the circumstances in which the observers are placed. The exact
measurement taken of the black disks upon a 'vyhite ground, and the
white disks upon a black ground, which were placed upon the palace
of Luxembourg, and visible at the Observatory, did not present auy
phenomena of irradiation."

t Plutarch, Moral., ed. Wytten., torn, iv., p. 786-789. The shad"-v
of Athos, which was seen by the traveler Pierre Belon {Observations -^
Sing-ularitis troitvSes en Grece, Asie, etc., 1554, liv. i., cbap. 25), reacl. 4
the brazen cow in the market-town Myrine in Lemnos.

160 COSMOS.

Mood, some of the spots are visible to the naked eye ; tha
ridge of the Apennines, the dark, elevated plain GHmaldus,
the inclosed Mare Crisium, and Tycho,* crowded round
with numerous mountain ridges and craters. It has been
affirmed, not without probability, that it was especially the
aspect of the Apennine chain which induced the Greeks to
consider the spots on the Moon to be mountains, and at the
same time to associate with them the shadow of Mount
Athos, which in the solstices reached the Brazen Cow upon
Lemnos. Another very fantastic opinion was that of Agesv-
nax, disputed by Plutarch, according to which the Moon's
disk was supposed, like a mirror, to present to us again, ca-
toptric ally, the configuration and outline of our continent,
and the outer sea (the Atlantic). A very similar opinion ap-
pears to have been preserved to this time as a popular belief
among the people in Asia Minor. f

By the careful application of large telescopes, it has grad-

* For proofs of the visibility of these four objects, see in Beer and
Madler, Der Mond., p. 241, 338, 191, and 290. It is scarcely necessary
to mention that all which refers to the topography of the Moon's surface
is derived from the excellent work of my two friends, of whom the
second, William Beer, was taken from us but too early. The beautiful
Uebersichtsblatt, which Madler published in 1837, three years after the
large map of the Moon, consisting of three sheets, is to be recommended
for the purpose of more easily becoming acquainted with the bearings.

+ Plut., De Facie in Orbe Lunee, p. 726-729, Wytten. This passage
is, at the same time, not without interest for ancient geography. — See
Humboldt, Examen Criiiqus de V Hist, de la G6ogr., torn, i., p. 145.
With regard to other views of the ancients, see Anaxagoras and De-
mocritus, in Plut., De Plac. Philos., ii., 25 ; Parmenides, in Stob., p. 419,
453, 516, and 563, ed. Heeren; Schneider, Eclogce Physicce, vol. i., p.
433-443. According to a very remarkable passage in Plutarch's Life
of Nicias, cap. 42, Anaxagoras himself, who calls "the mountainous
Moon another Earth," had made a drawing of the Moon's disk. {Com-
pare also Origines, Philosophumena, cap. 8, ed. Mtilleri, 1851, p. 14.)
I was once very much astonished to hear a very well-educated Per-
sian, from Ispahan, who certainly had never read a Greek book, men-
tion, when I showed him the Moon's spots in a large telescope in Paris,
the hypothesis of Agesiuax (alluded to in the text) as to the reflection,
as a widely-diffused popular belief in his country. '* What we see
there in the Moon," said the Persian, "is ourselves; it is the map of
our Earth." One of the interlocutors in Plutarch's Moon-dialogue would
not have expressed himself otherwise. If it can be supposed that men
are inhabitants of the Moon, destitute "of water and air, the Earth, with
its spots, would also present to them such a map upon a nearly black
sky by day, with a surface fourteen times greater than that w^hich the
full Moon presents to us, and always in the same position. But the
constantly varying clouds and obscurities of our atmosphere would con-
fuse the outlines of the continents. — Compare MUdler^B A str on-, p. 169
and Sir John Herschel, Outlines, $ 43G.

THE MOON. 151

aally become possible to construct a topographical chart of
the Moon, based upon actual observations ; and since, in the
opposition, the entire half-side of the Earth's satellite presents
itself at the same moment to our investigation, we knov^^ more
of the general and merely formal connection of the mountain
groups in the Moon, than of the orography of a whole terres-
trial hemisphere containing the interiors of Africa and Asia.
Generally the darker parts of the disk are the lower and more
level ; the brighter parts, reflecting much sunhght, are the
more elevated and mountainous. Kepler's old description of
the two as sea and land has long been given up ; and the
accuracy of the explanation, and the opposition, was already
doubted by Hevel, notwithstanding the similar nomenclature
introduced by him. The circumstance principally brought
forward as disproving the presence of surfaces of water on
the Moon was, that in the so-called seas of the Moon, the
smallest parts showed themselves, upon closer examination
and very different illumination, to be completely uneven, pol-
yhedric, and consequently giving much 'polarized hght. Ar-
ago has pointed out, in opposition to the arguments which
have been derived from the irregularities, that some of these
surfaces may, notwithstanding the irregularities, be covered
with water, and belong to the bottoms of seas of no great
depth, since the uneven, craggy bottom of the ocean of our
planet is distinctly seen when viewed from a great height,
on account of the preponderance of the light issuing from be-
low its surface over the intensity of that which is reflected
from it. {Annuaire du Bureau des Longitudes for 1836,
p. 339-343.) In the work of my friend, which will shortly
appear, on astronomy and photometry, the probable absence
of water upon our satellite will be deduced from other optical
grounds, which can not be developed in this place. Among
the low plains, the largest surfaces are situated in the north-
ern and eastern parts. The indistinctly bounded Oceanus
Procellarum has the greatest extension of all these, being
360,000 geographical miles. Connected with the Mare Ini-
hrium (64,000 square miles), the Mare Nubium, and, to
some extent, with the Mare Humorum, and surrounding in-
sular mountain districts (the Rijohcei, Kepler, Cojoernicus,
and the Carpathians), this eastern part of the Moon's disk
presents the most decided contrast to the luminous south-
tvestern district, in which mountain is crowded upon mount-
ain.* In the northwest region, two basins present them-
* Beer and Madler, p. 273.

152 COSMOS.

selves AS being more shut in and isolated, the Msre Crisiiirtk
(12,000 square miles) and the 3Iare Tranquillitatis (23,200
square miles).

The color of these so-called i>tas is not in all cases gray.
The Mare Crisium is gray mixed with dark green ; the Mare
Serenitatis and Mare Humorum are likewise green. Near
the Hercynian mountains, on the contrary, the isolated cir-
cumvallation Lichtenherg presents a pale reddish color, the
same as Palus Somnii. Circular surfaces, without central
mountains, have for the most part a dark steel-gray color,
bordering upon bluish. The causes of this great diversity in
the tints of the rocky surface, or other porous materials which
cover it, are extremely mysterious. While, to the northward
of the Alpine mountains, a large inclosed plain, Plato (called
by Hevel Lacus niger major), and still more Grimaldus in
the equatorial region, and Endymion on the northwest edge,
are the three darkest spots upon the whole Moon's disk, Aris-
tarchus, with its sometimes almost star-hke shining points, is
the brightest and most brilliant. All these alternations of
light and shade affect an iodized plate, and may be repre-
sented in Daguerreotype, by means of powerful magnifiers,
with wonderful truthfulness. I myself possess such a mooji-
light picture of two inches diameter, in which the so-called
ieas and ring-formed mountains are distinctly perceptible ; it
was executed by an excellent artist, Mr. "Whipple, of Boston.

If the circular form is striking in some of the s,ea$ ( Cris-
ium, Serenitatis, and Humorurri), it is still more frequently
— indeed, almost universally, repeated in the mountainous
part of the disk, especially in the configuration of the enor-
mous mountain-masses which occupy the southern hemisphere
from the pole to near the equator, where the mass runs out
in a point. Many of the annular elevations and inclosed
plains (according to Lohrmann, the largest are more than
4000 square miles in extent) form connected series, and, in-
deed, in the direction of the meridian, between 5° and 40°
south latitude.* The northern polar region contains cpm-
paratively few of these crowded mountain circles. In the
western edge of the northern hemisphere, on the contrary,
they form a connected group between 20° and 50° north
latitude. The North Pole itself is within a few degrees of
the Mare Frigoris, and thus, like the whole level northeast-
ern space, including only a few isolated annular mountain?
{Plato, Mairan, Aristarch, Copernicus, and Kepler), pre
* Schumacher's Jahrbuch for 1841, p. 270.

THE MOON. ' 153

Bents a great contrast to the South Pole, entirely covered with
mountains. Here lofty peaks shine during whole lunations
in eternal light, in the strictest sense of the word ; they are
true lig^ht islands, which become perceptible, even with feeble
magnifying powers.*

As exceptions to this type of circular and annular configu-
rations, so universally predominant upon the Moon, are the
actual mountain-chains which occur almost in the middle of
the northern half of the Moon {^Apennines, Cauca.sus, and
Alps). They extend from south to north in a slight curve to-
ward the west, through nearly 32° of latitude. Innumer-
able mountain crests and extraordinary sharp peaks are here
thronged together. Few annular mountains, or crater-Hke
depressions, are intermingled {Coiion, Hadley, Calippus),
and the whole resembles more the configuration of our mount-
ain-chains upon the Earth. The lunar Alps, which are in-
ferior in height to the lunar Caucasus and Apermines, pre-
sent a remarkable brojd transverse valley, which intersects
the chain from southeast to northwest. It is surrounded by
mountain peaks which exceed in 'height that of Tenerifie.

The relative height of the elevations in proportion to the
diameters of the Moon and the Earth, gives the remarkable
result, that since in the four times smaller satellite the high-
est peaks are only 3836 feet lower than those of the Earth,
the lunar mountains amount to ^-i^, the mountains on the
Earth to y^g-y of the planetary diameters, f Among the 1095
points of elevation already measured upon the Moon, I find
39 are higher than Mont Blanc (16,944 feet), and six higher
than 19,000 feet. The measurements were effected either
by light tangents (by determining the distance of the illumin-
ated mountain peak on the right side of the Moon from the
boundary of the light) or by the length of the shadows. The
former method was already made use of by Galileo, as is seen
from his letter to the Father Grienberger upon the Montu-
ositd della Luna.

According to Madler's careful measurements by means of
the length of the shadows, the culminating points of the

* Madler, Astron., p. 16G.

t The highest peak of the Himalayas, and (up to the present time!)
of the whole Earth, Kinchin-jnnga, is, according to Waugh's recent
measurement, 4406 toises, or 28,178 English feet; the highest peak
among the Moon's mountains is, according to Madler, 3800 toises (ex-
actly four geographical miles). The diameter of the Moon is 1816,
that of the Earth 6872 geographical miles ; whence it follows for the
Moon ^^j, for the Earth yj^y

G 2

154 COSMOS.

Moon are in descending order at the south edge, very near tho
Pole, D'orfel and Leibnitz, 24,297 feet ; the annular mountain
Newton, where a part of the deep hollow is never lighted,
neither by the Sun nor the Earth's disk, 23,830 feet ; Casa-
tus, eastward of Newton, 22,820 feet ; Calippus, in the Cau-
casian chain, 20,396 feet; the Apennines, hetween 17,903
and 19,182 feet. It must be remarked here, that in the en-
tire absence of a general niveau-line (the plane of equal dis-
tance from the center of a cosmical body, as is presented on
our planet by the level of the sea), the absolute heights are
not to be compared strictly with each other, since the six
numerical results here given properly express only the differ-
ences between the peaks and the immediately surrounding
plains or hollows.* It is, however, very remarkable that
G-alileo likewise assigned to the loftiest lunar mountains the
height of about four geographical miles (24,297 feet), " in-
drca miglia quatro,"' and, in accordance with the extent of
\iis hypsometric knowledge, considered them higher than any
5f the mountains on the Earth.

An extremely remarkable and mysterious phenomenon
which the surface of our satellite presents, and which is only
optically connected wdth a reflection of light, and not hyp-
Bometrically with a difference of elevation, consists in the nar-
row streaks of light which disappear when the illuminating
rays fall obliquely ; but in the full Moon, quite in opposition
to the Moon-spots, become most visible as systems of rays.
They are not mineral veins, cast no shadow, and run with
equal intensity of light from the plains to elevations of more
than 12,780 feet. The most extensive of these ray-systems
commences from TycJio, where more than a hundred streaks
of ^ight may be distinguished, mostly several miles broad.
Similar systems which surround the Aristarchus, Kepler, Co-
pernicus, and the Carpathians, are almost all in connection
with each other. It is difficult to conjecture, by the aid of
induction and analogy, what special transformations of the
surface give rise to these luminous, ribbon-like rays, proceed-
ing from certain annular mountains.

The frequently mentioned type of circular configuration,
almost every where preponderating upon the Moon's disk, in
the elevated plains which frequently surround central mount-
ains ; in the large annular mountains and their craters (22
are counted close together in Bayer, and 33 in Albateg?iius)

* For the six heights which exceed 19,182 feet, see Beer and Mad-
iei% p. 99, 125. 231 242. 330. and 331.

THE MOON. 155

must have early induced a deep-thinker like Robert Hooke
to ascribe such a form to the reaction of the interior of the
Moon upon the cxtejior — "the action of subterranean fire,
and elastic eruptive vapors, and even to an ebullition in
eruptive bubbles." Experiments with thickened boiling lime
solutions appeared to him to confirm his opinion ; and the cir-
cumvallations, vidth their central mountains, were at that time
already compared with " the forms of JEtna, the Peak of
TenerifFe, Hecla, and the Mexican volcanoes described by
Gage."^

One of the annular plains of the Moon reminded Galileo,
as he himself relates, of the configuration of countries entirely
surrounded by mountains. I have discovered a passage! in
which he compares these annular plains of the Moon with
the great inclosed basin of Bohemia. Many of the plains are,
in fact, not much smaller, for they have a. diameter of from
1 00 to 1 20 geographical miles. $ On the contrary, the real an-
nular mountains scarcely exceed 8 or 12 miles in diameter.
Conon in the Apennines is 8 ; and a crater which belongs to
the shining region of Aristarchus is said to present a breadth
of only 25,576 feet, exactly the half of the diameter of the
crater of Rucu-Pichincha, in the table-land of Gluito, meas-
ured trigonometrically by myself

Since we have in this place adhered to comparisons with
well-known terrestrial phenomena and relations of magnitude,
it is necessary to remark that the greater part of the plains
and annular mountains of the Moon are to be considered in
the first place as craters of elevation, without continuous
phenomena of eruption in the sense of the hypothesis of Leo-
pold von Buch. What, according to the European standard,

* Robert Hooke, Micrographia, 1667, Obs. Ix., p. 242-246. '' These
ieem to me to have been the effects of some motions within the body
of the Moon, analogous to our earthquakes, by the eruption of which,
as it has thrown up a brim or ridge round about higher than the am-
bient surface of the Moon, so has it left a hole or depression in the mid-
dle, proportjonably lower." Hooke says of his experiment with boil,
iug alabaster, that " presently cecsiug to boyl, the whole surface will
appear all over covered with small pits, exactly shaped like those of
the Moon. The earthy part of the Moon has been undermined, or
heaved up by eruptions of vapors, and thrown into the same kind of
figured holes as the powder of alabaster. It is not improbable, also,
that there may be generated within the body of the Moon divers such
kind of internal fires and heats as may produce exhalations "

t Cosmos, vol. ii., p. 319, note.

\ Beer and Madler, p. 126. Ptolemaeus is 9Q miles in diameter
Alphons and Hipparchus, 76 miles.

156 COSMOS.

we call great upon the Earth — ^the elevation crater of Rocca
Monsina, Palma, TenerifFe, and Santorin — becomes insignifi-
cant when compared with Ptolemy, Hipparchus, and many
others of the Moon. Palma has only 24,297 feet diameter ;
Santorin, according to Captain Graves, new measurement,
33,148 feet; Teneriffe, at the utmost, 53,298 feet: conse-
quently, only one eighth or one sixth of the two craters of
elevation of the Moon just mentioned. The small crater of
the Peak of Tenerifie and Vesuvius (from 319 to 426 feet in
diameter) could scarcely be seen by the aid of telescopes.
The by far greater number of the annular mountains have
no central mountain ; and where there is one, it is described
as being dome-formed or level {Hevelius, Macrobius), not as
an erupted cone with an ope7ti7ig.'^ The active volcanoes
which are stated to have been seen in the right side of the
Moon (May 4, 1783) ; the phenomena of light in Plato, which
Bianchini (August 16, 1725) and Short (April 22, 1751) ob-
served, are here mentioned only as of historical interest, since
the sources of deception have long been fathomed, and lie in
the more powerful reflection of the terrestrial light which
certain parts of the surface of our planet throw upon the ash-
colored night side of the Moon.f

* Arzachel and Hercules are supposed to be exceptions : the former
to have a crater upon its summit, the second a lateral crater. These
points, important in a geognostic point of view, deserve fresh investi-
gation vv^ith more perfect instruments. (Schroter, Selenotopographische
Fragmente, th. ii., tab. 44 and 68, fig. 23.) Hitherto no signs have ever
been detected of lava streams collected in deep hollows. The radiated
^mes which issue from Aristoteles in three directions are ranges of hills.
(Beer and Madler, p. 236.)

t Op. cit., p. 151. Arago, in the Annuaire for 1842, p. 526. (Com-
pare also Immanuel Kant, Schriften der Physischen Geographie, 1839,
p. 393-402.) According to recent and more complete investigations,
the temporary changes said to have been observed upon the surface of
the Moon (the formation of new central mountains and craters in the
Mare Crisium, Hevelius, and Cleomedes), are illusions of a similar na-
ture to the supposed volcanic eruptions perceptible to us upon the Moon.
(See Schrbter, Selenotopographische Fragmente, th. i., p. 412-523 ; th. ii.,
p. 268-272.) The question, what is the smallest object whose height
can be measured with the instruments which are at present at our com-
mand? is in general difficult to answer. According to the report of Dr.
Robinson upon the beautiful reflecting telescope of Lord Rosse, extents
of 220 feet (80 to 90 yards) are discerned with the greatest distinctness.
Madler calculates that, in his observations, shadows of 3" were capable
of being measured ; a length which, under certain presuppositions as to
the position of a mountain, and the altitude of the San, would indicate
a mountain elevation of 120 feet. However, he points out, at the same
time, that the shadows must have a certain degree of breadth in order
to be visible and measurable. The shadow of the great pyramid of

THE MOON 157

Attention has been repeatedly, and Avith justice, directed
to the fact, that in the absence of water upon the Moon (even
the rills, very narrow, mostly rectilinear hollows,^ are not riv-
ers), we must represent to ourselves the surface of the Moon
as being somewhat similarly constituted as was the Earth in
its primitive and most ancient condition, while yet uncovered
ilotz strata, by bowlders and detritus, which were spread out
by the transporting force of the ebb and flood or currents.
Sun and Earth floods are naturally wanting ; where the liquid
element is absent, shght coverings of decomposed conglomer-
ates are scarcely conceivable. In our mountain-chains, up-
heaved upon fissures, partial groups of elevations are begin-
ning gradually to be discovered here and there, forming, as it
were, egg-shaped basins. How entirely different the Earth's
surface would have appeared to us if it were divested of the
flotz and tertiary formations !

The Moon, by the variety of its phases, and the more rapid
change of its relative position in the sky, animates and beau-
tifies the aspect of the firmament under every zone more than
all the other planets. She sheds her agreeable Hght upon
men, more especially in the primitive forests of the tropical
world, and the beasts of the forests. f The Moon, in virtue

Cheops, according to the known dimensions of this monument (super-
ficial extent), would be, even at the point of commencement, scarcely
one ninth of a second broad, and consequently invisible. (Madler, in
Schumacher's Jahrbuch for 1841, p. 264.) Arago calls to mind that,
with a 6000-fold magnifying power, which, nevertheless, could not be
applied to the Moon with proportionate results, the mountains upon the
Moon would appear to us just as Mont Blanc does to the naked eye when
seen from the Lake of Geneva.

* The rills do not occur frequently ; are, at the utmost, thirty miles
long; sometimes forked (Gassendi); seldom resembling mineral veins
(Triesnecker) ; always luminous; do not cross mountains transversely;
are peculiar to the level landscapes ; are not characterized by any pe
culiarities at the terminal points, without becoming broader or narrow-
er. (Beer and Madler, p. 131, 225, and 249.)

t See my Essay upon the Nocturnal Life of Animals in the Primceval
Forest, in the Views of Nature, Bohn's ed., p. 198. Laplace's reflections
upon a perpetual moonlight {Exposition du Systeme du Monde, 1824, p.
232) have met with a disproval in the M6m. of Liouville surun caspar-
ticulier du problem des Trois Corps. Laplace says, *' Quelques partisans
des causes finales ont imagine que la Lune a ete donnee k la Terra pour
I'^clairer pendant les nuits ; dans ce cas, la nature n'aurait point atteint
ie but qu'elle se serait propose, puisque nous sommes souvent prives k
la fois de la lumiere du Soleil et de celle de la Lune. Pour y parvenir,
il eiit suffi de raettre k I'origine la Lune en opposition avec le Soleil
dans le plan m6me de I'ecliptique, k une distance egale k la centieme

Eartie de la distance de la Terre au Soleil, et de donner k la Lune et k
I Terre des vitesses parallel es et proportionnelles ^ leurs distances ik

158 COSMOS.

of the attractive force which she exercises in common with
the Sun, excites motion in our ocean — the liquid portion of
the Earth — gradually changes the surface by periodical floods,
and the outlines of continental coasts, by the destructive agen-
cy of the tides, hinders or favors the labor of men ; afibrds
the greater part of the material from which sandstones and
conglomerates are formed, and which are again covered by
the rounded, loose, transported detritus.^ Thus the Moon,
as one of the sources of motion, continues to act upon the ge-
ognostic relations of our planet. The indisputable! influence

cet astre. Alors la Lune, sans cesse eu opposition au Soleil, eAt decrit
autour de lui une ellipse semblable k celle de la Terre ; ces deux astres
86 seraient succede I'un a I'autre sur I'horizon ; et comme k cette dis-
tance la Lune n'efit point 6te 6clipsee, sa lumiere aurait certainement
remplace celle du Soleil." " Several partisans of final causes have im-
agined that the Moon has been given to the Earth to light it during the
night ; in that case, nature would not have attained the object which
she had proposed, because we are frequently deprived at the same time
of the light of the Sun and Moon. To have attained this end, it would
have been sufBcient in the beginning to place the Moon in opposition
with the Sun, in the same plane of the ecliptic, at a distance equal to
the. hundredth part of the distance of the Earth from the Sun, and to
give to the Moon and the Earth velocities parallel and proportional to
their distances from that body. Then the Moon, constantly in opposi
tion to the Sun, would have described an ellipse round it like that of
the Earth ; these two bodies would have succeeded each other in the
horizon, and as at that distance the Moon would never have been
eclipsed, its light would certainly have replaced that of the Sun." Liou-
ville finds, on the contrary, " Que, si la Lune avait occupe k I'oiigine la
position particuliere que I'illustre auteur de la Micanique Celeste lui
dssigne, elle n'aurait pu s'y njaintenir que pendant un temps tres court."
'* That if the Moon had occupied at the beginning the particular posi-
tion assigned to her by the illustrious author of the Micanique Cilesle,
she would not have been able to maintain it for more than a very short
time."

* On the Transporting Power of the Tides, see Sir Henry de la Beche,
Geological Manual, 1833, p. 111.

t Arago, Sur la question de savoir si la Lune exerce sur notre Atmo-
sphere une injluence appreciable, in the Annuaire for 1833, p. 157-206.
The principal advocates of this opinion are Scheibler ( Untersuch. uber
Einfluss des Mondes anf die Vcranderungenin unserer Atmosphdre, 1830,
p. 20); Flangergues {Zwanzigjdhrige Beobachtungen in Viviers, Bibl.
Universelle, Sciences et Arts; torn, xl., 1829, p. 265-283, and in Kastncr's
Archivf. die ges. Naturlehre, bd. xvii., 1829, sees. 32-50); and Eisenlohr
(Toggend., Annalen der Physih, bd. xxxv., 1835, p. 141-160, and 309-
329). Sir John Herschel considers it very probable that a very high
temperature prevails upon the Moon (far above the boiling-point of
water), as the surface is uninterruptedly exposed for fourteen days to
the full action of the Sun. Therefore, in the opposition, or some few
days after, the Moon must be, in some small degree, a source of heat
for the Earth ; but this heat, radiating from a body far below the tem-
[•erature of ignition, can not reach the surface of the Earth, since it ia

MARS. * 159

of tlie satellite upon atmospheric pressure, aqueous depositions,
and the dispersion of clouds, will be treated of in the last and
purely telluric part of the Cosmos.

Mars.

The diameter of this planet, notwithstanding its considera-
bly greater distance from the Sun, is only 0*5 19 of the Earth's,
or 3568 geographical miles. The eccentricity of his orbit is
0-0932168, next to Mercury the greatest of all the planetary
orbits ; and also on this account, as well as from its proximi-
ty to the Earth, the most suitable for Kepler's great discove-
ry of the elliptical form of the planetary orbits. His period
of rotation^ i^, according to Miidler and Wilhelm Beer, 24h.
37m. 23s. His sidereal revolution round the Sun occupies 1
year 321d. I7h. 30m. 41s. The inclination ofMars's orbit
toward the Earth's equator is 24° 44' 24"; his mass, ^^.^1--^;
his density, in comparison to that of the Earth, 0-958. The
mass of Mars will be hereafter corrected by means of the dis
turbances which he may experience from his influence with
the Comet of DeYico, in the same way that the close approach
of Encke's Comet was taken advantage of to ascertain the
mass of Mercury.

The flattenmg of Mars, which (singularly enough) the great
Konigsberg astronomer permanently doubted, was first recog-
nized by William Herschel (1784). With regard to the amount
)f the flattening, however, there was long considerable uncer-

'xbsorbed in the upper strata of our atmosphei'e, where it converts visi-
ble clouds into transparent vapor." The phenomenon of the rapid dis-
persion of clouds by the full Moon, when they are not extremely dense,
is considered by Sir John Herschel " as a meteorological fact, which,"
he adds, "is confirmed by Humboldt's own experience and the uni-
versal belief of the Spanish sailors in the tropical seas of Arherica." —
See Report of the Fifteenth Meeting of the British Association for the
Advancement of Science, 1846, Notices, p. 5 ; and Outlines, p. 201.

* Beer and Madler, Beitrdge zur Phys. Kenntniss des Sonnensystems,
1841, p. 113, from observations in 1830 and 1832 ; Madler, Astronomie,
1849, p. 206. The first considerable improvement in the data for the
period of rotation, which Dominique Cassini found 24h, 40m., was the
result of laborious observations by William Herschel (between 1777 and
1781), which gave24h. 39m. 21-7s. Kunowsky found, in 1821, 24h. 36m.
403., very near to Madler's result. Cassini's oldest observation of the
rotation of a spot upon Mars (Delambre, Hist, de VAstron. Mod., torn.
:i.,p. 694) appears to have been soon after the year 1670; but in the
very rare Treatise, Kern, Diss, de Scintitlatione Stellarum, Wittenb.,
1686, § 8, 1 find that the actual discoverers of the rotations of Mars and
Jupiter are stated to have been " Salvator Serra and Father ^gidius
Franciscus de Cottignez, astronomex-s of the Collegio Romano."

160 ' COSMOS.

tainty. It was stated by William Herschel to be j\ ; accord*
ing to Arago's more accurate measurement,^ with one of E,o-
chon's prismatic telescopes, in the first instance (before 1824),
only in the proportion of 189 : 194, i. e., -^^.^ ; by a subsequent
measurement (1847), J^; still, Arago is inclined to consider
the flattening somewhat greater.

If the study of the Moon's surface calls to mind many ge-
agnostic relations of the surface of the Earth, so, on the con-
trary, the analogies which Mars presents with the Earth are
entirely of a meteorological nature. Besides the dark spots
— some of which are blackish ; others, though in very small
numbers, yellowish-red, f and surrounded by the greenish con-
trast colors, so-called seasj — there are seen upon the disk of
Mars two white, brilliant, snow-like spots, § either at the poles
which are determined by the axis of rotation, or at the poles
of cold alternately. They were recognized as early as 1716
by Philip Maraldi, though their connection with climatic
changes upon the planet was first described by the elder
Herschel, in the seventy-fourth volume of the Philosophical
Transactions for 1784. The white spots become alternately
larger or smaller, according as the poles approach their win-
ter or summer. Arago has measured, by means of his polari-
scope, the intensity of the light of these snoiv zones, and found
it twice as great as that of the remaining part of the disk.
The Physikalisch-astronomischen Beitrdgen of Madler and
Beer contain some excellent graphic representations!! of the
north and south hemispheres of Mars ; and this remarkable
phenomenon, unparalleled throughout the whole planetary
system, is there investigated with reference to all the changes
of seasons, and the powerful action of the polar summer upon
the melting snow. Careful observations, during a period of
ten years, have also taught us that the dark spots upon Mars
preserve a constant form and relative position. The period-
ical formation of snow-spots, as meteoric depositions depend-
ent upon change of temperature, and some optical phenom-
ena which the dark spots present as soon as they have, by the
rotation of the planet, reached the edge of the disk, make the
existence of an atmosphere upon Mars more than probable.

* Laplace, Expos, du Syst. du Monde, p. 36. Schr6ter's very imper-
fect measurement of the diameter of the planet gave Mars a flattening
of only -gL.. t Beer and Madler, Beiirage, p. Ill

t Sir John Herschel, Outlines, $ 510.

$ Beer and Madler, Beitrdge, p. 117-125.

\ Madler, in Schumachei's Astr, Nachr., No. 192.

THE SMALL PLANETS. IGl

The Small Planets.

We have already, in the general consideration'*' of the
planetary bodies, characterized the group of small planets
{asteroids, planetoids, co-planets, telescopic or ultra-zodiacal
planets) under the name of an intermediate group, which,
to a certain extent, forms a zone of separation between the
four interior planets (Mercury, Venus, the Earth, and Mars),
and the four exterior planets of our solar system (Jupiter, Sat-
urn, Uranus, and Neptune). Their most distinctive features
consist in their interlaced, greatly inclined, and extremely ec-
centric orbits ; their extraordinary smallness, as the diameter
of Vesta does not appear to equal even the fourth part of the
diameter of Mercury. When the first volume of the Cosmos
appeared (1845), only four of the small planets were known :
Ceres, Pallas, Juno, and Vesta, discovered by Piazzi, Olbers,
and Harding (between January 1, 1801, and March 29, 1807) ;
at the present time (July, 1851), the number of the small
planets has already increased to 14 ; they form numerically

* Cosmos, vol. iv., p. 101. With regard to the chronology of the dis-
coveries of the small planets, compare p. 100 and 131 ; their relations
of magnitude to the meteor-asteroids (aerolites), p. 105. With respect
to Kepler's conjecture of the existence of a planet in the great chasm
between Mars and Jupiter — a conjecture, hov^rever, w^hich by no means
led to the discovery of the first of the small planets ( Ceres), compare p.
111,116, and 117, note t. The bitter reproach which has been thrown
upon a highly esteemed philosopher, " because at a time when he might
have known of Piazzi's discovery certainly five months before, but was
unacquainted with it, he denied not so much the probability, as much
more the necessity of a planet being situated between Mars and Jupi-
ter," appears to me to be little justifiable. Hegel, in his Dissertatio de
Orbitis Planetarum, composed in the spring and summer of 1801, treats
of the ideas of the ancients of the distances of the planets ; and when
he quotes the arrangement of which Plato speaks in the Timceus (p.

35, Steph.), 1.2. 3. 4. 9. 8. 27 (compare Cosmos, vol. iv., p.

109, note X), he denies the necessity of a chasm. He says only, "Quae
series « verior naturce ordo git, quam arithmetica progressio, inter quar-
tum et quintum locum magnum esse spatium, neque ibi planetam de-
siderari apparet." " If the order of nature is more precise tiian an
arithmetical progression, there appears to be a great space between
the fourth and fifth place, and that no planet is required there." (He-
gel's WerTce, bd. xvi., 1834, p. 28; and Hegel's Leben von Rosenkranz ,
1844, p. 154.) Kant, in his ingenious work, Naturgeschichte desHim-
mels, 1755, says merely that at the time of the fonnation of the planets,
Jupiter occasioned the smallness of Mars by the enormous attractive
force which the former possessed. He only once mentions, and then
'n a very indecisive manner, " the members of the solar system which
are situated far from each other, and between which the intermediate
parts have not yet been discovered." Immanuel Kant, SdmmtlichA
Werke, th. vi., 1833 p. 87, 110, and 1913.)

?62 COSMOS

the thiid part of all the 43 known planetary bodies, i. 0., of
all principal and secondary planets.

Although the attention of astronomers was long directed
m the solar regions to increasing the number of the members
of partial systems — the Moons which revolve round principal
planets — and to the planets to be discovered in the furthest
regions beyond Saturn and Uranus, now, since the accidental
discovery of Ceres by Piazzi, and especially since the foreseen
discovery of Astrea by Encke, as well as the great improve-
ments in the star-charts* (those of the Berlin Academy con-
tain all stars as far as the 9th, and partly to the 10th mag-
nitudes), a nearer space presents to us the richest, and per-
haps inexhaustible field for astronomical industry. It is an
especial merit of the Astronomischeii Jahrbuch, which is
published in my native town by Encke, the Director of the
Berlin Observatory, with the assistance of Dr. Wolfers, that
the ephemerides of the increasing host of small planets are
treated of with particular completeness. Up to the present
time, the region nearest to the orbit of Mars appears to be
the most filled ; but the breadth of this measured zone is in
itself more considerable than the distance of Mars from the
Sun,t " when the difierence of the radii-vectores in the near-
est perihelion (Victoria) and the most distant aphelion (Hy-
giea) is taken into consideration."

The eccentricities of the orbits, of which those of Ceres,
Egeria, and Yesta are the smallest, and Juno, Pallas, and
Iris the greatest, have already been alluded to$ above, as
well as their degrees of inclination toward the ecliptic, which
decreases from Pallas (34° 37') and Egeria (16° 33') to Hy-
giea (3° 47'). A tabular view of the elements of the small
planets follows here, for which I am indebted to my friend
Dr. Galle.

* With regard to the influence of improved star-charts upon the dis-
eovery of the small planets, see Cosmos, vol. iii., p. 116.

t D'Arrest, Ueber das System der Kleinen Planeten zwischen Mara mu-
fupiter, 1851, p. 8. X Cosmos, vol. iv., p. 102 and 172.

THE SMALL PLANETS.

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164 COSMOS

The aisoovery of a fifteenth new planet (Eunomia) hat
just been announced. It was discovered by De Gasparis
upon the 19th of July, 1851. The elements, which have
been calculated by Riimker, are the following :

Epoch of mean longitude in mean Greenwich time. ) o t 1 -f)

Mean longitude 321° 25' 29"

Longitude of perihelion 27 35 38

Longitude of ascending node 293 52 55

Inclination 11 48 43

Eccentricity 0-188402

Half major axis 2-64758

Mean of motion 823-C30

Period of revolution 1574 days.

The mutual relation of the orbits of the asteroids and the
enumeration of the individual pairs of orbits has been made
the subject of acute investigation, first by Gould^ in 1848, and
more recently by D'Arrest. The latter says, " The strongest
evidence of the intimate connection of the whole group of
small planets appears to be, that if the orbits are supposed to
be represented materially as hoops, they all hang together in
such a manner that the whole group may be replaced by an^
given one. If it so happened that Iris, which Hind discov-
ered in August, 1847, was still unknown, as many other bod-
ies in this region certainly are, the group would consist of two
separate parts — a result which must appear so much the more
unexpected, as the zone which these orbits occupy in the solar
system is wide."t

We can not take leave of this wonderful group of planets
without mentioning, in this fragmentary enumeration of the
individual members of the solar system, the bold view of a
gifted and deeply investigating astronomer as to the origin of
the asteroids and their intersecting orbits. A result deduced
from the calculations of Gauss, that Ceres approaches extreme-
ly near to Pallas in her ascending passage through the plane
of that planet's orbit, led Olbers to form the conjecture that
" both planets, Ceres and Pallas, maybe fragments of a sin-
gle large principal planet which has been destroyed by some
natural force, and formerly occupied the gap between Mars
and Jupiter, and that the discovery of an additional number
of similar fragments which describe elliptical orbits round the
Sun, in the same region, may be expected."!

* Benjamin Althorpe Gould (now at Cambridge, Massachusetts,
U. S.), Untersuchungen uber die gegeruseitige Lage der Bahnen zwischen
Mars und Jupiter, 1848, p. 9-12. t D'Arrest, op. cit., p. 30.

X Zach, Monatl. Ccrresp., bd> vi., p. 88.

JUPITER. 165

The possibility of determining by calculation, even approx-
imatively, the epoch of such a cosmical event, which it is sup-
posed would be at the same time the epoch of the formation
of the small planets, remains more than doubtful, from the
complication produced by the already large number of the
" fragments" known, the peculiar retrogression of the apsides,
and motion of the nodes.* Olbers describes the region of the
nodes of the orbits of Ceres and Pallas as corresponding to
the northern wing of the Virgin and the constellation of the
Whale. Certainly Juno was discovered in the latter by
Harding, though accidentally, in the construction of a star-
catalogue, scarcely two years after the discovery of Pallas,
and even Yesta in the latter, after a long search during five
years, conducted upon hypothesis. This is not the place to
determine whether these results alone are sufficient to estab-
lish the hypothesis. The cometary clouds, in which the small
planets were at first supposed to be enveloped, have disap-
peared on investigation with more perfect instruments. The
considerable changes of light to which they were said to be
^ibject were ascribed by Olbers to their irregular figure as
oeing " fragments of a single destroyed planet."!

Jupiter.

The mean distance of Jupiter from the Sun, expressed in
fractional parts of the Earth's distance from the central body,
amounts to 5-202767. The true mean diameter of this plan-
et, the largest of all, is 77,176 geographical miles; equal,
therefore, to 1 1-255 terrestrial diameters, about one fifth great-
er than the diameter of the more remote Saturn. His side-
real revolution occupies lly. 314d. 20h. 2m. 7s.

The flattening of Jupiter, according to the measurements
by Arago with the prismatic micrometer (which were intro-
duced into the Exposition du Systeme du Monde, p. 38),
is as 167 : 177, consequently y|.y, which agrees very closely
with the later determination (1839) of Beer and Madler,t

• Gauss, Monatl. Corresp., bd. xxvi., p. 299.

t Mr. Daniel Kirkwood (of the Pottsville Academy) has ventured
upon the undertaking of restoring the exploded primitive planet from
the fragmentary remains in the saitie manner as the animals of the prim-
itive Earth. He finds for it a diameter greater than Mars (of more
than 4320 geographical miles), and the slowest rotation of all the priu-
cipal planets — a length of day of fifty-seven hours and a half. (Report
of the British Assoc, 1850, p. xxxv.)

}. Beer and Madler, Beitrdge zur Phys. Kenntniss der Himl. Korpevt
p. 104-106. Older and le*.s certain observations by Hussey gave ^^.

166 COSMOS.

^^ho found the flattening to "be between yi if and ^| g. Han-
sen and Sir John Herschel give the preference to Jj. The
earliest observation of the flattening, by Dominique Cassini,
is older than the year 1666, as I have already pointed out
elsewhere. This circumstance has an especial historical im«
portance, on account of the influence which, according to Sir
David Brewster's acute remark, the discovery of this flatten-
ing by Cassini exercised upon Newton's ideas as to the figure
of the Earth. The Frincipia PhilosophicB Naturalis bears
witness to this, but the epochs at which the Principia and
Cassini's observation of equatorial and polar diameters of
Jupiter appeared, might excite chronological doubts.*

As the mass of Jupiter after that of the Sun is the most
important element of the whole planetary system, its accurate
determination, which has recently been effected through the
disturbances of Juno and Vesta, as well as by the elongation
of his satellites, especially the fourth,! must be considered as
one of the most productive improvements of calculating astron-
omy. The valua of the mass of Jupiter is greater now than
formerly ; that of Mercury, on the contrary, smaller. The
former, together with that of the four satellites, is to4 7^T9'
while Laplace gave it as yoeVog-^

Jupiter's period of rotation is, according to Airy, 9h. 55'
21 "-3 mean solar time. Dominique Cassini first found it
(1665) to be between 9h. 55m. and 9h. 56in., by means of a
spot which was visible^ for many years, even indeed to 1691,
and was always of the same color and outline. Tho greater
part of these spots are of greater blackness than the streaks
upon Jupiter. They do not, however, appear to belong to

Laplace {Syst. du Monde, p. 266) found it theoretically between -^^
and -^^j with increasing density of the strata.

* Newton's immortal work, Philosophice Naturalis Principia Mathe
matica, appeared as early as May, 1687, and the papers of the Paris
Academy did not contain the notice of Cassini's determination of the
flattening (y^^) until the year 1691 ; so that Newton, who might cer-
tainly have known of Richer's pendulum-experiment at Cayenne, fronr
the account of the journey printed in 1679, must have become acquaint-
ed with the configuration of Jupiter by verbal intercourse and the act-
ive correspondence of that time. With regard to this subject, and tho
only apparent early acquaintance of Huygens with the pendulum-ex
periment of Richer, compare Cosmos, vol. i., p. 165, note, and vol. ii.,
p. 146, note.

t Airy, in the Mem. of the Royal Astron. Soc., vol, ix., p. 7 ; vol. x.,
p. 43.

t As early as the year 1824. (Laplace, op. cit., p. 207.)

$ Delambre, /fW. de t Astron. Mod., torn, ii., p. 754.

JUPITER. 167

the surface of the planet itself, as they sometimes have a dif-
ferent velocity from that of the equatorial regions. Accord-
ing to a very experienced observer, Heinrich Schwahe, of Des-
sau, the dark, more sharply-bounded spots have been several
years in succession exclusively peculiar to the two gray gir
dies bordering upon the equator, sometimes the north and
sometimes the south. The process of spot-formation is, there-
fore, locally variable. Schwabe's observations, made in No-
vember, 1834, likewise show, that the spots on Jupiter, seen
with a 280-fold magnifying power in a Fraunhofer telescope,
sometimes resemble the small nucleoid spots surrounded by
a halo upon the Sun. But still their darkness is less than
that of the satellite shadows. The nucleus is probably a part
of the body of Jupiter itself, and if the atmospheric opening
remains fixed above the same spot, the motion of the spots
gives the true rotation. They also separate sometimes, like
the Sun-spots, as Dominique Cassini discovered as early as
1665.

In the equatorial zone of Jupiter are situated two broad
principal streaks or girdles, of a gray or grayish-brown col-
or, which become paler toward the edges, and finally disap-
pear entirely. Their boundaries are very irregular and va-
riable ; both are separated by an intermediate bright equa-
torial streak. Toward the poles, also, the whole surface is cov-
ered with numerous, narrower, paler, frequently interrupted,
even finely branched streaks, always parallel to the equator.
*' These phenomena," says Arago,^ "are most easily explain-

* " On salt qii'il existe au-dessus et au-dessous de I'equateur de Ju-
piter deux baiides moins brillantes que la surface generale. Si on les
examine avec une lunette, elles paraissent moins distinctes el mesure
qu'elles s'eloiment du centre, et m6me elles deviennent tout-4-fait in-
visibles pres des bords de la planete. Toutes ces apparences s'expli-
quent en admettant I'existence d'une atmosphere de nuages inter-
rompue aux environs de I'equateur par une zone diaphane, produite
peut-etre par les vents alises, L'atmosphere de nuages reflechissaut
plus de lumi^re que le corps solide de Jupiter, les parties de ce corps
que Ton verra k travers la zone diaphane, auront moins d'eclat que le
reste et formeront les bandes obscures. A mesure qu'on s'eloignera du
centre, le rayon visuel de I'observateur traversera des epaisseurs de plus
en plus grandes da la zone diaphane, en sorte qu'jl la lumiere reflechie
par le corps solide de la planete s'ajoutera la lumiere reflechie par cett»
/one plus epaisse. Les bandes sei'ont par cette raison moins obscures
en s'eloignant du centre. Enfin aux bords memes la lumidre reflechie
par la zone vue dans la plus grande epaisseur pourra faire disparaitre la
difference d'intensite qui existe entre les quantit^s de lumiere reflechie
par la planete et par l'atmosphere de nuages; on cessera alors d'aper
cevoir les bandes qui n'oxistent qu'en vertu de cette difference. Oo

168 COSMOS".

able by assuming the existence of an atmosphere partially
condensed by strata of clouds, in which, however, the region
resting upon the equator is free from vapor and diaphanous
probably in consequence of the trade-winds. Since, as Will-
iam Herschel already assumed in a treatise in the 83d vol.
of the Philosophical Transactions, which appeared in 1793,
the cloud-surface reflects a more intense light than the sur-
face of the planet, so that part of the ground which we see
through the clearer air must have less light (appear darker)
than the strata of clouds reflecting large quantities of light.
On that account gray (dark) and clear bands alternate with
each other ; the former appear so much the less dark-colored
in proportion to the distance from the center, when, the visual
radius of the observer being directed obliquely toward the edge
of the planet, at a small angle, they are seen through a larger
and thicker mass of atmosphere, reflecting more light.

observe dans les pays de montagnes quelque chose d'analogue : quand
on se trouve pres d'un for^t de sapin, elle paralt noire ; mais k mesure
qu'on s'en 61oigne, les couches d'atmosph^re interposees deviennent de
plus en plus epaisses et reflechissent de la lumiere. La difference de
teinte entre la foret et les objets voisins diminue de plus en plus, elle
finit par se confondre avec eux, si I'on s'en eloigne d'une distance con-
venable." (From Arago's Reports on Astronomy, 1841.) " It is known
that there exist above and below^ the equator of Jupiter two bands less
brilliant than the general surface. If these are examined with a tel-
escope, they appear less distinct in proportion as the distance from the
center increases, and they even become quite invisible near the edges
of the planet. All these appearances may be explained by admitting
the existence of an atmosphere of clouds, internipted near the equatot
by a transparent zone, produced, perhaps, by the trade-winds. The at-
mosphere of clouds reflects more light than the solid body of Jupiter.
Those parts of him which are seen through the transparent zone would
have less brightness than the remainder, and would form obscure bands.
In proportion as the distance from the center increases, the visual ray
of the observer traverses greater and greater thicknesses of the trans
parent zone, in such a way that to the light reflected by the solid body
of the planet is added the light reflected by the denser zone. The
bands would be, from this reason, less obscure the greater the distance
from the center. Finally, at the very edges of the planet's disk, the
light reflected by the zone, seen in its greatest thickness, would cause
the difference of intensity which existed between the quantities of light
reflected by the planet and by the atmosphere of clouds to disappear,
and the bands which exist only in virtue of that difference would cease
to be visible. Something analogous is observed in mountainous coun-
tries ; in the neighborhood of a forest of fir-trees they appear black,
but in proportion as the observer removes to a greater distance, the
interposed atmospheric strata become thicker and thicker, and reflect
light. The difference of tint between the forest and the objects near
diminishes more and more, and ends by their being confounded to
gether on removing to a sufficieut distance."

THE SATELLITES OF JUPITER.

169

The Satellites of Jupiter.

Even so early as the brilliant epoch of Galileo, the correct
opinion was formed that the subordinate planetary system
of Jupiter might present, in many relations of space and time,
a picture in miniature of the Solar System. This view, rap-
idly diffused at that time, as well as the discovery, shortly
afterward, of the phases of Venus (February, 1610), contrib-
uted greatly to the general introduction of the Copernican
system. The quadruple group of satellites of Jupiter is the
only one of the exterior principal planets which has not been
increased by any new discovery, during a period of nearly
two centuries and a half, since the epoch of their first dis-
covery by Simon Marius on the 29th of December, 1609.

The following table contains the periods of sidereal revo-
lution of the satelhtes of Jupiter, their mean distances ex-
pressed in diameters of the primary, their diameters in geo-
graphical miles, and their masses as parts of the mass of
Jupiter.

Satellite*.

Period of Rev-
olution.

Distance from
Jupiter.

Diameter in
Geogr. Miles.

Maes.

1
2
3
4

d. h. m.

1 18 28

3 13 14

7 3 14

16 16 32

6,049

9,623

15,350

26,998

2116
1900
3104
2056

0-0000173281
0-0000232355
0-0000884972
0-0000426591

•"•^ ToTT-TT 9 expresses the mass of Jupiter with his satel-
lites, then his mass without the satellites is" TiTT/ojg" ' °^ly
about eoVo" sinaller.

The comparisons of the magnitudes, distances, and ec-
centricities with other satellite systems has already been
given {Cosmos, vol. iv., p. 105-127). The luminous in-
tensity of Jupiter's satellites is various, and not in propor-
tion to their volume, since, as a general rule, the third and
the frst, whose relation of magnitude is as 8 : 5, appear the
brightest. The smallest and densest of all — the second — is
generally brighter than the langcT fourth, which is ordinarily
called the least luminous. Accidental (temporary) fluctua-
tions in the luminous intensity have, as already remarked,
been ascribed sometimes to changes of the surface, sometimes
to obscurations in the atmosphere of the satellites.* They
all appear, moreover, to reflect a more intense light than the
primary. "When the Earth is situated between Jupiter and
the Sun, and the satellites, therefore, moving from east to
* Sir John Herschel, Oxtlines, $ 540.

Vol. IV.— H

170 COSMOS.

west; apparently enter on the eastern edge of Jupiter, they
hide from us, in their passage, successive portions of the disk
of their primary, and can be perceived with telescopes of
moderate pow^er, since they stand out in lumhious relief
from the disk. The visibility of the satellite is attended
with more difficulty the nearer it approaches the center of
the primary. From this phenomenon, which was early ob-
served. Pound, Newton's and Bradley's friend, inferred that
the disk was less luminous near the edge than at the center.
Arago considers that this assumption, renewed by Messier,
involves difficulties which can only be solved by new and
more delicate observations. Jupiter was seen without any
satellites by Molyneux in November, 1681 ; by Sir William
Herschel on the 23d of May, 1802 ; and, lastly, by Griesbach,
on the 27th of September, 1843. Such a non- visibility of the
satellites has reference, however, to the space without the
disk of Jupiter, and is not inconsistent with the theorem that
all the four satellites can not be eclipsed at one time.

Saturn.

The period of sidereal or true revolution of Saturn is 29y.
166d. 23h. 16m. 32s. His mean diameter is 62,028 geo-
graphical miles, equal to 9022 terrestrial diameters. The
period oi rotation, deduced from the observation of some dark
spots (knot-like condensations of the bands) upon the surface,*
is lOh. 29m. 17s. Such a great velocity of rotation corre-
sponds to the considerable ^«^^em?^g•. William Herschel esti-
mated it, in 1776, at -^^.^ ; Bessel, after corresponding observ-
ations during a period of more than three years, found that at

* The earliest and careful observations of William Herschel, in No-
vember, 1793, gave for Saturn's period of rotation lOh. 16m. 44s. It
has been incorrectly attributed to the great philosopher, Immanuel
Kant, that he conjectured the period of Saturn's rotation from theo-
retical considerations in his Allgemeincn Naturgeschichte des Himmels,
forty years before Herschel. The number that he gives is 6h. 23m.
53s. He calls his determination " the mathematical calculation of an
unknown motion of a heavenly body, which is, perhaps, the only pre-
diction of that kind in pure Natural Philosophy, and awaits confirma-
tion at a future period." This confirmation of his conjecture did not
take place at all ; observations have shown an error of f of the whole,
i. e., of four hours. In the same work it is said respecting the ring of
Saturn,. " that in the aggregation of particles which constitute it, those
of the inner edge complete their revolution in 10 hours, those of tho
external edge in 15 hours. The first of these ring-numbers is the only
one which accidentally comes near the planet's observed period of ro-
tation (lOd. 29m. 17s.). Compare Kant, Sdmmtlicke Werke, th. vir., 1389
p. 135 and 140.

SATURN. 171

a mean distance the polar diameter was 15"-381 ; the equato-
rial diameter 17"-053, consequently a flattening of y^ 3 .^ The
body of the planet has also ribbon-like stripes, which are, how-
ever, less perceptible, though, at the same time, rather broader
than those of Jupiter. The most constant of them is a gray
equatorial stripe. Next to this follow several others, but
with variable forms, indicating an atmospheric origin. Will-
iam Herschel did not always find them parallel to the rings,
neither do they extend as far as the poles. The region round
the poles presents a very remarkable phenomenon, a change
in the reflection of light which is dependent upon Saturn's
seasons. This region is more brightly luminous in Avinter, a
phenomenon which calls to mind the variable snow-region of
Mars, and did not escape the penetration of William Herschel,
Whether such an increase of luminous intensity is to be as-
cribed to the temporary formation of ice and snow, or to an
extraordinary accumulation of clouds,! it is still indicative of
the action of changes in temperature, and of the existence of
an atmosphere.

We have already stated the mass of Saturn to be ^iItq •
it, together with the enormous volume of the planet (its diam-
eter is I of the diameter of Jupiter), leads us to infer a very
small density decreasing toward the surface. If the density
were quite homogeneous (yVo of that of water), the flattening
would be still greater.

The planet is surrounded in the plane of its equator with
at least two fully suspended and extremely thin rings, both
situated in the same plane. Their luminous intensity is great-
er than that of Saturn itself, and the outer ring is still brightei
than the inner.$ The division of the ring seen by Huygens
in 1655, as a single one,§ was indeed observed by Dominique

* Laplace {Expos, du Syst. du Monde, p. 43) estimates the flattening
at JL. The extraordinary deviation of Saturn from the spheroidal fig
ure, according to which William Herschel, after a series of laborious
observations, made with very different telescopes, found the major axis
of the planet, not in the equator itself, but in a diameter which inter-
sected the equatorial diameter at an angle of about 45°, was not con-
firmed by Bessel, but found to be incorrect.

t Arago, Annuaire for 1842, p. 555.

X This difference in the luminous intensity of the outer and inner
rings was also stated by Domini(^ue Cassini {M6m. de VAcad&mie dea
Sciences, annee, 1715, p. 13).

$ Cosmos, vol. ii., p. 323. The public announcement of the discovery,
or, rather, the complete explanation of all the phenomena which are
presented by Saturn and his ring, did not take place until the year
1659, four years afterward, in the Sy sterna SatumiTim.

172 COSMOS.

Cassiniin 1 675, but first accurately described by William Her
schel in 1789-1792. Since Short's time the outer has been
found to be streaked by numerous fine stripes, but these lines
or stripes have never been constant. Very recently, during
the latter months of the year 1850, a third very pale, feebly
luminous, and darker ring has been discovered between the
planet and the ring hitherto called the inner one. The dis-
covery was made nearly simultaneously by Bond, at Cam-
bridge (U. S.), on the 11th of November, by means of the
great refractor of Mertz with a fourteen-inch object-glass, and
by Dawes, near Maidstone, on the 25th of November. This
ring is separated from the second by a black line, and occu-
pies the third part of the space, between the second ring and
the body of the planet, which was formerly stated to be va-
cant, and through which Derham affirmed that he saw small
stars.

The dimensions of the divided ring of Saturn have been de-
termined by Bessel and Struve. According to the latter, the
exterior diameter of the outer ring, at Saturn's mean distance,
appears to us under an angle 40"'09, equal to 153,200 geo-
graphical miles ; the interior diameter of the same ring, un-
der an angle of 35"-29, equal to 134,800 geographical miles.
For the exterior diameter of the inner (second) ring is ob-
tained 34"-47 ; for interior diameter of the same ring, 26"-67.
Struve fixes the space between the last-mentioned ring and
the surface of the planet at 4"-34. The entire breadth of the
first and second rings is 14,800 miles; the distance of the
rings from the surface of Saturn, about 20,000 ; the space
which separates the first from the second ring, and which
represents the black line of division seen by Dominique Cas-
sini, is only 1560 miles. The mass of the rings is, according
to Bessel, yj-j of the mass of Saturn. They present a few
elevations^ and irregularities, by means of which it has been
possible to determine approximatively their period of rotation
— exactly the same as that of the planet. The irregulari-
ties of form become perceptible on the disappearance of the
nngs, when one is generally lost sight of before the other.

A very remarkable phenomenon was discovered by Schwabe,
at Dessau, in September, 1827 — the eccentric position of Sat-
urn. The ring is not concentric with the planet itself, but

♦ Such mountain-like inequalities of surface have recently been again
noticed by Lassell in Liverpool, by means of a twenty-feet reflecting
telescope of his ow^n construction. — Report of the British Associationp
1850, p. 35.

SATURN. 173

the latter is situated somewhat to the westward. This ob-
servation has been confirmed — partly by micrometi cal meas-
urements— by Harding, Struve,* John Herschel, and South.
The small differences in the degree of eccentricity, appearing
periodically, which result from the corresponding observations
of Schwabe, Harding, and De Vico in Rome, are perhaps con-
sequences of oscillations of the center of gravity of the ring
about the geometrical center of Saturn. It is surprising that,
so early as the end of the seventeenth century, a priest of
Avignon, nsLmed Gallet, attempted unsuccessfully to direct
the attention of astronomers to the eccentric position of Sat-
urn, t With the extremely minute density of Saturn (per-
haps scarcely | the density of water) and its decrease toward
the surface, it is difficult to form a conception of the molecu-
lar condition or material constitution of the body of the plan-
et, or even to decide whether this constitution actually pre-
supposes fluidity, i. e., mobility of the smallest particles, or
solidity, according to the frequently adduced analogies of
pine wood, pumice-stone, cork, or a solidified liquid — ice.
Horner, the astronomer of the Krusenstern expedition, calls
the ring of Saturn a train of clouds ; he maintains that the
mountains of Saturn consist of masses of vapor.$ Conjec-
tural astronomy exercises here an unrestricted and tolerated
play. Of an entirely different nature are the serious specu-
lations of two distinguished American astronomers. Bond and
Peirce, as to the possible stability of Saturn's rings, founded
upon observations and the analytical calculus. § Both agree

* Compare Harding's Kleine Ephemeriden for 1835, p. 100; and
S*.ruve, in Schumacher's Astr. Nachr., No. 139, p. 389.

t la the Aciis Eruditorum pro anno 1684, p. 424, is an extract from
the Systema PhcEuomenorum, Saturni, autore Galletio, proposito eccl.
Avenionensis : " Nonnuuquam corpus Saturni non exacie annuli medium
obtinere visum fuit. Hinc evenit, ut, quum planeta orientalis est, cen-
trum ejus extremitati orientali annuh propius videatur, et major pars
ab occidentali latere sit cum ampliore obscuritate." "Sometimes the
mass of Saturn appeared not to reach exactly the middle of his ring.
Hence it happens that when that planet is in the east, his center appears
nearer to the eastern extremity of the ring, and the greater part is away
from the western side with greater obscurity."

X Horner, in Gehlen's Neiiem Physik. Wdrterb., bd. viii., 1 836, p. 174.

§ Benjamin Peirce, On the Constitution of Saturn'' s Rii.g,'\u. Gould's
Astron. Journal, 1851, vol. ii., p. 16. "The ring consists of a stream
or of streams of a fluid, rather denser than water, flowing round the
primary." Compare also Silliman's Amer. Journal, ser. ii., vol. xii,,
1851, p. 99; and with regard to the superficial inequalities of the ring,
as well as disturbing and consequently preserving influences of the sat-
ellites Sir John Herschel, Outlines, p. 320.

174

COSMOS.

in their results in favor of fluidity, as well as continuous vari-
ability in the figure, and divisibility of the outer ring. The
permanence of the whole is considered by Peirce as depend-
ent upon the influence and position of the satellites, because
without this dependence, even with inequalities in the ring,
the equilibrium could not be maintained.

The Satellites of Saturn.

The five satellites of Saturn which have been known lon-
gest were discovered between the years 1655 and 1684 (Ti-
tan, the sixth according to distance, by Huygens ; and four
by Cassini, viz., Japetus, the outermost of all, Rhea, Tethys,
and Dione). These were followed by the discovery, by Will-
iam Herschel, in 1789, of two, Mim^as and Enceladus, situ-
ated nearest to the planet. Finally, the seventh satellite,
Hyperion, the last but one according to distance, was dis-
covered almost simultaneously by Bond, at Cambridge (U. S.),
and by Lassell at Liverpool, in September, 1848. The rela-
tive magnitudes and relations of distances in this partial sys-
tem have been already treated of {Cosmos, vol. i., p. 97 ;
vol. iv., p. 105-118.) The periods of revolution and the
mean distances, the latter expressed in fractional parts of the
equatorial radius of the primary, are, according to the observ-
ations instituted by Sir John Herschel at the Cape of Good
H.ope,='^ between 1835 and 1837, the following :

Satellites according

Satellites accord-

to the Order of their

ing to their Dis-

Period of Revolution.

Mean Distance.

Discovery.

tances.

f

1. Mimas

0 22 37 22-9

3-3607

g

2. Enceladus

1 8 53 6-7

4-3125

e

3. Tethys

1 21 18 25-7

5-3396

d

4. Dioue

2 17 41 8-9

6-8398

c

5. Rhea

4 12 25 10-8

9-5528

a

6. Titan

15 22 41 25-2

22-1450

h

7. Hyperion

22 12 ?

28-0000?

b

8. Japetus

79 7 53 40-4

64-3590

Between the first four satellites nearest to Saturn a re-
markable relation oi commensurability in the period of rev-
olution presents itself. The period of the third satellite ( Te-
thys) is double that of the first {Mimas) ; that of the fourth
(Dione) double that of the second {Enceladus). The close-

* Sir John Herschel, Results of Astron. Observations at the Cape of
Good Hope, p. 414-430 ; the same, in the Outlines of Astr., p. 650, and
apon the law of distances, $ 550.

URANUS. 175

ness of this relation extends to ji^ of the longer periods.
This unnoticed result was communicated to me by Sir John
Herschel in a letter as long back as 1845. The four satel-
lites of Jupiter present a certain regularity in their distances,
forming very nearly the series 3, 6, 12. The distance of the
second from the first, expressed in diameters of Jupiter, is
3-6 ; the distance of the third from the second, 5*7 ; that of
the fourth from the third, 11-6. Moreover, Fries and Chal-
lis have endeavored to prove the so-called law of Titius in all
•satellite systems, even in that of Uranus.^

Uranus.

The acknowledged existence of this planet, the great dis-
covery of William Herschel, has not only increased the num-
ber of the principal planets known for thousands of years, and
more than doubled the diameter of the solar regions — it has
also, after the lapse of sixty-five years, led to the discovery of
Neptune, through the disturbances which it underwent from
the influence of the latter. Uranus was discovered accident-
ally (13th March, 1781), during the examination of a small
group of stars in Gemini, by its small disk, which, with mag-
nifying powers of 460 and 932, increased far more consider-
ably than was the case with other adjacent stars. The saga-
cious discoverer, so thoroughly acquainted with all optical phe-
nomena., also observed that the luminous intensity decreased
considerably in proportion as stronger magnifying powers
were employed, while in the fixed stars (6th and 7th magni-
tude) it remained nearer the same.

When Herschel first announced the existence of Uranus,
he called it a comet,-f and it was only by the united labors of
Saron, Lexell, Laplace, and Mechain, which were consider-
ably facilitated by the discovery made by the meritorious
Bode, in 1784, of the previous observations of the planet by
Tobias Mayer (1756) and Flamstead (1690), that the ellip-
tical orbit of Uranus and the whole of its planetary elements
were determined with admirable celerity. According to Han-
sen, the mean distance of Uranus from the Sun is 1,918,239,
or 1585 million geographical miles; his period of sidereal
revolution 84y. 5d. 19h. 41m. 36s.; the inclination of his

orbit to the ecliptic, 0° 46' 28" ; his apparent diameter at

•>

* Fries, Vorlesungen iiher die Stemhunde, 1833, p. 325 ; Challis, in the
Transact, of the Cambridge Philos. Society, vol. iii., p. 171.

t William Herschel, Account of a Comet in the Philos. Transact, for
I781,vol, Ixxi., p. 492.

176 COSMOS.

the mean distance from the Earth, 9"-9. His ?nass, which
was determined as y Tj-g-yj from the first observations of the
BateUites, is, according to Lamont's observations, only 24^0 s >
consequently his dmisity would be between those of Jupiter
and Saturn.* A flattening of Uranus was already conjec-
tured by Herschel from his -observations with magnifying
powers of from 800 to 2400. According to Madler's meas-
urements in 1842 and 1843, it would appear to fall between
y^-Y and g?^.! The original supposition that Uranus had
two rings was found to be an optical illusion by the discoverer
himself, in all cases so cautious and persevering in confirming
his discoveries.

The Satellites of Uranus.

" Uranus," says Sir John Herschel, " is attended by satel-
lites— four, at least, probably five or six." They present a
great and hitherto unparalleled peculiarity, viz., that while
all satellites (those of the Earth, of Jupiter, of Saturn), as
well as all the principal planets, move from west to east, and
with the exception of a few asteroids, in orbits not much in-
clined toward the ecliptic, the satellites of Uranus move from
east to west in orbits which are nearly circular, and form an
angle of 78° 58' with the ecliptic — ^very nearly perpendicu-
lar to it. In the case of the satellites of Uranus, as well aa
those of Saturn, the arrangement and nomenclature, accord-
ing to their distances from the primary, are to be distin-
guished from the arrangement according to the epoch of
discovery. According to a private communication from Six
John Herschel (November 8th, 1851), Mr. Lassell has dis-
tinctly observed on the 24th, 28th, and 30th of October, and
2d of November of the above year, two satellites of Uranus.,
which appear to be situated still nearer to the primary than
the first satellite observed by Sir William Herschel, to which
he ascribed a period of revolution of about 5 days and 21
hours, but which was not recognized. The periods of revo-
lution of the two satellites now seen by Lassell were near to
4 and 21 days. Of the satellites of Uranus, the second and
fourth were first discovered by William Herschel in 1787,
then the first and fifth in 1790, and, finally, the sixth and
third in 1794. During the fifty-six years which have elapsed
since the last discovery *bf a Uranus satellite (the third), the

* Cosmos, vol. iv., p. 119.

t Madler, in Schumacher's Astr. Nachr., No. 493. (With regard to
the flattening of Uranus, compare Arago, Annn,i^re for 1842, p. 577-579.)

NEPTUNE. 177

existence of six satellites has frequently "been unjustly doubt-
ed ; the observations of the last twenty years have gradually
proved how trustworthy the great discoverer of Slough has
been in this as in all other branches of planetary astronomy.
Those satellites of Uranus which have been seen again up to
this time are the first, second, iourth, and sixth. Perhaps it
may be ventured to add the third, after the observations of
Lassell on the 6th of November, 1848. On account of the
large opening of his reflecting telescope, and the abundance
of hght thus obtained, the elder Herschel considered that
with the sharpness of his vision, under favorable atmospheric
circumstances, a magnifying power of 157 was sufficient ; his
son recommends, in general, a power of 300 for these ex-
tremely small luminous disks (luminous points). The second
and fourth satellites were seen again the earliest, the most
frequently and positively by Sir John Herschel, from 1828 to
1834, in Europe and at the Cape of Good Hope, subsequently
by Lament at Munich and Lassell at Liverpool. The first
satellite of Uranus was found by Lassell (September 14th to
November 9th, 1847), and by Otto Struve (October 8th to
December 10th, 1847). The outermost (the sixth) by La-
ment (October 1st, 1837). The fifth appears never to have
been seen again, and the third not satisfactorily enough.^
The particulars here put together are not without importance,
also for the reason that they tend to excite caution in not
placing too much confidence in so-called negative evidence.

Neptune.

The merit of having successfully conducted and announced
an inverse problem of disturbance, that " of deducing from
the given disturbances of a known planet the elements of an
unknown one," and even of having, by a bold prediction, oc-
casioned the important discovery of Neptune by Galle on the
23d of September, 1846, belongs to the faculty of acute rea-
soning and the persevering industry of Leverrier.f This is,
as Encke expresses himself, the most brilliant of all planeta-
ry discoveries, because purely theoretical investigations have
rendered possible the prediction of the existence and the
place of the new planet. The celerity with which the plan-

* For the observations of Lassell at Starfield (Liverpool), and of Otta
Struve, compare Monthly Notices of the Royal Astron. Soc, vol. viii.,
1848, p. 43-47 and 135-139 ; also Schum., Asfr. Nachr., No. 623, p. 3fi5

t Berhard von Liadenau, Beitrag zur Gcschichte der Neptuns-xhi:-
deckung, in the supplementary sheet to Schum. Astr. Nachr., ] 849, p i

H 2

178 COSMOS.

et was afterward found was itself favored by the excellent
star-chart drawn up by Bremiker for the Berlin Academy. =^

While among the distances of the exterior planets from the
Sun, that of Saturn (9 53) is nearly double as great as the
distance of Jupiter (5-20), t^ distance of Uranus (19-18) is,
however, tnore than double that of Saturn ; so the distance
of Neptune (30-04) is less than that which would be re-
quired for a repeated doubling of the distance by full ten
times the distance of the Earth from the Sun, i. e., an entire
third of Neptune's distance from the Sun. The ^^Za^ie^ary
boundaries were at that time 2484 million of geographical
miles from the central body. By the discovery of Neptune,
the landmark of our planetary knowledge has been advanced
more than 892 million miles further (more than 10-8 times
the distance of the Sun from the Earth). According as the
disturbances are recognized which each last planet expe-
riences, so will other planets be gradually discovered which
now remain invisible by means of our telescopes on account
of their remoteness.!

According to the most recent determinations, Neptune's
period of revolution is 60126-7 days, or 164 years and 226
days, and his half major axis 30-03628. The eccentricity
of his orbit, next to that of Venus the smallest, is 0-00871946 ;
his mass, 74 ^4 e \ his apparent diameter, according to Encke
and Cxalle, 2"-70, according to Challis even 3"-07, which
gives as his density, in comparison with the Earth, 0-230 ;
greater, therefore, than that of Uranus 0-173.$

Soon after the first discovery of Neptune by Galle, a ring
was ascribed to him by Lassell and Challis. The former em-
ployed a magnifying power of 567, and endeavored to determ-
ine the considerable inclination of the ring to the ecliptic ; but
subsequent investigations have, as long before in the case of
Uranus, contradicted the opinion of the existence of a ring
round Neptune.

I dare scarcely allude in this work to the certainly earlie'
labors of the distinguished and acute English geometrician,

* Astr. Nachr., No. 580.

t Leverrier, Recherches sur les Movvemens de la Planete Herschel,
1846, in the Connaissance dcs Temps pour Van 1849, p. 254.

X The very important element of the mass of Neptune has been grad-
nally increased from -^^^^y accordhig to Adams, y^|y^ according to
Peirce, -^^^^ according to Bond, and ^itw according to Sir John
Herschel, y^|^^ according to Lassell, to y^j^^ according to Otto and
August Struve. The last result has been adopted in the text.

NEPTUNE. 179

Mr. Adams, of St. John's College, Cambridge. The historic-
al facts which refer to these labors, and to Leverrier's and
Galle's happy discovery of the new planet, have been circum-
stantially and impartially developed from reliable sources in
two works, by the astronomer royal, Airy, and by Bernhard
von Lindenau.=^ Intellectual endeavors, almost' simultane-

* Airy, in the Monthly Notices of the Royal Astronomical Society, vol.
vii.-, No. 9 (November, 1846), p. 121-1.52. Bernhard von Lindenau,
Beitrag ziir Geschichte des Neptuns-Entdechmig, p. 1-32, and 235-238.
At the instigation of Arago, Leverrier commenced, in the summer of
1845, his investigations of the theory of Uranus. The results of this in-
vestigation he laid before the Institute on the 10th of November, 1845,
the 1st of June, 31st of August, and 5th of October, 1846, and published
them at the same time ; but the most extensive and important of Lever-
rier's labors which contained the solution of the whole problem appeared
in the Connaissance des Temps four Van 1849. Adams laid the first
results which he had obtained for the disturbing planet before Profes-
sor Challis in September, 1845, without having them printed, and, to
gether with some alterations in October of the same year, before the
astronomer royal, still without making them public. The latter re-
ceived the final results of Adams, with fresh corrections referring to a
decrease of the distance, in the commencement of September, 1846.
The young Cambridge geometrician expresses himself upon the chro-
nological succession of the investigations which were directed to one
and the same object with as much modesty as self-denial : " I mention
these earlier dates merely to show that my results were arrived at in-
dependently and previously to the publication of M. Leverrier, and not
w^ith any intention of interfering with his just claims to the honor of
the discovery ; for there is no doubt that his researches were first pub-
lished to the world, and led to the actual discovery of the planet by Dr.
Galle ; so that the facts stated above can not detract in the slightest
degree from the credit due to M. Leverrier." Since, in the history of
the discovery of Neptune, mention is frequently made of an early share
which the great Konigsberg astronomer took in the hope already ex-
pressed by Alexis Bouvard (the author of the tables of Uranus) in the
year 1834, "of the disturbance of Uranus by a yet unknown planet,"
it will, perhaps, not be unacceptable to many readers of the Cosmos if
I introduce here part of a letter which Bessel wrote to me on the 8th
of May, 1840 (therefore two years before his conversation with Sir
John Herschel, during his visit to CoUingwood) : " You request me to
give you information as to the planet beyond Uranus. I could indeed
refer you to friends in Konigsberg who, from misunderstanding, fancy
that they know more about the matter than I do myself. I chose as
the subject of a public lecture delivered upon the 28th of February,
1840, the development of the connection hetween astronomical obsffnoa-
tions and astronomy. The public know no diflerence between the two;
consequently, their opinion was to be corrected. The indication of the
development of astronomical knowledge from observations naturally
led to the remark that we can by no means affirm that our theory ex-
plains all the motions of the planets. Uranus afforded a proof of this,
the old observations of which do not at all accord with elements which
coincide with the later observations from 1783 to 1820. I believe that

180 COSMOS.

ously directeu to the same important end, present in their
laudable competition so much the more interest, as they testi-
fy, by the selection of means, to the present distinguished con'
dition of higher mathematical knowledge.

The Satellites of Neptune.

While in exterior planets the existence of a ring presents
itself only in one solitary instance, and its rarity permits of
the conjecture that the organ and formation of an unconnect'
ed girdle depends upon the conjunction of peculiar and diffi*
cultly fulfilled conditions, so, on the contrary-, the existence of
satellites accompanying the exterior planets (Jupiter, Saturn,
Uranus) is a phenomenon as universal as the former is rare.
Lassell discovered with certainty* the first satellite of Nep-
tune so soon as the commencement of August, 1847, in his
large twenty- feet refl.ector, with a 24-inch aperture. Las-
sell's discovery was confirmed by Otto Struvef at Pulkowa

I once told you that I have worked much upon this subject, but have
come to no other result than the certainty that the present theory, or,
much rather, its application to the solar system, as we are acquainted
icith it, was insufficient to solve the mystery. Nevertheless, it must not,
on that account, be considered upon my opinion to be unsolvable. We
must first know accurately and completely what has been observed of
Uranus. By the aid of one of my young hearers, Flemming, I have
had all the observations reduced and compared, and thus the existing
facts now lie before me complete. While the old observations do not
agree with the theory, the more recent ones agree still less ; for now
the error is a whole minute, and increases annually about 7" to 8", so
that it will soon be much greater. I was therefore of opinion that the
time might come when the solution of this mystery might perhaps be
found in the discovery of a new planet whose elements might be ascer-
tained by its influences upon Uranus, and confirmed by those exerted
upon Saturn. That this time has already amved I am far from saying,
but I shall examine now how far the existing facts can carry us. This
is an investigation which I have pursued for so many years, and on ac-
count of which I have followed so many views, that its results espe-
cially interest me, and shall therefore be brought to an end as soon as
possible. I have great confidence in Flemming, who will, in Dantzic
to which place he has been called, continue the same reduction of ob-
servations for Saturn and Jupiter which he has now made for Uranus.
It is, in my opinion, fortunate that he has (for the present) no means
of observation, and has no lectures to deliver. A time will indeed come
when he must institute observations with a definite aim; then he should
no longer want the means of carrying them out any more than he doea
the ability to do so."

* The first letter in which Lassell announced the discovery was on
the 6th of August, 1847. (Schumacher, Astr. Nachr., No. 611, p. 165.)

t Otto Struve, in the Astr. Nachr., No. 629. August Struve, in Doi>
pat, calculated the orbit of the first satellite of Neptune from the observ
ations at Fulkowa.

COMETS. 181

(September 11th to December 20th, 1847), and Bond,* the
director of the observatory at Cambridge (U. S.), (September
16th, 1847). The Pulkowa observations gave : the period
of rotation of Neptune's satellite, 5d. 21h. 7m. ; the inclina-
tion of its orbit to the plane of the echptic, 34° 7' ; the dis-
tance from the center of the primary, 216,000 geographic-
al miles ; the 7naiS,-^-^\-^-^. Three years afterward (August
14th, 1850), Lassell discovered a second satellite, for the ex-
amination of which he employed a magnifying power of 628. t
This last discovery has not, I beheve, been' confirmed by othel
observers.

III.

THE COMETS.

The comets, which Xenocrates and Theon of Alexandria
call light-clouds, and which, according to an old Chaldean
belief, Apollonius Myndius considered to " ascend periodically
from great distances in long-regulated orbits," though subject
to the attractive force of the central body, form a peculiar
and separate group in the solar regions. They are distin-
guished from the planets, properly so called, not merely by
the eccentricity of their orbits, and, what is still more import-
ant, their intersection of the planetary orbits ; they also pre-
sent a variability of figure, a change of outline, which in some
instances has been observable during the space of a few hours ,
as, for example, in the Comet of 1744, so accurately described
by Hensius, and at the last appearance of Halley's Comet in
1835. Before Encke had discovered the existence oi inte-
rior comets of short periods of revolution, whose orbits were
inclosed within those of the planets, dogmatic speculations,
founded upon false analogies as to the increasing eccentricity,
magnitude, and decreasing density in proportion to the dis-
tance from the Sun, led to the opinion that planetary bodies
of enormous volume would be discovered beyond Saturn, re-
volving in eccentric orbits, and '' forming an intermediate
group between planets and comets, and, indeed, th at the last
exterior planet ought to be called a comet, since perhaps its
orbit intersected that of Saturn, the planet next to it.":j: Such

* W. C. Bond, in the Proceedings of the American Academy of Arts and
Sciences, vol. ii., p. 137 and 140.

t Schum., Astr. Nachr., No. 729, p. 143.

t " By means of a series of intermediate members," says Immanuet

182 COSMOS.

an opinion of the connection of forms in \ie universe, analo
gous to ihd frequently misemployed doctrine of transition in
organic nature, was shared by Immanuel Kant, one of the
greatest minds of the eighteenth century. At two epochs,
twenty-six and ninety-one years after the Naturgeschichtt
des Himmels was dedicated to the great Frederick by the
Konigsberg philosopher, Uranus and Neptune were discovered
by William Herschel and G-alle ; but the orbits of both plan-
ets have a less degree of eccentricity than that of Saturn ;
if even the latter is 0*056, so, on the contrary, Neptune, the
outermost of all known planets, moves in an orbit whose ec-
centricity is 0-008, nearly the same as that of Venus (O.OOG).
In addition to this, Uranus and Neptune present none of the
predicted cometary characters.

As, in more recent times (since 1819), the discovery of-
Encke's Comet was gradually followed by those of five inte
rior comets, forming, as it were, a peculiar group, the semi-
major axis of whose orbits for the most part resembles those
of the small planets, the question was raised as to whether
the group of interior comets may not, as is conjectured by
Olbers, in his hypothesis respecting the small planets, origin-
ally have formed a single cosmical body ; whether the large
comet may not have been separated into several by the influ-
ence of Mars, in the same way that such a separation, as it
were a bipartition, took place under the eye of the observer
in the year 1846, on the occasion of the last return of the
interior comet of Biela. Certain similarities in their elements
have induced Professor Stephen Alexander, of the College of
New Jersey, to institute investigations^ as to the possibility

Kant, " the last planets beyond Saturn would gradually pass into com-
ets, and so the last species would be connected with the first. The law
according to which the eccentricity of the planetary orbits is propor-
tionate to the distances of the plauets from the Sun, supports this con-
jecture. The eccentricity increases with the distance, and, conseque^-jt-
,y, the more distant planets approach nearer to the definition of com-
ets. The last planet and the fTrst comet may be called that body which
in its perihelion intersects the orbit of the adjoining planet, perhaps
that of Saturn. Our theory of the mechanical formation of the cosmical
bodies is also clearly proved by the magnitudes of the planetary masses
which increase with the distance from the Sun." — Kant, Naturge-
schichte des Himmels (1755), in his Sdmmtliche Werke, th. vi., p. 88 and
195. At the commencement of the fifth section (p. 131), he speaks of
the former cometary nature which Saturn was supposed to have pos«
pessed.

* Stephen Alexander, "On the Similarity of arrangement of the As«
teroids and the Comets of short pei'iod, and the possibility of their
common origin," in Gould's Astronom. Journal, No. 19, p. 147, and No

COMETS, 183

of a comi.ion oiigin of the asteroids between Mars and Ju-
piter, with some or even all of the comets. The grounds of
analogy which have been deduced from the nebulous envel-
opes of the asteroids must, according to all more recent and
accurate observations, be renounced. The orbits of the small
planets are not parallel to each other ; that of Pallas certain-
ly presents the phenomenon of an extreme inclination ; but,
with all the want of parallehsan between their own orbits,
still theij do not intersect in a cometary manner any one of
the orbits of the large older, i. e., earlier discovered planets
This circumstance, so extremely essential in every assumption
of a primitive projectile direction and projectile velocity, ap-
pears, besides the difference in the physical constitution of the
interior comets, and the entirely vaporless small planets, to
•render the similarity of origin of both kinds of cosmical bodies
very improbable. Laplace, also, in his theory of planetary
genesis from rings of vapor revolving round the Sun, in which
matter aggregates into spheres aromid a nucleus, considered
it necessary to separate the comets from the planets : " Dans
Vhypothese des zones de vapeurs et d'un noyau s' accroissant
far la condensation de V atmosphere qui V environne, les co-
metes sont etrangeres au systeme planet aire T^ " According
to the hypothesis of zones of vapor, and of a nucleus increas-
ing by the condensation of the atmosphere which surrounds
them, the comets are strangers to the planetary system. '

We have already directed attention, in the Delineations of
Nature.^ to the fact that the comets at the same time pos-
sess the smallest mass, and occupy the largest space, of any
bodies in the solar regions ; in their number, also, they ex-
ceed all other planetary bodies ; the theory of probabilities,
applied to the data of the equable distribution of the orbits,
the boundaries, the perihelions, and the possibility that some

20, p. 181. The author distinguishes, with Hind (Schum., Astr. Nachr.,
No. 724), "the comets of short period, whose semi-axes are all nearly
the same with those of the small planets between Mars and Jupiter;
and the other class, including the comets whose mean distance or semi-
axis is somewhat less than that of Uranus." He concludes the first es-
say with this remark: ** Different facts and coincidences agree in indi-
cating a near appulse, if not an actual collision, of Mars with a large
comet in 1315 or 1316, that the comet was thereby broken into three
parts, whose orbits (it may be presumed) received even then their pres-
ent form, viz., that still presented by the Comets of 1812, 1815, and
1846, which are fragments of the dissevered comet."

* Laplace, Expos, du Syst. du Monde (ed. 1824), p. 414.

t On Comets: in the Delineation of Nature, s^e Cosmog, vol. i , p
lOO-UO.

184 COSMOS.

remain i?ivisible, indicates the existence of many tliousands.
"VVe except the aerolites or meteoric asteroids, as their nature
is still enveloped in great obscurity. Among the comets,
those must be distinguished whose orbits have been calcula-
ted by astronomers, and such of which there are only incom-
plete observations, or mere indications recorded. As, accord-
ing to Galle's last accurate enumeration, 178 had been cal-
culated up to the year 1847, so it may be admissible to adopt
as the total number, with those which have been merely in^
dicated, the assumption of six or seven hundred observed com-
ets. When the Comet of 1682, predicted by Halley, appeared
again in 1759, it was considered very remarkable that three
comets should be visible in the same year. At the present
time, the investigation of the heavens is carried on simultane-
ously at several parts of the globe, and with such energy,
that in each of the years 1819, 1825, and 1840, four were
discovered and calculated; in 1826, five; and in 1846, even
eight. »

Of comets visible with t^ » naked eye, more have been ob-
served recently than during the latter part of the previous
century ; but among them, those which have a great brill-
iancy in the head and tail still remain, on account of their
unfrequency, remarkable phenomena. It will not be with-
out interest to enumerate how many comets, visible in -Europe
to the naked eye, have appeared during the last centuries.*
The epoch in which they were most numerous was the six-
teenth century, during which twenty-three such comets were
<5een. The seventeenth numbered twelve, and of these only
two during its first half In the eighteenth century only eight
appeared, but nine during the first fifty years of the nineteenth
century. Among these, the most beautiful were those of
1807, 1811, 1819, 1835, and 1843. In earlier ages, thirty
or forty years have frequently passed without such a spec-
tacle presenting itself in a single instance. In the years,
however, during which comets seldom appear, there may be
a number of large comets whose perihelia are situated be-
yond the orbits of Jupiter and Saturn. Of the telescopic
comets, there are at the present time, upon an average, at
least two or three discovered annually. In three successive
months (1840) Galle discovered three new comets ; from 1764
to 1798, Messier discovered twelve ; from 1801 to 1827, Pons
discovered twenty-seven. Thus Kepler's expression as to the

* 111 the seven half centuries from 1500 to 1850, altogether 52 cometa
have appeared which were visible to the naked eye; iu separate succea

4.

COMETS,

185

nui^ber of comets in the universe appears to hold good : ut
jrisces in oceano.

Of not less importance is the careful catalogue of comets
which have appeared in China, and which Edward Biot has
made known from the collection of Ma-tuan-lin. It reaches
back beyond the foundation of the Ionic school of Thales and
ths Lydian Alyattes, and comprises, in two sections, the place
of the comets from 613 years before our own era until 1222
years afterward, and then from 1222 to 1644, the period in

seven equal periods, 13

,10; 2, 10,

4, 4, and 9. The follow

individual years

1500—1550

1550—1600

13 Com.

10 Com.

1600—1650

1650—1700

1607

1652

1618

1664

2 Com.

1665
1668
1672
1680
1682
1686
1689

•

^•

1696
10 Cora.

1700—1750

1750—1800

1702

1759

1744

1766

1784 (2)

1769

4 Com

1781
4 Com.

1800—1850

1807

.

1811

1819

1823

1830

1835

1843

1845

18

47

9 Com.

or the 28 Comets visible to tlje naked eye which are here enumerated
In the sixteenth century (the epoch of Apianus, Girolamc Fracastoro,
Landgravine William IV. of Hesse, Mastlin, and Tycho), 10 were de-
scribed by Pingre, namely, those of 1500, 1505, 1506, 1512, 1514, 1516,
1518, 1521, 1522, and 1530; further, the Comets of 1531, 1532, 1533
1556, 1558, 1569, 1577, 1580, 1582. 1585, 1590, 1593, and 1596.

186 COSMOS.

which the dynasty of Ming ruled. I repeat here (see Cos-
mos, vol. i., p. 99), that while from the middle of the third
to the end of the fourteenth century it was necessary to cal
culate comets exclusively from the Chinese observations, the
calculation of Halley's Comet, on its appearance in the year
1456, was the first calculation which was made from alto-
gether European observations, those of Regiomontanus. These
latter were again followed by the very accurate observations
of Apianus at Ingoldstadt, upon the occasion of the reappear-
ance of Halley's Comet in August of the year 1531. In the
interval (May, 1500) appeared a magnificently brilliant com-
et,* rendered famous by African and Brazilian travels of dis-
covery, which was called in Italy Signor Asto7ie, the great
Asta. Laugierf has detected, by similarity of the elements
in the Chinese observations, a seventh appearance of Hal-
ley's Comet (that of 1378) ; as well as that the third comet
of 1840, discovered by Galle,^ on the 6th of March, appears
to be identical with that of 1097. The Mexicans also con-
nected events in their records with comets and other ob-
servations of the heavens. The Comet of 1490, which I
discovered in the Mexican manuscript of St. Tellier, and of
which an engraving is inserted in my Monumens des Peuples
indighies de V Amerique, I have found, singularly enough,
to be mentioned as having been observed in December of
that year only in the Chinese comet-register. § The Mexi-
cans had inserted it in their register twenty-eight years be-
fore the first appearance of Cortez upon the coasts of Vera
Cruz (Chalchinhcuecan).

I have, in the Delineations of Nature [Cosmos, vol. i., p.
101), treated fully of the configuration, alterations of form,

* This is the " evil-disposed" comet to which was ascribed the death
of the celebrated Portuguese discoverer Bartholomsjeus Diaz, by ship-
wreck, as he was saihng to the Cape of Good Hope; Humboldt, Ex
amen Crit. de V Hist, de la G6ogr., tom. i., p. 296, aud torn, v., p. 80
(Sousa, Asia Portug., tom. i., p. i., cap. v., p. 45.)

t Laugier, in the Cojinaissance des Temps pour Van 1846, p. 99.
Compare also Edward Biot, Recherches sur les Anciennes Apparitions
Chinoises de la Comete de Halley ant&rieures a Vann€e 1378, op. cit., p.
70-84.

X Upon the comet discovered by Galle in March, 1840, see Schu-
macher, Astr. Nachr., bd. xviii., p. 188.

$ See my Vues des Cordilleres (ed. in folio), pi. Iv., fig. 8, p. 281, 282
The Mexicans had also a very correct view of the cause of a solar
eclipse. The same Mexican manuscript, written at least a quarter of
a century before the arrival of the Spaniards, represents the Sun as al
most entirely covered by the Moon's disk, and with gtarrf visible at the
same time.

COMETS. 187

light, ai^d color of comets, the emanations from their heads
which, bent backward,^ form the tails, from the observations
of Hensius (1744), Bessel, Struve, and Sir John Herschel.
Besides the magnificent Gsmet of 1843,t which could be
seen by Bowring, in Chihuahua (N."W. America), as a small
white cloud from nine o'clock in the morning until sunset,
and by Amici, in Parma, at full noon, 1° 23' eastward of
ihe Sun,$ the first comet of the year 1847, discovered by

* This iformation of ike tail at the anterior part of the comet's head,
which has occupied Bessel's attention so much, was the opinion of New-
ton and Winthrop (compare Newton's Principia, p. 511, and Philos.
Transact., vol. Ivii., for the year 1767, p. 140, tig. 5). Newton consid-
ei-ed that the tail was developed most considerably and longer near the
Sun, because the cosmical ether (which we call, with Encke, the resist-
ing medium) was the densest tliere, and the particulce caudce, strongly
heated and supported by the ether, ascended more easily. Winthrop
considered that the principal effect did not take place until some time
after the perihelion passage, because, according to the law established
by Newton (Principia, p. 424 and 466), the maxima are universally re-
tarded (in periodical changes of heat as well as in ocean tides).

t Arago, in the Annuaire for 1844, p. 395. The observation was made
by the younger Amici.

X With regard to the Comet of 1843, which appeared with unexam-
pled splendor in Northern Europe during the month of March, near
Orion, and approached nearer- to the Sun than any hitherto observed
and calculated comet, all the details are collected in Sir John Herschel's
Outlines of Astronomy, $ 589-597 ; and in Peirce, American Almanac
for 1844, p. 42. On account of physiognomical resemblances whose
uncertainty was already shown by Seneca {Nat. Quecst., lib. ii., caps,
xi. andxvii.), it was at first considered to be identical with the comets
of 1668 and 1689 {Cosmos, vol. i., p. 139, note; Galle, in Olbers's Come-
tenbahnen, Nos. 42 and 50). Boguslawski (Schum., Astr. Nachr., No.
545, p. 272) believes on tlie contrary, that its previous appearances were
with a revolution of 147 years, those of 1695, 1548, and 1401 ; he even
calls it the Comet of Aristotle, " because he traces it back to the year
371 before our era, and, together with the talented Hellenist Thiersch,
of Munich, considers it to be a comet which is mentioned in the Mete-
orologicis of Aristotle, book i., cap. vi." But I'would call to mind that
the name Comet of Aristotle is vague and indefinite. If that one is
meant which Aristotle states to have disappeared in Orion, and which
ne connects with the earthquake in Achaia, it must not be forgotten
that this comet is stated by Callisthenes to have appeared before, by
Diodorus after, and by Aristotle at the time of the earthquake. The
«ixth and eighth chapters of the Meteorology treat of four comets whose
epochs of appearance are characterized by the archons at Athens, and
by unfortunate events. In this place those are mentioned in order:
the western comet which appeared on the occasion of the great earth-
quake at Achaia, accompanied with floods (cap. vii., 8) ; then the comet
which appeared during the time of the Archon Eucles, the son of Mo-
Ion ; afterward (cap. vi., 10) the Stagirite comes again to the western
comet, that of the great earthquake, and at the same time calls the Ar
chon Asteus — a name which incoiTect readings have changed into Aria

188 COSMOS.

Hind near Capella, has very recently been visible at London,
near the Sun, on the day of its perihelion.

taDus, and which was, on that account, erroneously considered by Pingr^,
in his Comitographie, to signify one and the same person as Aristhcnes
or Alcisthenes. The brilHancy of this comet of Asteus diffused itself
over the third part of the sky ; the tail, which was called its way {odog),
was also 60° in length. It extended nearly as far as Orion, where it
gradually disappeared. In cap. vii., 9, the comet is mentioned which
appeared simultaneously with the famous fall of aerolites near ^^gos
Potamos {Cosmds, vol. i., p. 117), and which can scarcely be a confu-
sion with the aerolite-cloud described by Damachos, which shone for
70 days, and poured forth falling stars. Finally, Aristotle mentions
(cap. vii., 10) a comet which appeared at the time of the Archon Ni-
comachus, to which was ascribed a storm near Corinth. These four ap-
pearances of comets occurred during the long period of 32 Olympiads :
viz., the fall of aerolites, according to the Parian Chronicle, 01. 78, 1
(468 B.C.), under the Archon Theagenides; the great comet of Asteus,
which appeared at the time of the earthquake at Achaia, and disap-
peared in the constellation of Orion, in Ol. 101, 4 (373 B.C.): Eucles,
the son of Molon, erroneously called Euclides Diodorus (xii., 53), in
Ol. 88, 2 (427 B.C.), as is also confirmed by the commentary of Jo-
hannes Philoponus ; the comet of Nicomachus, in Ol. 109, 4 (341 B.C.).
The date assigned by Pliny for the jubce effigies mutata in hastam, i*
Ol. 108 {Plinius, ii., 2.5). Seneca also agrees in connecting the comet
of A&teus {Ol. 101, 4) immediately with the earthquake in Achaia, as
he mentions the downfall of Bura and Helice, which towns Aristotle
does no\ expressly mention, in the following manner: " Effigiem ignis
longi fiiisse, Callisthenes tradit, antequam Burin et Helicen mare ab-
sconderet. Aristoteles ait, non trabem illam, sed cometam fuisse."
" Callisthenes affirms that the fiery shape appeared long before the sea
overwhelmed Bui-is and Helice. Aristotle says that this was not a
meteor, but a comet." (Seneca, Nai. Qucest., vii., 5.) Strabo (viii.,
p. 384, Cas.) places the downfall of these two frequently mentioned
towns two years before the battle of Leuctra, whence again results the
date, Ol. 101, 4. Finally, after Diodorus Siculus had more fully de-
scribed this event as having occurred under the Archon Asteus (xv.,
48, 49), he places the brilliant comet which threw shadows (xv., 50)
under the Archon Alcisthenes, a year later, Ol. 102, 1 (372 A.C.), and
as a prediction of the decline of the Lacedaemonian rule; but the later
Diodorus had the habit of transferring an event from one year to an-
other; and the oldest and most reliable witnesses, Aristotle and the
Parian Chronicle, speak in favor of the epoch of Asteus before that of
Alcisthenes. Now since the assumption of a period of revolution for
the beautiful Comet of 1843 of 147f years, leads Boguslawski to assign
to its appearances the dates 1695, 1548, 1401, and 1106, up to the year
371 before our era, the comet of the earthquake of Achaia corresponds
with it, according to Aristotle, within two — according to Diodorus, to
within one year ; which, if we could know any thing of the similarity
of the orbit, is, when taking into consideration the probable disturban-
ces during a period of 1214 years, certainly a very small error. When
Pingr6, in the Com^tographie (1783, tom. i., p. 259-262), relying upon
Diodorus and the Archon Alcisthenes instead of Asteus, places the
comet in question in Orion, in Ol. 102, and still in the commencement
of July, 371 before Christ, instead of 372, the reason perhaps lies in the

COMETS. 189

For the explanation of what has been said above of the re-
mark of Chinese astronomers on the occasion of their observ-
ation of the Comet of March, 837, in the dynasty of Thang,
I insert here a translation from Ma-tuan-lin of the verbal
statement of the law of direction of the tail. It is said there,
*' In general, the tail of a comet which is situated eastward
from the Sun is directed toward the east, calculating from
the nucleus ; but if the comet appears to the west of the Sun,
the tail turns toward the west."* Fracastoro and Appia-
nus say, still more correctly, "that a line produced through
the head of a comet in the direction of the axis of the tail
meets the Sun." The words of Seneca are also characteristic :
" The tails of comets fly from the Sun's rays." [Nat. Qucest.,
vii., 20.) While, among the yet known planets and comets,
the periods of rotation dependent upon the half major axis,
the shortest and the longest of the planetS) are in the propor-
tion of 1 : 683, the proportion in the case of the comets is as
1: 2670. Mercury (87d-97) is here compared with Neptune

circumstance that, like some other astronomers, he characterizes the
first year before the Christian era as anno 0. It is to be observed, in
conclusion, that Sir John Herschel assumes for the Comet of 1843, seen
in full daylight near the Sun, an entirely different period of revolution,
one of 175 years, which leads to the years 1668, 1493, and 1318, as the
dates of its previous appearances. (Compare Outlines, p. 208-372, with
Galle, in Olbers's Cometenbahnen, p. 208; and Cosmos, vol. i., p. 137.)
Other combinations by Peirce and Clausen lead to periods of revolution
of even 21| or 7^ years: a sufficient proof how hazardous it is to trace
back the Comet of 1843 to the archonship of Asteus. The mention of
a comet under the archonship of Nicomachus, in the Meteorol., lib. i.,
cap. vii., 10, has at least the advantage of showing us that this work
was written when Aristotle was at least 44 years of age. It has al-
ways appeared to me remarkable that the great man, as he was already
14 years old at the time of the earthquake at Achaia, and of the appear-
ance in Orion of the great comet with a tail 60° in length, should speak
with so little animation of so brilliant an object, and content himself
with enumerating it among the other comets " whioh had appeared in
his time." The astonishment increases when, in the same chapter, the
statement is found that he had seen with his own eyes something misty,
even a feeble haza {ko/xtj), round a fixed star in the hip-bone of the Dog
(perhaps Trocyon in the small Dog), {Meteorol., i., 6, 9). Aristotle also
speaks (i., 6,11) of his observation of the occultation of a star in Gemini
by the disk of Jupiter. With regard to the vaporous or nebulous en-
velope of Procyon (?), it recalls to my mind a phenomenon of which
frequent mention is made in the old Mexican annals according to the
Codex Tellerianns. " This year,' it is said there, " Citlalcholoa smoked
again;" this is the name of the planet Venus, also called Tlazoteotl in
the Aztec language (see my Vues des Cordilleret, tom. ii., p. 303) : this
is probably, in the Grecian as well as the Mexican sky, a phenomenon
of atmospheric refraction — the appearance of small halos.

• Edward Biot, in the Comptes Rendus, tom. xvi., 1843. p. 751.

190 ~ COSMOS.

(60,126d-7), and the Comet of Encke (3-3 years) witli the
Comet of 1680 (8814 years), observed by Gottfried Kirch at
Coburg, Newton, and Halley. The distance of the fixed star
nearest to our solar system (a Centauri) from the aphehon
(point of greatest distance from the Sun) of the last-named
comet is determined by Encke in an excellent treatise. The
small velocity of its motion (ten feet in a second) in this out-
ermost part of its orbit, the greatest proximity which the
Comet of Lexell and Burckhardt (1770) has attained to the
earth (six times the distance of the Moon), and the Comet
of 1680 (and still more that of 1843) to the Sun, I have al-
ready treated of in Cosmos, vol. i., p. 109, and vol. iv., p.
53-55. The second comet of the year 1819, which ap-
peared, in Europe, suddenly to break forth from out of the
Sun's rays in considerable magnitude, passed, according to
the calculation of its elements, across the Sun's disk on the
26th of June ;=^ unfortunately, its passage was not observed.
This must also have been the case with the Comet of 1823,
which, besides the ordinary tail turned from the Sun, had
also another turned directly toward it. If the tails of both
comets had a considerable length, vaporous parts of them
must have mixed with our atmosphere, as certainly often hap-
pens. The question has been raised as to whether the won-
derful mists of 1783 and 1831, which covered a great part of
the Continent, were consequences of such an admixture J\

"While the quantity of radiant heat received by the Comets
of 1680 and 1843 in such close proximity to the Sun has
been compared to the focal temperature of a 32-inch burn-
ing mirror,$ a highly-deserving§ astronomical friend of mine

* Galle, ill the Supplement to Olbers's Cometenhahnen, p. 221, No.
130. (With respect to the probable passage of the two-tailed comet of
1823, see Edinb. Rev., 1848, No. 175, p. 193.) The treatise shortly be-
fore quoted in the text, containing the true elements of the Comet of
1680, contradicts Halley's fantastic idea, according to which, with a
presumed period of 575 years, it had appeared at all the great epochs
of the human race: at the time of the Deluge according to Hebrew tra-
ditions, in the age of Ogyges according to Greek traditions, at the Tro-
jan war, on the destruction of Nineveh, on the death of Julius Caesar,
&c. The period of revolution resulting from Encke's calculation is
8814 years. The least distance from the surface of the Sun was, on the
17th of December, 1680, only 128,000 geographical miles ; consequently,
80,000 less than the distance of the Earth from the Moon. The aphe
lion is 853-3 times the distance of the Earth from the Sun, and the
proportion of the smallest to the greatest distance from the Sua is as
1 : 140,000. t Arago, in the Annuaire for 1832, p. 236-255.

X Sir John Herschel, Outlines, $ 592.

^ Bernhard von Lindenau, in Schum., Astr. Nachr., No. 698, p. 25.

COMETS. 191

maintains that " all comets which are without a solid nu-
cleus (on account of their extremely small density) have no
solar heat, only the temperature of cosmical space. "^ If wo
take into consideration the numerous and striking analogies
of the phenomena which, according to Melloni and Forbes,
luminous and non-luminous sources of heat present, it ap-
pears difficult, in the present state of our physical reasoning,
not to assume that processes go on in the Sun itself which si-
multaneously produce radiant light and radiant heat by vi-
brations of the ether (waves of different lengths). The dark-
ening of the Moon by a comet, stated to have taken place in
the year 1454, which the Jesuit Pontanus, the first trans-
lator of the Byzantine author, George Phranza, beheved that
he had discovered in a monkish manuscript, has long been
mentioned in many astronomical works. This statement
of the passage of a comet between the Earth and Moon in
1454 is quite as erroneous as that asserted by Lichtenberg
of the Comet of 1770. The Chronicon of Phranza first ap-
peared complete at Vienna in 1796, and it is said there ex-
pressly, that in the year of the world 6962, while an eclipse
of the Moon took place, a comet like a Qiiist appeared and
came near to the Moon quite in the ordinary manner, ac-
cording to the order and circular orbits of the heavenly
luminaries. The year of the world ( = 1450) is incorrect,
as Phranza says distinctly the eclipse of the Moon and the
appearance of the comet were seen after the taking of Con-
stantinople (May the 19th, 1453), and an eclipse of the Moon
actually happened upon the 12th of May, 1454. (See Jacobs,
in Zach's Monatl. Corresp., bd. xxiii., 1811, p. 196-202.)

The relation of Lexell's Comet to the satellites of Jupiter,
and the perturbation which it suffers from them without in
fluencing their periods of revolution [Cosmos, vol. i,, p. 110),
have been more accurately investigated by Leverrier. Mes-
sier discovered this remarkable comet as a feeble nebulous
spot in Sagittarius upon the 14th of June, 1770 ; but eight
days after, its nucleus shone as brightly as a star of the 2d
magnitude. Before the perihelion passage, no tail Avas vis-
ible ; afterward it developed itself by slight emanations
scarcely one degree in length. Lexell found for his comet
an elliptic orbit, and the period of rotation of 5* 585 years,
which Burckhardt confirmed in his excellent prize essay
According to Clausen, it had approached the Earth upon the
Ifit of July, 1770, to a distance of 363 times the Earth's ra-
* Cosmos, vol. iii., p. 36 and 37.

.92 COSMOS.

dius (1,244,000 geographical miles, or six times the Moon's
distance). That the comet was not se^^n before March, 1776,
and not later than October, 1781, according to Lexell's pre-
vious conjecture, is analytically demonstrated by Laplace, in
the fourth volume of the Mecanique Celeste, from the per-
turbations occasioned by the Jovial system on the occasion
of the approximations in the years 1767 and 1779. Lever-
rier finds that, according to one hypothesis respecting the
cometary orbits, this comet passed through orbits of the sat-
ellites in 1779 ; according to another, that it remained at a
considerable distance without the fourth satellite.^

The molecular conditions of the head or nucleus, so seldom
possessing a definite outline, as well as the tail of the com-
ets, is rendered so much the more mysterious from the fact
that it causes no refraction, and, as was proved by Arago's
important discovery {Cosmos, vol. i., p. 105, and note), that
the cometary light contains a portion oi polarized light, and
consequently reflected sun-light. Although the smallest stars
are seen in undiminished brilliancy through the vaporous em-
anations of the tail, and even through the center of the nu-
cleus itself, or at least in very great proximity to the center,
(per centrum non alitor quam per nubem ulteriora cernatur :
Seneca, Nat. Qucest., vii., 18) ; so, on the contrary, the an-
alysis of the cometary light in Arago's experiments, during
which I was present, shows that the vaporous envelopes are
capable! of reflecting light, notwithstanding their extremely
slight density, and that these bodies have " an imperfect
transparency, t since light does not pass through them unim-
peded." In this group of vaporous bodies, the solitary in-
stances of great luminous intensity, as in the Comet of 1843,
or the star-like shining of a nucleus, excite so much the more
astonishment when it is assumed that their light proceeds
solely from a reflection of the solar rays. Is there not, how-
ever, in addition to this, a peculiar light-producing process
going on in the comets ?

The brush-like membered tails emanating from the comets,
and consisting of vapory matter of millions of miles in length,
diffuse themselves in space, and form, perhaps, either the re-
sisting mediums itself, which gradually contracts the orbit

* Leverrier, in the Comptes Rendvs, torn, xix., 1844, p. 982-993.

t Newton considered that the most brilliant comets shone only with
reflected sun-light. " Splendent cometa;," says he, " luce Solis a se
reflexa." (Princ. Mathem., ed. Le Seur et Jaquier, 1760, torn, iii,,
p. 5r7.) X Bessel, in Schum. Jahrbuch for 1837, p. 169.

$ Cosmos, vol. i., p. 106, and vol. iii., p. 39.

COMETS 193

of Encke's Comet, or they mix with the old cosmicai matter
which has not aggregated into spheres, or condensed into the
rings, and which appears to us as the zodiacal light. We
see, as it were, before our eyes, material particles disappear,
and can scarcely conjecture where they again collect. How-
ever probable may be the condensation, in the neighborhood
of the central body of our system, of a gaseous fluid filling
space, still, in the case of the comets, whose nuclei, accord-
ing to Val?., diminish in the perihelion, this fluid, condensed
there, can scarcely be looked upon as pressing upon a vesicu-
lar vapory envelope. =^ Although in the streamers of the
comets the outlines of the reflecting portion of the vapory
envelope is generally very indefinite, the circumstance that,
in some individuals (for example, Halley's Comet at the 2d
of January, 1836, at the Cape of Good Hope), a sharpness
of outline has been observed on the anterior parabolic part
of the body, such as our masses of clouds seldom present, is
so much the more striking and instructive as to the molecular
condition of these bodies. The celebrated observer at the
Cape compared the unusual appearance, testifying to the in-
tensity of the mutual attraction of the particles, with that of
an alabaster vessel strongly illuminated in the interior.!

Since the appearance of the astronomical part of my De-
lineation of Nature, the cometary world has presented a
phenomenon whose mere possibility could scarcely have been
suspected beforehand. Biela's Comet, an interior one of
short period, 6f years in its revolution, has separated into
two comets of similar figure though unequal dimensions, both
having a head and tail. So long as they could be observed,
they did not unite again, and proceeded on their course sep-
arately, almost parallel with each other. Hind had, on the

* Valz, Essai sur la Determination de la Densiti de V Ether dans Vespace
PlanHaire, 1830, p. 2; and Cosmos, vol. i., p. 106. The so-carefully
observing and always unprejudiced Hevelius had also directed atten-
tion to the increase in the size of the cometary nuclei, with increased
distance from the Sun. (Pingre, Com^tographie, torn, ii., p. 193.) The
determinations of the diameter of Encke's Comet in the perihelion is
very difficult, if accuracy is desired. The comet is a nebulous mass, in
which the center, or one point of it, is the brightest, even prominently
bright. From this point, which, however, presents no appearance of a
disk, and can not be called a comet-head, the light decreases very rapid-
ly all around, and at the same time the vapor elongates toward one disk,
so that this elongation appears as a tail. The measurements, therefore,
refer to this mass of vapor, whose circumference, without having really
dsfinite boundaries, decreases in perihelion.

i Sir John Herschel, Results of Astronomical Observations at the Cap^
of Good Hope, 1847, $ 366, pi. xv. and xvi.
Vol. IV.— I

1 94 COSMOS.

19th of DecemlDer, 1845, already remarked a kind of pro-
tuberance toward the north ; but on the 21st there was, ac-
cording to Encke's observation in Berlin, still no signs of a
separation visible. The subsequent separation was first de-
tected in North America on the 29th of December, 1845 ;
in Europe, not until the middle and end of January, 1846.
The new smaller comet proceeded toward the north. The
distance of the two was at first 3', afterward (February 20th),
according to Otto Struve's interesting drawing, 6'.* The
luminous intensity varied in such a manner that the gradu-
ally increasing secondary comet for some time exceeded the
principal comet in brightness. The. nebulous envelopes which
surrounded each of the nuclei had no definite outlines : that
of the larger comet, indeed, showed a less luminous protuber-
ance toward S.S.W. ; but the space between the two comets
was seen at Pulkowa quite free from nebulous matter. f A
few days later. Lieutenant Maury, in AYashington, remarked,
with a nine-inch Munich refractor, rays which proceeded from
the larger older comet to the smaller new one, so that a kind
of bridge-like connection was produced for some time. On
the 24th of March, the smaller comet was scarcely percepti-
ble, on account of the decreasing luminous intensity. The
larger one only was seen up to the 16th or 20th of April,
when this also disappeared. I have described the wonderful
phenomenon in detail,$ so far as it could be observed. Un-
fortunately, the actual separation and the immediately previ-
ous condition of the older comet escaped observation. Did
the separated comet become invisible only on account of dis-
tance and feeble luminosity, or did it resolve itself? Will it
be again detected as an attendant, and will the Comet of
Biela present similar anomalies at other reappearances ?

The formation of a neiv planetary body by separatioji nat-
urally excites the question whether, in the innumerable com-
ets revolving round the Sun, several have not originated by
a similar process, or do not daily originate so ? whether they

* The subsequent (5th of March) mcrease of distance seen to the ex
tent of 9° 19' was, as Plantaraour has shown, merely apparent, and do
pendent upon the approximation to the Earth. Both parts of the douhU
comet remained at the same distance from each other from February
until the 10th of March.

t " Le 19 Fevrier, 1846, on aper9oit le fond noir du ciel qui separe les
deux cometes." — Otto Struve, in the Bulletin Physico-matMmatique de
VAcad. des Sciences de St. Pitesbourg, tom. vi., No. 4.

t Compare Outlines, $ 580-583 ; Galle, in Olbers's Comeienbahnenf
V. 232.

COMETS. VJb

may not acquire different orbits by retardation, i. e., unequal
velocity of revolution, and the unequal influence of perturba-
tions ? In a treatise already alluded to, Stephen Alexander
has attempted to explain the genesis of all the interior com-
ets by the assumption of such an hypothesis, certainly but in-
adequately founded. In antiquity, also, similar occurrences
appear to have been observed, but not sufficiently described.
Seneca states, upon the authority, as he himself says, of an
unreliable witness, that the comet which was considered to
have caused the destniction of the two towns of Helice and
Bura separated into two parts. He adds ironically, why has
no one seen two comets unite to form one ?^ The Chinest-
astronomers speak of " three dome-formed comets," which ap-
peared in the year 896, and pursued their course together.f
Among the great number of calculated comets, there are,
up to the present time, eight known, whose period of revolu-
tion is shorter than that of Neptune. Of these eight, six are
interior comets, i.e., such whose aplielia are within the orbit
of Neptune, viz., the comets of Encke (aphelion, 4*09), of
De Yico (502), Brorsen (5-64), Faye (5-93), Biela (6- 19),
and D'Arrest (6-44). If the distance of the Earth from the
Sun is taken as = 1 , the orbits of all these six interior com-
ets have aphelia which are situated between Hygeia (3 "15),
and a limit which is nearly \\ the Earth's distance from the
Sun beyond Jupiter. The two other comets, likewise of a
shorter period of revolution than Neptune, are the 74-year
Comet of Olbers, and the 76-year Comet of Halley. Up to
the year 1819, when Encke first discovered the existence of
an interior comet, these two latter ones were those of the
shortest period among the then calculated comets. Olbers's
Comet of 1815, and Halley's Comet are, since the discovery
of Neptune, situated in their aphelia only 4 and 5| times the
Earth's distance from the San — beyond the limits which
would allow of their being considered interior comets. Al-
though the term interior comet may suffer alteration from the

* " Bphorus non religiosissimae fidei, saepe decipitur, saepe decipit. Si-
cut hie Cometem, qui omnium mortalium oculis custoditus est, quia in-
gentis rei traxit eventus, cum Helicen et Burin ortu suo merserit, ait
ilium discessisse in duas Stellas : quod prseter ilium nemo tradidit. Quis
enim posset observare illud momentum, quo Cometes solutus et in duas
partes redactus est ? Quomodem autem, si est qui viderit Cometem in
duas dirimi, nemo vidit fieri ex duabus?" — Seneca, Nat. Qucest., lib.
vii., cap. 16.

t Edward Biot, Recherches sur les ComHes de la Collection de Ma-
iuan-li.„, in the Comptes Rcndus, tom. xx., 1845, p. 334.

196 COSMOS.

discovery of Tra7is-neptitnian planets since the boundary
which determines whether a comet is to be called an interior
one is changeable, still this term is preferable to that of com
ets of short period, from the fact that it is in each epoch of
our knowledge dependent upon something definite. The six
interior comets now accurately calculated certainly vary in
their periods of revolution only from 3-3 to 7 4 years ; but if
tlie return of the comet discovered by Peters at Naples, upon
the 26th of June, 1846 (the 6th comet of the year 1846, with
a half-major axis of 6*32), after a period of 16 years, should
be confirmed, *" it may be foreseen that intermediate members,
in reference to the duration of the period of revolution, will
gradually be discovered between the Comets of Faye and
Olbers. Then it would be difficult in future to fix a limit
for the shortness of the period. Here follows the table in
which Dr. Galle has arranged the elements of the six interior
comets.

* Galle, in Olbers's Methode der Cometenbahnen, p. 232, No. 174. The
comets of Colla and Bremiker, of the years 1845 and 1840, present el-
liptical orbits with proportionately not very short periods of revolution.
(I allude to the 3065 and 8800 years of the Comets of 1811 and 1680.)
They appear to have periods of revolution of only 249 and 344 yeare.
(See Galle, op. cit., p. 229 and 231.)

COMETS.

197

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199 COSMOS.

From the summary here given, it foUow^s that, since the
discovery of Encke's Cornet^ as an interior one in the year
1819, up to the discovery of the interior comet of D' Arrest,
scarcely 32 years have elapsed. Yvon Yillarceau has also
given elliptic elements for the last-named in Schumacher's
Astron. Nachr., No. 773, and has, at the same time with
Valz, put forward some conjectures as to its identity with
the Comet of 1678, ohserved by La Hire, and calculated by
Douwes. Two other comets, apparently of from 5 to 6 year
'periods of revolution, are the 3d of 1819, discovered by Pons,
and calculated by Encke ; and the 4th of 1819, discovered
by Blanpain, and, according to Clausen, identical with the 1st
of 1743. But neither of these can be classed with those
which, from longer and more accurate observations, present
a greater certainty and completeness of their elements.

The inclination of the orbits of the interior comets to the
plane of the ecliptic is, upon the whole, small, between 3°
and 13°; that ofBrorsen's Comet alone is very considerable,

* The short period of revolution of 1204 days was discovered by
Encke on the reappearance of his comet in the year 1819. See the first
calculated elliptical orbits in the Berliner Astron. Jahrbuch for 1822,
p. 193, and for the constants of the resisting medium assumed to explain
the accelerated revolution. Encke's Vierte Abhandlburg in the Schrif-
ten der Berl. Akademie for the year 1844. (Compare Arago, in the^;i-
nuaire for 1832, p. 181 ; in the Lettre a M. Alexandre de Humboldt, 1840,
p. 12 ; and Galle, in Olbers's Cometenbahnen, p. 221.) As belonging to
the history of Encke's Comet, it must here be' called to mind that, so far
as our knowledge of the observations extends, it was first seen upon two
days by Mechain on the 17th of January, 1786; then by Miss Carolina
Herschel from the 7th to the 27th of November, 1795; afterward by
Bouvard, Pons, and Huth, from the 20th of October to the 19th of No-
vember, 1805; finally, as the tenth reappearance since Mechain's dis-
covery in the year 1786, by Pons from the 25th of November, 1818, to
the 12th of January, 1819. The first reappearance, calculated before-
hand by Encke, was observed by RUmker at Paramatta. (Galle, op.
cit., p. 215, 217, 221, and 222.) Biela's interior comet, or, as it is also
called, Biela's and Gambart's, was first seen by Montaigne on the 8th
of March, 1772 ; then by Pons on the 10th of November, 1805 ; after-
ward on the 27th of February, 1826, at Josephstadt in Bohemia, by Von
Biela ; and on the 9th of March by Gambart, at Marseilles. The ear-
liest rediscoverer of the Comet of 1772 is undoubtedly Biela, and not
Gambart; but, on the other hand, he calculated the elliptical elements
of its orbit earlier than Biela, and nearly at the same time as Clausen.
(AragO; in the Annuaire of 1832, p. 184; and in the Comptes Rendus,
tom. iii., 1836, -p. 415.) The first reappearance of Biela's Comet, cal-
culated beforehand, was observed by Henderson, at the Cape of Good
Hope, in October and December, 1832. The already mentioned won-
derful doubling of Biela's Comet by separation took place at its elev-
enth reappearance since 1772, at the end of the year 1845. (See Gallo,
by Gibers, p. 214, 218, 224, 227, and 232.)

COMETS. 199

and reaches 31*^ All the hitherto discovered interior com-
ets have, jiko the principal and secondary planets of the en-
tire solar system, a direct motion (from west to east, pro-
ceeding in th«^ir orbits). Sir John Herschel has directed at-
tei *;ion to the great rarity of retrograde motion of comets
^lainng a slight inclination to the plane of the ecliiitic.^
Thii opposite direction of motion, which occurs only with a
certam class of planetary bodies, is of great importance in
reference to the very universally prevaihng opinion as to thf
formation of the planetary bodies belonging to one system,
and as to the primitive, impulsive, and projectile force. It
shows us the cmnetary world, although subject even at the
remotest distances to the attraction of the central body, in
greater individuality and independence. Such a mode of
viewing the subject has led to the idea of considering the
comets as olderf than the planets — as it were primitive
forms of the loosely aggregating matter in space. Under
these presuppositions, it becomes a question whether, not-
withstanding the enormous distance of the nearest fixed
stars, whose parallax we know from the aphelion of the
Comet of 1680, some of the comets which appear in the
heavens may not be merely wanderers, through our solar
system, moving from one Sun to another ?

Next in order to the group of comets, I shall speak of the
ring of the zodiacal light, as v/ith grea4; probability belong-
ing to our solar region, and after that of the swarms 'tf inc-
teoric asteroids which sometimes fall upon our eartfr, and
with regard to whoso existence, as bodies in spaco, by no
means unanimous opinions prevail. As, in acf;(3rd*anco with
the course adopted by Chladni, Olbers, Laplace, Arago, Sir
John Herschel, and Bessel, I consider the aerolites to bo of
decidedly extra-terrestrial cosmical origin, I may venture, at
the conclusion of the section upon the planets, confidently to
express the expectation that, by continued accuracy in the
observation of aerolites, fire-balls, and shooting- stars, the op-
posite opinion will disappear in the same way that the opin-

* Oxitlims, $ 601.

t Laplace, Expos, du Systtme du Monde, p. 396 and 414. The special
view of Laplace as to the comets being " wandeiniig nebulae" (petites
nebnlouses errantes de systemes en systeraes solaires), " stands in op-
position to the progress which has been made since the death ol iho
great man, in the resolvability of so many nebulous spots into crow ded
neaps of stars; the circumstance, also, that the comets have a portion
o{ reflected polarized light, which the self-luminous bodies are destitute
of. Compare Cosmos, vol. iii., p. 142 ; vol. iv., p. 22.

200 COSMOS.

ion, universally diffused up to the sixteenth century, as to the
meteoric origin of the comets, has long done. While these
bodies were considered by the astrological corporation ot
"* Chaldeans in Babylon," by the greater part of the Pythago-
rean school, and by Apollonius Myndius, as cosmical bodies
reappearing at definite periods in long planetary orbits, the
powerful anti-Pythagorean school of Aristotle and that of
Epigenes, controverted by Seneca, declared the comets to be
productions of meteorological processes in our atmosphere. ^'^^

* There were divisions of opinion at Babylon in the learned Chaldean
school of astrologers, as well as among the Pythagoreans, and, properly
speaking, among all ancient schools. Seneca {Nat. Qm«s<., vii., 3) quotes
the antagonistic evidence of Apollonius Myndius and Epigenes. The
latter is seldom mentioned, yet Plinius (vii., 57) repi-esents him as
" gravis auctor in primis," as does also, without praise, Censorius, De
die Natali, cap. xvii., and Stob., Eel. Phys., i., 29, p. 586, ed. Heeren.
(Compare Lobeck, Aglaoph., xi.) Diodorus (xv., 50) believes that the
universal and prevailing opinion among the Babylonian astrologers
(the Chaldeans) was, that the comets reappeared at definite times in
their certain orbits. The division which prevailed between the Pytha-
goreans as to the planetary nature of the comets, and which is mentioned
by Aristotle (MeteoroL, lib. i., cap. vi., 1) and Pseudo-Plutarch (De Plac.
Philos., lib. iii., cap. ii.), extended, according to the former {MeteoroL,
i., 8, 2), also to the nature of the Milky, Way, the forsaken course of
the Sun, or of the overthrown Pha6ton. (Compare also Letronne, in
the M6m. de VAcad. des Inscriptions, 1839, tom. xii., p. 108.) By some
of the Pythagoreans the opinion of Aristotle was advanced, " that the
comets belonged to the number of those planets which, like Mercury,
only became visible after a long time when rising in the course above
the horizon." In the extremely fragmentary Pseudo-Plutarch it is said
that they "ascend at definite times after a complete revolution." A
great deal of matter, contained in separate works, referring to the na-
ture of the comets, has been lost to us — that of Airian, which Stobaeus
employed ; of Charimander, whose mere name has been retained only
by Seneca and Pappus. Stobteus brings forward, as the opinion of the
Chaldeans {Eclog., lib. i., cap. xxv., p. 61, Christ. Plantinus), that the
reason the comets remain so seldom visible to us is because they hide
themselves in the depths of the ether ("of space), like the fish in the
depths of the ocean. The most graceful, and, in spite of its rhetorical
coloring, the best founded opinion of antiquity, and the one correspond-
ing most closely with pi'esent views, is that of Seneca. In the Nat.
Qucest., lib. vii., cap. xxii., xxv., and xxxi., we read, " Non enim existi-
mo cometem subitaneum ignem sed inter aetenia opera naturae. Quid
enim miramur, cometas, tam rarum mundi spectaculum, nondum teneri
legibus certis? nee initia illorum finesque patescere, quorum ex ingeu-
tibus intervallis recursus est? Nondum sunt anni quirtgenti, ex quo
Grascia .... stelhs numeros et nomina fecit. Multseque hodie sunt
gentes, quae tantura facie noverit coelum ; quae nondurr sciant, cur Luna
deficiat, quare obumbretur. Hoc apud nos quoque nuper ratio ad cer-
ium perduxit. Veniet tempus, quo ista, quae nunc latent, in lucem dies
extrahat et longioris aevi diligentia. Veniet tempus, quo posteri nostri
lam aperta nos nescisse mirentur. Eleusis servat, quod ostendat revi

ZODIACAL LIGHT. • 201

Analogous fluctuations between cosmical and terrestrial hy-
potheses, between universal space and the atmosphere, still
lead, at last, to a more correct view of natural phenomena.

IV.

THE RING OP THE ZODIACAL LIGHT.

In our solar system, so rich in varieties of form, the exist-
ence, place, and configuration of many individual members
have been discovered, since scarcely a century and a half,
and at long intervals of time : first, the subordinate, or 'par-
ticular systems., in which, analogous to the principal system
of the Sun, smaller spherical cosmical bodies revolve round a
larger ; then concentric rings round one, and that, indeed,
one of the less dense and exterior planets which possesses
the greatest number of satellites ; then the existence, and
probably material cause, of the mild, pyramidal-formed, zo-
diacal light, very visible to the naked eye ; then the mutu-
ally intersecting orbits of the so-called small planets, ox as-
teroids, inclosed between the regions of two principal planets,
and situated beyond the zodiacal zone ; finally, the remarka-
ble group of interior comets, whose aphelia are smaller than
those of Saturn, Uranus, and Neptune. In a cosmical repre-

sentibus. Rerum natura sacra sua non simul tradit. Initiatos nos cre-
diraus; in vestibulo ejus hyeremus. Ilia arcana non promiscue nee om-
nibus patent, reducta et in interiore sacrario clausa sunt. Ex quibus
aliud ha3C aetas, aliud quae post nos subibit, dispiciet. Tarde magna
proveniunt." " For I do not think that comets are a casual outburst
of fire, but belong to the eternal works of nature. For why should it
surprise us that comets, so rare a phenomenon, should not yet be sub-
ject to the regulation of any known laws ? and that their origin and
ends should be hid from us, who see them only at immense intervals ?
It is not yet five hundred years since Greece gave names and number
to the stars. And to this day there are many nations who know nothing
of the heavenly bodies but as they appear to the eye, who are still ig
norant of the causes of the waves and eclipses of the moon ; even we
ourselves have only lately attained an accurate knowledge of these phe-
nomena. The time will arrive when the diligence of a remoter age
shall throw light on subjects which are now involved in obscurity.
The time will arrive when our posterity will wonder at our ignorance
of things so plain to them. Eleusis reserves her favors for those who
repeat their visits. Nature does not permit us to explore her sanctua-
ry all at once. , We believe we are initiated, whereas we halt at the
very threshold. Those mysteries are not revealed indiscriminately to
all ; they are laid up and enshrined within the penetralia. Some are
revealed to the men of our age, some to those who shall come after us
Great results proceed slowly."

I 2

202 • COSMOS.

sentdtioii of universal space, it is necessary to call to mind
the difference of the members of the solar system, which by
no means excludes similarity of origin and lasting depend-
ence upon the moving forces.

Great as is the obscurity which still envelops the material
cause of the zodiacal light, still, however, with the mathe-
matical certainty that the solar atmosphere can not reach
beyond -^-^ of the distance of Mercury, the opinion supported
by Laplace, Schubert, Arago, Poisson, and Biot, according to
which the zodiacal light radiates from a vapory, flattened
ring, freely revolving in space between the orbits of Venus
and Mars, appears in the very deficient state of observation
to be the most satisfactory. The outermost limits of the Sun's
atmosphere, like that of Saturn (a subordinate system), could
only extend to that point where the attraction of the uni-
versal or partial central body exactly balanced the centrifu-
gal force ; beyond this point the atmosphere must escape at
a tangent, and continue its course either aggregated into
spherical planets and satellites, or, when not aggregated into
spheres, as solid and vaporous rings. From this point of
view the ring of the zodiacal light comes within the cate-
gory of planetary forms, which are subject to the universal
laws of formation.

From the small progress which this neglected part of our
astronomical knowledge makes on the path of observation, I
have little to add to that which I derived from the experience
of others and myself, and have previously developed in the
Delineation of Nature (vol. i., p. 127-134 ; vol. iv., p. 308).
If, 22 years before Dominique Cassini, to whom the first de-
tection of the zodiacal light is erroneously ascribed, Chil-
drey, the chaplain of Lord Henry Somerset, had already re-
commended this phenomenon to the attention of astronomers
in his Britannica Baconica, published in 1661, as one which
had previously been unnoticed and observed by him during
several years, in February and the commencement of March,
so must I also mention (according to a remark of Olbers) a
letter which Rothmann wrote to Tycho, from whence it re-
sults that Tycho saw the zodiacal light as early as the end
of the sixteenth century, and considered it to be an abnormal
spring-evening twihght. The strikingly greater luminous in-
tensity of this phenomenon in Spain, upon the coasts of Va-
lencia and the plains of New Castile, first incited me to con
tinuous observation before I left Europe. The strength of
the light— it might almost be called illumination — increased

ZODIACAL LIGHT, 'iUb

surprisingly the more I approached the equator in South
America and the South Sea. In the continually dry, clear
air of Cumana, in the grass-steppes [llanos) of Caraccas, upon
the elevated plains of Q,uito and the Mexican seas, especial-
ly at heights from eight to twelve thousand feet, where I
could remain longer, the brightness sometimes exceeded that
of the most beautiful sparks of the Milky Way, between the
fore part of Argus and Sagittarius, or, to speak of our part of
the hemisphere, between the Eagle and the Swan.

Upon the whole, the brightness of the zodiacal light did
not appear to me to increase at all perceptibly with the ele-
vation of the point whence it was seen, but much rather to
depend principally upon the interior variability of the phe-
nomenon itself — upon the greater or less intensity of the
light-giving process, as is shown by my 'observations in the
South Sea, in which, indeed, a reflection was remarked like
that seen on the going down of the Sun. I say principally,
since I do not deny the possibility of a simultaneous influence
of the condition of the air (greater or less diaphaneity) of the
higher strata of the atmosphere, while my instruments indi-
cated in the lower strata no hygrometric variations, or, much
rather, favorable ones. Advances of our knowledge of the
zodiacal light are to be expected especially from the tropics,
where the meteorological processes attain the "highest degree
of uniformity or regularity in the periodical recurrence of the
changes. The phenomenon is there perpetual ; and a careful
comparison of observations at points of diflerent elevation and
under diflerent local conditions, would, with the application
of the theory of probabilities, decide what should be ascribed
to cosmical light-processes, what to merely meteorological in-
fluences.

It has been repeatedly aflirmed that in Europe scarcely
any zodiacal light, or only a feeble trace of it, could be seen
in several successive years. Has the light appeared propor-
tionately weakened in such years in the equinoctial zone
also ? The investigation must not, however, be restricted to
the statement of the configuration according to the distance
/rom known stars or direct measurements. The intensity of
the light, its uniformity or probable intermittence (darting
and flashing), its analysis by the polariscope, should be espe-
cially investigated. Arago [Annuaire for 1836, p. 289) has
•,lready pointed, out that the comparative observation of Dom-
inique Cassini would perhaps clearly prove "que la supposi-
tion des intermittences de la diaphanite atmospherique ne

204 COSMOS.

Baurait suffire a I'explication des variations signalees par cet
astronome" — "that the supposition of intermittent variations
in the diaphaneity of the atmosphere would not suffice for the
explanation of the changes indicated by that astronomer. '

Immediately after the observations of this great astronomer
at Paris, and of his friend Fatio de Duillier, an inclination to
similar labors showed itself in Indian travelers (Father Noel,
De Beze, and Duhalde) ; but isolated reports (for the greater
part only describing the gratification experienced at the un-
usual prospect) are not available for the sound discussion of
the causes of the variabihty. It is not by rapid travels or so-
called voyages round the world, as the labors of the active
Horner have recently shown (Zach, Monatl. Coi'resp., bd. x.,
p. 337-340), that tlie deserved object is to be obtained. It
is only by a permanent stay of several years in some tropical
country that the problem of variable configuration and lu-
minous intensity can be solved. Therefore, the most is to be
expected for the subject which now occupies us, as well as for
the entire science of meteorology, from the ultimate difilision
of scientific culture throughout the equinoctial world — the for-
mer Spanish America — where large populous towns, Cuzco,
La Paz, Potosi, are situated between 10,700 and 12,500 feet
above the level of the sea. The numerical results which
Houzeau was able to obtain, though certainly based upon
only a small number of observations, make it probable that
the major axis of the zodiacal light no more coincides with
the plane of the Sun's equator, than the vapory mass of the
ring whose molecular condition is unknown to us extends be-
yond the Earth's orbit. (Schum., Astr. Nachr., No. 492.)

V.

FALLING STARS, FIRE-BALLS, AND METEORIC STONES.

Since the spring of 1845, when I published the Delinea-
tions of Nature, or the general survey of cosmical phenomena,
the pri3vious results of the observation of aerolites and periodic
streams of falling stars have been abundantly extended and
corrected. Much has been subjected to a stricter and more
careful criticism, especially the discussion, so important for
the whole of this mysterious phenomenon, of the divergence,
i. €., the situation of the point of departure .in the recurring
epochs of swarms of falling stars. The number of these
epochs, also, of which, for a bng time, the August and No-

SHOOTING STARS. 205

veniber 'pp.riods alone attracted attention, has been increased
by recent observations, whose results present a high degi'ce
of probability. From the meritorious labors, first of Brandes,
Benzenberg, Olbers, and Bessel, subsequently of Erman, Bo-
guslawski, Gluetelet, Feldt, Saigey, Edward Heis, and Juhus
Schmidt, corresponding measurements have been commenced,
and a more generally diffused mathematical spirit has ren^
dered it more difficult, through self-deception, to make uncer-
tain observations agree with a preconceived theory.

The progress in the study of fire-meteors would be so much
the quicker in proportion as facts are impartially separated
from opinions, and details put to the test ; but not every thing
discarded as being imperfectly observed which can not yet be
explained. It appears to me most important to separate the
'physical relations from the geometrical and numerical rela-
tions, which latter are, upon the whole, capable of being es-
tablished Avith greater certainty. To this class belong alti-
tude, velocity, individuality, and multiplicity, of the points of
departure when divergence is detected ; the mean number of
fire-meteors in sporadic ox periodic appearances, reduced, ac-
cording to their frequency, to the same measure of time ; the
magnitude and configuration in connection with the time of
year, or with the length of time from midnight. The inves-
tigation of both kinds of relations, the physical and the geo-
metrical, will gradually lead to one and the same end — to
genetic considerations as to the intrinsic nature of the phe-
nomenon.

I have already pointed out the fact that, upon the ivhole,
intercourse with universal space and its contents is restricted
to that which we acquire through oscillations exciting light
and heat, as well as by the mysterious attractive forces which
remote masses (cosmical bodies) exercise upon our terrestrial
globe, its oceans and atmospheric envelope, according to the
quantity of their material particles. The luminous vibra-
tions which proceed from the smallest telescopic stars of a
resolvable nebula, and of which our eyes are sensible, brings
us a testimony of the oldest existence of matter, in the same
way that it mathematically demonstrates to us the certain
knowledge of the velocity and aberration of light.=^ A sen-

* The aspect of the starry heavens presents to us objects o{ unequal
date. Much has long ceased to exist before the knowledge of its pres-
ence reaches usi much has been otherwise arranged. Cosmos, vol. i.,
p. 154, and vol. iii., p. 89, and note. (Compare also Bacon, Nov. Organ.^
Lend., 1733, p. 371, andW. Herschel,in Ph%l. Trans, for 1802, p. 498.^

206 COSMOS.

satifin of light from the depths of the star- filled space of
heaven leads us back, by means of a chain of ideas, through
myriads of centuries into the depths of antiquity. Although
the impression of light which streams of falling stars, explod-
ing aerolite fire-balls, or similar fire-meteors give, may be of
an entirely different nature ; although they may not take fire
until they enter the Earth's atmosphere, still the falling
aerolites present the sohtary instance of a material connec-
tion with something which is foreign to our planet. We
are astonished " at being able to touch, weigh, and chem-
ically decompose metallic and earthy masses which belong
to the outer world, to celestial space," to find in them the
minerals of our native earth, making it probable, as the
great Newton conjectured, that the materials which be-
longed to one group of cosmical bodies are for the most part
the same.*"

For the knowledge of the most ancient falls of aerolites
which are determined with chronological accuracy, we are
indebted to the industry of the all-registering Chinese. Such
reports reach back to the year 644 before our era ; therefore
to the time of Tyrtseus and the second Messenian war of the
Spartans, 179 years before the fall of the enormous meteoric
mass near ^Egos Potamos. Edward Biot has found in Ma-
tuan-lin, which contains extracts from the astronomical sec-
tion of the most ancient annals of the empire, sixteen falls of
aerolites for the epoch from, the middle of the seventh cen-
tury before Christ up to 333 years after Christ, while the
Greek and Roman authors mention only four such phenom-
ena during the same space of time.

It is remarkable that the Ionian school, in accordance with
our present opinions, early assumed the cosmical origin of
meteoric stones. The impression which such a magnificent
phenomenon as that of JEgos Potamos (at a point which be-
came still more celebrated sixty-two years afterward by the
conclusion of the Peloponnesian war by the victory of Lysan-
der over the Athenians), made upon all the Hellenic races,
must have exerted a decisive and not sufficiently regarded
influence upon the direction and development of the Ionian
physiology.] Anaxagoras of Clazomena was at the mature
age of thirty two years when that event of nature took place
According to him, the stars are masses torn away from the

* Cosmos, vol. i., p. 132.

t See the opinions of the Greeks as to the falls of meteoric stones, in
Cosmos, vol. i., p. 133 ; vol. ii., p. 309, note *.

SHOOTING STARS. 207

earth by the violence of the rotation (Plut., De Plac. Philos.f
iii., 13). He considers that the whole heavens may be com-
posed of stones (Plato, De Legib., xii., p. 967). The stony
solid bodies are made to glow by the fiery ether, so that they
reflect the light communicated to them by the ether. Lower
than the Moon, and still between her and the Earth, there
move, says Anaxagoras, according to Theophrastus (Stobseus,
Eclog. Phijs., lib. i., p. 560), yet other dark bodies, which
can also produce eclipses of the Moon (Diog. Laert., ii., 12 ;
Origenes, JPhilosophum, cap. viii.). Diogenes of Apollonia,
who, if he is not a disciple of Anaximenes,=* still probably
belongs to an epoch between Anaxagoras and Democritus,
expresses himself still more distinctly as to the structure of
the world, and, as it were, more moved by the impression of
the great fall of aerolites. According to him, as I have al-
ready mentioned, " invisible (dark) masses of stone move with
the visible stars, and remain, on that account, unknown. The
former sometimes fall upon the earth, and are extinguished,
as happened with the stony star which fell near Mgos Po-
tamos." (Stob., Eclog., p 508. )t

The " opinion of some physicists" as to fiery meteors (fall-
ing stars and aerolites), which Plutarch develops in detail in
the life of Lysander (cap. xii.), is precisely that of the Cre-
tan Diogenes. " FaUing stars," it is said there, " are not
ejections and waste of the ethereal fire, which, when they
enter our atmosphere, are extinguished after their ignition ;
they are much rather the off-shoots of celestial bodies, of such
a nature that, by a slackening of the revolution, they are shot

* Brandis, Gesch. der Grieckisch-Rom. Pkilosophie, torn, i., p. 272-
277, against Schleiermacher, in the Abhandl. der Berl. Akad. from the
year 1804-1811 (Berl., 1815), p. 79-124.

t When Stobseus, in the same passage {Eclog. Phys., p. 508), ascribes
to the Apollonian that he had called the stars pumice-sione-like bodies
(therefore porous stones), the occasion for this term might have been
the idea so generally dimised in antiquity, that all celestial bodies were
nourished by moist exhalations. The Sun gives back again what is
absorbed. (Aristot., Meteorol., ed. Ideler, tom. i., p. 509 ; Seneca, Nat.
Q,u(Est., lib. iv., 2.) The pumice-stone-like cosmical bodies have their
peculiar exhalations. " These, which can not be seen so long as they
wander round in the celestial space, are stones; they ignite and art
extinguished again when they fall to the earth." (Plut., De Plac
Philos., ii., 13.) Pliny considers the fall of meteoric stones as frequent
(Plinius, i., 59) : " Decidere tamen crebro, non erit du.bium." He also
knew that the fall in clear air produced aloud noise (ii., 43). The ap-
parently analogous passage in Seneca, in which he mentions Anaxime-
nes {Nat. Qucest., lib. ii., 17), refers probably to the thunder in a
9torm-cloud

208 COSMOS.

down."* We find nothing of this view of the structure of
the universe, this assumption of dark cosmical bodies whicli
fall upon our earth, in the doctrines of the old Ionic schools,
from Thales and Hippocrates to Empedocles.f The impres-
sion made by the occurrence of nature in the 78th Olympiad
appears to have powerfully called forth the idea of the fall
of dark masses. In the more recent Pseudo-Plutarch (Plac,
ii., 13), we read merely that the Milesian Thales considered
*' all stars to. be earthy Midi fiery bodies (yecjdr) Kal tfiTTvpa)."
The endeavors of the earlier Ionic physiology were directed
to the discovery of the primitive cause of all things, forma-
tion by mixture, gradational change and transition of one
kind of matter into another : to the processes of genetic de-
velo'pnient by solidification or dilution. The revolution of
the sphere of the heavens, " which holds the Earth firmly in
the center," was already conceived by Empedocles as an act-
ively moving cosmical force. Since, in these first attempts
at physical theories, the ether, X\iQ fire-air (and, indeed, fire
itself), represents the expansive force of heat, so the idea of
the propelling revolution rending fragments from the Earth
became connected with the \ohy region of the ether . There-
fore Aristotle calls (MeteoroL, i., 339, Bekker) the ether "the
eternally moving body,"$ as it were the immediate substra-
tum of motion, and seeks for etymological reasons for this as-
sertion. On this account, we find in the biography of Ly-
sander " that the relaxation of the centrifugal force causes
the fall of celestial bodies ;" as also in another place, where
Plutarch, evidently alluding again to opinions of Anaxago-
ras, or Diogenes of Apollonia {De Facie in Orbe Lu7ice, p.
9-23), puts forward the assertion "that the Moon would fall
to the Earth like a stone in a sling if its centrifugal force

* This remarkable passage (Plut, Lys., cap. xii.), literally translated
runs thus : " But there is another and more probable opinion, which
holds that falling stars are not emanations or detached parts ot" the el-
ementary fire, that go out the moment they are kindled, nor yet a quan-
tity of air bursting out from some compression, and taking fire in the
upper regions ; but that they are really heavenly bodies, which, from
some relaxation of the rapidity of their motion, or by some irregular
concussion, are loosened and fall, not so much upon the habitable part
of the globe as into the ocean, which is the reason that their substance
is seldom seen."

t With regard to absolutely dark cosmical bodies, or such in which
the light-procens ceases {periodically?); as to the opinions of moderns
(Laplace and Bessel) ; and Bessel's observation, confirmed by Peters in
K6nigsberg, of a variability of the proper rrotion of Procyon, see Cotmos,
vol- iii., p. 164-166. t Compare Cosmos, vol. iii., p. 31-33.

SHOOTING STARS. 209

ceased."* Thus we see in this simile, after the assumption
of a centrifugal revolution which Empedocles perceived in
the apparent rotation of the celestia.. sphere, a centripetal
force gradually arise as an ideal antithesis. This force was
specially and most distinctly described by the acute inter-
preter of Aristotle, Simplicius (p. 491, Bekker). He explains
the non falling of the celestial bodies thus : " that the cen-
trifugal force predominates over the proper fallforce, the
draiviiig downward T These are the first conjectures re-
specting active central forces ; and the Alexandrian, JohaU'
ues Philoponus, a disciple of Ammonius Hermea, probably
of the sixth century, as it were, recognizing also the inertia
of matter, first ascribes " the motion of the revolutionary
planets to a primitive impulse,'' which he ingeniously (De
Creatione Mundi, lih. i., cap. xii.) imites with the idea of
the " fall, a tendency of all heavy and light bodies toward
the Earth." We have thus endeavored to show how a great
phenomenon of nature and the earliest purely cosmical ex-
planation of a fall of aerolites essentially contributed in
Grecian antiquity, step by step, but certainly not by math-
ematical reasoning, to develop the germ which, fostered by
the intellectual labors of the following centuries, led to Huy-
gens's discovery of the laws of circular motion.

Commencing from the geometrical relations of the periodic
(not sporadic) falling stars, we direct our attention especially
to what recent observations as to the divergence or point of
departure of the meteors, and their entirely planetary ve^
locity, have made known. Both these circumstances, di-
vergence and velocity, characterize them with a high degree
of probability as luminous bodies which present themselves
independently of the Earth's rotation, aud penetrate into our'
atmosphere from ivitliout, from space. The North Amer-
ican observations of the November period on the occasion of
the falls of stars in 1833, 1834, and 1837, indicated as the
point of departure the star y Leonis ; the observations of
the August phenomenon, in the year 1839, Algol in Perseus,
or a point between Perseus and Taurus. These centers of
divergence were about the constellations toward which the
Earth moved at the same epoch. t Saigey, who has submit-

• The remarkable passage alluded to in the text in Plutarch, Be Facit
in, Orbe Lutkb, p. 923, is literally translated, " However, the motion of
the Moon and the violence of the revolution itself prevents it from fall-
ing, just as things placed in a sling are prevented from falling by theif
motion in a cii'cle " t Cosmos, vol. i., p. 118, 119

210 COSMOS.

ted the Auierican observations of 1833 to a very accurate in-
vestigation, remarks that the fixed radiation from the con-
stellation Leo is only observed properly after midnight, in the
last three or four hours before daybreak ; that of eighteen ob-
servers between the town of Mexico and Lake Huron, only
ten perceived the same general point of departure of the me-
teors,=^ which Denison Olmsted, Professor of Mathematics in
New Haven (Connecticut), indicated.

The excellent work of Edward Heis, of Aix-la-Chapelle,
which presents in a condensed form the very accurate ob-
servations of falling stars made by himself during ten years,
contains results as to the phenomena of divergence, which
are so much the more important as the observer has dis-
cussed them with mathematical strictness. According to
him,t " the falling stars of the November period present the
peculiarity that their paths are more dispersed than those of
the August period. In each of the two periods there were
simultaneously several points of departure by no means al-
ways proceeding from the same constellation, as there was
too great a tendency to assume since the year 1833," Be-
sides the principal point of departure of Algol in Perseus,
Heis finds in the August periods of the years 1839, 1841,
1842, 1843, 1844, 1847, and 1848, two others in Draco and
the North Pole.X " In order to deduce accurate results as
to the points of departure of the paths of the falling stars in
the November periods for the years 1839, 1841, 1846, and
1847, for the four points (Perseus, Leo, Cassiopeia, and the
Dragon's Head), the mean path belonging to each was drawn
upon a thirty-inch celestial globe, and in every case the po-
sition of the point ascertained from which the greatest num-
ber of paths proceeded. The investigation showed that of
407 of the falling stars indicated according to their paths,
171 came from Perseus, near the star 7/ in Medusa's Head,
63 from Leo, 35 from Cassiopeia, near the changeable star o,

* Coulvier-Gravier and Saigey, Rccherches sur les Etoiles Filantes,
1847, p. 69-86.

t " The periodical falling stars, and the results of the phenomena de-
duced from the observations carried on during the last ten years at Aix-
la-Chapelle, by Edward Heis," 1849, p. 7 and 26-30.

X The statement of the North Pole being a center of radiation in the
August period is founded only upon the observations of the one year
1839 (10th of August), A traveler in the East, Dr. Asahel Grant, re-
ports from Mardin, in Mesopotamia, "that about midnight the sky was,
as it were, furrowed with falling stars, all of which proceeded from tha
region of the polar star^ (Heis, p. 28, from a letter of Herrick's to
^uetelet's and Grant's Diary,)

SHOOTING STARS. 211

-to from the Dragon's Head, but full 78 from undetermined
points. The number of falling stars issuing from Perseus
consequently amounted to nearly double those from Leo."=^

The divergence from Perseus has consequently shown it
self in both periods as a very remarkable result. An acute
observer, Julius Schmidt, attached to the Observatory at
Bonn, w^ho has been occupied w^ith meteoric phenomena for
eight or ten years, expresses himself upon this subject with
great decision in a letter to me (July, 1851) : " If I deduct
from the abundant falls of shooting stars in November, 1833,
and 1834, as well as from subsequent ones, that kind in which
the point in Leo sent out whole swarms of meteors, I am at
present inclined to consider the Perseus point as that point
of divergence which presents not only in August, but through
out the ivhole year, the most meteors. This point is situated,
according to the result deduced from 478 observations by
Heis, in Rt. Asc. 503° and Decl. 51-5o (holding good for
1844-6). In November, 1849 (from the 7th to the 14th),
I saw some hundreds more shooting stars than I have ever
remarked since 1841. Of these only a few, upon the whole,
came from Leo ; by far the greater number belonged to the
constellation of Perseus. It follows from this, as it appears
to me, that the great November phenomenon of 1799 and
1833 did not appear at that time (1841). Olbers also be-
lieves that the maximum November appearance has a pe-
riod of thirty-four years {Cosmos, vol. i., p. 127). If the di-
rections of the meteor-paths are considered in their full com-
plication and periodical recurrence, it is found that there are
certain points of divergence which are always represented^
others which appear only sporadically and changeably."

Whether, moreover, the different points of divergence alter
with the years — which, if closed rings are assumed, would
indicate an alteration in the situation of the ring in which

* This preponderance of Perseus over Leo, as a point of departure,
did not by any means obtain in the observations at Bremen on the night
of the i|th November, 1838. A very experienced observer, Roswinkel,
saviT, on the occasion of a very abundant fall of shooting stars, almost all
the paths proceed from Leo and the southern part of Ursa Major; while
in the night of the ||th of November, on the occasion of a fall but little
less abundant, only four paths proceeded from Leo. Olbers (Schum.,
Attr. Nachr., No. 372) adds very significantly. On this night paths did
not appear at all parallel to each other, and showed no relation to Leo:
they appear, on account of the want of parallelism, to belong to the
sporadic and the periodic class of falling stars. The proper November
period was, however, certainly not to be compared in brilliancv with
those of the years 1799, 1832, and 1833."

212 COSMOS.

the meteors move — can not at present be determined wrtn
certainty from the observations. A beautiful series of such
observations by Houzeau (during the years 1839 to 1842)
appears to offer evidence against a progressive alteration.*
Edward Heisf has very correctly remarked that, in Grecian
and Roman antiquity, attention had already been directed to
a certain temporary uniformity in the direction of shooting
stars darting across the sky. That direction was then con-
sidered as the result of a wind already blowing in the higher
regions of the atmosphere, and predicted to the sailors an ap-
proaching current of air descending thence into the lower re-
gions.

If the periodic streams of shooting stars are distinguished
from the sporadic by the frequent parallelism of their paths,
proceeding from one or more points of divergence, a second
criterion of them is the numerical — the number of individua.
meteors referred to a definite measure of time. We come
here to the much-disputed question of the distinction of an
extraordinary from an ordinary fall of shooting stars. Two
excellent observers, Olbers and duetelet, have given as the
mean number of meteors which can be reckoned hourly in
the range of vision of one person upon not extraordinary
days, the former five to six, the latter eight meteors4 For
the discussion of this question, which is as important as the
determination of the laws of motion of shooting stars, in ref-
erence to their direction, a great number of observations are
required. I have therefore referred with confidence to the
already-mentioned observer, Herrn Julius Schmidt at Bonn,
who, long accustomed to astronomical accuracy, takes up
with his peculiar energy the whole phenomena of meteors —
of which the formation of aerolites and their fall to the Earth
appear to him merely a special phase, the rarest, and there-
fore not the most important. The following are the principal
results of the communications which I requested from him.§

* Saigey, p. 151 ; and upon Erman's determination of the points of con-
vergence diametrically opposed to the points of divergence, p. 125-129.

t Heis, Period. Sternschn., p. 6. (Compare also Anstot., Problem.,
xxvi., 23; Seneca, Nat. Qucest., lib. i., 14: " Ventum significat stella-
rum discurrentium lapsus, et quidem ab ea parte qua erumpit.") I
have myself long believed in the influence of the wind upon the direc-
tion of the shooting stars, especially during my stay at Marseilles at the
time of the Egyptian expedition. J Cosmos, vol. i., p. 113.

$ All that is marked in the text with inverted commas I am indebted
for to the friendly communication of Herrn Julius Schmidt, attached to
the observatory at Bonn.
BPe Saigey, p. 159.

SHOOTING STARS. 213

'* The mean number of sporadic shooting stars appearing
there has been found, from many years of observation (be-
tween 3 and 8 years), a fall of from four to five in the hour
This is the ordinary condition when nothing periodic occurs
The mean numbers of sporadic meteors in the individual

months give for the hour, January, 3*4 ; February,

March, 4-9 ; April, 2-4 ; May, 39 ; June, 53 ; July, 4-5
August, 53 ; September, 4*7 ; October, 4*5 ; November, 5-3 ;
December, 4'0.

" Of the periodic meteors there may be expected, on the
average, in each hour, above 13 or 15. For a single period,
that of August, the stream of Laurentius presented the follow-
ing gradual increases from sporadic to periodic, upon an av-
ei J2^e of from three to eight years of observation.

Time.

6th of August

7th
8th
9th
10th "

Number of
meteors in
one hour.

.... 6 ...

11 . ..

. ... 15 . ..

. . . . 29 . . .

... 31 . ..

stand

. 3 ]

. 8
. 16
. 18
. 3
. 1

Number
of years.

.. 1

.. 3
.. 4

.. 8
. . 6

nth

12th "

.... 19 ...

7 . .

.. 5
. . 3

The last year g'ave for the hour, notwith
moonlight :

On the 7th of August

8th "

mg the clear
Meteors.

9th
10th

nth '*

12th

Meteoi,

(According to Heis, there were observed on the 10th of Au-
gust:

1839, in one hour, 160 Meteors.

1841 '' 43

1841 " 50

In the August meteor-stream in 1842, there fell at the time
of the maximum, in ten minutes, 34 shooting stars.) All
these numbers refer to the circle of vision of one observer.
Since the year 1838, the November falls have been less brill-
iant. (On the 12th of November, 1839, Heis still counted
hourly 22 to 35 meteors ; likewise, on the 13th of Novem-

J214 C0 3MOS.

ber, 1846, upon the average, 27 to 33.) So variable ia tlie
abundance of the periodic streams in individual years ; but
the number of the falling meteors always remains consider-
ably greater than in ordinary nights, which show in one hour
only four or five sporadic falls. The m'^teors appear to be
the most seldom in Jaauaiy (calculating from the 4th), Feb-
ruary, and March. ^

"Although the August and November periods are justly
the most celebrated, still, since the shooting stars have been
observed with greater accuracy, as to their number and par-
allel direction, yet five others have been discovered.

January : during the first days between the 1st and 3d ;
probably somcA^hat doubtful.

Apiil : 18th or 20th? already conjectured by Arago.
(Great streams: 25th of April, 1095, 22d of April 1800,
20th of April, 1803 ; Cosmos, vol. i., p. 125-126. An
nuaire for 1836, p. 297.)
May: 26th?

July: 26th to the 30th; Gluetelet. Maximum prop-
erly between the 27th and 29th of July. The most an-
cient Chinese observations gave Edward Biot (unfortunate-
ly too soon taken away) a general maximum between the
18th and 27th of July.

August, but before the Laurentius stream, especially be-
tween the 2d and 5th of the month. For the most part,
no regular increase is remarked from the 20th of July t4
the 10 th of August.

The Laurentius stream itself, M usschenbrock

and Brandes {Cosmos, vol. i., p. 124, and note >). Decided
maximum on the 10th of August ; observed for many years.
(According to an old tradition, which is diffused among
the mountain regions about Pelion in Thessaly, on the feast
of the Transfiguration, the 6th of March, the heavens open
during the night, and the lights (Kav5r]Xia) appear in the
midst of the opening ; Herrick, in Silliman's Amer. Jour-
nal, vol. xxxvii., 1839, p. 337 ; and duetelet, in the Nouv.
Mem. de V Acad, de Bruxelles, tom. xv., p. 9.)

October : the 19th and the days about the 26th ; due-
telet; Boguslawski, in the ^' Arbeiteiuder schles. GeselU
scliaftfur vaterl. Culture 1843, p. 178 ; and Heis, p. 83.

* 1 have, however, myself observed a considerable fall of shooting
stars on the T6th of March, 1803, iu the South Sea (Lat. IS^o N.).
Also, 687 years oefore our era. tvf c weteor-strearas were seen in China,
in the month of ivlareii {^Cosmos, vol. i., p. 128).

SHOOTING STARS. 215

The latter instituted observations on the 21st of October,
1766, 18th October, 1838, 17th October, 1841, 24th of
October, 1845, |ith October, 1847, and ||th October, 1848.
(See remarks upon three October phenomena, in the years
902, 1202, and 1366, Cosmos, vol. i., p. 128, and note f.)
The conjecture of Boguslawski, that the Chinese swarm;:;
of meteors, of the 18th and 27th of July, and the fall of
shooting stars of the 21st of October (O.S.), 1366, may be
the now advanced August and November periods, loses
much of its weight after the recent experience of 1838-
1848.=^

November: yfth, very seldom the 8th or 10th. The
great fall of meteors of 1799, in Cumana, on the j^th of
November, which Bonpland and I have described, so far
gave occasion to believe in periodic appearances upon
certain days, that on the occasion of the great fall of me-

* An entirely similar fall of shooting stars as that which the younger
Boguslawski found for October 21st, 1366 (O. S.), in Benesse de Horo-
vie, Chronicon EcclesifB Pragensis {Cosmos, vol. i., p. 128), is fully de-
scribed in the famous historical work of Duarte Nunez do Liao {Chron-
icas dos Reis de Portugal Reformados, pt. i., Lisb., 1600, f. 187), but
placed in the right of the 22d to 23d of October (0. S.). Were there
two streams seen in Bohemia, and on the Tagus, or has one of the
chroniclers erred in a day ? The following are the words of the Portu-
guese historian : " Vindo o anno de 1366, seudo andados xxii. dias do
mes de Octubro, tres meses antes do fallecimento del Rei D. Pedro (de
Portugal), se fez no ceo hum movimento de estrellas, qual os homees
nao virao nem ouvirao. E foi que desda mea noite por diante correrao
todalas strellas do Levante para o Ponente, e acabado de serem juntas
come^arao a correr humas para huraa parte e outras para ontra. 1
despois descerao do ceo tantes e tam spessas, que tanto que forao baxas
no ar, pareciao grandes fogueiras, e que o ceo e o ar ardiao, e que a
mesma terra queria arder. O ceo parecia partido em muitas partes,
aUi onde strellas nao stavao. E isto durou per muito spa^o. Os que
isto viaOjhouverao tam grande medo e pavor, que stavao como attoni-
tos e cuidavao todos de ser mortos, e que era vinda a fim do mundo."
" In the year 1366, and xxii. days of the month of October being past,
three months before the death of the king, Dom Pedro (of Portugal),
there was in the heavens a movement of stars, such as men never be-
fore saw or heard of. At midnight, and for some time after, all the stars
moved from the east to the west ; and after being collected together,
they began to move, some in one direction, and others in another. And
afterward they fell from the sky in such numbers, and so thickly to-
gether, that as they descended low in the air, they seemed large and
fiery, and the sky and the air seemed to be in flames, and even the
earth appeared as if ready to take fire. That portion of the sky where
there were no stars seemed to be divided into many parts, and this
lasted for a long time. Those who saw it were filled with such great
fear and dismay, that they were astounded, imaginiiig they were struck
dead, and that the end of the world had come."

216 COSMOS.

teors in 1833 (November, jf^^h) the phenomenon of the

year 1799 was called to mind.^

December: -^oth.; but in 1798, according to Brandes's

observation, December the ^th ; Herrick, in New Haven,

1838, Dec. |th ; Hiis, 1847, December 8th and 10th.

" Eight or nine epochs of periodic meteoric streams, of
which the last five are most certainly determined, are here
recommended to the industry of observers. The streams of
different months are not alone different from each other ; in
different years, also, the abundance and brilHancy of the
same stream varies strikingly.

" The upper limits of the height of shooting stars can not
be ascertained with accuracy, and Olbers considers all heights
above 120 miles as being less certainly determined. The
lower boundaries which were formerly {^Cosmos, vol. i., p

* Nearer epochs of comparison might have been brought forward, if
they had been known at that time ; for example, the streams of meteors
observed by Kloden, 1823, Nov. i|th, in Potsdam; by Berard, 1831, Nov.
|-|th, on the Spanish coast; and by GTraf Suchtelu, at Orenberg, 1832,
Nov. ||th {Cosmos, \o\. i., p. 124; and Schum., Astr. Nackr., No. 303.
p. 242). The great phenomenon of the 11th and 12th of November,
which Bonpland and I have described {Voyage aux Regions Equi-
noxiales, liv. iv., chap, x., tom. iv., p. 34, 53d ed., 8vo), lasted from
two to four o'clock in the morning. Upon the whole journey which we
made through the forest region of the Orinoco southward, as far as Rio
Negro, we found that the enormous fall of meteors had been seen by
the missionaries, and in some cases recorded in the church books. In
Labrador and Greenland, it threw the Esquimaux into a state of utter
amazement as far as Lichtenau and New Hernihut (lat. 64° 14'). At
Itterstadt, near Weimar, the pastor Zeising saw the same phenomenon
that was at the same time Visible under the equator, and near the north
polar circle in America. Since the periodicity of the St. Laureiitius
stream, August 10th, did not attract general attention until long after
the November period had, I have carefully placed together all the con-
siderable and accurately-observed falls of shooting stars on the i|th
November known to me up to 1846. There are 15 : 1799, 1818, 1822,
1823; 1831-1839, every year; 1841 and 1846. I exclude those falls
of meteors which differ by one or two days, such as those of the 10th
of November, 1787, 8th of November, 1813. Such a periodicity close-
ly connected with individual days is so much the more wonderful, as
bodies of such a small mass are easily exposed to disturbances, and the
breadth of the ring in which the meteors are supposed to be contained
may surround the Earth for some days. The most brilliant November
streams took place in 1799, 1831, 1833, 1834. (In my description of
the meteor of 1799, the largest fire-ball has ascribed to it a diameter
of 1^ and li*^, when it should be 1 and li lunar diameter.) This is
also the place to mention the fire-ball which attracted the special at-
tention of the director of the observatory at Toulouse, M. Petit, and
w hose revolution' round the Earth he has calculated. ( Compies Rendus
9 Aoat, 1847; and Schum., Astr. Nachr.,lio. 701, p. 71.)

SHOOTING STARS. 217

120) generally estimated at 16 miles (over 97,388 feet), must
be greatly contracted. Some, according to measurement, de-
scend very nearly to the level of the summit of Chimborazo
and Aconcagua, to the distance of four geographical miles
above the level of the sea. Heis remarked, on the contrary,
a falling star seen simultaneously at Berlin and Breslau on
the 10th of July, 1837, had, according to accurate calcula-
tion, a height of 248 miles when its light first became visi-
ble, and a height of 168 on its disappearance; others disap-
peared during the same night at a height of 56 miles. From
the older labors of Brandos (1823), it follows that of 100 well-
defined shooting stars seen from two points of observation, 4
had an elevation of only 4 to 12 miles ; 15 between 12 and
24 m. ; 22 from 24 to 40 m. ; 35 (nearly one third) from 40
to 60 m. ; 13 from 40 to 80 m. ; and only 11 (scarcely one
tenth) above 80 m., their heights being between 180 and
240 miles. From 4000 observations collected during nine
years, it has been inferred, with regard to the color of the
shooting stars, that two thirds are white, one seventh yellow,
one seventeenth yellowish red, and only one thirty-seventh
green."

Olbers reports, that during the fall of meteors in the night
of the 12th and 13th of November, in the year 1838, a beau-
tiful northern light was visible at Bremen, which colored
large parts of the sky with an intense blood-red light. The
shooting stars darting across this region maintained their
white color unaltered, whence it may be inferred that the
northern light was further removed from the surface of the
Earth than the shooting stars were at that point where they
became invisible. (Schum., Astr. Nadir., No. 372, p. 78.)
The relative velocity of shooting stars has hitherto been es- .
timated at from 18 to 36 geographical miles a second, while
the Earth has only a translatory velocity of 16*4 miles.
{Cosmos, vol. i., p. 120, note =^.) Corresponding observations
of Julius Schmidt at Bonn, and Heis at Aix-la-Chapelle
(1849), gave as the actual minimum for a shooting star,
which stood 48 miles vertically above St. Goar, and shot over
the Lake of Laach, only 14 miles. According to other com-
parisons of the same observer, and of Houzeau in Mons, the
velocity of four shooting stars was found to be between 46
and 95 miles in the second, consequently two to five times
as great as the planetary velocity of the Earth. The cos-'
mical origin is indeed most strongly proved by this result,:
together with the constancy of the simple or multiple points

Vol. IV.— K

218 COSMOS.

of divergence, i. e., together with the circumstance that
periodic shooting stars, independently of the rotation v{ the
Earth, proceed during several hours from the same star,
even when this star is not that toward which the Earth is
moving at the same time. According to the existing meas-
urements, fire-balls appear to move slower than shooting
Btars ; but it nevertheless remains striking, that when the
former meteors fall, they sink such a little way into the
ground. The mass at Ensisheim, in Alsace, weighing 276
pounds (November 7th, 1492), penetrated only 3 feet, and
the aerolite of Braunau (July 14th, 1847) to the same depth.
I know of only two meteoric stones which have plowed up
the loose earth for 6 and 18 feet : these are the aerolites of
0 astro villari, in the Abruzzi (Febnmry 9th, 1583), and that
of Hradschina, in the Agram district (May 6th, 1751).

Whether any thing has ever fallen from the shooting staris
to the Earth, has been much discussed in opposite senses.
The straw roofs of the parish Belmont (Departement de 1' Ain,
Arondissement Belley), which were set on fire by a meteor
in the night of November 13th, 1835, just at the epoch of
the known November phenomenon, received the fire, as it ap-
pears, not from a falling shooting star, but from a bursting
fire-ball, which problematical aerolite is said to have fallen,
according to the statements of Millet d' Aubenton. A similar
conflagration, caused by a fire-ball, occurred on the 22d of
March, 1846, about three o'clock in the afternoon, in the com-
mune of St. Paul, near Bagnere de Luchon. Only the fall
of stones in Angers (on the 9th of July, 1822) was ascribed
to a beautiful falling star seen near Poitiers. This phenom-
enon, not sufiiciently described, deserves great attention. The
falling stars resembled entirely the so-called Roman candles
used in fire-works. It left behind it a straight streak, very
narrow above, and very broad below, which lasted for ten
or twelve minutes with great brilliancy. Seventeen miles
northward of Poitiers an aerohte fell with a great detona-
tion.

Does all that the shooting stars contain burn in the outer-
most strata of the atmosphere, whose refracting power causes
the phenomenon of twilight ? The above-mentioned various
colors, during the process of combustion, admit of the infer-
ence of a chemical difference in the substances. In addition
to this, the forms of these fiery meteors are exceedingly vari-
able ; some form merely phospJwrescent lines of such fine-
n1^8S and number, that Forster, in the winter of 1832, sa>*

AEROLITES. 21^

the sky illuminated by them with a feeble glow.^ Many
shooting stars move merely as luminous points, and leave no
tail behind them. The combustion, attended with rapid or
slow disappear anf30 of the tails, which are generally many
miles in length, is so much the more remarkable, as the burn-
ing tails sometimes bend and sometimes move onward. The
shining for some hours of the tail of a fire-ball which had long
disappeared, observed by Admiral Krusenstern and his com
panions during their voyage round the world, vividly calls to
mind the long shining of the cloud from which the great
aerolite of JEgos Potamos is said to have fallen, according to
the certainly not quite trustworthy relation of Damachos.
{Cosmos, vol. i., p. 133, and note f.)

There are shooting stars of very different magnitude, in-
creasing to the apparent diameter of Jupiter or Venus ; on
the occasion, also, of the fall of shooting stars seen at Tou-
louse (April 10th, 1812), and the observation of a fire-ball at
Utrecht, on the 23d of August of the same year, they were
seen to form, as it were, from a luminous point, to shoot out
in a star-like manner, and then to expand to a sphere of the
size of the Moon. In very abundant falls of meteors, such
as those of 1799 and 1833, there have been undoubtedly
many fire-balls, mixed with thousands of shooting stars ; but
the identity of both kinds of fiery meteors has not been by
any means proved hitherto. Relation is not identity. There
still remains much to be investigated as to the physical rela-
tions of both — as to the influence pointed out by Admiral
Wrangel,! of the shooting stars upon the development of the
polar light on the shores of the Frozen Sea, and as to the
number of luminous processes indistinctly described, but not,
on that account, to be hastily denied, which have preceded
the formation of fire-balls. The greater number of fire-balls
appear unaccompanied by shooting stars, and show no pe-
riodicity in their appearance. What we know of shooting
stars, with regard to their divergence from definite points, is
at present only to be applied to fire-balls with caution.

Meteoric stones fall the most rarely in a quite clear sky,
without the previous formation of a black meteor-cloud, with-
out any visible phenomenon of light, but with a terrible crack
ling, as upon the 6th of September, 1843, near Klein-Wenden,
not far from Miihlhausen ; or they fall, and this more fre-
quently, shot out of a suddenly-formed dark cloud, accompa-

* Forster's M^moire sur les Etoiles F'dantes, p. 31.
t Cotmos, vol. i., p, 126, and note *.

220 COSMOS.

nied by phenomena of sound, though without light ; finally,
and, indeed, the most frequently, the falls of meteoric stones
present themselves in close connection with brilliant fire
balls. Of this connection, the falls of stones at Barbotan
(Dep. des Landes) on the 24th of July, 1790, with a simul-
taneous appearance of a red fire-ball and a ichite meteoric
cloud,* from which the aerolites fell ; the fall of stones at
Benares, in Hindostan, 13th December^ 1798, and that of
Aigle (Dep. de L'Orne) on the 26th of April, 1803, aflbrd
v/ell-described and indubitable examples. The last of the
phenomena here mentioned — that which among all has been
investigated and described with the greatest care by Biot —
has finally, 23 centuries after the great Thracian fall of stones,
and 300 years since a Frate was killed by an aerolite at C re-
ma,! put an end to the skepticism of the academists. A

* Kanitz, Lehrhnch der Meteorologie, vol. iii., p. 277.

t The great fall of aerolites at Creraa and on the shores of Adda is
described with especial vivacity, but unfortunately in a rhetorical and
vague manner, by the celebrated Petrus Martyr, of Anghiera {^Opus
Episiolarum, Amst., 1670, No. cccclxv., p. 245-246). What preceded
the fall itself was an almost total dai-kening on the 4th of September,
1511, at the noon hour. " Fama est, pavonem immensum in aCrea Cre-
mensi plaga fuisse visum. Tavo visus in pyramidem converti, adeoquo
celei-i ab occidente in orientera raptari cursu, ut in hora) momento
magnam hemisphserii partem, doctorum inspectantium sententia, per-
volagse credatur. Ex nubium illico densitate tenebras ferunt surrex-
'sse, quales viventium nulhis unquam se cognovisse fateatur. Per earn
aoctis faciem, cum formidolosis fulguribus, inaudita tonitrua regionem
--ircumsepserunt." " The report is, that an enormous peacock was seen
flying in the sky above the town of Crema. The peacock appeared to
change into a pyramid, and was carried from west to east with such
rapidity, that in a moment it seemed to ti*averse the whole hemisphere,
as some learned men imagined who saw it. Immediately afterward
such darkness arose from the denseness of the clouds as was never
known by mortal before. During this midnight gloom, unheard-of
thunders, mingled with awful lightnings, resounded through that quar-
ter of the heavens." . The illuminations were so intense, that the in-
habitants round Bergamo could see the whole plain of Crema during
the darkness. " Ex hori'endo illo fragore quid irata natura in eam re-
gionem pepererit, percunctaberis. Saxa demisit in Cremensi planitie
(ubi nullus unquam a^quans ovum lapis visus fuit) immensa; magnitu
dini, pendens egregii. Decem fuisse reperta centilibralia sexa ferunt."
•'You will perhaps inquire what accompanied that terrific commotion
of nature. On the plain of Crema, where never before was seen a stone
the size of an e^^, there fell pieces of rock of enormous dimensions and
of immense weight. It is said that ten of these were found weighing
a hundred pounds each. Birds, sheep, and even fish were killed."
Under all these exaggerations, it may still bo seen that the meteoru.
el&ud out of which the stones fell must have been of uncommon black
ue8s and thickues.=; Tlie " pavo" was undoubtedly a long and broad

AEROLITES.

221

large fire-ball, which moved from S.E. to N.W., was seen at
one o'clock in the afternoon at Alen9on, Falaise, and Caen,
while the sky was quite clear. Some moments afterward
there was heard near Aigle (Dep. de L'Orne) an explosion in
a small, dark, almost motionless cloud, lasting for five or six
minutes, which was followed three or four times by a noise
like a cannon and a rattle of muskets, mixed with a number
of drums. At each explosion, parts of the vapor, of which
the cloud consisted, were removed. No appearance of light
was visible in this instance. There fell at the same time
upon an elliptical surface, whose major axis, from S.E. to
N.W., had a length of six miles, a great number of meteoric
stones, the largest of which weighed only 17^ pounds. They
were hot but not red,=^ smoked visibly, and, what is very strik-

tailed fire-ball. The terrible noise in the meteoric cloud is here repre-
sented as the thunder accompanying the lightning (?). Anghiera him-
self received in Spain a fragment, the size of a fist {ex fiiustris disrup-
torum saxorum), and showed it to King Ferdinand the Catholic, in the
presence of the famous warrior Gonzalo de Cordova. His letter ends
with the words, " Mira super hisce prodigiis conscripta fanatice, physice,
theologice ad nos missa sunt ex Italia. Quid portendant, quomodoque
gignantur, tibi utraque servo, si aliquando ad nos veneris." " From
these prodigies Italy has furnished us with many a marvel of supersti-
tion, physic, and theology ; what they portend, and how they are to
come to pass, you will learn whenever you come to us." (Written
from Burgos to Fagiardus.) Cardanus {Opera, ed. Lugd., 1663, torn,
iii., lib. XV., cap. Ixxii., p. 279) aftirms, still more accurately, that 1200
aerolites fell among them, one of 120 pounds* weight, iron gray, of
great density. The noise is said to have lasted two hours : " ut mi-
rum sit, tamtam molera in acre sustineri potuisse ;" " it is marvelous
that such a mass could be supported in the air," He considered the
tailed fire-ball to be a comet, and errs in the date of the phenomenon
by a year : " Vidimus anno 1510." Cardanus was at that time nine or
ten years old.

* Recently, on the occasion of the fall of aerolites at Braunau (July
14th, 1847), the fallen masses of stone were so hot, that after six hours
they could not be touched without causing a burn. I have already
treated {Asic Centrale, tom. i., p. 408) of the analogy which the Scyth-
ian myth of sacred gold presents with a fall of meteors. *'5.*As the
Scythians say, theirs is the most recent of all nations; and it arose in
the following manner. The first man that appeared in this country,
which was a wilderness, was named Targitaus : they say that the par-
ents of this Targitaus, in my opinion relating what is incredible — they
Bay, however, that they were Jupiter and a daughter of the River Bo-
rysthenes; that such was the origin of Targitaus; and that he had three
sons, who went by the names ot Lipoxais, Apoxais, and the youngest,
Colaxais; that during their reign a plow, a yoke, an ax, and a bowl of
golden workmanship dropping down from heaven, fell on the Scythian
territoiy; that the eldest, seeing them first, approached, intending to
take them up, but as he came near, the gold began to burn; when he
had retired the second went up, and it did the same again ; according

222 COSMOS.

ing, they were more easily broken during the first day afto»
the fall than subsequently. I have intentionally given more
time to this phenomenon, in order to be able to compare it
with another of the 13th of September, 1768. About half
past four o'clock in the afternoon of the above-mentioned day,
a dark cloud was seen near the village of Luce (Dep. d'Eure
et Loire), four miles westward of Chartres, in which a noise
was heard Uke a cannon shot, and at the same time a hissing
was perceived in the air, caused by the fall of a black stone
moving in a curve. The stone, which had penetrated into
the Earth, weighed 7^1bs., and was so hot that it could not
be touched. It was very imperfectly analyzed by Lavoisier,
Fougeroux, and Cadet. No phenomena of light were per-
ceived throughout the whole occurrence.

As soon as the observation of periodic falls of shooting stars
was commenced, and their appearance on certain nights ex-
pected, it wias remarked that the frequency of the meteors in-
creased with the length of time from midnight, and that the
greatest number fell between two and five in the morning.
Already, on the occasion of the great fall of meteors at Cu
mana in the night of the 11th and 12th of November, 1799,

ly, the burning gold repulsed these ; but when the youngest went up
the third, it became extinguished, and he carried the things home with
him; and that the elder brothers, in consequence of this giving way,
surrendered the whole authority to the youngest. 6. From Lipoxais,
they say, are descended those Scythians who are called Auchatae ; from
the second, Apoxais, those who are called Catiari and Traspies; and
from the youngest of them, the royal race, who are called Paralatae
But all have the name of Scoloti, from the surname of their king; but
the Grecians call them Scythians. 7. The Scythians say that such was
their origin ; and they reckon the whole number of years from their
first beginning, from King Targitaus to the time that Darius crossed over
against them, to be not more than a thousand years, but just that num
ber. This sacred gold the kings watch with the greatest care, and an-
nually approach it with magnificent sacrifices to render it propitious.
If he who has the sacred gold happens to fall asleep in the open air on
the festival, the Scythians say he can not survive the year, and on this
account they give him as much land as he can ride round on horseback
in one day. The country being very extensive, Colaxais established
three of the kingdoms for his sons, and made that one the largest in
which the gold is kept. The parts beyond the north of the inhabited
districts the Scythians ^ay can neither be seen nor passed through, by
reason of the feathers shed there ; for that the earth and air are full of
feathers, and that it is these which intercept the view." — Herodotus, iv.,
5 and? (translation, Bohn's Classical Library, p. 238). But is the myth
of sacred gold merely an ethnographical myth — an allusion to three
kings' sons, the founders of three races of Scythians ? an allusion to the
prominent position which the race of the youngest son, the Paralatae,
attained? (Brandstatter, Scythica, de aurea Caterva, 1837, p. 69 and 81. •

AEROLITES. 223

my fellow- travelers saw the greatest swarm of sliociting stars
between half past two and four o'clock- A very meritorious
observer of the phenomena of meteors, Coulvier-Gravier, con-
tributed an important essay to the Institute at Paris upon la
variation horaire des etoiles jilantes. It is difficult to con-
jecture the cause of such an hourly variation, an influence
of the distance from the hour of midnight. If, under differ-
ent meridians, the shooting stars do not become especially
visible until a certain early hour, then, in the case of their
dosmical origin, we must assume, what is still but little prob-
able, viz., that these night, or, rather, early morning hours,
fire especially adapted to the recognition of the shooting stars,
while in other hours of the night more shooting stars pass
by before midnight invisible. We must still long and pa-
, tiently collect observations. BtUQCIoft LibxMrv

The principal characters of the solid masses whicn lalf
from the air I believe I have treated of with tolerable com-
pleteness (^Cosmos, vol. i., p. 129), in reference to their chem-
ical relations and the granular structure, especially investi-
gated by Gustav Rose in accordance with the state of our
knowledge in the year 1845. The successive labors of How-
ard, Klaproth, Thenard, Vauquelin, Proust, Berzelius, Stro-
meyer, Laugier, Dufresnoy, Gustav and Heinrich Rose, Bous-
singault, Rammelsberg, and Shepard, have afforded a rich
material,* and yet two thirds of the fallen meteoric stones,
which lie at the bottom of the sea, escape our observation.
Although it is striking that, under all zones, at points most
distant from each other, the aerolites have a certain phys-
iognomic resemblance — in Greenland, Mexico, and South
America, in Europe, Siberia, and Hindostan — still, upon a
closer investigation, they present very great differences
Many contain yW of iron ; others (Siena) scarcely y|o '■>
nearly all have a thin black, brilliant, and, at the same time,
veined coating : in one (Chantonnay) this crust was entire-
ly wanting. The specific gravity of some meteoric stones
amounts to as much as 4-28, while the carbonaceous stone
of Alais, consisting of crumbling lamellae, showed a specific
gravity of only 1*94. Some (Juvenas) have a doleritic struc-
ture, in which crystallized olivin, augite, and anorthite are
to be recognized separately ; others (the masses of Pallas)
afford merely iron, containing nickel and olivin ; and others,

* The metals discovered in meteoric stones are nickel, by Howard ;
cobalt, by Stromeyer ; copper and chromium, by Laugier ; tin, byBcr
ae'.ius.

224 COSMOS.

again (to judge from the proportions cf tlio ingredients), are
aggregates of hornblende and albite (Chateau-Renard), or of
hornblende and labrador (Blansko and Chantonnay).

According to the general summary of results given by a
sagacious chemist, Professor Rammelsberg, who has recently
occupied himself uninterruptedly, and as actively as success-
fully, with the analysis of aerolites and their composition from
simple minerals, "the separation of the masses fallen from
the air into meteoric iron and meteoric stones is not to be
admitted in its strictest sense. Meteoric iron is sometimes
found, though seldom, with silicates intermixed (the Siberian
mass weighed again by Heis of 1 270 Russian pounds, with
grains of olivin), and, on the other hand, many meteoric stones
contoin metallic iron.

"A. The tneteoric ^Vo?^, whose fall it has been possible to
observe only a few times (Hradschrina, near Agram, on the
26th of May, 1751, Braunau, 14th of July, 1847), while most
analogous masses have already laid long upon the surface of
the earth, possesses in general very similar physical and chem-
ical properties. It almost always contains sulphuret of iron
mixed with it in finer or coarser particles, which, however,
do not appear to be either iron pyrites or magnetif; pyrites,
but a sulphuret of iron. ^ The principal mass of such a me-
teoric iron is also not pure metal, but consists of an alloy of
iron and nickel, so that this constant presence of nickel (on
the average 10 per cent., sometimes rather more, som.etimes
rather less) serves justly as an especial criterion for the me-
teoric nature of the whole mass. It is only an alloy of tico
isomer 2'>hous metals, not a combination in definite proportions.
There are also present in minute quantity, cobalt, manganese,
magnesium, copper, and carbon. The last-mentioned sub
stance is partly mixed mechanically, as difficultly combusti-
ble gi'aphite ; partly in chemical combination with iron, and
therefore analogous to many kinds of bar-iron. The princi-
pal mass of the meteoric iron contains also always a peculiar
combination of 'pliosjihorus loith iron and nickel, which, on
the solution of the iron in hydrochloric acid, remains in the
form of silver-white, microscopic, crystalline needles and lam-
ina?.

"B. The meteoric stones, properly so called, it is customary
to divide into tico classes, according to their external appear-
ance. The stones of one class present, in an apparently ho
mogeneous mass, grains and splinters o^meteoriciron, which

* Raramelsberg, in Poggendoi-fi', Annalen, vol. Ixxiv., 1849, p. 142

AEROLITES. 225

are attracted b} the magnet, and possess entirely the nature
of that found in larger masses. To this class belong, for ex-
ample, the stones of Blansko, Lissa, Aigle, Ensisheim, Chan-
tonnay, Klein- Wenden near Nordhausen, Erxleben, Chateau-
Renard, and Utrecht. The stones of the other class are free
from metallic admixtures,, and present rather a crystalline
mixture of difierent mineral substances ; as, for example, the
stones of Juvenas, Lontalax, and Stannern.

" Since the time that Howard, Klaproth, and Vauquelin
first instituted the chemical investigation of meteoric stones,
for a long time no regard w'^as paid to the fact that they
might be mixtures of separate combinations ; but they were
examined only for their total constituents, and it was consid-
ered sufficient to draw out the iron by the magnet. After
Mohs had directed attention to the analogy between some
aerolites and certain telluric rocks, Nordenskjold endeavored
to prove that the aerolite of Lontalax, in Finland, consisted
of olivin, leucite, and magnetic iron ore ; but the beautiful
observations of Gustav Rose first placed it beyond doubt that
the stone of Juvenas consists of magnetic pyrites, augite, and
a feldspar very much resembling labrador. Guided by this,
Berzelius endeavored, in a more extended essay {Kongl. Veten-
skaps-Academiens Handlingar fur 1834), to eliminate, also
by chemical methods, the mineralogical nature of the sepa-
rate combinations in the aerolites of Blansko, Chantonnay, and
Alais. The road happily pointed out by him beforehand has
subsequently been abundantly followed.

" a. The first and more numerous class oi meteoric stones,
those with metallic iron, contain this disseminated through
them, sometimes in larger masses, which occasionally form a
skeleton, and thus constitute the transition to those meteoric
masses of iron in which, as in the Siberian mass of Pallas,
the other materials disappear more considerably. On account
of the constant presence of olivin, they are rich in magnesia.
The olivin is that part of the meteoric stone which is decom-
posed when it is treated with acids. Like the telluric, it is
a silicate of magnesia and protoxide of iron. That part which
is not attacked by acids is a mixture of feldspathic and au-
gitic matter, whose nature admits of being determined solely
by calculation from its total constituents, as labrador, horn-
blende, augite, or ohgoclas.

'* Q. The second much rarer class of meteoric stones have
been less examined. They contain partly magnetic iron ore,
olivin, and some feldspathic and augitic matter ; some of

K 2

226 COSMOS.

them consist merely of the two last-mentioned simple mmei
als, and the feldspar tribe is then represented by anorthite.^
Chrome iron ore (oxyd of chromium and protoxyd of iron)
is found in small quantity in all meteoric stones ; i^lio^.'phoric
acid and titanic acid, which Rammelsberg discovered in the
very remarkable stone of Juvenas, perhaps indicate a'patitB
and titanite.

" Of the simple substances hitherto detected in the meteoric
stones, there are 18 if oxygen, sulphur, phosphorus, carbon^
silicium, aluminum, magnesium, calcium, potassium, sodi-
um, iron, nickel, cobalt, chromium, manganesium, copper ^
tin, and titanium. The proximate constituents are, (a.)
metallic: nickel-iron, a combination of phosphorus with iron
and nickel, sulphuret of iron and magnetic pyrites ; {b.) oxy-
dized: magnetic iron ore and chrome iron ore ; {c.) silicates:
olivin, anorthite, labrador, and augite."

In order to concentrate the greatest number of important
facts separated from hypothetic conjectures, it still remains
for me to develop the manifold analogies which some mete-
oric stones present as rocks with older, so-called trap rocks
(dolerites, diorites, and melaphyren), with basalts and more
recent lava. These analogies are so much the more strik-
ing, as " the metallic alloy of nickel and iron, which is con-
stantly contained in certain meteoric masses," has not hither-
to been discovered in telluric minerals. The same distin-
guished chemist whose friendly communications I have made
use of in these last pages, enters fully into this subject in a
special treatise, $ the results of which will be more appropri-
ately discussed in the geological part of the Cosmos.

* Shepard, in Silliman's American Jotirnal of Science and Arts, ser.
ii., vol. ii., 1846, p. 377; Rammelsberg, in Poggend., Ann., bd. Ixxiii.,
1848, p. 377.

t Compare Cosmos, vol. i., p. 130.

X Zeitschrift der Deutschen Geolog. Gesellschaft, bd. i., p. 232. All
the matter in the text from p. 224 to p. 226, which is between inverted
commas, was taken from the manuscript of Professor Rammelsberg
(May, 1851).

CONCLUSION.

In concluding the uranological part of the physical de-
scription of the U7iiverse, in taking a retrospect of what I
have attempted (I do not say accomplished), after the exe-
cution of so difficult an undertaking, I think it necessary once
more to call to mind that this execution could have been ef
fected only under those conditions which have been indicated
in the hitroduction to the third volume of Cosmos.- The
attempt to carry out such a cosmical treatment of the subject
is limited to the representation of space and its material con-
tents, whether aggregated into spheres or not. The character
of the present work differs, therefore, essentially from the more
comprehensive and excellent eleme^itarij ivorks on astronomy
which the various literatures of modern times possess. As-
tronomij, as a science, the triumph of mathematical reason-
ing, based upon the sure foundation of the doctrine of gravi-
tation and the perfection of the higher analysis (a mental in-
strument of investigation), treats of phenomena of motion
measured according to space and time ; locality (position) of
the cosmical bodies in their mutual and perpetually-varying
relations to each other; change of form, as in the tailed
comets ; change of light, as the sudden appearance or total
extinction of the light of distant suns. The quantity of mat-
ter present in the universe remains always the same ; but
from what has already been discovered in the telluric sphere
of physical laws of nature, we see working in the eternal
round of material phenomena an ever-unsatisfied change,
presenting itself in numberless and nameless cojnhinations.
Such an exercise of force by matter is called forth by its at
least apparent heterogeneity. Exciting motion in immeas-
urably minute spaces, this heterogeneity of matter compli-
cates all the problems of terrestrial phenomena.

The astronomical problems are of a simpler nature.
Hitherto unencumbered by the above-mentioned complica-
tions, directed to the consideration of the quantities of pon-
derable matter {masses), to the oscillations producing light
and heat — the mechanics of the heavens has, precisely on
account of this simplicity, in which every thing is reduced to

228 COSMOS.

motion, remained in all its branches amenable to mathemat-
ical treatment. This advantage gives to the elementary
works on theoretical astronomy a great and entirely peculiar
charm. In them is reflected what the intellectual labors of
later centuries have achieved by the analytical methods ;
how configuration and orbits are determined ; how, in the
phenomena of planetary motion, only small oscillations about
a mean condition of equilibrium can take place ; how the
planetary system, from its internal arrangement, works its
preservation and permanence by the compensation of ^:?er-
turbations.

The examination of the means of forming a general con
ception of the universe, the ex])lanation of the complicated
celestial phenomena, do not belong to the plan of this work.
The physical description' of the universe relates to what fills
space, and organically animates it, in both spheres of urano-
logical and telluric relations. It adheres to the consideration
of the discovered laws of nature, and treats of them as ac-
quired facts, as immediate results of empirical induction. In
order to carry out the work of the Cosmos within the appro-
priate limits, and not with too great extension, it must not
be attempted to establish theoretically the connection of phe-
nomena. In this Hmitaticn of the plan laid down beforehand,
I have, in the astronomical volume of Cosmos, applied so
much the more care to the individual facts and their arrange-
ment. From the consideration of universal space, its tem-
perature, the degree of its transparency, and the resisting
medmm which fills it, I have passed on to natural and tele-
scopic vision, the limits of visibility, the velocity of light, ac-
cording to the difference of its sources, the imperfect meas-
urements of luminous intensity, and the new optical means
of distinguishing direct from reflected hght. Then follows
the heaven of fixed stars ; the numerical statement of its
dclf-luminous suns so far as their position is determined ; their
probable distribution ; the changeable stars which reappear
at well-defined periods ; the proper motion of the fixed stars ;
the assumption of the existence of dark cosmical bodies, and
their influence upon the motion of the binary stars ; the
nebulous spots, in so far as these are not remote and very
dense swarms of stars.

The transition from the sidereal part of uranology — from
the heaven of the fixed stars to our solar system, is merely
a transition from the universal to the particular. In the
class of binary stars, self-luminous cosmical bodies move about

CONCLUSION. 220

a conltaon center of gravity. In our solar system, which is
constituted of very heterogeneous elements, dark cosmical
bodies revolve round a self-luminous one, or much rather
again round a common center of gravity, which at diiierent
times is situated within and without the central body The
individual members of the solar system are of dissimilar na-
ture— more dissia-dlar than for many centuries astronomeis
were justified in supposing. They are principal and sec
ondary planets ; among the principal planets a group whose
orbits intersect each other ; an innumerable host of comets ;
the ring of the zodiacal hght ; and, with much probability,
the periodic meteor- asteroids.

It still remains to state here fully, as actual relations, the
three great laws of planetary motion, discovered by Kepler.
First laiv : each orbit of a planetary body is an ellipse, in
one of whose foci the Sun is situated. Second law : each
planetary body describes in equal times equal sectors round
the Sun. Third laiv : the squares of the times of revolu-
tion of two planets are as the cubes of their mean distances.
The second law is sometimes called the first, because it was
discovered earlier. (Kepler, Astronomia Nova, seu Physica
Codestis, tradita Commentariis de Motibics stellm Martis,
ex observ. Tychonis Brahi elaborata, 1602 ; compare cap.
xl. with cap. lix.) The first two laws would be applicable
if there were only a single planetary body ; the third and
most important, which was discovered nineteen years after-
ward, fixes the motions of two planets to one law. (The
manuscript of the Hartnonice Mundi, which appeared in
1619, was already completed on the 27th of May, 1618.)

While the laws of planetary motions were empirically dis-
covered at the commencement of the seventeenth century ;
while Newton first discovered the force, of whose action Kep-
ler's laws were to be considered as necessary consequences ;
so the end of the eighteenth century has had the merit of de-
monstrating the stability of the planetary system by the now
path which the perfected calculation of infinitesimals opened
to the investigation of astronomical truths. The principal
elements of this stability are, the invariability of the major
axes of the planetary orbits, proved by Laplace (1773 and
1784), Lagrange, and Poisson ; the long periodic change
(comprised within narrow limits) of the eccentricity of two
larger planets more distant from the sun, Jupiter and Saturn,
themselves only -^-^^-^ of the mass of the all-governing central
body ; finally, the arrangement that, according to the eternaJ

£30 COSMOS.

plan of creation, and the nature of the formation of the
planets, they have all a translatoiy and rotatory motion in
one direction ; that this motion takes place in orbits of slight
and but little varying ellipticity, in planes of moderate dif-
ferences of inclination ; and that the periods of the planeta-
ry revolutions have among each other no common measure
Such elements of stability, as it were the maintenance and
duration of the planets' existence, are dependent upon the
condition of mutual action with a separate circle. If, by the
entry of a cosmical body coming from without, and not pre-
viously belonging to the planetary system, that condition
was disturbed (Laplace, Expos, du Syst. du Monde, p. 309
and 391), then this disturbance, as the consequence of new
attractive forces, or of a collision, might certainly become
destructive to the existing system, until finally, after long con-
flict, a new equilibrium was produced. The arrival of a
comet upon an hyperbolic orbit from a great distance, even
when want of mass is made up for by immense velocity, can
excite apprehension only in an imagination which is not sus
ceptible of the earnest assurances of the calculation of proba-
bilities. The wandering clouds of the interior comets are
not more dangerous to our solar system than the great incli-
nation of the orbits of some of the small planets between
Mars and Jupiter. Whatever must be characterized as mere
probability, lies beyond the domain of a phijsical description
of the universe ; science must not wander into the cloud-
land of cosmological dreams.

INDEX TO VOL. IV.

Abdubrahman Sufi, his notice of neb-
ulous spots, 15, 44.
Absence of solar spots and bad harvests,

supposed connection of, Sir William

Herschel on, 68.
Acosta, on the black specks of the south-
ern hemisphere, 50.
Adams and Leverrier, claims of, to the

discovery of Neptune, 179.
Aerolites, of extraterrestrial cosmical

origin, 199 ; fall of, 219.
Alphonsine Tables, their date, 15.
Anaxagoras of Clazomene, on meteoric

stones, 206.
Andromeda, nebula in, its discovery, 16 ;

further researches, 17, 18 ; not noticed

by Huygens, 38.
Anghiera. See Peter Martyr.
Annular nebula}, rare, 32.
April, falling stars in, 214.
Apsides, line of motion of, 123.
Arabian notices of the Magellanic Clouds,

15, 44.
Arago, on the physical constitution of the

Sun, 62.
Arago and Plateau, different views of, on

irradiation, 148.
ij Argtis, nebula round, its magnificent

effulgence, 41.
Asterion, spiral nebula in, 42.
Asteroids, 57 ; numerical data, 213 ; 01-

bers'a conjecture as to their origin,

164;
Astraea, discovery of, 100 ; elements, 163.
Atmosphere, lunar, disproved, 147.
August, falling stars in, 214.
Axes of rotation, inclination of, 121.
Axial rotation of the planets, periods of,

120.

Bessel, on the planet beyond Uranus, 179.

Biela's Comet, separation of, into two
parts, 193 ; elements, 197.

Black specks in the southern hemisphere,
50.

Bode, on solar spots, 66 ; his law of plan-
etary distance, 116.

Bond, nebulae resolved by, 32, 39.

Brorsen's Comet, elements, 197.

Cadamosto seeks for a south polar star, 28.

Canes Venatici, spiral nebula in Asterion,
one of, 4»2; a most remarkable phe-
nomenon, 42.

Canopi, three, of Vespucci, 46.

Cape Catalogue (or Southern Catalogue)
of Sir John Herschel, 26.

Oape Clouds, or Magellanic Clouds, 43 ;
eoutliem cloiflis vaguefy so called, 45,

Cassini, on nebulae, 19 ; on the Suo'i
spots, 65.

Ceres, discovery of, 100 ; elements, 163.

Chinese statements as to the obliquity of
the ecliptic, 125 ; as to comets, 186 ; aa
to falling stars and meteoric stones, 206.

Classification of nebulae, 19, 32 ; of plan-
ets, 101.

Coal-bags, or coal-sacks, in the southern
hemisphere, 50.

Colored glasses, early use of, by Belgian
pilots, 65.

Comet of Aristotle, 187.

Comet of Colla and Bremiker, 196.

Comet, Halley's, 186, 195.

Comet, Olbers's, 195.

Comets, orbits of, indicate the limits of
the solar system, 57 ; called light-
clouds by the Greeks, 181 ; hypothesis
of their similarity to asteroids, 182;
number discovered annually, 184 ; re-
appearance of Halley's Comet, 186;
Chinese statements, 186; Comet of Aris-
totle, 187; tails of comets, 189, 192; ra-
diant heat, 191 ; Lexell's Comet, 191 ;
Biela's Comet, 193; numerical data,
195; elements of the six interior com
ets, 197 ; inclination of the orbits, 198 ;
Chaldean opinions on, 200.

Craters of the Moon, 155.

Crema, great fall of aerolites at, 220.

Cusa, Cardinal de, his remarkable viewa
of the physical constitution of the Sun,
62 ; on the motion of the Earth, 64.

Cygnus, nebula in, 46.

D' Arrest's Comet, elements, 197.

Days and hours, planetary, 94.

December, falling stars in, 216.

De Hoces discovers the southern ex-
tremity of the new continent, 46.

Densities of the planets, 119.

De Vico's Comet, elements, 197.

Dione, a sateUite of Saturn, 174.

Distances of the planets from the Sun,
107.

Double nebulae, 32.

Double stars differ in their natural char-
acter from our solar system, 53.

Dunlop, his observations of nebulae at
Paramatta, 22, 26.

Earth, the, distance, and other numerica.
data, 141 ; nutation, 105, 125.

Earth-light, what, 144 ; known to Leon-
ardo da Vinci, 145.

Egeria, discovery of, 101 ; elements, 163.

Elliptical nebulae, named the norma]
type, 31.

232

COSMOS.

Enceladus, a satellite of Saturn, 174.
Encke's Comet, elements, 197 ; its reap-
pearance, 198.
Epochs, main, of planetary discovery, 57.
Eccentricity of the planetary orbits, 127.
Exterior planets, 102.

Fabricius first observes the solar spots, 64.
Faculee and shallows, 86.
Page's Comet, elements, 197.
FaHing stars, 204.

Faraday on atmospheric magnetism, 84.
Fire-balls, 198.

Flora, discovery of, 101 ; elements, 163.
Fontaney, the Jesuit, on the Magellanic
Clouds, 47.

Galileo, his contro%'ersy vs^ith Marius, 16 ,
his Mundus Jovialis, 17 ; use of colored
glasses neglected by, 65.

Geminus mentions nebulous stars, 15.

Gnomons, ancient, 127.

Halley's observations on nebulae, 19.
Halley's Comet, reappearances of, 186.
Heat, rays of, 83.

Heat possessed by the Moon's light, 143.
Hebe, discovery of, 101 ; elements, 163.
Heis's observations on shooting stars, 212.
Herschel, Sir William, his estimate of the
extent of nebulous spots, 14; his dis-
coveries, 21 ; on the nebula of Orion,
40; on solar spots, 67; opposed to the
assumption of a lunar atmosphere, 147.
Herschel, Sir John, on nebulte and stellar
clusters, 27, 31 ; on irregular nebulous
masses, 35 ; on the nebula in Orion, 38 ;
on the nebula round tj Argus, 41 ; on
the nebula in Vulpes, 41; his descrip-
tion of the Magellanic Clouds, 47 ; on
the black specks and coal-bags of the
southern hemisphere, 51 ; on the heat
of the Moon's surface, 131.
Herschel, Miss, discovery of a nebula by,

31.
Hipparchus mentions nebulous stars, 15.
jlouzeau's observations on the zodiacal

light, 204.
Humboldt, Alexander von, works of,
quoted in various notes :
Asie Centrale, 222.
De Distributione Geographies Plan-

tarum, 123.
Examen Critique de I'Histoire de la
Geographic du Nouveau Conti-
nent, 15. 28, 45, 151.
Kleinen Schriften, 114.
Voyage aux Regions Equinoxiales,

215.
Vues des Cordilleres et Monumens
des Peuples Indigenes de I'Am^-
rique, 98.
Huygens discovers the nebula in the

sword of Orion, 19, 37.
Hygeia, discovery of, 101 ; elements, 163.
Hyperion, a satellite of Saturn, 174.

Intensity of the solar light on the planets,

130.
Interior comets, 197.

I Interior planets, 103
! Irene, discovery of, 101 ; elements, 163.
; Iris, discoveiy of, 101 ; elements, 103.
i Irregular nebulous masses, 33 ; situats
near the Milky Way, 34 ; extraordinary
size and singular forms, 36.
Isaac, Aben Sid Hassan, introduces tho
Latinized term nebulosaj into the Al-
phonsine Tables, 15.
Jacob, Captain, on the nebula round i)

Argus, 41.
Japetus, a satellite of Saturn, 174.
July, falling stars in, 214.
Juno, discovery of, 100 ; elements, 163.
Jupiter, numerical data, 165; streaks, or

girdles, 167.
Jupiter's satellites, numerical data, 169.

Kant's speculations on nebulae and star-
formation, 20.

Kepler on planetary distances, 110 ; lawa
of planetary motion discovered by, 229.

Lacaille, his classification of nebulsB, 19.

Lambert's speculations on nebulse, 20.

Lassell, discovery of a satellite of Saturn
by, 174; of satellites of Neptune by,
180.

Laurentius stream of falling stars, 214.

Le Geutil's study of nebulae, 20.

Leonardo da Vinci, Earth-light known to,
145.

Leverrier and Adams, claims to the dis-
covery of Neptune, 179.

Lexell's Comet, 191.

Light, time required to traverse the radiut
of the Earth's orbit, 60 ; solar and arti-
ficial, 82 ; diflerence of intensity in the
different planets, 130.

Light, zodiacal. See Zodiacal hght.

Light-clouds, comets so styled by th«
Greeks, 181.

Lucerna Mundi, the Sun, 59.

Lunar atmosphere disproved, 147,

Lunar spots, 149.

Magellanic Clouds, early notices of, 15;
termed Cape-clouds by the Portu
guese, 43 ; general adoption of the
name, 46 ; described by Sir John Her-
schel, 48; not connected with one an-
other, 48 ; nor with the Milky Way, 43.

Magnitude, absolute and apparent, of
planets, 105.

Map of the Moon, 151.

Mars, numerical data, 159 ; raeteorologic
al analogies with the Earth, 159.

Masses of the planets, 118.

Ma}-, falling stars in, 214.

Mayer, of Gunzenhausen (Simon Marius)
first describes a nebula, 16.

Mercury, distance, diameter, mass, donsi
ty of, 1.37.

Messier, his discoveries regarding nebu
las, 21.

Meteor asteroids, 57.

Meteoric stones, 57 ; seldom fall from ■
clear sky, 219 ; remarkable falls oC
219 ; analysis, 223.

Metis, discovery of, 101*; elements, 163.

INDEX.

233

Micholl conceives all nebulae to bt stellar
clustors, 20.

Milky Way, Iluygens on the, 38.

Mimas, a satellite of Saturn, 174.

Moon, myths respecting the, 113, 115 ;
estimate of the heat of its surface, 130 ;
numerical data, 141 ; moonlight, 142 ;
capable of producing heat, 143 ; styled
by the Indians, King of the stars of

. cold, 143 ; eclipses, 145 ; predictions
from the color of the eclipsed body,
147 ; lunar twilight disproved, 147 ;
probably a voiceless wilderness, 148 ;
irradiation, 148; spots, 149; supposed
to reflect the surface of our planet, 150;
topographical chart, 151 ; so-called seas,
151 ; mountains, 153 ; comparison of
height with the mountains of the
Earth, 15.3; ray-systems, 154 ; annular
plains, 154 ; craters of elevation, 155 ;
rills, 157; influence on the Earth, 157.

Mountains of the Moon, 153.

Mundus Jovialis, a work by Galileo, 16.

Nebula, the first isolnted, discovered, 16.

NebulcB, l-acaille's classification of, 19 ;
discoveries of the Kerschels, 21 ; of the
Earl of Rosse and others, 22 ; probably
no essential physical distinction be-
tween, and clusters of stars, 23 ; ques-
tion of the existence or non-existence
of a self-luminous, vaporous matter, 24 ;
elliptical, 31; annular, 32; planetary,
33 ; nebulous stars, 34 ; galaxy of, not
confirmed by recent observation, 36.

Nebular theoiy, the, 20; independent of
the theory of sidereal aggregation, 21.

Nebulous masses, regular, 29 ; irregular,
33 ; these latter mostly situate near the
Milky Way, 34 ; extraordinary size of
some, and singular forms of others, 36.

Nebulous spots, 13 ; number whose posi-
tions have been determined, 14 ; early
notices of, 14 ; Galileo's discoveries, 17 ;
Huygens, 19 ; Lacaille, 19 ; other in-
vestigators, 20; the discoveries of the
Herschels. 21 ; the Earl of Rosse, 22 ;
Sir John Ilerschel's distribution of, 27.

Nebulous stars, mentioned by Hippar-
chus, Geminus, and Ptolemy, 15 ; a
modern division of regular nebulse, 34.

Neptune, considerations on the distance
of, 178 ; numerical data, 178 ; claims to
the discovery of, 178.

Neptune, satellites of, 180.

Northern Catalogue of the IIen:chels, 25.

Northern hemisphere poasesoes many
nebulffi, and but few clusters of stars,
27.

November period, meteors of the, 209,
21.5.

Nubecula Major and Minor, 20, 46.

Number and epoch of discovery of the
principal planets, 89.

Nutation of the Earth's axio, 105, 125.

October, falling stars in, 214.

Olbers's conjecture as to the asteroids
being fragments of a single destroy^J
planet, 164 ; on shooting stars, 216,

Orbits, inclination of, planetary, 121 ;
cometary, 198.

Orion, nebula in the sword of, 18, 36 ; in
the head of, 36 ; trapezium not sur-
rounded by a nebula, 39 ; new stars
discovered in the trapezium, 39.

Pallas, discovery of, 100 ; elements, 161.

Parthenope, discovery of, 101 ; elements,
163.

Penumbras of the solar body, 67.

Periodic meteons, number of, observed
at different hours, and in difterent
months, 213.

Perpetual spring, its undesirable nature,
123.

Perseus, falling stars issuing from, 210.

Peruvian seven-day week, an error, 98.

Peter Martyr, his description of the Ma-
gellanic Clouds, 46; on a fall of aero-
htes, 219.

Photosphere of the nebulous stars, 34 ;
of the Sun, 62.

Picard investigates the nebula in Orion,
19.

Pisces, nebulous region of, 28.

Planetary discovery, epochs of, 58.

Planetary motion, three great laws of, 228.

Planetary nebulae, 33; mainly found in
the southern hemisphere, 33.

Planetary system, stability of, how de-
monstrated, 229.

Planets and their satellites, general con-
siderations, 88 ; principal planets, 89 ;
discovery, 89 ; names, 91 ; planetary
signs, not of ancient date, 94 ; days and
metals named from, 94 ; early conjec-
tures that other planets remained to
be discovered, 99 ; periods of discovery
since the invention of the telescope,
■100; classification in two groups, 102;
exterior, generally larger than the in
teiior, 103; absolute and apparent mag
nitudes, 104 ; arrangement and dis-
tances, 107 ; assumed laws, by Titiu
and Bode, and Wurm, 116; masses
118; densities, 119 ; periods of revolu
tion, and axial rotation, 120; inclina
tion, 121; eccentricitv, 127; intensit)
of the Sun's light, 130r

Planets, secondary, numerical data, 131,

Planets, the small, numerical data, 160 ,
table of elements, 163; Olbers's con-
jecture as to their origin, 164. -

Plateau on irradiation, 148.

Principal planets, 89.

Proselenes, astronomical myth of the.
113.

Ptolemy mentions nebulous stars, 15.

Regular nebulas, classification of, 29.
Revolution, periods of, of the planets,

120 ; of comets, 195.
Rhea, a satellite of Saturn, 174.
Robinson, Dr., neb»la3 resolved by, 22.
Rosse, Earl of, discoveries by means of

his powerful telescope, 22 ; his caution.

23.
Sabbath, used as a name for thi whola

week, 95.

2M

COSMOS

Sagittar.us, nebula in, 41.

Sanscrit names of planets, 93.

Satellites, general considerations on, 131.

Saturn, numerical data, ITO ; rings, 171 ;
eccentric position, 172.

Sat'irn's satellites, numerical data, 174.

Schwabe's observations on the solar
spots, 85 ; on the eccentric position of
Saturn, 172.

feJcythien myth of a fall of gold (meteors),
221.

Seas (so called) of the Moon, 151.

Secondary planets, 131.

Sheeting e4;ars, upper limits of the height
of, unascertained, 217 ; various colors,
217 ; magnitudes, 219.

Siderj BorLonia and Sidera Austriaca,
64.

Sidereal aggregation, theory of, 21.

Sidereal periods of revolution and axial
rotation of the planets, 120.

Sirius, and other fixed stars, estimates
of the distance of, 55.

Small planots, 160.

Snow spots in Mars, 160.

Solar system, ditference between, and the
system of double stars, 53 ; its limits in-
dicated by the orbits of comets, 57 ; its
constituents, 57.

South, Sir James, nebulae resolved by, 22.

South polar star, search for a, 29.

Southern Catalogue of the Herachels,
25.

Southern Cross, planetary nebula in, 33 ;
black spot in, 46, 51.

Southern hemisphere, with fewer nebulse,
possesses relatively more clusters of
stars than the northern, 29 ; the Magel-
lanic Clouds, 15, 45.

Spiral nebula in Asterion, 42.

Spots, solar, 72, 86 ; lunar, 149 ; on Mars,
160.

Star catalogues, early, 47 ; the Herschels',
25 ; the Northern, 26 ; the Southern, 26.

Star clusters, 17; predominate in the
southern hemisphere, 27.

Star-formation theory, the, 21 ; inde-
pendent of the nebular theory, 21.

Stellar clusters, probably no essential
physical difference between, and nebu-
IcB, 23 ; in the northern and the south-
ern hemispheres, 27.

Stemhaufen, star clusters, 17.

Subel, a vague term of the Arabian astron-
omers, 46

Sun, domain of the, 53 ; its constituents
57; translatory motion, 134.

Sun, considered as the central body, 59 ,
numerical data, 60 ; conjectures as to
its physical character, 61 ; envelopes,
62 ; penumbras, 67 ; protuberances, 70.
135 ; distribution of solar spots, 72 •
chronological list of remarkable ap-
pearances of, 74 ; intensity of solar
light, 79 ; comparison of artificial light,
82 ; rays of light and rays of heat, 83 ;
Schwabe's table of occurrence of solar
spots, 86.

Telescope, discoveries of planets since

the invention of the, 100 ; the Earl of

Rosse's, 22.
Tethys, a satellite of Saturn, 174.
Titan, a satellite of Saturn, 174.
Titius, on the law of planetary distances,

116.
Transits of Venus, 139.
Trapezium of Orion, discovery of new

stars in, 39.

Uranus, numerical data, 175.

Uranus, satellites of, peculiarity of their
motion, 176 ; their number undeterm-
ined, 177.

Ursa Major, planetary nebula in, 33.

Ursa Minor, /3 and y, 29.

Venus, distance, brilliancy, rotation, trans*

its, spots, mountains of, 138.
Vespucci searches for a south polar star,

29 ; his mention of the Magellanic

Clouds, 45.
Vesta, discovery of, 100 ; elements, 163.
Victoria, discovery of, 101 ; elements, 163.
Virgo, nebulous region of, 28.
Volcanoes of the Moon, 156.
Vulpes, nebula in, 41.

Week, or seven-day period, early diffused

among the Semitic nations, 95; the

Peruvian, an error, 98.
White Ox, the large Magellanic Cloud, so

called by the Arabians, 15, 43.
Wilson, on solar spots, 66.
Wurm, his correction of Bode's law of

planetary distance, 118.

Zodiacal light, early speculations on, 25;
later opinions, 202 ; observRtions by
the author and others, 203.

w