being amazed at the vaſt Magnitude and noble Attendance of theſe two
Planets, in reſpect of this little Earth of ours? Or can they force
themſelves to think, that the wiſe Creator has diſpoſed of all his
Animals and Plants here, has furniſh’d and adorn’d this Spot only, and
has left all thoſe Worlds bare and deſtitute of Inhabitants, who might
adore and worſhip him; or that all thoſe prodigious Bodies were made
only to twinkle to, and be ſtudied by ſome few perhaps of us poor
Mortals?
[This proportion true according to all modern Obſervations.]
I do not doubt but there will be ſome who will think we are very much
miſtaken about the Magnitude of theſe Planets. For will you pretend to
make them who are taken up in admiring the Largeneſs of this Globe, its
multitude of Nations, Cities, and Empires; can you pretend I ſay to
make them ever believe that there are Places in compariſon of which the
Earth is as inconſiderable as this Figure would make it? But they ought
to be inform’d, that theſe Proportions are thoſe which the beſt
Aſtronomers of this Age have agreed upon. For if the Earth be diſtant
from the Sun ten or eleven thouſand of its own Diameters, according to
the Accounts of Monſieur Caſſini in France, and Mr. Flamſted in
England, wherein they made uſe of very exact Obſervations of the
Parallaxes of Mars; or if, according to a very probable Conjecture of
mine, it be diſtant twelve thouſand, then the Magnitudes of the other
Orbs will very near anſwer the Proportions here ſettled.
[The apparent magnitude of the Sun in Jupiter, and a way of finding
what Light they there enjoy.]
But to return to Jupiter. The Sun appears to them who are upon it five
times leſs than to us, and conſequently they have but the five and
twentieth part of the Light and Heat that we receive from it. But that
Light is not ſo weak as we imagine, as is plain by the Brightneſs of
that Planet in the Night; and alſo from hence, that when the Sun is ſo
far eclipſed to us, as that only the 25th part of his Disk remains
uncovered, he is not ſenſibly darken’d. But if you have a mind exactly
to know the Quantity of Light that Jupiter enjoys, you may take a Tube
of what Length you pleaſe. Let one end of it be cloſed with a Plate of
Braſs, or any ſuch thing, in the middle of which there muſt be a Hole,
whoſe Breadth muſt have the ſame proportion to the length of the Tube,
as the Chord of 6 Minutes bears to the Radius; that is, about as one is
to 570. Let the Tube be turned ſo to the Sun, that no Light may fall
upon a white Paper placed at the End of it, but what comes through the
little Hole at the other end of the Tube. The Rays that come through
this will repreſent the Sun upon the Paper of the ſame Brightneſs that
the Inhabitants of Jupiter ſee it in a clear Day. And if removing the
Paper you place your Eye in the ſame Place, you will ſee the Sun of the
ſame Magnitude and Brightneſs as you would were you in Jupiter.
[And in Saturn.]
If you make the Hole twice as little in breadth, you will ſee the ſame
in Saturn. And altho’ his Light be but the hundredth part of ours, yet
you ſee it makes him ſhine tolerably bright in a dark Night. But in
both theſe Planets, if there ever be any cloudy Days, it muſt be very
dark in compariſon of us; yet without doubt the Inhabitants have no
more reaſon to complain of the want of Light, than our Owls and Batts,
to whom the Twilight or the Night itſelf is more agreeable than the
Brightneſs of the Day.
[In Jupiter their days are five Hours.]
But it’s a little ſtrange, that when Jupiter is ſo much bigger than our
Planet, their Days and Nights ſhould be but five of our Hours. By this
we may ſee that Nature has not obſerv’d that proportion that their Bulk
ſeems to require, ſeeing in Mars the Days are very little different
from ours. But in the length of their Years, that is, in the Revolution
of the Planets round the Sun, there is an exact proportion to their
diſtances from the Sun followed. For as the Cubes of their Diſtances,
ſo are the Squares of their Revolutions, as Kepler firſt ſound out.
Which proportion the Moons of Jupiter and Saturn keep in their Courſes
round thoſe [Always of the ſame length.] Planets. As the Years and Days
in Jupiter are different from ours in this reſpect, ſo are the Days in
another; namely, that they are all of the ſame length. For they there
enjoy a perpetual Equinox, their Axis having little or no inclination
to their Orbit, as the Earth’s has, as has been diſcovered by
Teleſcopes. The Countries that lie near their Poles have little or no
Heat, by reaſon the Rays of the Sun fall ſo obliquely upon them; but
then they are freed from the Inconveniency that ours are troubled with,
of tedious long half-year Nights, and have the conſtant returns of Day
and Night every five Hours. Indeed ſuch ſhort Days would not be
agreeable to us, but we think our ſelves much better done by, that ours
are more than twice as long, tho’ upon no other account, but that
whatever is our own, we are apt to imagine, muſt be beſt.
The reſt of the Planets are ſo near the Sun (Mars himſelf never being
above 18 degrees from it) that in Jupiter they have the ſight only of
Saturn. But we cannot deny but that their four Moons ſtand them in
greater ſtead than our one doth us, if ’twere only that they ſeldom
know any ſuch Thing as to be without Moonſhiny Nights. And they are of
great Advantage to them, as we ſaid before, in their Navigation, if
they have any ſuch thing. Not to mention the pleaſant Sights of their
frequent Conjunctions and Eclipſes, Things that they are ſeldom a Day
without.
Saturn enjoys all thoſe Pleaſures and Advantages in a ſtill higher
Degree, as well for his five Moons, as for the delightful Proſpect that
the Ring about him affords his Inhabitants Night and Day. But we will
give an account of their Aſtronomy, as we have done of the reſt of the
Planets.
[They ſee the fix’d Stars juſt as we do.]
And firſt of all we ſhall obſerve what we might have remark’d before,
but which will be more ſtrange here, that the fix’d Stars appear to
them of the ſame Figure and Magnitude, and with the ſame degree of
Light that they do to us: and this, by reaſon of their immenſe
diſtance, of which we ſhall have occaſion to ſpeak by and by. In
compariſon with which the Space that a Bullet-ſhot out of a Cannon
could travel in 25 Years, would be almoſt nothing.
Their Aſtronomers have all the ſame Signs of the Bear, the Lion, Orion,
and the reſt, but not turning upon the ſame Axis with us: for that’s
different in all the Planets.
As Jupiter can ſee no Planet but Saturn, ſo Saturn knows of no Planet
but Jupiter; which appears to him much as Venus doth to us, never
removing above 37 Degrees from the Sun. The Length of their Days I
cannot determine: But if from the Diſtance and Period of his innermoſt
Attendant, and comparing it with the innermoſt of Jupiter’s, a Man may
venture to give a Gueſs, they are very little different from Jupiter’s,
10 Hours or ſomewhat leſs. But whereas in Jupiter theſe are equally
divided between Light and Darkneſs, the Inhabitants of Saturn muſt
perceive a more ſenſible difference than we, eſpecially between Summer
and Winter. For our Axis inclines to the Plane of the Ecliptick but 23
degrees and a half, but there’s above 31. Upon this Account his Moons
muſt decline very much from the Path that the Sun ſeems to move in, and
his Inhabitants can never have a full Moon but juſt at the Equinoxes;
Two of which fall out in 30 of our Years. ’Tis this Poſition of the
Axis too that is the Cauſe of thoſe delightful Appearances, and
wonderful Proſpects that its Inhabitants enjoy: For the better
underſtanding of which I ſhall draw a Figure of Saturn with his Ring
about him: in which the Proportion between the Diameters of the Globe
and Ring is as 9 to 4. And the empty Space between them is of the ſame
Breadth with the Ring itſelf. All Obſervations conſpire to prove that
That is of no great Thickneſs, altho’ if we ſhould allow it ſix hundred
German Miles, I think, conſidering its Diameter, we ſhould not overdo
the Matter.
Suppoſe then, agreeable to what has been ſaid, the Globe of Saturn,
[Fig. 4.] whoſe Poles are A, B. G N is the Diameter of the Ring, as you
view it ſideways, repreſenting a narrow Oval. Thoſe that live about the
Poles within the Arches C A D, E B F, each of which are 54 Degrees, (if
the Cold will ſuffer any Body to live there) never have a Sight of the
Ring. [The Appearances of the Ring in Saturn.] From all other parts it
is continually to be ſeen for fourteen Years and nine Months, which is
juſt half their Year. The other Half it is hid from their View. Thoſe
then that dwell between the Polar Circle C D, and the Equator T V, all
that time that the Sun enlightens the Part oppoſite to them, have every
Night the Sight of a Piece of it H G L, much in the Shape of a ſhining
Bow, which comes from the Horizon, but is darken’d in the Middle by the
Shadow of Saturn G H, which reaches moſt commonly to the outermoſt Rim
of it. But after Midnight that Shadow by little and little begins to
move towards the right Hand to thoſe in the Northern, but the Left to
thoſe in the Southern Hemiſphere. In the Morning it diſappears, leaving
behind it a Likeneſs indeed of a Bow, but much paler and weaker than
our Moon is in the Day time. For they, as I ſaid before, have an
Atmoſphere, or an Air ſurrounding them enlightened by the Sun.
Otherwiſe Night and Day they would have their Ring, their Moons, and
all the fix’d Stars, equally conſpicuous. Another thing that muſt make
the Sight of their Ring very curious, is, that by ſome Spots in it, it
is diſcover’d to turn round upon it ſelf: A thing that thoſe that are
ſo near cannot but take notice of, when we that live at this Diſtance
can deſcry a great Inequality, the inſide of it being brighter much
than the outſide is. When the Shadow of the Globe falls upon that part
of the Ring G H, the Shadow of the Ring at the ſame time darkens
another Part of the Globe about P F, which otherwiſe would have the Sun
upon it. So that there is always a Zone of the Globe P Y F E, ſometimes
of a larger extent than at others, which is depriv’d of the Sight both
of the Sun and Ring for a conſiderable time, the latter of which hides
ſome part of the Stars from it too. And certainly an amazing Thing it
muſt be, all of a ſudden to have the Sun intercepted and to become as
dark as Midnight, without ſeeing any Cauſe of ſuch an Accident. All
which time their Moons are their only Comfort. The other half of the
Year the Hemiſphere T B V enjoys the ſame Light that T A U before did,
and then this undergoes thoſe long Eclipſes that That before ſuffer’d.
At the Equinoxes, when the Sun is in the ſame Plane with the Ring, the
Inhabitants of Saturn cannot well perceive it: no not even we with our
Glaſſes, by reaſon of its Darkneſs. This happens when Saturn, view’d
from the Sun, is advanced one and twenty degrees and a half in Virgo or
Piſces, as I have ſhow’d formerly in my Syſtem of Saturn: Where there
is an Account given of the Riſings of the Sun above the Ring,
throughout all the Saturnian Year.
With Saturn in this Scheme you have the Globes of the Earth and Moon
drawn in their true proportion, to put you in mind again of a Thing
worth remembring, viz. how very ſmall our Habitation is when compar’d
with that Globe or the Ring about it. And now any one, I ſuppoſe, can
frame to himſelf a Picture of the Night in Saturn, with two Arches of
the Ring, and five Moons ſhining about, and adorning him. This then is
what I had to ſay to the primary Planets.
We are now come a little lower, to make an enquiry into the Attendants
of theſe Planets, eſpecially our own. And here we ſhall not only
conſider their Aſtronomy, but ſhall alſo ſearch into their Furniture
and Ornament, if they are found to have any ſuch thing, which we have
deferred conſidering till now.
[Very little to be ſaid of the Moon.]
And here one would think that when the Moon is ſo near us, and by the
Means of a Teleſcope may be ſo nicely and exactly obſerv’d, it ſhould
afford us Matter for more probable Conjectures than any of the other
remote Planets. But it is quite otherwiſe, and I can ſcarce find any
thing to ſay of it, becauſe I have not a Planet of the ſame Nature
before my Eyes, as in all the primary ones I have. For they are of the
ſame kind with our Earth; and ſeeing all the Actions, and every thing
that is here, we may make a reaſonable Conjecture at what we cannot ſee
in thoſe Worlds.
[The Guards of Jupiter and Saturn of the ſame nature with our Moon.]
But this we may venture to ſay, without fear, that all the Attendants
of Jupiter and Saturn are of the ſame Nature with our Moon, as going
round them, and being carried with them round the Sun juſt as the Moon
is with the Earth. Their Likeneſs reaches to other Things too, as
you’ll ſee by and by. Therefore whatſoever we can with reaſon affirm or
conjecture of our Moon (and we may ſay a little of it) muſt be ſuppos’d
with very little Alteration to belong to the Satellites of Jupiter and
Saturn, as having no reaſon to be at all inferior to that.
[The Moon hath Mountains.]
The Surface of the Moon then is found, by the leaſt Teleſcopes of about
three or four Foot, to be diverſified with long Tracts of Mountains,
and again with broad Valleys. For in thoſe Parts oppoſite to the Sun
you may ſee the Shadows of the Mountains, and often diſcover the little
round Valleys between them, with a Hillock or two perhaps riſing out of
them. Kepler from the exact roundneſs of them would prove that they are
ſome vaſt work of the rational Inhabitants. But I can’t be of his mind,
both for their incredible Largeneſs, and that they might eaſily be
occaſioned by natural Cauſes. Nor can I find any thing like Sea there,
tho’ he and many others are of the contrary Opinion I know. For thoſe
vaſt Countries which appear darker than the other, commonly taken for
and called by the Names of Seas, are diſcover’d with a good long
Teleſcope, to be full of little round Cavities; whoſe Shadow falling
within themſelves, makes them appear of that Colour: and thoſe large
Champains there in the Moon you will find not to be always even and
ſmooth, if you look carefully upon them: neither of which two [But no
Sea.] Things can agree to the Sea. Therefore thoſe Plains in her that
ſeem brighter than the other Parts, muſt conſiſt, I ſuppoſe, of a
whiter ſort of Matter than they. Nor do I believe [Nor Rivers.] that
there are any Rivers, for if there were, they could never eſcape our
Sight, eſpecially if they run between the Hills as ours do. Nor have
they [Nor Clouds.] any Clouds to furniſh the Rivers with Water: For if
they had, we ſhould ſometimes ſee one part of the Moon darkened by
them, and ſometimes another, whereas we have always the ſame Proſpect
of her.
[Nor Air, and Water.]
’Tis certain moreover, that the Moon has no Air or Atmoſphere
ſurrounding it as we have. For then we could never ſee the very
outermoſt Rim of the Moon ſo exactly as we do, when any Star goes under
it, but its Light would terminate in a gradual faint Shade, and there
would be a ſort of a Down as it were about it; not to mention that the
Vapours of our Atmoſphere conſiſt of Water, and conſequently that where
there are no Seas or Rivers, there can be no Atmoſphere. This is that
notable difference between the Moon and us that hinders all probable
Conjectures about it. If we could but once be ſure that there were Seas
and Rivers in it, it would be no weak Argument to prove that it has
alſo all other Furniture which belongs to our Earth, and the Opinion of
Xenophanes might be true, that it has its Inhabitants, Cities, and
Mountains. But as ’tis, I cannot imagine how any Plants or Animals,
whole whole nouriſhment comes from liquid Bodies, can thrive in a dry,
waterleſs, parch’d Soil.
[The Conjecture of its Plants and Animals very dubious.]
What then, is it credible that this great Ball was made for nothing but
to give us a little Light in the Night-time, or to raiſe our Tides in
the Sea? May there not be ſome People there that may have the Pleaſure
of ſeeing our Earth turn upon itſelf, preſenting them ſometimes with a
Proſpect of Europe and Africa, and then of Aſia and America; ſometimes
half of it bright, and ſometimes full? And muſt all thoſe Moons round
Jupiter and Saturn be condemned to the ſame Uſeleſneſs? I do not know
what to ſay concerning it, becauſe I know of nothing like them to found
a Conjecture upon. And yet ’tis not improbable that thoſe great and
noble Bodies have ſomewhat or other growing and living upon them,
though very different from what we ſee and enjoy here. Perhaps their
Plants and Animals may have another ſort of Nouriſhment there. Perhaps
the Moiſture of the Earth there is but juſt ſufficient to cauſe a Miſt
or Dew, which may be very ſuitable to the Growth of their Herbs. This I
remember is Plutarch’s Opinion, in his Dialogue upon this Subject. For
in our Earth a very little Water drawn from the Sea into Dew, and
falling down again upon the Herbs, would be ſufficient for all our
Needs, without any Rain or Showers. But theſe are mere Gueſſes, or
rather Doubts, but yet they are the [Jupiter’s and Saturn’s Moons turn
always the ſame Side to them.] beſt we can make of this, and all thoſe
other Moons: for, as I ſaid before, they are all of the ſame nature,
which is proved likewiſe by this, that as our Moon can afford us the
Sight never but of one Side of her, ſo they turn always the ſame Face
to their primary Planets. It may perhaps ſeem ſtrange, how we ſhould
come to know this; but ’tis no hard matter, after that Obſervation
which I juſt now made, that the outermoſt of Saturn’s Moons can never
be ſeen but when ſhe is on the Weſt-ſide of her Planet. The reaſon of
which is plainly this, that one Side of her is darker, and does not
reflect the Light ſo much as the other, which when it is turned towards
us, we cannot ſee by reaſon of its weak Light. This always happening
when ’tis Eaſt of him, and never on the other Side, is a manifeſt proof
that ſhe always keeps the ſame Side toward Saturn. Now ſince the
outermoſt of Saturn’s and our Moon carry themſelves thus to the Planets
round which they move, who can well doubt it of all the reſt round
Jupiter and Saturn? And there’s a very good reaſon for it, namely, that
the matter of which thoſe Moons conſiſt, being heavier, and more ſolid
on the Side that is averſe from us, than on that which we have the
Sight of, does conſequently fly with a greater force from the Centre of
its Orbit: for otherwiſe, according to the Laws of Motion, it ſhould
turn the ſame Side always, not to its Planets, but to the ſame fix’d
Stars.
This Poſition of the Moons, in reſpect of their Planets, muſt occaſion
a great many very ſurprizing Appearances to their Inhabitants, if they
have any, which is very doubtful, but may for the preſent be ſuppos’d.
An enquiry into our Moon may ſerve for all the reſt. Its Globe is
divided into two Parts, in ſuch a manner, that thoſe who live on one
Side never loſe the ſight of us, and thoſe on the other never enjoy it.
Except only ſome few who live on the Confines of each of theſe, who
loſe us, and ſee us again by turns. The Earth to them muſt ſeem [The
Aſtronomy of the Inhabitants of the Moon.] much larger than the Moon
doth to us, as being in Diameter above four times bigger. But that
which is moſt ſurprizing, is, that Night and Day they ſee it always in
the very ſame part of the Heaven, as if it never moved: ſome of them as
if ’twas falling upon their Heads: others ſomewhat above the Horizon,
and others always in the Horizon, ſtill turning upon it ſelf, and
preſenting them every twenty ſour Hours with a View of all its
Countries, even of thoſe that lie near the Poles (I could wiſh my ſelf
in the Moon only for the ſight of them) yet unknown and undiſcovered by
us. They have it in its monthly Wane and Increaſe, they ſee it half,
and horned, and full, by turns, juſt as we do the Body of the Moon. But
the Light that they receive of us is five times larger than what we
receive from them. So that in dark Nights that part that hath the
Advantage of being towards us, receives a very glorious Light from us,
tho’ Kepler thought otherwise. Their Days are always of the ſame Length
with their Nights; and the Sun riſing and ſetting to them but once in
one of our Months, makes the time both of their Light and Darkneſs to
be equal to 15 of our Days. If their Bodies were of the ſame Materials
with ours, thoſe that have the Sun pretty high in their Horizon, would
be almoſt roaſted in ſuch long Days. For the Sun is not farther from
them than he is from us. This will be the Caſe of thoſe that live upon
the Borders of the two Hemiſpheres we mentioned; but thoſe that live
under the Poles of the Moon will be juſt about as hot as our
Whale-fiſhers about Iſland and Nova Zemla are, in the Summer-time: who
are in ſo little danger of being roaſted, that in the middle of their
Summer, in their Days of three Months length, they very often find it
extreme Cold. I call thoſe the Poles of the Moon, round which the fix’d
Stars ſeem to turn to its Inhabitants, which are different from ours,
and alſo from thoſe of the Ecliptick, although they move round theſe
latter, at the diſtance of five Degrees, in a period of nineteen Years.
Their Year they count by the Motion of the Stars, and their return to
the Sun, and ’tis the ſame with ours. They can eaſily do it, becauſe
they have the Stars Day and Night, notwithſtanding the Light of the
Sun: for they have no Atmoſphere (which is the only reaſon that we
don’t every Day enjoy the ſame Sight) to hinder their Obſervations. Nor
have they any Clouds to obſtruct their View, ſo that it is eaſier for
them to find out the Courſes of the Planets, but more difficult to make
a true Syſtem of them. For they will be apt to lay a wrong Foundation,
by ſuppoſing that their Earth ſtands ſtill, which will lead them into
more dangerous Errors than [This may be applied to the Moons about
Jupiter and Saturn.] ever it did us. All that I have ſaid belongs as
well to Jupiter’s and Saturn’s Satellites as to our Moon, in reſpect of
the Planets they move round. The Length of their Day and Night is
always equal to the Time of their Revolution: For example, the fifth
Moon moves round Saturn in 80 Days, and the Days and Nights there are
equal to Forty of ours. Both their Summer and Winter (Saturn moving
round the Sun in thirty Years) are fifteen Years long. Therefore it is
impoſſible but that their way of living muſt be very different from
ours, having ſuch tedious Winters, and ſuch long watching and ſleeping
times.
Having thus explained the primary and ſecondary Planets round the Sun,
we ſhould next ſet about the third Sort, the Sun and fix’d Stars; but
before we do that, it would be worth while to ſet before you at once,
in a clearer and more plain Method than hitherto, the Magnificence and
Fabrick of the Solar Syſtem. Which we can’t poſſibly do in ſo ſmall a
Space as one of our Leaves will but admit of, becauſe the Bodies of the
Planets are ſo prodigiouſly ſmall in companion of their Orbs. But what
is wanting in Figure ſhall be made up in Words. Going back then to the
firſt Scheme, ſuppoſe another [Fig. 1.] like it, and proportionable,
drawn upon a very large ſmooth Plain; whoſe outermoſt Circle
repreſenting the Orb of Saturn, muſt be conceived three hundred and
ſixty Foot in Semidiameter. In which you muſt place the Globe and Ring
of Saturn of that [Fig. 2.] Bigneſs as the 2d Figure ſhows you. Let all
the other Planets be ſuppoſed every one in his own Orbit, and in the
middle of all the Sun, of the ſame Bigneſs that That Figure repreſents,
namely, about four Inches in Diameter. And then the Orbit or Circle in
which the Earth moves, which the Aſtronomers call the Magnus Orbis,
muſt have about ſix and thirty Foot in Semidiameter. In which the Earth
muſt be conceived moving, not bigger than a grain of Millet, and her
Companion the Moon ſcarcely perceivable, moving round her in a Circle a
little more than two Inches Diameter, as in [Fig. 5.] the Figure here
adjoined, where the Line A B repreſents a ſmall portion of that Circle
which the Earth moves in: the ſmall Circle therein C is the Earth, and
the Circle D E the Path of the Moon round it, in which the Body of the
Moon is D.
The outermoſt of Saturn’s Moons moves in an Orbit whoſe Semidiameter is
29 Inches; that of Jupiter in a ſomewhat ſmaller, whoſe Semidiameter is
19 and a quarter.