CHAPTER VIII

DESCRIPTION OF CELESTIAL OBJECTS MENTIONED IN 'PARADISE LOST'

THE SUN

The surpassing splendour of the Sun, as compared with that of any of the

other orbs of the firmament, is not more impressive than his stupendous

magnitude, and the important functions which it is his prerogative to

fulfil. Situated at the centre of our system--of which he may be

regarded as 'both eye and soul'--the orb has a diameter approaching

1,000,000 miles, and a mass 750 times greater than that of all the

planets combined. These, by his attractive power, he retains in their

several paths and orbits, and even far distant Neptune acknowledges his

potent sway. With prodigal liberality he dispenses his vast stores of

light and heat, which illumine and vivify the worlds circling around

him, and upon the constant supply of which all animated beings depend

for their existence. Deprived of the light of the Sun, this world would

be enveloped in perpetual darkness, and we should all miserably perish.

The Sun is distant from the Earth about 93,000,000 miles. His diameter

is 867,000 miles, or nearly four times the extent of the radius of the

Moon's orbit. The mass of the orb exceeds that of the Earth 330,000

times, and in volume 1,305,000 times. The Sun is a sphere, and rotates

on his axis from west to east in 25 days 8 hours. The velocity of a

point at the solar equator is 4,407 miles an hour. The density of the

Sun is only one-fourth that of the Earth, or, in other words, bulk for

bulk, the Earth is four times heavier than the Sun. The force of gravity

at the Sun's surface is twenty-seven times greater than it is on the

Earth; it would therefore be impossible for beings constituted as we are

to exist on the solar surface.

The dazzling luminous envelope which indicates to the naked eye the

boundary of the solar disc is called the PHOTOSPHERE. It is most

brilliant at the centre of the Sun, and diminishes in brightness towards

the circumference, where its luminosity is but one-fourth that of the

central portion of the disc. The photosphere consists of gaseous vapours

or clouds, of irregular form and size, separated by less brilliant

interstices, and glowing white with the heat derived from the interior

of the Sun. In the telescope the photosphere is not of uniform

brilliancy, but presents a mottled or granular appearance, an effect

created by the intermixture of spaces of unequal brightness. Small

nodules of intense brilliance, resembling 'rice-grains,' but which,

according to Nasmyth, are of a willow-leaf shape with pointed

extremities, which form a network over portions of the photosphere, are

sprinkled profusely over a more faintly luminous background. These

'grains' consist of irregular rounded masses, having an area of several

hundred miles. By the application of a high magnifying power they can be

resolved into 'granules'--minute luminous dots which constitute

one-fifth of the Sun's surface and emit three-fourths of the light. This

granulation is not uniform over the surface of the photosphere; in some

parts it is indistinct, and appears to be replaced by interlacing

filamentous bands, which are most apparent in the penumbrae of the spots

and around the spots themselves. The 'granules' are the tops of

ascending masses of intensely luminous vapour; the comparatively dark

'pores' consist of similar descending masses, which, having radiated

their energy, are returning to be again heated underneath the surface of

the photosphere.

In certain regions of the photosphere several dark patches are usually

visible, which are called 'sun-spots.' At occasional times they are

almost entirely absent from the solar disc. It has been observed that

they occupy a zone extending from 10 deg. to 35 deg. north and south of the

solar equator, but are not found in the equatorial and polar regions of

the Sun. A sun-spot is usually described as consisting of an irregular

dark central portion, called the _umbra_; surrounding it is an edging or

fringe less dark, consisting of filaments radiating inwards called the

_penumbra_. Within the umbra there is sometimes seen a still darker

spot, called the _nucleus_. The umbra is generally uniformly dark, but

at times filmy luminous clouds have been observed floating over it. The

nucleus is believed to be the orifice of a tubular depression in the

floor of the umbra, prolonged downwards to an unknown depth. The

penumbra is brightest at its inner edge, where the filaments present a

marked contrast when compared with the dark cavity of the umbra which

they surround and overhang. Sometimes lengthened processes unite with

those of the opposite side and form bands and 'bridges' across the

umbra. The darkest portion of the penumbra is its external edge, which

stands out conspicuously against the adjoining bright surface of the

Sun. One penumbra will sometimes enclose several umbrae whilst the nuclei

may be entirely wanting.

[Illustration: FIG. 6.--A Sun-spot magnified.

(_Janssen._)]

Sun-spots usually appear in groups; large isolated spots are of rare

occurrence, and are generally accompanied by several smaller ones of

less perfect formation. The exact moment of the origin of a sun-spot

cannot be ascertained, because it arises from an imperceptible point; it

grows very rapidly, and often attains its full size in a day.

Prior to its appearance there is an unusual disturbance of the solar

surface over the site of the spot: luminous ridges, called _faculae_, and

dark 'pores' become conspicuous, between which greyish patches appear,

that seem to lie underneath a thin layer of the photosphere; this is

rapidly dispelled and a fully formed spot comes into view. When a

sun-spot has completed its period of existence, the photospheric matter

overwhelms the penumbra, and rushes into the umbra, which it

obliterates, causing the spot to disappear. The duration of sun-spots is

subject to considerable variation; some last for weeks or months, and

others for a few days or hours. A spot when once fully formed maintains

its shape, which is usually rounded, until the period of its breaking

up. Spots of long duration rotate with the Sun. Those which become

visible at the edge of the Sun's limb have been observed to travel

across his disc in less than a fortnight, disappearing at the margin of

the opposite limb; afterwards, if sufficiently long-lived, they have

reappeared in twelve or thirteen days on the surface of the orb where

first observed. It was by observation of the spots that the period of

the axial rotation of the Sun became known.

Sun-spots vary very much in size--some are only a few hundred miles in

width, whilst others have a diameter of 40,000 or 50,000 miles or

upwards. In some instances the umbra alone has a breadth of 20,000 or

30,000 miles--three times the extent of the diameter of the Earth. Spots

of this size are visible to the naked eye when the Sun is partially

obscured by fog, or when his brilliancy is diminished by vapours near

the horizon. A year seldom passes without the occurrence of several of

such spots being recorded. The largest sun-spot ever observed had a

diameter of about 150,000 miles. A group of spots, including their

penumbrae, will occupy an area of many millions of square miles.

By long observation it has been ascertained that sun-spots increase and

diminish in number with periodical regularity, and that a maximum

sun-spot period occurs at the end of each eleven years. When spots are

numerous on the Sun's disc there is great disturbance of the solar

surface, accompanied by fierce rushes of intensely heated gases. This

solar activity is known to influence terrestrial magnetism by causing a

marked oscillation of the magnetic needle, and giving rise to so-called

'magnetic storms,' accompanied by magnificent displays of aurorae, with

variations in electrical earth-currents. It would therefore appear that

sun-spots have a pronounced effect upon magnetic terrestrial phenomena,

but how this is produced remains unknown.

Besides sun-spots, there are seen on the solar disc bright flocculent

streaks or ridges of luminous matter called _faculae_; they are found

over the whole surface of the Sun, but are most numerous near the limb

and in the immediate vicinity of the spots. They have been compared to

immense waves--vast upheavals of photospheric matter, indicative of

enormous pressure, and often extending in length for many thousands of

miles.

Nearly all observers have arrived at the conclusion that sun-spots are

depressions or cavities in the photosphere, but considerable difference

of opinion exists as to how they are formed. The most commonly accepted

theory is that they are caused by the pressure of descending masses of

vapour having a reduced temperature, which absorb the light and prevent

it reaching us. Our knowledge of the Sun is insufficient to admit of any

accurate conclusion on this point; though we are able to perceive that

the surface of the orb is in a state of violent agitation and perpetual

change, yet his great distance and intense luminosity prevent our

capability of perceiving the ultimate minuter details which go to form

the _texture_ of the solar surface. 'Bearing in mind that a second of

arc on the Sun represents 455 miles, it follows that an object 150 miles

in diameter is about the _minimum visible_ even as a mere mathematical

point, and that anything that is sufficiently large to give the

slightest impression of shape and extension of surface must have an

area of at least a quarter of a million square miles; ordinarily

speaking, we shall not gather much information about any object that

covers less than a million.'[13] Since the British Islands have only an

area of 120,700 square miles, it is evident that on the surface of the

Sun there are many phenomena and physical changes occurring which escape

our observation. Though the changes which occur in the spots and faculae

appear to be slow when observed through the telescope, yet in reality

they are not so. Tremendous storms and cyclones of intensely heated

gases, which may be compared to the flames arising from a great furnace,

sweep over different areas of the Sun with a velocity of hundreds of

miles an hour. Vast ridges and crests of incandescent vapour are

upheaved by the action of internal heat, which exceeds in intensity the

temperature at which the most refractory of terrestrial substances can

be volatilised; and downrushes of the same photospheric matter take

place after it has parted with some of its stores of thermal energy.

Sun-spots of considerable magnitude have been observed to grow rapidly

and then disappear in a very short period of time; occasionally a spot

is seen to divide into two or more portions, the fragments flying

asunder with a velocity of not less than 1,000 miles an hour. It is by

these upheavals and convulsions of the solar atmosphere that the light

and heat are maintained which illumine and vivify the worlds that

gravitate round the Sun.

During total eclipses of the Sun, several phenomena become visible which

have enabled astronomers to gain some further knowledge of the nature of

the solar appendages. The most important of these is the CHROMOSPHERE,

which consists of layers of incandescent gases that envelop the

photosphere and completely surround the Sun. Its average depth is from

5,000 to 6,000 miles, and when seen during an eclipse is of a beautiful

rose colour, resembling a sheet of flame. As seen in profile at the edge

of the Sun's disc, it presents an irregular serrated appearance, an

effect created by the protuberance of luminous ridges and

processes--masses of flame which arise from over its entire surface. The

chromosphere consists chiefly of glowing hydrogen, and an element called

_helium_, which has been recently discovered in a terrestrial substance

called cleveite; there are also present the vapours of iron, calcium,

cerium, titanium, barium, and magnesium. From the surface of this ocean

of fire, jets and pointed spires of flaming hydrogen shoot up with

amazing velocity, and attain an altitude of ten, twenty, fifty, and even

one hundred thousand miles in a very short period of time. They are,

however, of an evanescent nature, change rapidly in form and appearance,

and often in the course of an hour or two die down so as not to be

recognisable. These _prominences_, as they are called, have been divided

into two classes. Some are in masses that float like clouds in the

atmosphere, which they resemble in form and appearance; they are

usually attached to the chromosphere by a single stem, or by slender

columns; occasionally they are entirely free. These are called

_quiescent_ prominences; they consist of clouds of hydrogen, and are of

more lasting duration than the other variety, called _eruptive_ or

metallic prominences. The latter are usually found in the vicinity of

sun-spots, and, besides hydrogen, contain the vapours of various metals.

They are of different forms, and present the appearance of filaments,

spikes, and jets of liquid fire; others are pyramidal, convoluted, and

parabolic.

These outbursts, bending over like the jets from a fountain, and

descending in graceful curves of flame, ascend from the surface of the

chromosphere with a velocity often exceeding 100 miles in a second, and

frequently reach an enormous height, but are of transient duration. They

are closely connected with sun-spots, and are evidence of the tremendous

forces that are in action on the surface of the Sun.

The CORONA is an aureole of light which is seen to surround the Sun

during a total eclipse. It is an impressive and beautiful phenomenon,

and is only visible when the Sun is concealed behind the dark body of

the Moon. Professor Young gives the following graphic description of the

corona: 'From behind it [the Moon] stream out on all sides radiant

filaments, beams, and sheets of pearly light, which reach to a distance

sometimes of several degrees from the solar surface, forming an

irregular stellate halo, with the black globe of the Moon in its

apparent centre. The portion nearest the Sun is of dazzling brightness,

but still less brilliant than the prominences, which blaze through it

like carbuncles. Generally this inner corona has a pretty uniform

height, forming a ring three or four minutes of arc in width, separated

by a somewhat definite outline from the outer corona, which reaches to a

much greater distance and is far more irregular in form. Usually there

are several "rifts," as they have been called, like narrow beams of

darkness, extending from the very edge of the Sun to the outer night,

and much resembling the cloud shadows which radiate from the Sun before

a thundershower. But the edges of these rifts are frequently curved,

showing them to be something else than real shadows. Sometimes there are

narrow bright streamers as long as the rifts, or longer. These are often

inclined, or occasionally even nearly tangential to the solar surface,

and frequently are curved. On the whole, the corona is usually less

extensive and brilliant over the solar poles, and there is a

recognisable tendency to accumulation above the middle latitudes, or

spot zones; so that, speaking roughly, the corona shows a disposition to

assume the form of a quadrilateral or four-rayed star, though in almost

every individual case this form is greatly modified by abnormal

streamers at some point or other.' The corona surrounds the Sun and its

other envelopes to a depth of many thousands of miles. It consists of

various elements which exist in a condition of extreme tenuity;

hydrogen, helium, and a substance called coronium appear to predominate,

whilst finely divided shining particles of matter and electrical

discharges resembling those of an aurora assist in its illumination.

[Illustration: FIG. 7.--The Corona during the Eclipse of May 1883.]

We possess no knowledge of the physical structure of the interior of the

Sun, nor have we any terrestrial analogy to guide us as to how matter

would behave when subjected to such conditions of extreme temperature

and pressure as exist in the interior of the orb. Yet we are justified

in concluding that the Sun is mainly a gaseous sphere which is slowly

contracting, and that the energy expended in this process is being

transformed into heat so extreme as to render the orb a great fountain

of light.

Milton in his poem makes more frequent allusion to the Sun than to any

of the other orbs of the firmament, and, in all his references to the

great luminary, describes him in a manner worthy of his unrivalled

splendour, and of his supreme importance in the system which he upholds

and governs. After having alighted on Mount Niphates, Satan is described

as looking

Sometimes towards Heaven and the full-blazing Sun,

Which now sat high in his meridian tower.--iv. 29-30.

He then addresses him thus:--

O thou that with surpassing glory crowned,

Look'st from thy sole dominion like the god

Of this new World--at whose sight all the stars

Hide their diminished heads--to thee I call,

But with no friendly voice, and add thy name,

O Sun, to tell thee how I hate thy beams,

That bring to my remembrance from what state

I fell, how glorious once above thy sphere.--iv. 32-39.

On another occasion:--

The golden Sun in splendour likest Heaven

Allured his eye.--iii. 572-73.

In describing the different periods of the day, Milton seldom fails to

associate the Sun with these times, and rightly so, since they are

brought about by the apparent diurnal journey of the orb across the

heavens. Commencing with morning, he says:--

Meanwhile,

To re-salute the world with sacred light,

Leucothea waked, and with fresh dews embalmed

The Earth.--xi. 133-36.

Soon as they forth were come to open sight

Of day-spring, and the Sun--who, scarce up-risen,

With wheels yet hovering o'er the ocean-brim,

Shot parallel to the Earth his dewy ray,

Discovering in wide landskip all the east

Of Paradise and Eden's happy plains.--v. 138-43

or some renowned metropolis

With glistering spires and pinnacles adorned,

Which now the rising Sun gilds with his beams.--iii. 549-51.

while now the mounted Sun

Shot down direct his fervid rays, to warm

Earth's inmost womb.--v. 300-302.

for scarce the Sun

Hath finished half his journey, and scarce begins

His other half in the great zone of Heaven.--v. 558-60.

To sit and taste, till this meridian heat

Be over, and the Sun more cool decline.--v. 369-70.

And the great Light of Day yet wants to run

Much of his race, though steep. Suspense in Heaven,

Held by thy voice, thy potent voice he hears,

And longer will delay, to hear thee tell

His generation, and the rising birth

Of Nature from the unapparent deep.--vii. 98-103.

The declining day and approach of evening are described as follows:--

Meanwhile in utmost longitude, where Heaven

With Earth and Ocean meets, the setting Sun

Slowly descended, and with right aspect

Against the eastern gate of Paradise

Levelled his evening rays.--iv. 539-43.

the Sun now fallen

Beneath the Azores; whether the Prime Orb,

Incredible how swift, had thither rolled

Diurnal, or this less volubil Earth,

By shorter flight to the east, had left him there

Arraying with reflected purple and gold

The clouds that on his western throne attend.--iv. 591-97.

the parting Sun

Beyond the Earth's green Cape and verdant Isles

Hesperian sets, my signal to depart.--viii. 630-32.

Now was the Sun in western cadence low

From noon, and gentle airs due at their hour

To fan the Earth now waked, and usher in

The evening cool.--x. 92-95.

for the Sun,

Declined, was hasting now with prone career

To the Ocean Isles, and in the ascending scale

Of Heaven the stars that usher evening rose.--iv. 352-55.

In the combat between Michael and Satan, which ended in the overthrow of

the rebel angels, Milton, in his description of their armour, says:--

two broad suns their shields

Blazed opposite.--vi. 305-306,

and in describing the faded splendour of the ruined Archangel, the poet

compares him to the Sun when seen under conditions which temporarily

deprive him of his dazzling brilliancy and glory:--

as when the Sun new-risen

Looks through the horizontal misty air

Shorn of his beams, or, from behind the Moon

In dim eclipse, disastrous twilight sheds

On half the nations, and with fear of change

Perplexes monarchs.--i. 594-99.

This passage affords us an example of the sublimity of Milton's

imagination and of his skill in adapting the grandest phenomena in

Nature to the illustration of his subject.

THE MOON

The Moon is the Earth's satellite, and next to the Sun is the most

important of the celestial orbs so far as its relations with our globe

are concerned. Besides affording us light by night, the Moon is the

principal cause of the ebb and flow of the tide--a phenomenon of much

importance to navigators. The Moon is almost a perfect sphere, and is

2,160 miles in diameter. The form of its orbit is that of an ellipse

with the Earth in the lower focus. It revolves round its primary in 27

days 7 hours, at a mean distance of 237,000 miles, and with a velocity

of 2,273 miles an hour. Its equatorial velocity of rotation is 10 miles

an hour. The density of the Moon is 3.57 that of water, or 0.63 that of

the Earth; eighty globes, each of the weight of the Moon, would be

required to counterbalance the weight of the Earth, and fifty globes of

a similar size to equal it in dimensions. The orb rotates on its axis in

the same period of time in which it accomplishes a revolution of its

orbit; consequently the same illumined surface of the Moon is always

directed towards the Earth. To the naked eye the Moon appears as large

as the Sun, and it very rapidly changes its form and position in the

sky. Its motions, which are of a very complex character, have been for

many ages the subject of investigation by mathematicians and

astronomers, but their difficulties may now be regarded as having been

finally overcome.

The phases of the Moon are always interesting and very beautiful. The

orb is first seen in the west, after sunset, as a delicate slender

crescent of pale light; each night it increases in size, whilst it

travels eastward, until it attains the figure of a half moon; still

growing larger as it pursues its course, it finally becomes a full

resplendent globe, rising about the time that the Sun sets and situated

directly opposite to him. Then, in a reverse manner, after full moon, it

goes through the same phases, until, as a slender crescent, it becomes

invisible in the solar rays; afterwards to re-appear in a few days, and,

in its monthly round, to undergo the same cycle of changes. The phases

of the Moon depend upon the changing position of the orb with regard to

the Sun. The Moon shines by reflected light derived from the Sun, and as

one half of its surface is always illumined and the other half totally

dark, the crescent increases or diminishes when, by the Moon's change of

position, we see more or less of the bright side. Visible at first as a

slender crescent near the setting Sun, the angular distance from the orb

and the width of the crescent increase daily, until, at the expiration

of seven days, the Moon is distant one quarter of the circumference of

the heavens from the Sun. The Moon is then a semi-circle, or in

quadrature. At the end of other seven days, the distance of the Moon

from the Sun is at its greatest--half the circumference of its orbit. It

is then visible as a circular disc and we behold the orb as full moon.

The waning Moon, as it gradually decreases, presents the same aspects

reversed, and, finally, its slender crescent disappears in the Sun's

rays. The convex edge of the crescent is always turned towards the Sun.

The rising of the Moon in the east and its setting in the west is an

effect due to the diurnal rotation of the Earth on her axis, but the orb

can be perceived to have two motions besides: one from west to east,

which carries it round the heavens in 29.53 days, and another from north

to south. The west to east motion is steady and continuous, but, owing

to the Sun's attractive force, the Moon is made to swerve from its path,

giving rise to irregularities of its motion called PERTURBATIONS. The

most important of these is the _annual equation_, discovered by Tycho

Brahe--a yearly effect produced by the Sun's disturbing influence as the

Earth approaches or recedes from him in her orbit; another irregularity,

called the _evection_, is a change in the eccentricity of the lunar

orbit, by which the mean longitude of the Moon is increased or

diminished. _Elliptic inequality_, _parallactic inequality_, the

_variation_, and _secular acceleration_, are other perturbations of the

lunar motion, which depend directly or indirectly on the attractive

influence of the Sun and the motion of the Earth in her orbit.

As the plane of the Moon's orbit is inclined at an angle of rather more

than 5 deg. to the ecliptic, it follows that the orb, in its journey round

the Earth, intersects this great circle at two points called the

'Nodes.' When crossing the ecliptic from south to north the Moon is in

its ascending node, and when crossing from north to south in its

descending node. In December the Moon reaches the most northern point of

its course, and in June the southernmost. Consequently we have during

the winter nights the greatest amount of moonlight, and in summer the

least. In the evenings the moonlight is least in March and greatest in

September, when we have what is called the Harvest Moon.

The telescopic appearance of the Moon is very interesting and beautiful,

especially if the orb is observed when waxing and waning. As no aqueous

vapour or cloud obscures the lunar surface, all its details can be

perceived with great clearness and distinctness. Indeed, the topography

of the Moon is better known than that of the Earth, for the whole of its

surface has been mapped and delineated with great accuracy and

precision. The Moon is in no sense a duplicate of its primary, and no

analogy exists between the Earth and her satellite. Evidence is wanting

of the existence of an atmosphere surrounding the Moon; no clouds or

exhalations can be perceived, and no water is believed to exist on the

lunar surface. Consequently there are no oceans, seas, rivers, or lakes;

no fertile plains or forest-clad mountains, such as are found upon the

Earth. Indeed, all the conditions essential for the support and

maintenance of organic life by which we are surrounded appear to be

nonexistent on the Moon. Our satellite has no seasons; its axial

rotation is so slow that one lunar day is equal in length to fourteen of

our days; this period of sunshine is succeeded by a night of similar

duration. The alternation of such lengthened days and nights subjects

the lunar surface to great extremes of heat and cold.

When viewed with a telescope, the surface of the Moon is perceived to

consist of lofty mountain chains with rugged peaks, numerous extinct

volcanoes called crater mountains, hills, clefts, chasms, valleys, and

level plains--a region of desolation, presenting to our gaze the

shattered and upturned fragments of the Moon's crust, convulsed by

forces of a volcanic nature which have long since expended their

energies and died out. The mountain ranges on the Moon resemble those of

the Earth, but they have a more rugged outline, and their peaks are more

precipitous, some of them rising to a height of 20,000 feet. They are

called the Lunar Alps, Apennines, and Cordilleras, and embrace every

variety of hill, cliff, mound, and ridge of comparatively low

elevation. The plains are large level areas, which are situated on

various parts of the lunar surface; they are of a darker hue than the

mountainous regions by which they are surrounded, and were at one time

believed to be seas. They are analogous to the prairies, steppes, and

deserts of the Earth.

_Valleys._--Some of these are of spacious dimensions; others are narrow,

and contract into gorges and chasms. Clefts or rills are long cracks or

fissures of considerable depth, which extend sometimes for hundreds of

miles across the various strata of which the Moon's crust is composed.

The characteristic features of the Moon's surface are the crater

mountains: they are very numerous on certain portions of the lunar disc,

and give the Moon the freckled appearance which it presents in the

telescope, and which Galileo likened to the eyes in the feathers of a

peacock's tail. They are believed to be of volcanic origin, and have

been classified as follows: 'Walled plains, mountain rings, ring plains,

crater plains, craters, craterlets, and crater cones.' Upwards of 13,000

of these mountains have been enumerated, and 1,000 are known to have a

diameter exceeding nine miles. Walled plains consist of circular areas

which have a width varying from 150 miles to a few hundred yards. They

are enclosed by rocky ramparts, whilst the centre is occupied by an

elevated peak. The depth of these formations, which are often far below

the level of the Moon's surface, ranges from 10,000 to 20,000 feet.

Mountain rings, ring plains, and crater plains resemble those already

described, but are on a smaller scale; the floors of the larger ones are

frequently occupied by craters and craterlets. The latter exist in large

numbers, and some portions of the Moon's surface appear honeycombed with

them, the smaller craters resting on the sides of larger ones and

occupying the bottoms of the more extensive areas. There is no kind of

formation on the Earth's surface that can be compared with these crater

mountains, which indicate that the Moon was at one time a fiery globe

convulsed by internal forces which found an outlet in the numerous

volcanoes scattered over her surface.

The most remarkable of these volcanic mountains have been named after

distinguished men. (1) Copernicus is one of the most imposing; its

crater is 56 miles in diameter, and situated at its centre is a mountain

with six peaks 2,400 feet in height. The ring by which it is surrounded

rises 11,000 feet above the floor of the crater, and consists of

terraces believed to have been created by the partial congelation and

periodic subsidence of a lake of molten lava which occupied the enclosed

area.

(2) Tycho is one of the most magnificent and perfect of lunar volcanoes,

and is also remarkable as being a centre from which, when the Moon is

full, there radiates a number of bright streaks which extend across the

lunar surface, over mountain and valley, through ring and crater, for

many hundreds of miles. Their nature is unknown, and nothing resembling

them is found on the Earth. Tycho has a diameter of 50 miles and a

depth of 17,000 feet. The peak which rises from the floor of the crater

attains a height of 6,000 feet, and the rampart consists of a series of

terraces which give variety to the appearance of the inner wall. The

surface of the Moon round Tycho is honeycombed with small volcanoes.

(3) Clavius is one of the most extensive of the walled plains; it has a

diameter of 142 miles and an area of 16,500 square miles. The rocky

annulus which surrounds it is very lofty and precipitous, and at one

point reaches a height of 17,300 feet. Upwards of 90 craters have been

counted within this space, one of the peaks attaining to an elevation of

24,000 feet above the level floor of the plain. It is believed that the

lowest depths of this wild and precipitous region are never penetrated

by sunlight, they are so overshadowed by towering crag and fell which

intercept the solar rays; and, as there is no atmosphere to cause

reflection, they are consequently enveloped in perpetual darkness.

(4) Plato has a diameter of about 60 miles and an area of 2,700 square

miles; its central peak rises to a height of 7,300 feet. It has an

irregular rampart which is broken up into terraces averaging about 4,000

feet high; three cones, each with an elevation of from 7,000 to 9,000

feet, rest on its western border.

(5) Theophilus is the deepest of the visible craters on the Moon. It has

a diameter of 64 miles, and the inner edge of the ring rises from the

level floor to a height ranging from 14,000 to 18,000 feet. A group of

mountains occupies the centre of the area, the highest peak of which

reaches an elevation of 5,200 feet. Cyrillus and Catharina, two adjacent

craters, are each about 16,000 feet deep and connected by a wide valley.

(6) Aristarchus is the brightest spot on the Moon, and appears almost

dazzling in the telescope. The crater has a diameter of 42 miles, the

centre of which is occupied by a steep mountain. The rampart on the

western side rises to a height of 7,500 feet, on the east it becomes a

plateau which connects it with a smaller crater called Herodotus. Bright

streaks radiate from Aristarchus when there is full moon, and extend for

a considerable distance over the surface of the orb.

Though the face of the Moon has been carefully scanned for two centuries

and a half, and selenographers have mapped and delineated her features

with the utmost accuracy and precision, yet no perceptible change of a

reliable character has been perceived to occur on any part of the orb.

The surface of the hemisphere directed towards the Earth appears to be

an alternation of desert plains, craggy wildernesses, and extinct

volcanoes--a region of desolation unoccupied by any living thing, and

'upon which the light of life has never dawned.' Owing to the absence of

an atmosphere, there is neither diffuse daylight nor twilight on the

Moon. Every portion of the lunar surface not exposed to the Sun's rays

is shrouded in darkness, and black shadows can be observed fringing

prominences of silvery whiteness. If the Moon were enveloped in an

atmosphere similar to that which surrounds the Earth, the reflection and

diffusion of light among the minute particles of watery vapour which

permeate it would give rise to a gradual transition from light to

darkness; the lunar surface would be visible when not illumined by the

direct rays of the Sun, and before sunrise and after sunset, dawn and

twilight would occur as upon the Earth. But upon the Moon there is no

dawn, and the darkness of night envelops the orb until the appearance of

the edge of the Sun's disc above the horizon, then his dazzling rays

illumine the summits and loftiest peaks of the lunar mountains whilst

yet their sides and bases are wrapped in deep gloom. Since the pace of

the Sun across the lunar heavens is 28 times slower than it is with us,

there is continuous sunshine on the Moon for 304 hours, and this long

day--equal to about a fortnight of our time--is succeeded by a night of

similar duration. As there is no atmosphere overhead to diffuse or

reflect the light, the Sun shines in a pitch-black sky, and at lunar

noonday the planets and constellations can be seen displaying a

brilliancy of greater intensity than can be perceived on Earth during

the darkest night. Every portion of the Moon's surface is bleak, bare,

and untouched by any softening influences. No gentle gale ever sweeps

down her valleys or disturbs the dead calm that hangs over this world;

no cloud ever tempers the fierce glare of the Sun that pours down his

unmitigated rays from a sky of inky blackness; no refreshing shower ever

falls upon her arid mountains and plains; no sound ever breaks the

profound stillness that reigns over this realm of solitude and

desolation.

[Illustration: A PORTION OF THE MOON'S SURFACE]

As might be expected, Milton makes frequent allusion to the Moon in

'Paradise Lost,' and does not fail to set forth the distinctive charms

associated with the unrivalled queen of the firmament. The majority of

poets would most likely regard a description of evening as incomplete

without an allusion to the Moon. Milton has adhered to this sentiment,

as may be perceived in the following lines:--

till the Moon,

Rising in clouded majesty, at length

Apparent queen, unveiled her peerless light,

And o'er the dark her silver mantle threw.--iv. 606-609.

now reigns

Full-orbed the Moon, and with more pleasing light,

Shadowy sets off the face of things.--v. 41-43.

The association of the Moon with the nocturnal revels and dances of

elves and fairies is felicitously expressed in the following passage:--

or faery elves,

Whose midnight revels, by a forest side

Or fountain, some belated peasant sees,

Or dreams he sees, while overhead the Moon

Sits arbitress, and nearer to the Earth

Wheels her pale course.--i. 781-86.

In contrast with this, we have Milton's description of the Moon when

affected by the demoniacal practices of the 'night-hag' who was believed

to destroy infants for the sake of drinking their blood, and applying

their mangled limbs to the purposes of incantation. The legend is of

Scandinavian origin and the locality Lapland:--

Nor uglier follow the night-hag, when called

In secret, riding through the air she comes,

Lured with the smell of infant blood, to dance

With Lapland witches, while the labouring Moon

Eclipses at their charms.--ii. 662-66.

In his description of the massive shield carried by Satan, the poet

compares it with the full moon:--

his ponderous shield

Ethereal temper, massy, large, and round,

Behind him cast. The broad circumference

Hung on his shoulders like the Moon.--i. 284-87.

The phases displayed by the Moon in her monthly journey round the Earth,

and which lend a variety of charm to the appearances presented by the

orb, are poetically described by Milton in the following lines:--

but there the neighbouring Moon

(So call that opposite fair star) her aid

Timely interposes, and her monthly round

Still ending, still renewing, through mid-Heaven

With borrowed light her countenance triform

Hence fills and empties, to enlighten the Earth,

And in her pale dominion checks the night.--iii. 726-32.

It is interesting to observe how aptly Milton describes the subdued

illumination of the Moon's reflected light, as compared with the

brilliant radiance of the blazing Sun, and how the distinguishing glory

peculiar to each orb is appropriately set forth in the various passages

in which they are described; their contrasted splendour enhancing rather

than detracting from the grandeur and beauty belonging to each.

THE PLANET EARTH[14]

No lovelier planet circles round the Sun than the planet Earth, with her

oceans and continents, her mountains, valleys, rivers, lakes, and

plains; surrounded by heaven's azure, radiant with the sunlight of her

day and adorned by night with countless sparkling points of gold. This

beautiful world, the abode of MAN, is of paramount importance to us, and

is the only part of the universe of which we have any direct knowledge.

The Earth may be regarded as one of the Sun's numerous family, and is

situated third in order from the refulgent orb, round which it revolves

in an elliptical orbit at a mean distance of 92,800,000 miles. The Earth

is nearest to the Sun at the end of December, and furthest away at the

beginning of July; the difference between those distances is 3,250,000

miles--the extent of the eccentricity of the planet's orbit. The figure

of the Earth is that of an oblate spheroid; it is slightly flattened at

the poles and bulges at the equator. Its polar or shortest diameter is

7,899 miles, its equatorial diameter is 7,926 miles--greater than the

other by 27 miles. The circumference of the Earth at the equator is

24,899 miles, and the total area of its surface is 197,000,000 square

miles. Its mean density is 5-1/2 times greater than that of water.

The two principal motions performed by the Earth are: (1) Rotation on

its axis; (2) its annual revolution round the Sun. The Earth always

rotates in the same manner, and in the same direction, from west to

east. As the axis of rotation corresponds with the shortest diameter of

the planet, it affords strong evidence that the Earth assumed its

present shape whilst rapidly rotating round its axis when in a fluid or

plastic condition. This would accord with the nebular hypothesis. The

ends of the Earth's axis are called the poles of the Earth; one is the

north, the other the south pole. The north pole is directed towards a

star in the Lesser Bear called the Pole Star. The south pole is directed

to a corresponding opposite part of the heavens. The Earth's axis is

inclined 63 deg. 33' to the plane of the ecliptic, and is always directed to

the same point in the heavens. The Earth accomplishes a revolution on

its axis in 23 hours 56 minutes 4 seconds mean solar time, which is the

length of the sidereal day. This rate of rotation is invariable. At the

equator, where the circumference of the globe exceeds 24,000 miles, the

velocity of a point on its surface is upwards of 1,000 miles an hour,

but, as the poles are approached, the tangential velocity diminishes,

and at those points it is entirely absent. The Earth accomplishes a

revolution of her orbit in 365 days 6 hours 9 minutes; in her journey

round the Sun she travels a circuit of 580,000,000 miles at an average

pace of 66,000 miles an hour. The Earth has other slight motions called

_perturbations_, which are produced by the gravitational attraction of

other members of the solar system. The most important of these is

Precession of the Equinoxes, which is caused by the attraction of the

Sun, Moon, and planets, on the protuberant equatorial region of the

globe. This attraction has a tendency to turn the Earth's axis at right

angles to her orbit, but it only results in the slow rotation of the

pole of the equator round that of the ecliptic, which is occurring at

the rate of 1 deg. in 70 years, and will require a period of 25,868 years to

complete an entire revolution of the heavens.

The spot on Earth round which is centred the chief interest in Milton's

poem is Paradise, which was situated in the east of Eden, a district of

Central Asia. It was here where God ordained that man should first

dwell--a place created for his enjoyment and delight. Satan, after his

soliloquy on Mount Niphates, directs his way to Paradise, and arrives

first in Eden, where he beholds from a distance the Happy Garden--

So on he fares, and to the border comes

Of Eden, where delicious Paradise,

Now nearer, crowns with her enclosure green,

As with a rural mound, the champain head

Of a steep wilderness, whose hairy sides

With thicket overgrown, grotesque and wild,

Access denied; and overhead upgrew

Insuperable highth of loftiest shade,

Cedar, and pine, and fir, and branching palm,

A sylvan scene, and, as the ranks ascend,

Shade above shade, a woody theatre

Of stateliest view. Yet higher than their tops

The verdurous wall of Paradise up-sprung;

Which to our general sire gave prospect large

Into his nether empire neighbouring round.

And higher than that wall, a circling row

Of goodliest trees, loaden with fairest fruit,

Blossoms and fruits at once of golden hue,

Appeared, with gay enamelled colours mixed;

On which the Sun more glad impressed his beams

Than in fair evening cloud, or humid bow,

When God hath showered the Earth: so lovely seemed

That landskip. And of pure now purer air

Meets his approach, and to the heart inspires

Vernal delight and joy, able to drive

All sadness but despair. Now gentle gales,

Fanning their odoriferous wings, dispense

Native perfumes, and whisper whence they stole

Those balmy spoils.--iv. 131-59.

Satan, having gained admission to the Garden by overleaping the tangled

thicket of shrubs and bushes which formed an impenetrable barrier and

prevented any access to the enclosure within, he flew up on to the Tree

of Life--

Beneath him, with new wonder, now he views,

To all delight of human sense exposed,

In narrow room Nature's whole wealth; yea, more!--

A Heaven on Earth: for blissful Paradise

Of God the garden was, by Him in the east

Of Eden planted, Eden stretched her line

From Auran eastward to the royal towers

Of great Seleucia, built by Grecian kings,

Or where the sons of Eden long before

Dwelt in Telassar. In this pleasant soil

His far more pleasant garden God ordained.

Out of the fertile ground he caused to grow

All trees of noblest kind for sight, smell, taste;

And all amid them stood the Tree of Life,

High eminent, blooming ambrosial fruit

Of vegetable gold; and next to life,

Our death, the Tree of Knowledge, grew fast by--

Knowledge of good, bought dear by knowing ill.

Southward through Eden went a river large,

Nor changed his course, but through the shaggy hill

Passed underneath ingulfed; for God had thrown

That mountain, as his garden mould, high raised

Upon the rapid current, which, through veins

Of porous earth with kindly thirst up-drawn,

Rose a fresh fountain, and with many a rill

Watered the garden; thence united fell

Down the steep glade, and met the nether flood,

Which from his darksome passage now appears,

And now, divided into four main streams,

Runs diverse, wandering many a famous realm

And country whereof here needs no account;

But rather to tell how, if Art could tell

How, from that sapphire fount the crisped brooks,

Boiling on orient-pearl and sands of gold,

With mazy error under pendent shades

Ran nectar, visiting each plant, and fed

Flowers worthy of Paradise, which not nice Art

In beds and curious knots, but Nature boon

Poured forth profuse on hill, and dale, and plain,

Both where the morning Sun first warmly smote

The open field, and where the unpierced shade

Imbrowned the noontide bowers.--iv. 205-46.

Milton's description of Paradise is not less remarkable in its way than

the lurid scenes depicted by him in Pandemonium. The versatility of his

poetic genius is nowhere more apparent than in the charming pastoral

verse contained in this part of his poem. The poet has lavished the

whole wealth of his luxuriant imagination in his description of Eden and

blissful Paradise with its 'vernal airs' and 'gentle gales,' its verdant

meads, and murmuring streams, 'rolling on orient-pearl and sands of

gold;' its stately trees laden with blossom and fruit; its spicy groves

and shady bowers, over which there breathed the eternal Spring.

In Book IX. Satan expresses himself in an eloquent apostrophe to the

primitive Earth, over which he previously wandered for seven days--

O Earth, how like to Heaven, if not preferred

More justly, seat worthier of gods, as built

With second thoughts, reforming what was old!

For what God, after better, worse would build?

Terrestrial Heaven, danced round by other Heavens,

That shine, yet bear their bright officious lamps,

Light above light, for thee alone, as seems,

In thee concentring all their precious beams

Of sacred influence! As God in Heaven

Is centre, yet extends to all, so thou

Centring receiv'st from all those orbs; in thee,

Not in themselves, all their known virtue appears,

Productive in herb, plant, and nobler birth

Of creatures animate with gradual life

Of growth, sense, reason, all summed up in Man,

With what delight I could have walked thee round,

If I could joy in aught--sweet interchange

Of hill and valley, rivers, woods, and plains,

Now land, now sea, and shores with forest crowned,

Rocks, dens, and caves.--ix. 99-118.

Though it is impossible to regard the Earth as possessing the importance

ascribed to it by the ancient Ptolemaists; nevertheless, our globe is a

great and mighty world, and appears to be one of the most favourably

situated of all the planets, being neither near the Sun nor yet very far

distant from the orb; and although, when compared with the universe, it

is no more than a leaf on a tree in the midst of a vast forest; still,

it is not the least important among other circling worlds, and

unfailingly fulfils the part allotted to it in the great scheme of

creation.

THE PLANET HESPERUS

This is the beautiful morning and evening star, the peerless planet that

ushers in the twilight and the dawn, the harbinger of day and unrivalled

queen of the evening. Venus, called after the Roman goddess of Love, and

also identified with the Greek Aphrodite of ideal beauty, is the name by

which the planet is popularly known; but Milton does not so designate

it, and the name 'Venus' is not found in 'Paradise Lost.' The ancients

called it Lucifer and Phosphor when it shone as a morning star before

sunrise, and Hesperus and Vesper when it became visible after sunset. It

is the most lustrous of all the planets, and at times its brilliancy is

so marked as to throw a distinct shadow at night.

Venus is the second planet in order from the Sun. Its orbit lies between

that of Mercury and the Earth, and in form approaches nearer to a circle

than that of any of the other planets. It travels round the Sun in

224.7 days, at a mean distance of 67,000,000 miles, and with an average

velocity of 80,000 miles an hour. Its period of rotation is unknown. By

the observation of dusky spots on its surface, it has been surmised that

the planet completes a revolution on its axis in 23-1/4 hours; but other

observers doubt this and are inclined to believe that it always presents

the same face to the Sun. When at inferior conjunction Venus approaches

nearer to the Earth than any other planet, its distance then being

27,000,000 miles. Its greatest elongation varies from 45 deg. to 47 deg. 12'; it

therefore can never be much more than three hours above the horizon

before sunrise, or after sunset. Venus is a morning star when passing

from inferior to superior conjunction, and during the other half of its

synodical period it is an evening star. The planet attains its greatest

brilliancy at an elongation 40 deg. west or east of the Sun--five weeks

before and after inferior conjunction. It is at these periods, when at

its greatest brilliancy, that it casts a shadow at night.

Though so pleasing an object to the unaided eye, Venus, when observed

with the telescope, is often a source of disappointment--this is on

account of its dazzling brilliancy, which renders any accurate

definition of its surface impossible. Sir John Herschel writes: 'The

intense lustre of its illuminated part dazzles the sight, and

exaggerates every imperfection of the telescope; yet we see clearly that

its surface is not mottled over with permanent spots like the Moon; we

notice in it neither mountains nor shadows, but a uniform brightness, in

which sometimes we may indeed fancy, or perhaps more than fancy,

brighter or obscurer portions, but can seldom or never rest fully

satisfied of the fact.' It is believed that the surface of the planet is

invisible on account of the existence of a cloud-laden atmosphere by

which it is enveloped, and which may serve as a protection against the

intense glare of the sunshine and heat poured down by the not

far-distant Sun. Schroeter, a German astronomer, believed that he saw

lofty mountains on the surface of the planet, but their existence has

not been confirmed by any other observer. The Sun if viewed from Venus

would have a diameter nearly half as large again as when seen from the

Earth; it is therefore probable that the planet is subjected to a much

higher temperature than what is experienced on our globe.

The phases of Venus are similar to those exhibited by the Moon, and are

caused by a change in position of the illumined hemisphere of the planet

with regard to the Earth. At superior conjunction the whole enlightened

disc of the planet is turned towards the Earth, but is invisible by

being lost in the Sun's rays. Shortly before or after it arrives at this

point, its form is gibbous, the illumined portion being less than a

circle but greater than a semi-circle. At its greatest elongation west

or east of the Sun the planet resembles the Moon in quadrature--a half

moon--and between those points and inferior conjunction it is visible

as a beautiful crescent. It becomes narrower and sharper as it

approaches inferior conjunction, until it resembles a curved luminous

thread prior to its disappearance at the conjunction. After having

passed this point it reappears on the other side of the Sun as the

morning star.

It would be only natural to imagine that this peerless orb, the most

beautiful and lustrous of the planets, upon which men have gazed with

longing admiration, and designated the emblem of 'all beauty and all

love,' should have impressed Milton's poetical imagination with its

charming appearance, and stimulated the flow of his captivating muse. He

addresses the orb as

Fairest of Stars, last in the train of night,

If better thou belong not to the dawn,

Sure pledge of day, that crown'st the smiling morn

With thy bright circlet, praise Him in thy sphere

While day arises, that sweet hour of prime.--v. 166-70.

In these lines the poet alludes to Venus as the morning star.

In the other passages in his poem Milton associates the planet sometimes

with the morning and at other times with the evening--

His countenance, as the Morning Star that guides

The starry flock.--v. 708-709.

Or if the Star of Evening and the Moon

Haste to thy audience, Night with her will bring

Silence, and Sleep listening to thee will watch.--vii. 104-106.

And hence the morning planet gilds her horns.--vii. 366.

The Sun was sunk and after him the Star

Of Hesperus, whose office is to bring

Twilight upon the Earth, short arbiter

Twixt day and night.--ix. 47-50.

and bid haste the Evening Star

On his hill top to light the bridal lamp.--viii. 519-20.

Milton knew of the phases of Venus and was aware that at certain times

the planet was visible in the telescope as a beautiful crescent. The

line in which he mentions her as gilding her horns is an allusion to

this appearance of Venus.

THE PLEIADES

The beautiful cluster of the Pleiades or Seven Sisters has been regarded

with hallowed veneration from time immemorial. The happy influences

believed to be shed down upon the Earth by those stars and their close

association with human destinies have rendered them objects of almost

sacred interest among the different races of mankind. In every region of

the globe and in every clime, among civilised nations and savage

fetish-worshipping tribes, the same benign influences were ascribed to

the stars which form this interesting group.

In Greek mythology they were known as the seven daughters of Atlas and

Pleione. Different versions are given of their fate. By some writers it

is said they died from grief in consequence of the death of their

sisters, the Hyades, or on account of the fate of their father, who,

for treason, was condemned by Zeus to bear on his head and hands the

vault of heaven, on the mountains of north-west Africa which bear his

name. According to others they were the companions of Diana, and, in

order to escape from Orion, by whom they were pursued, the gods

translated them to the sky.

All writers agree in saying that after their death or translation they

were transformed into stars. Their names are Alcyone, Electra, Maia,

Merope, Sterope, Taygeta, and Celaeno. The seventh Atlantid is said to

be the 'lost Pleiad,' but it can be perceived without difficulty by a

person possessing good eyesight. In the book of Job there is a beautiful

allusion to the Pleiades (chap. xxxviii.) when God speaks out of the

whirlwind and asks the patriarch to answer Him--

Canst thou bind the sweet influences of the Pleiades, or loose the

bands of Orion?

Canst thou bring forth Mazzaroth in his season? or canst thou guide

Arcturus with his sons?

Knowest thou the ordinances of heaven? canst thou set the dominion

thereof in the earth?

Admiral Smyth says that this noble passage is more correctly rendered as

follows:

Canst thou bind the delightful teemings of Cheemah?

Or the contractions of Chesil canst thou open?

Canst thou draw forth Mazzaroth in his season

Or Ayeesh and his sons canst thou guide?

He writes: 'In this very early description of the cardinal

constellations, _Cheemah_ denotes Taurus with the Pleiades; _Chesil_ is

Scorpio; Mazzaroth is Sirius in "the chambers of the south;" and Ayeesh

the Greater Bear, the Hebrew word signifying a _bier_, which was shaped

by the four well-known bright stars, while the three forming the tail

were considered as children attending a funeral.' The Greeks at an early

period were attracted by this cluster of stars, and Hesiod alludes to

them in his writings. One passage converted into rhyme reads as follows:

There is a time when forty days they lie,

And forty nights, conceal'd from human eye;

But in the course of the revolving year,

When the swain sharps the scythe, again appear.

Their heliacal rising was considered a favourable time for setting out

on a voyage, and their midnight culmination, which occurred shortly

after the middle of November, was celebrated by some nations with

festivals and public ceremonies. Considerable diversity of opinion

existed among the ancients with regard to the number of stars which

constitute this group. It was affirmed by some that only six were

visible, whilst others maintained that seven could be seen. Ovid writes:

Quae septem dici, sex tamen esse solent.

Homer and Attalus mention six; Hipparchus and Aratus seven. The legend

with regard to the lost Pleiad would seem to indicate that, during a

period in the past, the star possessed a superior brilliancy and was

more distinctly visible than it is at the present time. This may have

been so, for, should it belong to the class of variable stars, there

would be a periodic ebb and flow of its light, by which its fluctuating

brilliance could be explained. When looked at directly only six stars

can be seen in the group, but should the eye be turned sideways more

than this number become visible. Several observers have counted as many

as ten or twelve, and it is stated by Kepler that his tutor, Maestlin,

was able to enumerate fourteen stars and mapped eleven in their relative

positions. With telescopic aid the number is largely increased--Galileo

observed thirty-six with his instrument and Hooke, in 1664, counted

seventy-eight. Large modern telescopes bring into view several thousand

stars in this region.

The Pleiades are situated at a profound distance in space. Their light

period is estimated at 250 years, indicating a distance of 1,500

billions of miles. Our Sun if thus far removed would be reduced to a

tenth-magnitude star. 'There can be little doubt,' says Miss Agnes

Clerke, 'that the solar brilliancy is surpassed by sixty to seventy of

the Pleiades. And it must be in some cases enormously surpassed; by

Alcyone 1,000, by Electra 480, by Maia nearly 400 times. Sirius itself

takes a subordinate rank when compared with the five most brilliant

members of a group, the real magnificence of which we can thus in some

degree apprehend.' This is the only star cluster which can be perceived

to be moving in space, or which has an ascertained common proper motion.

Its constituents form a magnificent system in which the stars bear a

mutual relationship to each other, and perform intricate internal

revolutions, whilst they in systemic union drift along through the

depths of space. There are two allusions to the Pleiades in 'Paradise

Lost.' In describing the path of the newly created Sun, Milton

introduces them as indicative of the joyfulness associated with the

birth of the Universe--

First in his east the glorious lamp was seen,

Regent of day, and all the horizon round

Invested with bright rays, jocund to run

His longitude through heaven's high road; the grey

Dawn, and the Pleiades before him danced,

Shedding sweet influence.--vii. 370-75.

It was believed that the Earth was created in the spring; and towards

the end of April this group rises a little before the Sun and precedes

him in his course, 'shedding sweet influences.' The ancients believed

that the good or evil influences of the stars were exercised not in the

night but during the day, when their rays mingled with those of the Sun.

The pernicious influence of the Dog-star is mentioned by Latin writers

as being most pronounced during the dog-days, at the end of summer and

commencement of autumn, the time of the heliacal rising of this star.

The other allusion to the Pleiades is in Book X., line 673, where

Milton, in describing the altered path of the Sun consequent upon the

Fall, mentions how the orb travels through Taurus with the Seven

Atlantic Sisters--the seven daughters of Atlas, the Pleiades, which are

situated on the shoulder of the animal representing this zodiacal

constellation.

THE GALAXY

The Galaxy or Milky Way is the great luminous zone encircling the

heavens, which can be seen extending across the sky from horizon to

horizon. Its diffused nebulous appearance caused the ancients much

perplexity, and many quaint opinions were hazarded as to the nature of

this celestial highway; but the mystery associated with it was not

solved until Galileo directed his newly invented telescope to this

lucent object, when, to his intense delight, he discovered that it

consists of myriads of stars--millions upon millions of suns so distant

as to be individually indistinguishable to ordinary vision, and so

closely aggregated, that their blended light gives rise to the milky

luminosity signified by its name. This stelliferous zone almost

completely encircles the sphere, which it divides into two nearly equal

parts, and is inclined at an angle of 63 deg. to the celestial equator. In

Centaurus it divides into two portions, one indistinct and of

interrupted continuity, the other bright and well defined; these, after

remaining apart for 120 deg., reunite in Cygnus. The Milky Way is of

irregular outline and varies in breadth from 5 deg. to 16 deg.; it intersects

the equinoctial in the constellations Monoceros and Aquila, and

approaches in Cassiopeia to within 27 deg. of the north pole of the heavens;

an equal distance intervenes between it and the south pole. Its poles

are in Coma Bernices and Cetus. The stars in the galactic tract are very

unevenly distributed; in some of its richest regions as many stars as

are visible to the naked eye on a clear night have been counted within

the space of a square degree. In other parts they are much less

numerous, and there have been observed besides, adjacent to the most

luminous portions of the zone, dark intervals and winding channels

almost entirely devoid of stars. An instance of this kind occurs in the

constellation of the Southern Cross, where there exists in a rich

stellar region a large oval-shaped dark vacuity, 8 deg. by 5 deg. in extent,

that appears to be almost entirely denuded of stars. In looking at it,

an impression is created that one is gazing into an empty void of space

far beyond the Milky Way. This gulf of Cimmerian darkness was called by

early navigators the Coal Sack. Similar dark spaces, though not of such

magnitude, are seen in Ophiuchus, Scorpio, and Cygnus.

The Galaxy, when viewed with a powerful telescope, is found to consist

of congeries of stars, vast stellar aggregations, great luminous tracts

resolvable into clouds of stars of overpowering magnificence, superb

clusters of various orders, and convoluted nebulous streams wandering

'with mazy error' among 'islands of light and lakes of darkness,'

resolved by the telescope into banks of shining worlds. The concourses

of stars which enter into the formation of this wonderful zone exhibit

in a marvellous degree the amazing profusion in which these orbs exist

in certain regions of space; yet those multitudes of stars perform their

motions in harmonious unison and in orderly array, and by their mutual

attraction sustain the dynamical equilibrium of this stupendous galactic

ring, the diameter of which, according to one authority, is not

traversed by light in less than 13,000 years.

[Illustration: FIG. 8.--A Portion of the Milky Way.]

Sir William Herschel, to whom we are indebted for most of what we know

of the Milky Way, commenced a series of observations in 1785 with the

object of acquiring a knowledge of the structure of the sidereal

heavens. In the accomplishment of this object, to which he devoted a

considerable part of his life, he undertook a systematic survey of that

portion of the Galaxy which is visible in the Northern Hemisphere. By a

method called star-gauging, which consisted in the enumeration of the

stars in each successive telescopic field as the instrument moved slowly

over the region under observation, he found that the depth of the star

strata could be approximately ascertained by counting the stars along

the line of vision; those were most numerous where the visual line

appeared of the greatest length and fewest in number where it was

shortest. Herschel perceived the internal structure of the Galaxy to be

exceedingly intricate and complex, and that it embraced within its

confines an endless variety of systems, clusters, and groups, branches,

sprays, arches, loops, and streaming filaments of stars, all of which

combined to form this luminous zone. 'It is indeed,' says a well-known

astronomer, 'only to the most careless glance, or when viewed through an

atmosphere of imperfect transparency, that the Milky Way seems a

continuous zone. Let the naked eye rest thoughtfully on any part of it,

and, if circumstances be favourable, it will stand out rather as an

accumulation of patches and streams of light of every conceivable

variety of form and brightness, now side by side, now heaped on each

other; again spanning across dark spaces, intertwining and forming a

most curious and complex network; and at other times darting off into

the neighbouring skies in branches of capricious length and shape which

gradually thin away and disappear.' Sir John Herschel, who was occupied

for four years at the Cape of Good Hope in exploring the celestial

regions of the Southern Hemisphere, describes the coming on of the Milky

Way as seen in his 20-foot reflector. He first remarks 'that all the

stars visible to us, whether by unassisted vision or through the best

telescopes, belong to and form part of a vast stratum or considerably

flattened and unsymmetrical congeries of stars in which our system is

deeply and eccentrically plunged; and, moreover, situated near a point

where the stratum bifurcates or spreads itself out into two sheets.' 'As

the main body of the Milky Way comes on the frequency and variety of

those masses (nebulous) increases; here the Milky Way is composed of

separate or slight or strongly connected clouds of semi-nebulous light,

and, as the telescope moves, the appearance is that of clouds passing in

a scud, as sailors call it.' The Milky Way is like sand, not strewed

evenly as with a sieve, but as if flung down by handfuls (and both hands

at once), leaving dark intervals, and all consisting of stars of the

fourteenth, sixteenth, twentieth magnitudes down to nebulosity, in a

most astonishing manner. After an interval of comparative poverty, the

same phenomenon, and even more remarkable, I cannot say it is nebulous,

it is all resolved, but the stars are inconceivably numerous and minute;

there must be millions and all almost equally massed together. Yet they

nowhere run to nuclei or clusters much brighter in the middle. Towards

the end of the seventeenth hour (Right Ascension) the globular clusters

begin to come in; they consist of stars of excessive minuteness, but

yet not more so than the ground of the Milky Way, on which not only they

appear projected, but of which it is very probable they form a part.

'From the foregoing analysis of the telescopic aspect of the Milky Way

in this interesting region, I think it can hardly be doubted that it

consists of portions differing exceedingly in distance, but brought by

the effect of projection into the same, or nearly the same, visual line;

in particular, that at the anterior edge of what we have called the main

stream, we see foreshortened a vast and illimitable area scattered over

with discontinuous masses and aggregates of stars in the manner of the

cumuli of a mackerel sky, rather than of a stratum of regular thickness

and homogeneous formation.'

The profound distance at which the stars of the Galaxy are situated in

space precludes the possibility of our obtaining any definite knowledge

of their magnitude and of the extent of the intervals by which they are

separated from each other, nor can we learn anything of the details

associated with the systems and combinations into which they enter. It

is believed that the majority of the stars in the Milky Way equal or

surpass the Sun in brilliancy and splendour. They are tenth to fifteenth

magnitude stars; now, the Sun at the distance indicated by these

magnitudes would in the telescope appear a much fainter object; he would

not reach the fifteenth magnitude. Consequently, the galactic stars are

regarded as his peers or superiors in magnitude and brilliancy. Those

myriads of suns are all in motion--in nature a stationary body is

unknown--and they are sufficiently far apart so as not to be unduly

influenced by their mutual gravitational attraction; a distance perhaps

equal to that which separates our Sun from the nearest fixed star may

intervene between each of those orbs. In the deepest recesses of the

Milky Way, Sir William Herschel was able to count 500 stars receding in

regular order behind each other; between each there existed an interval

of space, probably not less extensive than the interstellar spaces among

the stars by which we are surrounded.

The richest galactic regions in the Northern Hemisphere are found in

Perseus, Cygnus, and Aquila. Night after night could be spent in

sweeping the telescope over fields where the stars can be seen in

amazing profusion. In the interval of a quarter of an hour, Sir William

Herschel observed 116,000 stars pass before him in the telescope, and on

another occasion he perceived 258,000 stars in the space of forty-one

minutes. In the constellation of the Swan there is a region about 5 deg. in

breadth which contains 331,000 stars. Photography reveals in a

remarkable manner the amazing richness of this stelliferous zone; the

impress of the stars on the sensitive plate of the camera, in some

instances, resembles a shower of descending snowflakes.

Though Sir William Herschel was able to fathom the Galaxy in most of its

tracts, yet there were regions which his great telescopes were unable

to penetrate entirely through. In Cepheus there is a spot where he

observed the stars become 'gradually less till they escape the eye so

that appearances here favour the idea of a succeeding more distant

clustering part.' He perceived another in Scorpio 'where, through the

hollows and deep recesses of its complicated structure, we behold what

has all the appearance of a wide and indefinitely prolonged area strewed

over with discontinuous masses and clouds of stars which the telescope

at length refuses to analyse.' The Great Cluster in Perseus, which lies

in the Milky Way, also baffled the penetrative capacity of Herschel's

instruments. We cannot help quoting Professor Nichol's description of

Herschel's observation of this remarkable object. He says: 'In the Milky

Way, thronged all over with splendours, there is one portion not

unnoticed by the general observer, the spot in the sword-hand of

Perseus. That spot shows no stars to the naked eye; the milky light

which glorifies it comes from regions to which unaided we cannot pierce.

But to a telescope of considerable power the space appears lighted up

with unnumbered orbs; and these pass on through the depths of the

infinite, until, even to that penetrating glass, they escape all

scrutiny, withdrawing into regions unvisited by its power. Shall we

adventure into these deeper retirements? Then, assume an instrument of

higher efficacy, and lo! the change is only repeated; those scarce

observed before appear as large orbs, and, behind, a new series begins,

shading gradually away, leading towards farther mysteries! The

illustrious Herschel penetrated on one occasion into this spot, until he

found himself among depths whose light could not have reached him in

much less than 4,000 years; no marvel that he withdrew from the pursuit,

conceiving that such abysses must be endless!' The Milky Way may be

regarded as a universe by itself, and our Sun as one of its myriad

stars.

Milton was aware of the stellar constitution of the Milky Way, which was

one of Galileo's discoveries. The poet gives a singularly accurate

description of this luminous path, which he glorifies as the way by

which the Deity returned up to the Heaven of Heavens after He finished

His great work of creation--

So sung

The glorious train ascending: He through Heaven,

That opened wide her blazing portals, led

To God's eternal house direct the way--

A broad and ample road, whose dust is gold,

And pavement stars, as stars to thee appear

Seen in the Galaxy, that Milky Way

Which nightly as a circling zone thou seest

Powdered with stars.--vii. 573-81.

COMETS

Records of the appearance of these remarkable objects have been handed

down from earliest times; and when one of those mysterious visitors,

travelling from out the depths of space, became visible in our skies, it

was regarded with apprehension and dread as betokening the occurrence

of calamities and direful events among the nations of the Earth.

The word comet is derived from the Greek {kome}, signifying

'hair,' to which the hazy, luminous appearance of those objects bears

some resemblance. A comet consists of a bright central part called the

_nucleus_; this is surrounded by layers of nebulous matter called the

_coma_, and both combined form the _head_, from which a long appendage

extends called the _tail_. The nucleus and tail are not essential parts

of a comet, for many have been observed in which both have been wanting.

The tail is frequently very conspicuous, and presents considerable

diversity both as regards its appearance and length. In some comets it

is entirely absent, and in others it has been observed to stretch over

an arc of sixty or seventy degrees, indicating a length of 100 to 150

million miles. Sometimes it is straight, and at other times it is curved

at the extremity; it has been observed bifurcated into two branches;

and, on rare occasions, comets have been seen with two or more tails.

The tail of a comet is always directed away from the Sun; it increases

in size as the comet approaches the orb, and diminishes as it recedes

from him. This depends upon the degree of heat to which the comet is

exposed, which has the effect of driving off or evaporating some of the

matter composing the head. During the time the comet is travelling round

the Sun there is a continuous emission of this highly attenuated matter,

which is visible as the tail, but when the comet begins to recede from

the orb and reaches cooler regions of space the tail diminishes in size

as the temperature becomes reduced, and ultimately it disappears.

The appearance of a comet in the sky is often sudden and unexpected, and

one of those erratic wanderers may become visible at any time and in any

part of the heavens. It was remarked by Kepler that there are as many

comets in the sky as there are fishes in the ocean. This may or may not

be true, for they only become visible when they approach the Sun, and

the time during which they remain so does not usually exceed a few weeks

or months. Ancient astronomers were much perplexed with the motions of

comets, which appeared to be much more irregular than those of other

celestial bodies and unconformed to any known laws. Tycho Brahe believed

that comets moved in circular orbits, and Kepler imagined that they

travelled in straight lines outwards from the Sun. Newton, however, was

able to demonstrate that any conic section can be described about the

Sun consistent with the law of gravitation, and that the orbits of

comets correspond with three of the four sections into which a cone can

be divided. Consequently, they obey the laws of planetary motion. Comets

which move in ellipses of known eccentricity and return with periodical

regularity may be regarded as belonging to the solar system. Twenty of

these are known, and eleven of them have more than once passed their

perihelion. Those most familiarly known complete their periods in years

as follows:--Encke's 3.3; Swift's, 5.5; Winnecke's, 5.6; Tempel's, 6;

Brorsen's, 5.5; Faye's, 7.4; Tuttle's, 13.8, and Halley's, 76. Comets

with parabolic and hyperbolic orbits may be regarded as stray objects

which visit our system once, and depart never to return again. Besides

those already mentioned there are many comets with orbits of such marked

eccentricity that their ellipses when near perihelion cannot be

distinguished from parabolae. The great comets of 1780, 1811, 1843, 1858,

1861, and 1882 traverse orbits approaching this form, and some of them

require hundreds and thousands of years to accomplish a circuit of their

paths.

Numerous instances of the appearance of remarkable comets have been

recorded in the annals of ancient nations. The earliest records of

comets are by the Chinese, who were careful observers of celestial

phenomena. A comet is said to have appeared at the time of the birth of

Mithridates (134 B.C.), which had a disc as large as that of the Sun; a

great comet also became visible in the heavens about the time of the

death of Julius Caesar (44 B.C.), and another was seen in the reign of

Justinian (531 A.D.). A remarkable comet was observed in 1106, and in

1456, the year in which the Turks obtained possession of Constantinople

and threatened to overrun Europe, a great comet appeared, which was

regarded by Christendom with ominous forebodings. The celebrated

astronomer Halley was the first to predict the return of a comet.

Having become acquainted with Newton's investigations, which showed that

the forms of the orbits of comets were either parabolae or extremely

elongated ellipses, he subjected the next great comet, which appeared in

1682, to a series of observations, calculated its orbit, and predicted

that it would return to perihelion in seventy-five or seventy-six years.

On referring to past records he discovered that a great comet appeared

in 1607, which pursued a path similar to the one traced out for his

comet, another was seen in 1531, and one in 1456. Halley perceived that

the intervals between those dates corresponded to a period of about

seventy-six years, the time which he calculated would be required for

his comet to complete a revolution of its orbit. He therefore had no

hesitation in predicting that the comet would appear again in 1758.

Halley knew that he would not be alive to witness the event, and alludes

to it in the following sentence: 'Wherefore if it should return

according to our prediction about the year 1758, impartial posterity

will not refuse to acknowledge that this was first discovered by an

Englishman.' As the time approached when the comet should be drawing

near to our system, much interest was excited among astronomers, who

would have an opportunity afforded them of testing the accuracy of

Halley's prediction. An eminent French mathematician named Clairaut

computed anew, by a method rather different to that adopted by Halley,

the retarding effect of the attraction of the planets upon the speed of

the comet, and arrived at the conclusion that it would reach perihelion

about the middle of April 1759; but, owing to unknown influences--Uranus

and Neptune not having been discovered--it might be a month before or

behind the calculated time. Clairaut made this announcement on November

14, 1758. Astronomers were now intently on the look-out for the comet,

and night after night the sky was swept by telescopes in search of the

expected visitor, which for upwards of seventy years had been pursuing

its solitary path invisible to mortal eyes. But the mental vision of the

mathematician did not fail to follow this celestial object, which was

now announced as being on the confines of our system. The comet was

first observed on December 25, 1758, it soon became conspicuous in the

heavens, and reached perihelion on March 12, 1759, a month before the

time assigned to it by Clairaut but within the limit of error allowed

for unknown influences. Halley's comet returned again in 1835, and may

be expected about the year 1911. The periodic appearance of this comet

has been traced back to the year 1305.

The celebrated comet of 1680 was noted as having been the one which

afforded Newton an opportunity of making observations which led to his

discovery that comets describe orbits round the Sun in conformity with

the different sections of a cone. The comet of 1811 was observed for

many weeks in the northern heavens as a brilliant object with a

beautiful fan-shaped tail; it completes a revolution of its orbit in

about 3,000 years. The comet of 1843 was also a splendid object. It

possessed a tail 200 million miles in length, and approached within

32,000 miles of the Sun. The heat to which it was exposed was sufficient

to volatilize the most infusible substances known to exist. Donati's

comet of 1858 will be long remembered as one of the most impressive of

celestial spectacles: its tail extended over an area of forty degrees,

and enveloped the star Arcturus, which could be seen shining through it

with undiminished brilliancy. Its period is estimated to be 2,100 years.

A great comet appeared in 1861, through the tail of which the Earth

passed without any perceptible effect having resulted. No remarkable

comets have appeared during recent years. In 1880, 1881, and 1882,

several were observed, and that of 1881 was the first successfully

photographed.

Comets consist of cosmical matter which exists in a condition of extreme

tenuity, and especially so in the coma and tail. Sir John Herschel

described them as almost spiritual in texture, and small stars have been

seen shining through their densest parts without any perceptible

diminution of their light. The nucleus is believed to be composed of a

congeries of meteoric fragments, and these, when exposed to the Sun's

heat, throw off luminous nebulous particles that are swept by some

repulsive force into space and form the appendage known as the tail.

Comets may be regarded as celestial objects that are perfectly

innocuous. Neither fear nor dread need be apprehended from their visits;

they come to please and instruct, not to injure or destroy.

Milton does not fail to introduce into his poem several allusions to

comets, and in doing so expresses the ideas and sentiments which in his

time were associated with those objects.

In describing the hostile meeting between Satan and Death before the

Gates of Hell, he writes:

On the other side,

Incensed with indignation, Satan stood

Unterrified, and like a comet burned,

That fires the length of Ophiuchus huge

In the arctic sky, and from his horrid hair

Shakes pestilence and war.--ii. 706-11.

This passage is eminently descriptive of the appearance of a great

comet, and the occasion on which it is introduced adds to the intensity

of the lurid imaginings and feelings of terror and dismay with which

these objects have always been regarded. The comparison of the enraged

Prince of Hell with one of those mysterious and fiery looking visitors

to our skies was a grand conception of the poet's, and one worthy of the

mighty combatant. Ophiuchus (the Serpent-bearer) is a large

constellation which occupies a rather barren region of the heavens to

the south of Hercules. It has a length of about forty degrees, and is

represented by the figure of a man bearing a serpent in both hands. It

is not easy to imagine why Milton should have assigned the comet to

this uninteresting constellation; he may possibly have seen one in this

part of the sky, or his poetical ear may have perceived that the

expression 'Ophiuchus huge,' which has about it a ponderous rhythm, was

well adapted for the poetic description of a comet.

The only other allusion in the poem to a comet is near its conclusion,

when the Cherubim descend to take possession of the Garden, prior to the

removal of Adam and Eve--

High in front advanced,

The brandished sword of God before them blazed,

Fierce as a comet; which with torrid heat,

And vapour as the Lybian air adust

Began to parch that temperate clime.--xii. 632-36.

FALLING STARS

On any clear night an observer can, by attentively watching the heavens,

perceive a few of those objects which become visible for a moment as a

streak of light and then vanish. They are the result of the combustion

of small meteoric masses having a celestial origin, and travelling with

cosmical velocity, and which, in their headlong flight, become so heated

by contact with the Earth's atmosphere that they are converted into

glowing vapour. This vapour when it cools condenses into fine powder or

dust, and gradually descends upon the Earth's surface, where it can be

detected.

Shooting stars become visible at a height varying between twenty and one

hundred and thirty miles, and their average velocity has been estimated

at about thirty miles a second. Though casual falling stars can be seen

at all times in every part of the heavens, yet there are certain periods

at which they appear in large numbers, and have been observed to radiate

from certain well-defined parts of the sky. When the radiant point is

overhead, the falling stars spread out and resemble a parachute of fire;

but when it is below the horizon, the stars ascend upwards like rockets

into the sky. The radiant point is fixed among the stars, so that at the

commencement of a shower it may be overhead, and before the termination

of the display it may have travelled below the horizon. The radiant is

usually named after the constellation in which it is observed.

The November meteors are called Leonids, because they radiate from a

point in the constellation Leo; those in Taurus are called Taurids; in

Perseus, Perseids; in Lyra, Lyraids; and in Andromeda, Andromedes,

because their radiant points are situated in those constellations.

The falling stars that have attracted most attention are those which

appear on or about November 13. Every year at this period they can be

seen in greater or less numbers, and on referring to numerous past

records it has been ascertained that a magnificent display of those

objects occurs every thirty-three years. The earliest historical

allusion to this meteoric shower is by Theophanes, who wrote that in the

year 472 A.D. the sky at Constantinople appeared to be on fire with

falling stars. In the year 902 A.D. another remarkable display took

place, and from that time until 1833 twelve conspicuous displays are

recorded as having occurred at recurring intervals of thirty-three

years. The grandest display of this kind that was ever witnessed

occurred in 1833. It was visible over nearly the whole of the American

continent, and, having commenced at midnight, lasted for four or five

hours. The falling stars were so numerous that they appeared to rain

upon the Earth, and caused the utmost consternation and terror among

those who witnessed the phenomenon, many persons having imagined that

the end of the world was at hand. The regular recurrence of these

meteoric displays has been satisfactorily explained by the assumption

that round the Sun there travels in an elliptical orbit with planetary

velocity a vast shoal of meteoric bodies some millions of miles in

length and several hundred thousand miles in breadth. The nearest point

of their orbit to the Sun coincides with the Earth's orbit, and the most

distant part extends beyond the orbit of Uranus. These bodies accomplish

a circuit of their orbit in 33-1/4 years. The Earth in her annual

revolution intersects the path of the meteors, and when this occurs some

falling stars can always be seen; but when the intersection happens at

the time the shoal is passing, then there results a grand meteoric

display. Numerous other meteoric swarms travel in orbital paths round

the Sun.

Milton, in his poem, alludes to falling stars upon two occasions. In

describing the fall of Mulciber from Heaven he says:--

from morn

To noon he fell, from noon to dewy eve,

A summer's day; and with the setting sun

Dropt from the zenith like a falling star,

On Lemnos the AEgaean isle.--i. 742-46.

The rapid flight of the archangel Uriel from the Sun to the Earth is

described in the following lines:--

Thither came Uriel, gliding through the even

On a sunbeam, swift as a shooting star

In autumn thwarts the night, when vapours fired

Impress the air, and shows the mariner

From what point of his compass to beware

Impetuous winds.--iv. 555-60.

Milton mentions the season of the year in which those stars are most

frequently seen, and refers to an ancient belief by which they were

regarded as the precursors of stormy weather. A translation from Virgil

contains a similar allusion to them--

Oft shalt thou see ere brooding storms arise,

Star after star glide headlong down the skies.

The standard borne by the Cherub Azazel is described as having--

Shone like a meteor streaming to the wind.--i. 537.