parallaxes at which they are seen from the changing position of the
spectator, but the true changes constantly going on in the regions of space,
afford us incontrovertible evidence of the 'dominion of the laws of
attraction' in the remotest regions of space, beyond the limits of our solar
system. The existence of these laws is revealed to us by many phenomena,
as, for instance, by the motion of double stars, and by the amount of
retarded or accelerated motion in different parts of their elliptic orbits.
Human inquiry need no longer pursue this subject in the domain of vague
conjecture, or amid the undefined analogies of the ideal world; for even
here the progress made in the method of astronomical observations and
calculations has enabled astronomy to take up its position on a firm basis.
It is not only the discovery of the astounding numbers of double and
multiple stars revolving round a center of gravity lying 'without' their
system (2800 such systems having been discovered up to 1837), but rather the
extension of our knowledge regarding the fundamental forces of the whole
material world, and the proofs we have obtained of the universal empire of
the laws of attraction, that must be ranked among the most brilliant
discoveries of the age. The periods of revolution of colored stars present
the greatest differences; thus, in some instances, the period extends to 43
years, as in πpi of Corona, and in others to several thousands,, as in 66
of Cetus, 38 of Gemini, and 100 of Pisces. Since Herschel's measurements in
1782, the satellite of the nearest star in the triple system of [Greek
letter] of Cancer has completed more than one entire revolution. By a
skillful combination of the altered distances and angles of position,* the
elements of these orbits may be found, conclusions drawn regarding the
absolute distance of the double stars from the Earth, and comparisons made
between their mass and that of the Sun.
[footnote] *Savary, in the 'Connaissance des Tems', 1830, p. 56 and 163.
Encke, 'Berl. Jahrb.', 1832, s. 253, etc. Arago, in the 'Annuaire' 1834, p.
260, 295. John Herschel, in the 'Memoirs of the Astronom. Soc.', vol. v.,
p. 171.
Whether, however, here and in our solar system, quantity of matter is the
only standard of the amount of attractive force, or whether 'specific'
forces of attraction proportionate to the mass may not at the same time come
into operation, as Bessel was the first to conjecture, are questions
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whose practical solution must be left to future ages.*
[footnote] * Bessel, 'Untersuchung. des Theils der planetarischen
Storungen, welche aus der Bewegung der Sonne entstchen' (An Investigation of
the portion of the Planetary Disturbances depending on the motion of the
Sun) in 'Abh. der Berl. Akad. der Wissensch.', 1824 (Mathem. Classe), s.
2-6. The question has been raised by John Tobias Mayer, in 'Comment. Soc.
Reg. Gotting.', 1804-1808, vol. xvi., p. 31-68.
When we compare our Sun with the other fixed stars, that is, with other
self-luminous Suns in the lenticular starry stratum of which our system
forms a part, we find, at least in the case of some, that channels are
opened to us, which may lead, at all events, to an 'approximate' and limited
knowledge of their relative distances, volumes, and masses, and of the
velocities of their translatory motion. If we assume the distance of Uranus
from the Sun to be nineteen times that of the Earth, that is to say,
nineteen times as great as that of the Sun from the Earth, the central body
of our planetary system will be 11,900 times the distance of Uranus from the
star 'a' in the constellation Centaur, almost 31,300 from 61 Cygni, and
41,600 from Vega in the constellation Lyra. The comparison of the volume of
the Sun with that of the fixed stars of the first magnitude is dependent
upon the apparent diameter of the latter bodies -- an extremely undertain
optical element. If even we assume, with Herschel, that the apparent
diameter of Arcturus is only a tenth part of a second, it still follows that
the true diameter of this star is eleven times greater than that of the Sun.*
[footnote] *'Philos. Trans.' for 1803, p. 225. Arago, in the 'Annuaire',
1842, p. 375. In order to obtain a clearer idea of the distances ascribed
in a rather earlier part of the text to the fixed stars, let us assume that
the Earth is a distance of one foot from the Sun; Uranus is then 19 feet,
and Vega Lyrae is 158 geographical miles from it.
The distance of the star 61 Cygni, made known by Bessel, has led
approximately to a knowledge of the quantity of matter contained in this
body as a double star. Notwithstanding that, since Bradley's observations,
the portion of the apparent orbit traversed by this star is not sufficiently
great to admit of our arriving with perfect exactness at the true orbit nd
the major axis of this star, it has been conjectured with much probability
by the great Konigsberg astronomer,* "that the mass of this double star can
not be very considerably larger or smaller than half of the mass of the
Sun."
[footnote] *Bessel, in Schum., 'Jahrb.', 1839, s. 53.
This result is from actual measurement. The analogies deduced from the
relatively larger mass of those planets in our solar system that are
attended by satellites, and from the fact that Struve has discovered six
times more double stars among
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the brighter than among the telescopic fixed stars, have led other
astronomers to conjecture that the average mass of the larger number of the
binary stars exceeds the mass of the Sun.*
[footnote] *Mädler, 'Astron.', s. 476; also in Schum, 'Jahrb.', 1839, s.
95.
We are, however, far from having arrived at general results regarding this
subject. Our Sun, according to Argenlander, belongs, with reference to
proper motion in space, to the class of rapidly-moving fixed stars.
The aspect of the starry heavens, the relative position of stars and
nebullae, the distribution of their luminous masses, the picturesque beauty,
if I may so express myself, of the whole firmament, depend in the course of
ages conjointly upon the proper motion of the stars and nebulae, the
translation of our solar system in space, the appearance of new stars, and
the disappearance or sudden diminution in the intensity of the light of
others, and lastly and specially, on the changes which the Earth's axis
experiences from the attraction of the Sun and Moon. The beautiful stars in
the constellation of the Centaur and the Southern Cross will at some future
time be visible in our northern latitudes, while other stars, as Sirius and
the stars in the Belt of Orion, will in their turn disappear below the
horizon. The places of the North Pole will successively be indicated by the
stars ß beta and a alpha Cephei, and ∂ delta Cygni, until after a period
of 12,000 years, Vega in Lyra will shine forth as the brightest of all
possible pole stars. These data give us some idea of the extent of the
motions which, divided into infinitely small portions of time, proceed
without intermission in the great chronometer of the universe. If for a
moment we could yield to the power of fancy, and imagine the acuteness of
our visual organs to be made equal with the extremest bounds of telescopic
vision, and bring together that which is now divided by long periods of
time, the apparent rest that reigns in space would suddenly disappear. We
should see the countless host of fixed stars moving in thronged groups in
different directions; nebulae wandering through space, and becoming
condensed and dissolved like cosmical clouds; the vail of the Milky Way
separated and broken up in many parts, and 'motion' ruling supreme in every
portion of the vault of heave, even as on the Earth's surface, where we see
it unfolded in the germ, the leaf, and the blossom, the organisms of the
vegetable world. The celebrated Spanish botanist Cavanilles was the first
who entertained the idea of "seeing grass grow," and he directed the
horizontal micrometer threads of a powerfully magnifying glass at one time to
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the apex of the shoot of a bambusa, and at another on the rapidly-growing
stem of an American aloe ('Agave Americana', precisely as the astronomer
places his cross of net-work against a culminating star. In the collective
life of physical nature, in the organic as in the sidereal world, all things
that have been, that are, and will be, are alike dependent on motion.
The breaking up of the Milky Way, of which I have just spoken, requires
special notice. William Herschel, our safe and admirable guide to this
portion of the regions of space, has discovered by his star-guagings that
the telescopic breadth of the Milky Way extends from six to seven degrees
beyond what is indicated by our astronomical maps and by the extent of the
sidereal radiance visible to the naked eye.*
[footnote] *Sir William Herschel, in the 'Philos. Transact.' for 1817, Part
ii p. 438.
The two brilliant nodes in which the branches of the zone unite, in the
region of Cepheus and Cassiopeia, and in the vicinity of Scorpio and
Sagittarius, appear to exercise a powerful attraction on the contiguous
stars; in the most brilliant part, however between beta and [Greek symbol]
Cygni, one half of the 330,000 stars that have been discovered in a breadth
of 5 degrees are directed toward one side, and the remainder to the other.
It is in this part that Herschel supposes the layer to be broken up.*
[footnote] *Arago, in the 'Annuaire', 1842, p. 569
The number of telescopic stars in the Milky Way uninterrupted by any nebulae
is estimated at 18 millions. In order, I will not say, to realize the
greatness of this number, but, at any rate, to compare it with something
analogous, I will call attention to the fact that there are not in the whole
heavens more than about 8000 stars between the first and the sixth
magnitudes, visible to the naked eye. The barren astonishment excited by
numbers and dimensions in space, when not considered with reference to
applications engaging the mental and perceptive powers of man, is awakened
in both extremes of the universe, in the celestial bodies as in the minutest
animalcules.*
[footnote] *Sir John Herschel, in a letter from Feldhuysen, dated Jan.
13th, 1836. Nicholl, 'Architecture of the Heavens', 1838, p. 22. (See,
also, some separate notices by Sir William Herschel on the starless space
which separates us by a great distance from the Milky Way, in the 'Philos.
Transact.' for 1817, Part ii., p. 328.)
A cubic inch of the polishing slate of Bilin contains, according to
Ehrenberg, 40,000 millions of the silicious shells of Galionellae.
The stellar Milky Way, in the region of which, according to Argelander's
admirable observations, the brightest stars of the firmament appear to be
congregated, is almost at right angles
p 151
with another Milky Way, composed of nebulae. The former constitutes,
according to Sir John Herschel's views, an annulus, that is to say, an
independent zone, somewhat remote from our lenticular-shaped starry stratum,
and similar to Saturn's ring. Our planetary system lies in an eccentric
direction, nearer to the region of the Cross than to the diametrically
opposite point, Cassiopeia.*
[footnote] *Sir John Herschel, 'Astronom.', 624; likewise in his
'Observations on Nebulae and Clusters of Stars' ('Phil. Transact.', 1833,
Part ii., p. 479, fig. 25): "We have here a brother system, bearing a real
physical resemblance and strong analogy of structure to our own."
An imperfectly seen nebulous spot, discovered by Messier in 1774, appeared
to present a remarkable similarity to the form of our starry stratum and the
divided ring of our Milky Way.*
[footnote] *Sir William Herschel, in the 'Phil. Trans.' for 1785, Part i.,
p. 257. Sir John Herschel, 'Astron.', 616. ("The 'nebulous' region of the
heavens forms 'a nebulous Milky Way', composed of distinct nebulae, as the
other of stars." The same observation was made in a letter he addressed to
me in March, 1829.)
The Milky Way composed of nebulae does not belong to our starry stratum, but
surrounds it at a great distance without being physically connected with it,
passing almost in the form of a large cross through the dense nebulae of
Virgo, especially in the northern wing, through Comae Berenicis, Ursa Major,
Andromeda's girdle, and Pisces Boreales. It probably intersects the stellar
Milky Way in Cassiopeia, and connects its dreary poles (rendered starless
from the attractive forces by which stellar bodies are made to agglomerate
into groups) in the least dense portion of the starry stratum.
We see from these considerations that our starry cluster, which bears traces
in its projecting branches of having been subject in the course of time to
various metamorphoses, and evinces a tendency to dissolve and separate,
owing to secondary centers of attraction -- is surrounded by two rings, one
of which, the nebulous zone, is very remote, while the other is nearer, and
composed of stars alone. The latter, which we generally term the Milky Way,
is composed of nebulous stars, averaging from the tenth to the eleventh
degree of magnitude,* but appearing, when considered individually, of very
different magnitudes, while isolated starry clusters (starry swarms) almost
always exhibit throughout a character of great uniformity in magnitude and
brilliancy.
[footnote] *Sir John Herschel, 'Astron.', 585.
In whatever part the vault of heaven has been pierced by powerful and
far-penetrating telescopic instruments, stars or luminous nebulae are every
where discoverable, the former, in
p 152
some cases, not exceeding the twentieth or twenty-fourth degree of
telescopic magnitude. A portion of the nebulous vapor would probably be
found resolvable into stars by more powerful optical instruments. As the
retina retains a less vivid impression of separate than of infinitely near
luminous points, less strongly marked photometric relations are excited in
the latter case, as Arago has recently shown.*
[footnote] *Arago, in the 'Annuaire', 1842, p. 282-285, 409-411, and
439-442.
The definite or amorphous cosmical vapor so universally diffused, and which
generates heat through condensation, probably modifies the transparency of
the universal atmosphere, and diminishes that uniform intensity of light
which, according to Halley and Olbers, should arise, if every point
throughout the depths of space were filled by an infinite series of stars.*
[footnote] *Olbers, on the transparency of celestial space, in Bode's
'Jahrb.', 1826, s. 110-121.
The assumption of such a distribution in space is, however, at variance with
observation, which shows us large starless regions of space, 'openings' in
the heavens, as William Herschel terms them -- one, four degrees in width,
in Scorpio, and another in Serpentarius. In the vicinity of both, near
their margin, we find unresolvable nebulae, of which that on the western
edge of the opening Scorpio is one of the most richly thronged of the
clusters of small stars by which the firmament is adorned. Herschel
ascribes these openings or starless regions to the attractive and
agglomerative forcesof the marginal groups.*
[footnote] *"An opening in the heavens," William Herschel, in the 'Phil.
Trans.' for 1785, vol. lxxv., Part i., p. 256. Le Francais Lalande, in the
'Connaiss. des Tems pour l'An.' VIII., p. 383. Arago, in the 'Annuaire',
1842, p. 425.
"They are parts of our starry stratum," says he, with his usual graceful
animation of style, "that have experienced great devastation from time." If
we picture to ourselves the telescopic stars lying behind one another as a
starry canopy spread over the vault of heaven, these starless regions in
Scorpio and Serpentarius may, I think, be regarded as tubes through which we
may look into the remotest depths of space. Other stars may certainly lie
in those parts where the strata forming the canopy are interrupted, but
these are unattainable by our instruments. The aspect of fiery meteors had
led the ancients likewise to the idea of clefts or openings ('chasmata') in
the vault of heaven. These openings were, however, only regarded as
transient, while the reason of their being luminous and fiery, instead of
obscure, was supposed to be owing to the
p 153
translucent illuminated ether which lay beyond them.*
[footnote] *Aristot., 'Meteor.', ii.,, 5, 1. Seneca, 'Natur. Quaest.', i.,
14, 2. "Coelum discessisse," in Cic., 'de Divin.', i., 43.
Derham, and even Huygens, did not appear disinclined to explain in a similar
manner the mild radiance of the nebulae.*
[footnote] *Arago, in the 'Annuaire', 1842, p. 429.
When we compare the stars of the first magnitude, which, on an average, are
certainly the nearest to us, with the non-nebulous telescopic stars, and
further, when we compare the nebulous stars with unresolvable nebulae, for
instance, with the nebula in Andromeda, or even with the so-called planetary
nebulous vapor, a fact is made manifest to us by the consideration of the
varying distances and the boundlessness of space, which shows the world of
phenomena, and that which constitutes its causal reality, to be dependent
upon the 'propagation of light'. The velocity of this propagation is
according to Struve's most recent investigations, 166,072 geographical miles
in a second, consequently almost a million of times greater than the
velocity of sound. According to the measurements of Maclear, Bessel, and
Struve, of the parallaxes and distances of three fixed stars of very unequal
magnitudes ('a' Centauri, 16 Cygni, and 'a' Lyrae), a ray of light requires
respectively 3, 9 1/4, and 12 years to reach us from these three bodies. In
the short but memorable period between 1572 and 1604, from the time of
Cornelius Gemma and Tycho Brahe to that of Kepler, three new stars suddenly
appeared in Cassiopeia and Cygnus, and in the foot of Serpentarius. A
similar phenomenon exhibited itself at intervals in 1670, in the
constellation Vulpis. In recent times, even since 1837, Sir John Herschel
has observed, at the Cape of Good Hope, the brilliant star [Greek symbol] in
Argo increase in splendor from the second to the first magnitude.*
[footnote] *In December, 1837, Sir John Herschel saw the star [Greek
symbol] Argo, which till that time appeared as of the second magnitude, and
liable to no change, rapidly increase till it became of the first magnitude.
In January, 1838, the intensity of its light was equal to that of 'a'
Centauri. According to our latest information, Maclear in March, 1843,
found it as bright as Canopus; and even 'a' Crucis looked faint by [Greek
symbol] Argo.
These events in the universe belong, however, with reference to their
historical reality, to other periods of time than those in which the
phenomena of light are first revealed to the inhabitants of the Earth: they
reach us like the voices of the past. It has been truly said, that with our
large and powerful telescopic instruments we penetrate alike through the
boundaries of time and space: we measure the former through the latter, for
in the course of an
p 154
hour a ray of light traverses over a space of 592 millions of miles. While
according to the theogony of Hesiod, the dimensions of the universe were
supposed to be expressed by the time occupied by bodies in falling to the
ground ("the brazen anvil was not more than nine days and nine nights in
falling from heaven to earth"), the elder Herschel was of opinion* that
light required almost two millions of years to pass to the Earth from the
remotest luminous vapor reached by his forty-foot reflector.
[footnote] *"Hence it follows that the rays of light of the remotest
nebulae must have been almost two millions of years on their way, and that
consequently, so many years ago, this object must already have had an
existence in the sidereal heaven, in order to send out those rays by which
we now perceive it." William Herschel, in the 'Phil. Trans.' for 1802, p.
498. John Herschel, 'Astron.', 590. Arago, in the 'Annuaire', 1842, p.
334, 359, and 382-385.
Much, therefore, has vanished long before it is rendered visible to us --
much that we see was once differently arranged from what it now appears.
The aspect of the starry heavens presents us with the spectacle of that
which is only apparently simultaneous, and however much we may endeavor, by
the aid of optical instruments, to bring the mildly-radiant vapor of
nebulous masses or the faintly-glimmering starry clusters nearer, and
diminish the thousands of years interposed between us and them, that serve
as a criterion of their distance, it still remains more than probable, from
the knowledge we possess of the velocity of the transmission of luminous
rays, that the light of remote heavenly bodies presents us with the most
ancient perceptible evidence of the existence of matter. It is thus that
the reflective mind of man is led from simple premises to rise to those
exalted heights of nature, where in the light-illumined realms of space,
"myriads of worlds are bursting into life like the grass of the night."*
[fotnote] *From my brother's beautiful sonnet "Freiheit und Gesetz."
(Wilhelm von Humboldt, 'Gesammelte Werke', bd. iv., s. 358, No. 25.)
From the regions of celestial forms, the domain of Uranus, we will now
descend to the more contracted sphere of terrestrial forces -- to the
interior of the Earth itself. A mysterious chain links together both
classes of phenomena. According to the ancient signification of the Titanic
myth,* the powers of organic life, that is to say, the great order of
nature, depend upon the combined action of heaven and earth.
[footnote] *Otfried Muller, 'Prolegomena', s. 373.
If we suppose that the Earth, like all the other planets, primordially
belonged, according to its origin, to the central body, the Sun, and to the
solar atmosphere that has been separated into nebulous
p 155
rings, the same connection with this continguous Sun, as well as with all
the remote suns that shine in the firmament, is still revealed through the
phenomena of light and radiating heat. The difference in the degree of
these actions must not lead the physicist, in his delineation of nature, to
forget the connection and the common empire of similar forces in the
universe. A small fraction of telluric heat is derived from the regions of
universal space in which our planetary system is moving, whose temperature
(which according to Fourier, is almost equal to our mean icy polar heat) is
the result of the combined radiation of all the stars. The causes that more
powerfully excite the light of the Sun in the atmosphere and in the upper
strata of our air, that give rise to heat-engendering electric and magnetic
currents, and awaken and genially vivify the vital spark in organic
structures on the earth's surface, must be reserved for the subject of our
future consideration.