مجھے ہے۔
Y
QB
44
+3
43.
1729
:
}
1
HLET.BINDER
Syracuse, N. Y.
Stockton, Calif.
Bunting
(ii)
13553.
TO THÈ
Lady CAIRNES
>
MADAM,
S the Deſign of theſe
Dialogues carries them
naturally into the Pa-
tronage of the Fair
Sex; fo your own
Merit, and my Duty, determine
them to your Ladyfhip.
To you, Madam! who are bleft
with all thoſe natural Graces and
Genteel Accompliſhments, which
juſtly command univerſal Eſteem;
while Perfons of true Tafte and
thorough Knowledge of Life,
with Pleaſure fee even those ex-
A 2
ceeded
iv
The Epiftle Dedicatory.
ceeded by intellectual Beauties,
and fuch as claim Addreſſes of
this Nature. For what can be
more engaging than to find at
Lady CAIRNE S's Table, the
greateſt Liberality and Elegance
of Entertainment, outdone by
improving Converſation; and
the Underſtanding more regaled
than the Senſes?
But I know I muft forbear ;
and not offend ſuch a Modeſty as
your's, even with Truth: How-
ever, I can't help fhewing that I
am neither infenfible of what all
the World admires, nor ungrate-
ful for the Obligations you have
fo generouſly conferr'd on,
MADAM,
Your Ladyfhip's
Moft Humble Servant,
J. HARRIS.
(v)
R
THE
PREFACE.
HIS Book was most of it
written a good while ago:
And being supposed to be
loft for Jome Tears, was
lately retrieved, and reviewed by its
Author, with the Difintereftedness
of a Stranger. However, I liked
it fo well, as to refolve upon its
prefent Publication, with fome few
Emendations and Additions. Of
which latter fort the Defcription of
the famous Orrery of Mr. Rowley,
is the most confiderable.
I wrote it in this diverting way,
in purſuit of a Defign, which, as
I have made the general Business
of my Life, So I can look back upon
its Success with Pleafure, viz. The
en-
vi
The PREFACE.
engaging Perfons of Birth and
Fortune in a warm Application to
ufeful and real Learning: Toin-
duce them to detach fome of their
happy Leifure from being loft by
Sports, Play, or worfe Avocations,
and to dedicate it to the Improve-
ment of their Minds.
For I have often been ashamed,
and fhocked to fee, how aukwardly
the few Modeft have look'd, in Con-
verfations where they could bear no
part; and how infolently others
have defpifed what they neglected
to understand.
But what glorious Improvements
might one expect from Perfons of
Fortune and Leifure, if they would
addict themselves to thefe Things?
who can bear the expence of good In-
ftruments for CæleftialObfervations.
For tho' there can hardly be a-
bove a Score in an Age who have
pursued thefe Studies thoroughly;
yet fuch great Lengths have been
run in spite of all Difadvantages,as
may
The PREFACE.
vii
may eafily convince us,what tohave
hoped for, if Great Men would now
and then divert themselves this way.
The Reader will easily fee that the
Converfation in thefe Dialogues is
feigned, and in Imitation of Thofe
of the Excellent Mr. Fontenelle,
Ön the Plurality of Worlds. And
that the Digreffions, Reflexions,
Poetry and Turns of Wit, are intro-
duced to render ThofeNotions plea-
fing and agreeable, which perhaps
without fuch a kind of Drefs, would
appear too crabbed and abstracted.
However, I don't perplex my fair
Aftronomer with any thing but the
true Syftem of the World: I
mislead her by no Notions of Cryf
talline Heavens, or Solid Orbs:
I embarrass her with no clumfey
Epicycles, or imaginary and indeed
impoffible Vortices: But I shew
her at first the Cœleftial World just
as it is; and teach her no Hypo-
thefes, which, like fome other things
taught at Places of great Name,
muft
viii
The PREFACE.
must be unlearned again, before
we can gain True Science.
And as I think it practicable to
explain and teach any Science in
this Facetious way (Facetè enim,
& commodè dicere quid vetat?)
So perhaps I may hereafter, if God
grant me Health, Eafe, and Lei-
Jure, make ſome other Attempts of
this kind. For the Lady may well
be ſuppoſed, tho' the fight of the
Globes firft ftruck her Fancy, and
turned her Defires this way, to have
made Excurfions into other Parts
of Mathematicks, and to have
difcourfed with her Friend on thoſe
Subjects. And perhaps all Thofe
Dialogues may not be loft, as thefe
had like to have been; but may, if
thefe find a fuitable Encouragement,
be communicated alſo to the World.
Multaque præterea tibi poffum Commemorando,
Argumenta, filem dictis conradere noftris :
Verum animo fatis hac Veftigia parva fagaci
Sunt; per qua poffis cognofcere cætera tute.
Lucret. Lib. 1.
Aftronomical Dialogues
BETWEEN A
GENTLEMAN and a LADY.
T is now about feven Years ago,
fince I prefented the moft enga-
ging Lady M.... with Mr. Fon-
tenelle's Book of the Plurality of
Worlds: And I remember well what fhe
faid a few Days after.
I have look'd over your Book, Sir,
faid fhe, as my way is, firft cursorily,
and I intend to give it a very careful fe-
cond Reading; but I perceive by it, you
have cut out much more Trouble for
your felf, than perhaps you imagin'd:
For I find there are many things pre-
viouſly neceffary to the underſtanding it,
which you muft oblige me with explain-
ing; but, continued fhe, a Converfation
of that kind with me, I doubt, will be
too dull and tedious, fince I am not blefs'd
with any of thofe fhining Qualifications,
B
with
2
Aftronomical Dialogues.
with which Mr. Fontenelle hath compli-
mented M. la Marquiefe; I fhould indeed,
faid fhe, except those two, which I fup-
poſe, in Complaifance to our Sex, he
makes the Foundation of Philoſophy, viz.
Ignorance and Inquifitiveness; for thoſe
I'm fure, I have in Perfection, as you have
long experienced.
I need not mention the Return I made,
nor how prettily fhe changed the Dif
courſe to fomething more general, when
fhe found I was going to fay juft things of
her; thoſe that knew her, don't want to
be reminded of the many Beauties, both
of Mind and Body, which render'd Lady
M....one of the moſt agreeable Perfons of
her Sex; which yet, were fhe living, tho'
a juft Debt to her Merit, I must not have
faid, for fear of offending her Modeſty.
ALL that is neceffary to introduce what
follows, is, to inform you, that fome
Years before her Death, when I went to
viſit that accompliſh'd Lady at her Coun-
try Scat; I was a little furprized to find
her, the next Morning after my Arrival,
ftudiouſly viewing a pair of large Globes,
which ſtood in the Drawing-Room, look-
ing into the Garden, and which I uſed to
make my Place of Study.
Good
Aftronomical Dialogues.
3
Good Morrow, faid I, Madam, what!
hath Fontenelle made an Aftronomer of
you in good earneft? Are you really con-
templating the Order and Motions of the
Heavenly Bodies? Or are you rather
feeking on the Earthly Globe, where to
make new Conquefts?
The Hiftorians foalifhly reprefent
Alexander the Great, as weeping, that
he could carry his no further than over
all the World; but I'm fure, were he
preſent now, to ſee you in that Poſture
commanding the Globe, and giving what
Turns you pleafe to it: that Thought of
your humble Servant's would appear juſt
enough;
Had the Pellaan Chief thy Form but view'd,
With far more Hafte he had the World fubdu'd:
Proud at thy Feet to lay the mighty Ball,
Whofe Eyes were form'd to triumph over all;
And then moft justly had he wept to fee,
One World too mean an Offering for thee!
O! Sir, faid fhe, your Servant, I
doubt you did not reft well laft Night?
What did your Imagination carry you in-
to the poetical Regions of Fairy-Land,
that you awake with Verfes in your
Mouth this Morning? But to ſpeak ſeri-
ously,
B 2
!
1
Aftronomical Dialogues.
ouſly, I wonder you don't bluſh to paint
ſo much beyond the Life, and yet fuppofe
the Picture to be like any one; you affect
to imitate our great Painters, if we fit to
them, they make us all handſome; but
they do it to fhew themfelves, not us,
and they don't care fo much whether it
be like or no, ſo it be but a fine Picture;
and in this our own Vanity too often in-
dulges them.
But pray, added fhe, let us lay afide
all theſe Fooleries; and be fo good as to
be ſerious with me for an Hour or two:
I have a great mind to be let a little into
the Knowledge of theſe Inftruments, the
Globes; and to know fomething of the
firſt Principles and Rudiments of Aftro-
nomy; or elſe I find I fhall loſe half the
Beauties of that very entertaining Book
Mr. Fontenelle's Plurality of Worlds,
which you formerly obliged me with, as
well as perhaps be led into fome Errors
by it: And don't defpife and neglect me
becauſe I am a Woman. I have heard you
ſometimes fay, you thought that there
was no difference of Sexes in Souls;
nay, that our Parts and natural Capaci
ties were often equal, at leaſt, if not fu-
perior, to thofe of Men. But perhaps
there were fome particular Reaſons for
your faying fo then, which now altering or
ceafing,
Aftronomical Dialogues.
5
ceafing, your Judgment and Opinion may
have done fo too.
I was going to affure her, that I was
ftill of the fame Sentiments, when put-
ting on a forbidding Look, with a ſerious
Countenance fhe procceded thus:
THESE Globes, Sir, came too late to Globes.
accompany a Relation of mine to India,
his Ship having failed before they were
finiſhed, which is the Reaſon you ſee them
here; and I have ordered them to be ſet
out this Morning, and fhall do fo from
Day to Day, tho' without obliging you
to what Fontenelle had with the French
Lady, an entire Week's Conference. But
I have a great mind to learn, from my
Friend, fomething of the Nature and Ufe
of them; for they appear to be made and
finiſhed up with that Curiofity and Care,
that fure fome very ufeful Knowledge is
to be learnt from them; and is it not bar-
barous in you Men to confine it all to
your felves?
MADAM, faid I, you will give me a
new Rife to value any thing that I under-
ftand; if I can render it acceptable to
you,
B 3
WELL
Aftronomical Dialogues.
WELL then, Sir, faid fhe, all Compli
ments apart, both to your felf and me,
pray let us go to our Bufinefs, the Tea
won't be ready this Hour, and there is a
little too much Dew for us to take a Walk
in the Garden. Let me underſtand then,
firft the Difference between thefe two
Globes, and why one hath the Cities,
Countries, and Places of the Earth drawn
on it, like a Map; and the other Circles
and Stars, and theſe odd uncouth Figures
of Beafts, Birds and Fiſhes : Pray why do
they turn round? What doth this Brafs
Hoop fignify in which they hang? For I
perceive that it alfo hath Numbers engrav'd
upon it: And what doth this broad wooden
thing ſerve for, that hath the Days of the
Month and other Letters, as well as Fi-
gures, pafted upon it?
✔
I am glad, faid I, Madam, by the
warm manner of your Enquiry, to find
that you are in earneft; and I have often
wifhed that the fame Curiofity and Love
of Knowledge would inſpire more of the
Fair Sex, for it would mightily enlarge
their Empire and Power over ours, by
endowing them with more real and laſt-
ing Beauties, fuch as would improve with
Time, and ftrengthen even in Age itſelf.
But
Aftronomical Dialogues.
But as to your prefent Queftions, Madam,
I will give you the moit fatisfactory Rc-
turns I can.
what.
And firft, Madam, it will be neceſſary
to acquaint you with the meaning of the-
Word Globe; and what the Propertics, in
general, of fuch a Figure or Body, arc.
Your Ladyship is to understand then, Globe,
that a Globe is a round Body of ſuch a
Nature, that every Part of its Surface or
Out-fide, is at an equal Diſtance from one
Point within it, which is called the Cen-
ter. This Body alfo is fometimes named
a Sphere, with regard to Aftronomical Sphere.
Speculations; and this Science which you
are now inquiring into, is hence called
The Doctrine of the Sphere.
I THINK I underſtand you, faid fhe,
the Figure of a Globe is not flattiſh like
that of a Cheefe or a common Ninepin-
Bowl; but rather like a Boy's Marble, or
a Bullet caft in a Mould.
EXACTLY right, Madam, faid I; and
further you are to know, that a ftrait
Line ſuppoſed to be drawn thro' the
Center of this Globe any where, from
one oppofite Point of the Surface to the
other, is called a Diameter.
B 4
I
Diame-
ter.
8
Aftronomical Dialogues
I THANK YOU, faid fhe, for that Ex-
plication, Sir; I have often met with the
Word, but never knew fully what Dia-
meter fignified before: But now I know
what the ingenious Mr. Butler meant,
when ſpeaking of the Moon, he ſaith,
that Sydrophil knew
What her Diameter to an Inch is,
And prov'd ſhe was not made of green Cheeſe.
And now I know what the Plummer meant
the other Day, when he talk'd of a Pipe
of Lead of fuch a Diameter; I now know
the meaning of Diametrically oppofite,
c. But, pray, Sir, go on.
You will next fee eafily, Madam,
faid I, that if a Globe were at liberty,
and any Power or Force at hand to move
it, it would eaſily turn or roll round any
one of its Diameters, as this Globe doth
round this Wire; which particular Dia-
Axis. meter, is called therefore its Axis; as
being the Axle-tree on which it turns.
But tho' this be true of the Nature of a
Globe in general, yet the Axis, as we
call it, of the Earth and Heavens, by the
Will of our All-wife Creator, is one fixed
and determinate Line; and about this the
fixed
Aftronomical Dialogues.
9
fixed Stars are uſually ſuppoſed to revolve,
without ever changing their Diſtance, or
deviating from one another, or from it.
I AM mightily pleaſed, returns fhe,
with the Nature of thefe Globes, becauſe
they are unbiaſſed and indifferent, as to
this or that particular way of turning;
and I fancy it to be a good Emblem of the
Freedom of our Minds in the State of In-
nocence, when they first came out of Na-
ture's Hands; they were then perfectly at
liberty to move any way, which they
lik'd beſt: and I dare fay, that all the
wrong Biaffes and particular Turns that
we find in any of them, are owing to
the Weight or Power, as you call it, of
our own corrupt Affections.
You moralize excellently well, ſaid I,
Madam, and are very juft in your Notions
of the Deity.
But ſhe went on, and faid; Yet I think
we might be glad to receive from the firft
Mover and Author of all Things, fuch a
determinate Way of moving, as you fay
God hath given to the Heavens and the
Earth; for our own whimſical Motions,
Turnings and Shiftings, feem to be as un-
accountable as they are various.
BUT
10
Aftronomical Dialogues.
vens.
Motion of BUT pray, faid fhe, let me underftand
the Hea- what you fay as to the preſent Point a
little further; Do the Heavens and the
Earth all really move round about one
Axis, as thefe two Globes do round
theirs? And are the Poles thus beautifully
defcribed by Mr. Dryden, the two Ends
of this Axis?
Polcs.
Two Poles turn round the Globe, one ſeen to rife
O'er Scythian Hill, and one in Lybian Skies;
The firft fublime in Heav'n, the laft is whirl'd
Below the Regions of the nether World :
Around our Poles the fpiry Dragon glides,
And like a wandring Stream the Bears divides,
The Lefs and Greater, who by Fate's Decrees
Abbor to dive beneath the Southern Seas;
There, as they say, perpetual Night is found,
In Silence brooding on th'unhappy Ground:
Or when Aurora leaves our Northern Sphere,
She lights the downward Heav'n, and rifes there;
And when on us fhe breathes the living Light,
Red Vefper kindles there the Tapers of the Night.
DRYDEN's Virgil.
Shall I ever come to know what theſe
Poles, and Dragons, and Bears, mean?
VERY
(
Aftronomical Dialogues.
II
VERY cafily, Madam, faid I, and you
will find that the Motion of the Earth Motion
alone round its Axis will fufficiently ac- of the
count for all the reft; for theſe fixed Stars Earth.
don't in Reality move at all, but only ap-
pear ſo to do. And you muſt know, that
there is one Star, or a Point very near it,
towards which this Pole, or End of the
Earth's Axis, (which is called the North-
Pole) doth always point: This is the Star
here on this Celeſtial Globe, and if it be PoleStar.
fair, and the Sky clear, in the Evening,
I will fhew it you in the Heavens: 'Tis
faid, by Aftronomers, to be in the Tip
of the Tail of the Little Bear, a Conftel-
lation of Stars fo called; you ſee there
are ſeven of theſe Stars in all, placed on
the Globe within the Picture or Figure of
a Bear: The Reaſon of the Figure I will
tell you hereafter.
PRAY, faid fhe, good Sir, don't take
it amifs if I interrupt you with one Que-
ftion: Is this Tip of the Bear's Tail, that
celebrated Tip of Cardan the Conjurer;
who, as Butler faith,
Firmly believ'd great States depend
Upon the Tip of th Bears Tail's End,
I
That
12
Aftronomical Dialogues.
That as fhe whisk'd it tow'rds the Sun,
Strow'd mighty Empires up and down.
THE very fame, Madam, faid I.
Go on then, ſaid ſhe,
THIS Star here by the Wire, Madam,
faid I, we call the Pole Star, and the Point
near it, thro' which the Wire runs, the
North Pole of the World. And let the
Earth be where it will, in its Annual
Courſe round the Sun, this North Point on
the Earth and here placed on the Globe, will
always be either exactly or nearly under that
North Pole Star or Point, in the Heavens.
But of this more when I fhall further explain
to you the Motions of the Earth; and this
Pofition of the Earth's Axis is fo firmly fixed
and determined by the Author of Nature,
that from it there hath never yet been ob
ferved any confiderable Variation,
PRAY, Sir, faid fhe, proceed: When
I come to look over Fontenelle again, I
perceive I fhall underſtand him and you
much better.
MADAM, faid J, the outward Figures
of theſe two Globes you fce are nearly
alike; but tho' they are hung alfo, and
fitted
Aftronomical Dialogues.
13
fitted up alike, yet they are almoſt as
different from one another in their Na-
tures and Properties, as are the different
Regions that they reprefent.
This Globe which is defigned to fhew Terre-
the Face of the Earth; and which there-ftrial
fore is called the Terreſtrial Globe, is truly Globe.
and properly a Reprefentation of it, round
or ſpherical as that nearly is, and it hath
the Sea and the Land, with all the Regions,
Countries, Nations, Iſlands and Cities
drawn upon it; juft in that Order and
Figure, that they are, in Reality, on the
Face of the Earth itself; and it is, if care-
fully drawn, a true Map, or Deſcription,
of what is ufually called The World:
Whereas all thofe flat Maps and Charts,
which you fee drawn upon Paper, cannot
be accurately fo, tho' they are exact c-
nough for common Ufe.
THAT Word World, faid fhe, I can't get
over without reflecting, what weak, vain,
and filly Mortals we are: We too often take
this poor Spot of Earth to be the only World
worth inquiring after; and fo we can but
acquire a little of its Dirt, we neglect all
Care for an eternal Manfion in the Heavens.
And further, I have no patience with
Ptolemy, I think they call him, and his
Aftronomers, that will needs have the
mighty
14
Aftronomical Dialogues.
mighty Sun, and all that infinite Orb of
fixed Stars, to be made only for the fake
of this little dirty Planet, as I remember
fomebody calls it; and to have no other
Ufe nor End, but only to dance round it,
which yet, as I have heard, is a meer,
Point, and ſcarce viſible to an Eye placed
in fome of the other Planets.
But to go on with my Leffon: Good
Sir, faid fhe, is the Figure of the Earth
thus really round? and have you any good
Reaſons to make you think fo For I
muſt own I had not till now a Notion of
its being round like a Ball; I took it ra-
ther to be round in Compaſs like a Diſh
or Plate.
Rotundi- VERY many and fubftantial ones,
ty of the Madam, faid I; and you will be fully
Earth. convinced by them, when they occur to
your reading hereafter, if you proceed on
in that way you are now going: But,
however, the Sun fhining fo bright into
this Room, will furnish me now with one
Argument to make that Notion plain to
you. You fee, Madam, when I hold any
folid Body in this Light of the Sun, its
Shadow will be nearly like the Shape and
Form of that of the Body; when I hold
this Book in the Light, its Shadow will
be
Aftronomical Dialogues.
15
be ſquare at the Sides, as the Book is; but
when I hold this Orange in the fame Light,
the Shadow, you ſee, hath a round Edge;
and therefore fince in the Eclipfes of the
Moon, the Shadow of the Earth, which you
know, Madam, occafions the Moon's being
covered with Darkneſs, appearing always
exactly round or circular, we juftly con-
clude that the Figure of the Earth is
round or ſpherical too, or elfe the Ter-
mination or Out-Line of its Shadow could
never be always in a Circular Form.
I THANK YOU for this eafy and natu-
ral Explication, faid the Lady, which I
think I comprehend; and I am beholden
to the Sun, that great Fountain of Light,
or rather to Him that made it, for being
now inftrumental to difpel the Darkneſs I
had in my Mind before about this Affair;
however, being no Perfian, I fhall not
worſhip the Sun for it. But pray, Sir, go
on with an Explication of the other
Globe.
THAT, Madam, is called the Celestial Celestial
one, ſaid I, becauſe 'tis defigned for a Re-Globe.
prefentation of the Firmament, and the
Concave Arch of the Heavens; and indeed
it doth well enough exhibit to us the
fixed Stars, and the Tracks or Circles of
the
16
Aftronomical Dialogues.
the Sun and Planets apparent Motions;
if you get a right Notion of it, as this
Vid. Fig. 1. Figure, which we call an Armillary
Sphere, will I think help you to ob-
tain: In order to which you muſt now
imagine your Eye placed within at the
Center of the Globe, or on the little
Ball there in the Figure which repreſents
the Earth; and that the Spherical Sur-
face of it, on which you fee the Stars
there painted and gilded, were tranſparent
like Glaſs; ſo that you could actually fee
thro' it, not only all the Circles drawn
upon it, but alſo all the Stars above in the
Heavens, as they really appear there in a
bright Night. And if you imagine fur-
ther, Madam, that ftrait Lines were
drawn from every Star in the Firmament
to your Eye fo placed, as before, in the
Center of this Globe, thofe Lines would
paſs thro' and cut the Spherical Surface of
the Globe in proper Points to paint, or to
place the Pictures of the Stars upon.
I THINK, I conceive you right, faid
the Lady, ſo that if there were Holes in
the Surface of this Globe in thofe Places
where theſe Stars are painted upon it,
and that my Eye were within at the Cen-
ter, and the Globe turn'd, fo as to con-
form itſeli to the prefent Pofition of the
Heavens
Fig. 1.
17
North Pole
Meridian
gg 05 of
99
Solficial
Circle
the
Colu
PIHOM
Tropick
Taurus
Idip tick
8 Ecliptick Y
Aries
Cancer
Pifces
Equator
Tropick
Axis
not
Antartick
018
South Pole
Axis
go
80
Circle
Horizon
Capricorn
20
10
Colure
Aftronomical Dialogues.
17
Heavens above; I fhould fee every Star
there thro' its correfponding Hole in the
Globe.
You are perfectly right, Madam, ſaid
I, and Ptolemy himſelf, could not have
expreffed it better. And juft in that Cen-
tral Point (and juft fuch a Point as that
is it) do Aftronomers of his Sect fuppofe Vid. Fig.1
the Earth to be placed, as you fee in the
Figure, in the middle of the Sphere of
the fixed Stars, which feem to revolve
round about it, once in 24 Hours, be-
cauſe the Earth doth turn round her own
Axis, tho' a contrary way, in the fame
Time.
OF this, replied Clarella, I have gotten
a tolerable Notion from what you faid
before, and from the French Author:
But, pray, let us now go on with our
Globes here; What is the meaning of
this broad wooden Circle placed round
each of them, and what is it called?
MADAM, ſaid I, it is called The Ho-
rizon; which is a Greek Word that fig-
nifies a Limiter or Determiner. And
to conceive it right, imagine your felf
placed, as before, on this poor little
Earth, within that immenfe Celeſtial
Globe;
C
18
Aftronomical Dialogues.
Globe; which you are to iuppoſe now
to be millions of millions of times greater
than it really appears to be: Then you
know, if you look round you on the
Earth, its Surface will extend every way
from your Eye, like a vaft Plain; which
will be under your Feet, and to which
your Body will be perpendicular or up-
right This Plain ftretching all round you
every way as far as your Eyes can fee, in
a flat open Country where no Hills inter-
Hemi- poſe: Or on the Surface of the Sea, will
Spheres. feem to divide or cut the concave Orb of
the Stars, or the Sky, into two Parts
(which they call Hemispheres) the one
feemingly above this Plain, which there-
fore they call the Upper, and the other
apparently below it, which therefore they
call the lower Hemifphere. Such a Plain
Horizon, as this is call'd the Horizon: And if it be
really that which any one's particular Eye
makes upon any occafional View, 'tis call'd
the fenfible Horizon: But if you imagine
this Plain, as you may eafily do, to paſs
through the very Center of the Earth on
the Surface of which you then ſtand, 'tis
called the real or rational Horizon; be-
cauſe that doth really or actually divide
the Starry Regions into two equal Hemi-
fpheres; and both theſe Horizons are well
enough repreſented by that wooden Cir-
2
cle,
Aftronomical Dialogues.
19
?
cle, which you now lay your fair Hand
upon.
I HOPE I take you right, faid fhe;
and now begin to underſtand better the
meaning of many Expreffions which have
often occurr'd to me before, but with leſs
Light. But why do you fo cautiouſly uſe
the Words apparently above and below?
BECAUSE, faid I, Madam, there is
in reality no fuch thing as any Difference
between above and below: The Heavens
are every where above or without what
they contain; but we, taking our Ideas of
things from ourſelves, do agree to call that
above or uppermost which is over our
Heads, and that below, which is beneath
us, or down under our Feet: And there-
fore as we call that Concave half of the
Region of the fixed Stars, which we fee
above our Horizon, the upper Hemisphere;
fo the other half takes the Name of the
lower Hemisphere.
I AM mightily pleaſed, faid the Lady,
with theſe Celeftial Beings that are fo per-
fectly above all the poor Trifles of Place
and Station; with which we Mortals
make fuch a buftle here below: Especial-
ly thofe of our Sex; as I will honeftly
C 2
own
20
Aftronomical Dialogises.
own to you, now you are my Mafter and
Teacher; for as Butler hath juftly obſerv'd,
To us the Joys of Place and Birth
Are the chief Paradife on Earth:
A Privilege fo facred held,
That none will to their Mothers yield,
But rather than not go before,
Will forfeit Heaven at the Door.
But let us go on. I perceive, faid the
Lady, that theſe Horizons will always
vary as we fhift the place of our View.
YES, Madam, ſaid I, and fo will the
Hemiſpheres too that they determine.
AND yet, faid fhe, we are often fo
vain as to take our little narrow View or
Horizon for the Bounds of all that is to
be ſeen; and judge, that what is not with-
in our Hemiſphere, to be either nothing
at all, or at leaft not worth our knowing
or enquiring after; for we are always fo
vain as to deſpiſe what we do not under-
ſtand. But I interrupt you with my im-
pertinent Reflections; pray, Sir, go on.
I BEG you to take notice farther, faid
I, Madam, that when the Sun, or any Star
or Planet, appears at the Eaſtern Edge of
our
Aftronomical Dialogues.
21
our Horizon, we fay it is Rifing; and
when it has got quite above it, we ſay it is
Rifen, or is Up. On the contrary, if it
appear towards the Weſtern Edge of it,
we ſay it is Setting; and when it is got-
ten below it, we lay it is Set. And this
Rifing and Setting always reſpects the Sen-
fible, and not the Real Horizon,
BUT what is the meaning of theſe Cir-
cles, demands fhe, which I fee drawn
here upon the Board of the Horizon, and
on both Globes alike ?
THE outermost of them, Madam, faid Sea Com-
I, repreſents the Points of the Compass,paſs.
as they are called by our Seamen; who
make uſe of an Inftrument called the Com-
pass, to fteer their Ships by at Sea.
PRAY let me know a little more of
that matter, faid fhe, for 'tis a Thing I
have heard much talk of.
You have ſeen, no doubt, Madam,
faid I, a Loadſtone; and know that it hath
that wonderful Virtue, among others as
ftrange, that if a Needle or long Iron-
Wire be drawn rightly over it, that Needle
will ever after that, when at liberty, point,
as they call it, due North and South.
C 3
Υου
Aftronomical Dialogues.
You are now, faid fhe, fo very good,
that I think I muſt feed your Vanity, by
owning, that I was once much pleaſed
with fome Verfes of yours occaſionally
given me; but am more ſo now, becauſe
I underſtand them better: after you had
talked in your ufual way of Love and Con-
ftancy, and I know not what; you thus,
as I remember, concluded,
So when the Needle hath been once drawn o'er
The Loadftone's Poles, and felt its wondrous Power,
"Twill e'en in Abfence keep its Truth and Worth,
And always point tow'rds its beloved North:
But when it once the Magnet's Prefence gains,
With Joy it trembles and the dear Object joins.
MADAM, faid I, you do me and my
Trifles a great deal of honour
HUSH! faid fhe, not a word! I won't
now allow you one Syllable of Trifling;
be quiet and go on with your Lecture.
PLEASE to let me inform you then,
Madam, faid I, that fuch a Wire as this,
fo touch'd, as they call it, or directed by
the Power of the Magnet, or Loadſtone,
they put into a round piece of Paſteboard,
on which they draw a Circle; dividing
it as this on the wooden Horizon of the
Globe
Aftronomical Dialogues.
23
Globe is, firft into four Quarters, for Eaſt,
Weſt, North and South, placing the Point
of North over that End of the Wire which
will point that way; then they divide each
Quarter into Halves; and by that means
they make in the whole 32 Diviſions,
which they call Points; and which are
there and here expreffed by the initial
Letters of their Names after this manner:
[See Fig. II.] And therefore the Uſe of
that Circle on the Horizon of the Globes
is to fhew, on what Point of the Compafs
the Sun, or any Star or Planet apparently
Rifes or Sets; as I fhall fhew you more
fully hereafter.
WELL! faith fhe, I fancy my ſelf half
a Sailor already; but for all that I muſt
confefs ingenuously to you, that I don't
know how to find the Points of Eaft, Weft,
North and South in the Heavens, or on
the Earth, unleſs I fee a Church, which,
they fay, ufually ftands Eaft and Weft.
MADAM, faid I, that is eafily known,
by the Noon-day, or Meridian Sun; for
the Sun at Twelve a-Clock being always
full South, when you turn your Face to-
wards it, the North will be on your Back,
the Eaft on your Left, and the Weft on
your Right-hand,
C 4
THAT'S
1
24
Aftronomical Dialogues.
THAT's true, faid fhe; but as obvious
as this Obfervation is, I never made it be-
fore. And really the Education of us Wo-
men, is for filly and crampt, that, generally
1peaking, we are never taught, nor enured
to think of any thing out of the common
Way, and beyond the Legend of the
Nurſery: Nothing but our Work, a lit-
tle Houfwifery, and a great deal of Gof-
Siping.
But pray let us go on: The next Cir-
Calendar cle I perceive is only an Almanack, with
both our Own, and the Foreign or New
Stile, or way of accounting Time: But
pray, Sir, of what Ufe is this innermoft
Circle, and how is it divided?
Divifi- MADAM, faid I, all Circles on the
ons of a Globes are fuppofed to be divided into
Circle. 360 cqual Parts, which they call Degrees,
and cach Degree into 60 leffer Parts;
which they call Minutes, and ſo on, by
a Sub divifion by 60 ftill, as far as you
pleaſe. This Circle is defign'd to fhew us
what we call the Sun's Place for every
Day in the Year; and therefore is divided
actually into 12 Parts, which are diftin-
guifh'd here, you fee, by theſe Pictures
of 12 eminent Conftellations, or Parcels
of Stars; and which, becauſe they do fign.
-OF
Aftronomical Dialogues.
25
or mark out a particular Place in the Hea-
vens, where the Sun is, or appears to be,
every Month, have been called the Twelve
Signs of the Zodiac: And each of theſe Signs of
Signs is divided into 30 equal Parts or De-the Zo-
grees, which makes up the whole 360.
HOLD a little, Sir, faid the Lady, for
I have now ſo many things to ask you, that
I know not where to begin
MADAM, faid I, all the Affair of the
Zodiac, of the 12 Signs, and of the Sun's
apparent yearly Motion through them, I
will fully explain to you hereafter: And
all you need know now is, That it is the
Ufe of this Circle to fhew you in what
Degree of it, or in what Place or Part of
any of the 12 Signs, in which the Sun is
fuppoſed to be at Noon, anfwers to each
particular Day of the Month. As for in-
ftance; You fee this Day, May the 20th,
is placed in the Calendar, juſt againſt the
firſt Degree of (II) Gemini, and therefore
that is the Sun's Place for this Day.
SINCE I muft wait, faid fhe, I will
be patient, and be content to be taught in
your own way; but I will never forgive
you if you don't tell me, just now, why 360
was only pitch'd upon for the Number of
Divifions,
diac.
26
Aftronomical Dialogues.
Sun's
Motion.
Divifions, or, as you call them, Degrees
of your Circles; and why any other Num-
ber would not have done as well?
•
MADAM, faid I, any other greater
Number that could have been broken into
Parts without Fractions would have done
better. But they had a particular Reaſon
to pitch upon this of 360, which yet I
beg you will excufe me from telling you
now, becauſe it will be much more uſe-
fully explain'd hereafter, and fave a great
many Digreffions at prefent.
WELL! faid fhe, I'm fure you keep
me out of this only to mortify me, and
to try my Patience; but that I may not
tire yours, I fubmit.
You are fo moderate and eaſy in your
Defires, Madam, reply'd I, that I will
now go out of the common Method, and
explain all that matter to you immediate-
ly.
The ancient Aftronomers obferved of
the Sun, that befides his apparent Motion
round the Earth in 24 Hours, by which
he made, as they fuppofed, Day and
Night; the former when he was above,
the latter when he was below the Hori-
zon of any place; which daily or diur-
nal
Aftronomical Dialogues.
27
nal Motion (by the by) they ſuppoſed to
be always made either in this very Equi-
noctial Circle, or in ſome other leffer ones
parallel to it, or equally diftant from it:
Theſe Parallel Circles alfo they ſuppoſed to
be, in the Summer half-year on the North-
fide, and in the Winter on the South-fide
of the Equinoctial. And they took no-
tice, Madam, that befides this Diurnal
Motion (which appear'd to be circular)
the Sun had alfo in appearance a progref
five one, forward on in another circular
Track in the Heavens; which, becauſe
they found that when ever the Moon came
into the very fame Circle, there would be
an Eclipſe of either Her, or of the Sun,
they call'd the Ecliptick. This is the Cir-
cle here on the Globe, which lies oblique
to, or askew, and cuts or croffes this o-
ther, which is drawn exactly in the middle
between the Poles, and is call'd the Equi-
noctial or Equator: This Ecliptick Circle
alfo, becauſe they perceived that the Sun
never deviated from it in his Annual Mo-
tion towards either Pole North or South,
they called the Way of the Sun: And they
found that in the Time of our Common
Year, he would appear to go quite round,
or pafs fucceffively through all the Parts
of this Circle.
BUT,
28
Aftronomical Dialogues.
BUT, faid the Lady, how could they
determine that? For when the Sun was
above the Horizon, no Stars at all could
be ſeen, to diſtinguiſh his Place or Situa
tion by.
YOUR Objection is juft, faid I, Ma-
dam, if you confider the thing after the
Sun was actually Riſen, and juſt before his
Setting: But they took notice of thoſe
Stars which were at or near the Edge of
the Horizon before his Rife, and ſuch as
were there after his Setting; and found
that the Sun would not continue to riſe
and fet always at the fame diſtance from
the fame Stars; but if, for inftance, on
March the Ioth, he would rife and fet
near theſe Stars which you fee here placed
on the Globe within this Conftellation
called Aries, about a Month after they
found that he would riſe and ſet with thoſe
in Taurus, which lie a 12th part of the
whole Circle more this way, or forwards
on, as the Numbers fhew, to the Eaft-
ward and after this manner the Sun pro-
ceeding ftill forward every Day, they
found that at the end of 12 Months he
would feem to have gone entirely round
in this Circle, and to rife and fet fuccef-
fively with or under all the Fixed Stars,
which
Aftronomical Dialogues.
29
which are in or near this Circular Tract
called the Ecliptic.
BUT, pray, Sir, faid fhe, what do you
mean by under the fixed Stars? Why,
don't the Sun move in among them, and
along with them?
No, by no means, Madam, faid I, the
fixed Stars are probably farther, a long
way, from the Sun, than that mighty Lu-
minary is from us; and the meaning of
the Sun's Place, or his being in ſuch a Sun's
Sign, is only his being for fuch a Time Place.
under that Star or Conſtellation, or be-
tween that and our Eyes; ſo that if a
Right Line were drawn from that Star to
your Eye, it would paſs thro' the Center
of the Sun.
I BEGIN, faid the Lady, I think, to
comprehend this a little better than I did;
but, pray, Sir, what is the meaning of
the Word Zodiac, which you uſed a while Zodiac.
ago, when you began to talk about the
Sun's Motion ?
THE ancient Aftronomers, Madam,
faid I, to diſtinguiſh theſe Conſtellations,
or Setts of Stars, under which the Sun.
conſtantly appeared to move in his An-
nual
30
Aftronomical Dialogues.
nual Courſe, gave them particular Names?
The firſt they called Aries, or the Ram;
the ſecond Taurus, or the Bull, &c. and
becauſe theſe Names were moſtly taken
from Animals, or living Creatures, they
called it the Zodiac; which is a Greek
Word expreffing fuch a Collection.
WELL, ſaid ſhe, as for your Greek, Í
İ
know nothing of the matter, but now I
begin to find out the Juftness of thoſe
Lines, in Hudibras; wherein he deſcribes
Sydrophil's Surprize at the Diſcovery of
his new Star, occafion'd by a Lanthorn at
the Tail of a School-Boy's Kite:
'Tis not among that mighty Scrowl,
Of Birds, and Beafts, and Fifb, and Fowl,
With which like Indian Plantations
The Learned stock the Conftellations.
And theſe, I fuppofe, are the Pictures,
continu'd fhe, of thofe animated Stars, or
rather, as Butler hath it in the fame Place,
the Signs of Thofe:
Nor those that drawn from Signs have been,
The Houſes where the Planets inn.
MIGHTY well remember'd, faid I,
Madam, you fee at once why the Aftro-
nomers
Aftronomical Dialogues.
31
nomers call them the Twelve Signs, be-
cauſe, as I faid before, they fign or mark
out the Place of the Sun in the Heavens
and alſo why the Aftrologers called them
Houſes,becauſe they affigned them as Dwel-
lings or Places of Abode for the Planets.
O! faid fhe, now you talk of Aftrology,
I must ask you a few Queſtions about that
either now or fome other time; for I
long to know whether there be any
thing in that Art or no; for I think I
have heard you throw out fome fufpicious
Words about it.
MADAM, faid I, if you pleaſe to go
on with your Aftronomy, you will foon
know enough to defpife that vain and
fooliſh Cheat, as a thing perfectly beneath
your Enquiry into.
VERY well, faid fhe, and fo if I will
be an Aftronomer, it ſeems, I muſt at once
bid adieu to that darling Pleaſure of our
Sex, Curiofity, and the Defire of know-
ing our Fortunes; this is very hard, and
you are really, Sir, a very bad Woman's
Man; you have philofophized me out of
many a tair Pleaſure already; Cenfure,
Satyr and Goffipping are almoſt gone;
and muſt dear inquifitiveness follow them
too?
}
32
Aftronomical Dialogues.
too? It fhall never be, let it be never fo
filly; I remember what Butler faith:
Doubtless the Pleasure is as great,
Of being cheated, as to cheat;
As thofe receive the moft Delight
Who leaft perceive a Fugler's Slight;
And ftill the lefs they understand,
The more admire the Slight of Hand.
But I ha'n't time to quarrel with you,
and to diſpute it out with you now;
pray, therefore, Sir, go on, about the
Sun's Motion, a little farther.
You muſt know then, Madam, ſaid I,
that theſe venerable Star-Gazers, finding
the Sun apparently to run thro' this Zo-
diac, in twelve Months, or a Year's time,
affigned one part of the Circle to a Day's
Motion and becauſe there are but a few
more than 360 Days in a Year, they fup-
poſed this Circle of the Sun's Annual Mo-
tion, to be divided into 360 equal Parts,
which they called Degrees, as I told you
before; and hence all Circles on the
Globes came to be divided after the fame
manner.
I thank you, Sir, faid fhe, now this
Matter begins to clear up to me; have
I
you
Aftronomical Dialogues.
33
you any thing more to teach me about
this Circle?
ONLY the Explanation of a few Terms,
or Words, which you will find ufed about
it, faid I, Madam: For you muſt know,
that the Aftronomers call the Diſtance of
the Sun's Place at any time of the Year,
from the Beginning of Aries here, which
you fee is placed at the Eaftern Point,
where this Circle of the Ecliptick, and
that of the Equinoctial cross one another,
they call that Diftance, I fay, his Longi-Sun's
tude; and tho' the Sun himſelf apparent- Longi-
tude.
ly moves always in one Circle, exactly
in the middle of the Zodiac, that is in
the Ecliptic, yet the Moon, and the other
Planets, do not, but fometimes are 5 or 6
Degrees to the North, and at others, as
far to the South of this Circle; and this
Deviation or Diſtance they call their La- Planets
titude; and you fhall be fhewn hercafter Latitude.
how to meaſure it; and the fame Word is
uſed alſo, with reference to thole fixed
Stars which are not in the Ecliptic, but
are diftant from it, any way, towards ei-
ther of its Poles; for the Diſtance of a fix-
ed Star from the Ecliptic, is alfo called its
Latitude.
D
BUT
34
Aftronomical Dialogues.
BUT, pray, Sir, faid fhe, is not the
Word Latitude ufed alfo with Reference
to the Terrestrial Globe? Surely I have
heard my Brother fpcak of Peking in
China's lying in fuch a Latitude; of the
Latitude of London, and of his Ship be-
ing haraffed by a Storm, in fuch a La-
titude; but I must own I never knew
the meaning of it: Am I Aftronomer e-
nough to be taught that now?
YES, Madam, faid I, and you will
very cafily comprehend it: Pleaſe to turn
your Eyes to this Terreftrial Globe;
this Circle which lies exactly in the
middle, between the two Poles of the
Equator. Earth, is here called the Equator, and
by the Sailors the Line; all Places which
lie under it, or which have the Equinoc-
tial in the Heavens, paffing over their
Heads, are ſaid to have no Latitude; but
all other Places that lie at any Diſtance
from it, cither North or South, are ac-
Latitude cordingly faid to have North or South
of Places. Latitude: And its Quantity is known by
turning the Globe about till the Place
come to this Brazen Circle in which the
Globe hangs, and there the Place will
fhew its own Latitude, in Degrees upon
that Circle: Thus, you fee, Madam,
when
Aftronomical Dialogues.
35
when I bring London to this Brafs Circle,
it appears to lie on the North Side of the
Equator, in 1 Degrees diftant from
it.
MIGHTY well, Sir, faid fhe, I now
conceive what paffing or croffing the Line
is, which I have heard the Sailors make
fuch a Fufs about; and I have read of
ftrange Ceremonies and Duckings, which
they make young Navigators undergo, at
the firſt time of their crossing the Equa-
tor: I perceive now, alto, the true mean-
ing of ſeveral Allegorical Expreffions,
which, no doubt, are taken from hence,
fuch as being a Latitudinarian in Notions,
&c. But pray, Sir, let us go on; now
you mention that Brass Hoop, in which
the Globes hang and turn round, pray
let me know its Name and Ufe?
THAT Brazen Circle, Madam, ſaid I, Meridi-
is called the Meridian; and 'tis a greater an.
Circle of the Sphere, which is ſuppoſed
to paſs thro' the Zenith and Nadir of any
particular Place, thro' the North and South
Points of its Horizon, and thro' the Poles
of the World.
I SEE, faid fhe, the latter part of what
you fay; but pray, what do you mean
D 2
by
36
Aftronomical Dialogues.
by the Terms Zenith and Nadir, the for-
mer of which Words I have often met
with in Books, but never knew the mean-
ing of it.
'Tis an Arabic Word, faid I, Madam,
and fignifies that Point in the Heavens that
is directly over your Head, as Nadir doth
the oppofite one in the lower Hemifphere,
that is under your Feet, at the oppofite End
of a Diameter of the Earth: And this Bra-
zen Circle is called the Meridian, becauſe,
whenever the Sun comes to the Meridian of
any place on the Earth, in his daily Courſe,
'tis then, what the Latins called Meridies,
i. e. Mid-day, or exactly Noon there.
O! Sir, faid fhe, this Aftronomy is
mighty inftructive; I now underſtand the
just meaning of fuch Expreflions, as theſe,
There Vice did in its Zenith reign,
Our bright Meridian Sun decline, &c.
But pray let me know the Ufe of this
Circle here on the Globcs.
I fhew'd you juſt now, ſaid I, Madam,
That on the Terreftrial Globe it fhewed
the Latitude of all Places, which, by
being brought fucceffively to it, as the
Globe
Aftronomical Dialogues.
37
Globe turns round its Axis, do each re-
ceive it for their own Meridian, for 'tis all
one as if a different Meridian had been
actually drawn on the Globe thro' every
Place.
No doubt on't, faid fhe, for 'tis the
fame thing, as to meeting, whether the
Mountain walks to Mahomet, or he ſtalk
to the Mountain : But methinks this
Earthly Meridian is either very lazy, or
elfe takes great State upon him, that all
Places must come to him, while he ftands
and ftruts here, and won't ftir the leaft
Step towards them.- Have you any
thing more to tell me about this Man of
Brass; Spencer did wifely to make his
Man Talus of Iron, that was to be Arthe-
gall's Page, and to bear fo bufy and active
a Part in his Story.
MADAM, faid I, this Brass Meridian.
ferves alfo, by its moving thus, round,
North or South, in this perpendicular Si- Height of
tuation to the Horizon, to clevate or raifethe Pole.
the Pole of any Place as much above its
Horizon in Degrees, as is the Latitude of
that Place, or its Diſtance from the Equa-
tor; and then that particular Place will be
brought to lie in the Zenith, or upper-
moft Point of the Globe.
D 3
PRAY
38
Aftronomical Dialogues.
PRAY explain this by an Inftance, faid
The.
I SHEWED YOu juft now, faid I, that
the Latitude of London is found by the
Help of this Meridian to be 51°; raiſe
therefore the North Pole ſo, that the Nor-
thern Edge of the Horizen cut 51° 30′
of this Brass Meridian, reckoning from
the Pole, and then London will be in the
Zenith Point of the Globe.
I SEE it is, faid the Lady, and I believe
I fee alfo the Reaſon why it muſt be ſo;
for it is juſt as far (viz. 90°) from the
Equator to the Pole, as from the Zenith
to the Horizon; fo that taking away the
middle Part, which is common to both,
the Latitude of any Place, and the Height
of the Pole above its Horizon are all one
in Quantity; and fo I fuppofe 'tis called
the Height of the Pole, becauſe the Pole
Star, which is near the Polar Point (as I
think you told me) will appcar, in the
Night, just fo high above the Horizon of
any Place, as is that Place's Latitude.
EXCELLENTLY cxplain'd, Madam,
faid I, and yet I fancy you want to be told
further, that the Height, or Altitude of
the
Aftronomical Dialogues.
39
the Pole Star, as well as all other Altitudes
of the Sun or Stars, is taken by an Inftru-
ment, which hath a circular Edge like this
graduated Meridian, divided on Purpoſe
into Degrees, Minutes, &c. with Sights
fitted to it, to look up at the Object.
I WAS just going to ask you about
that, faid fhe; for I remember to have
often seen you peering up at the Stars, or
catching the Sun-Beams with juſt ſuch a
kind of thing as you defcribe: But, pray,
what Ufe is this Meridian of, on the Ce-
leftial Globe?
THERE, Madam, faid I, it fhews the
Declination of the Sun or Stars, by bring-
ing the Sun's or Stars Place in the Ecliptic
on the Globe to it, as we did the Places
on the Earth upon the other Globe, to find
their Latitudes.
Declination! faid fhe, there's a new Sun's De-
Word for me to learn! which, I fuppofe, clination.
the Aftronomers have coined, to avoid
that of Latitude; which, when it relates
to the Stars or Planets, I think you told
me regards the Ecliptic only: Well! I
doubt my Head will never retain the Me-
mory of all theſe Cramp Terms.
D 4
YES,
40
Aftronomical Dialogues.
YES, Madam, faid I, very cafily, when
you so perfectly understand their mean-
ing, for we only forget what we underſtand
but by Halves; things thoroughly known
become part of our Nature, as it were;
and People can alfo generally remember
what they have a mind to. But, how-
ever, if you pleafe to look over Dr. Har-
ris's little Book of the Globes, you may
have your Memory refreſh'd at any
time very briefly, and yet plainly and
fully.
I THANK you, Sir, faid fhe, for that
Information; I fhall, I hope, be able to
underſtand a little of Books of this Kind,
by Degrees: But, pray, have you any
thing more to fhew me, relating to theſe
Circles?
}
MADAM, faid I, 'twill be proper for
you to know, that as our Aftronomers
Greater make fix greater, ſo they make alſo four
and leffer leffer Circles of the Sphere; two of which
Circles they call the Tropicks, and the other two
of the the Polar Circles. The meaning of the
Sphere. Word Tropicks is, returns back again; for
indced neither the Sun feemingly, nor the
Earth really, goes any further in its Annual
Courſe, to the Northward or Southward
of
Aftronomical Dialogues.
41
of the Equinoctial than 23 Degrees and 2;
but after it hath gone fo far, returns again
toward it: And becauſe the Points in the
Heavens, where thefe Returns are made,
are under the Beginning of the Signs
Cancer and
Capricorn; they ſuppoſe
two Circles to be there drawn in the Hea-
vens and on the Earth, parallel to the
Equator; and the moſt Northern of theſe,
and which therefore is our Summer Tro-
pick, is called the Tropick of Cancer, and
the Winter, or Southern one, that of Ca-
pricorn; becauſe they always fall at the
Beginning of thoſe Signs.
I LIKE our Earth mightily, faid fhe,
for her Steadineſs in her Way, and for
her not going too far North or South to-
wards the Poles: I love moderate Wea-
ther, and would have it be in neither of
the Extreams of Heat nor Cold: But, Sir,
this matter now begins to clear up to me
apace; when the Sun is in the Northern
Tropick, I fee our Days are at the longeft,
and all of them longer than our Nights,
during the time of his whole Stay on the
North-fide of the Equinoctial: Whereas
the very Reverſe, I fee, must come to
paſs, while the Sun is on the Southern
Side of the Line. But, pray, of what
Uſe
42
Aftronomical Dialogues.
Polar
Ufe are the Polar Circles? for 1 ſee they
Circles are drawn on both Globes, as well as the
and Tro-Tropicks, and juft as far from the Poles as
picks.
the Tropicks are from the Equinoctial.
Zones,
Of no very neceffary Ufe, Madam, ſaid
I, but only to help to diſtinguiſh the Ter-
reftria. Globe into the five Parts, which
the Ancients called Zones, and which they
fancied to be like fo many Girdles or Belts
(as the Word Zone fignifies) encompaſſing
the Earth.
O PRAY, faid fhe, let me have fome
true Knowledge about thefe Zones, for I
have heard and read a good deal of them,
without being a Jot the wiſer.
THE great Space on the Earth, faid I,
Madam, which lies between the two Tro-
picks, having the Equator 'paffing thro'
the middle of it, the Ancients called the
Torrid. Torrid, the Fiery or Roasted Zone; for
they fancied the Sun, keeping always
over it, had fuch a Power here, as to have
burnt all things up; and becauſe they had
no Knowledge of it, concluded it not in-
habitable; whereas 'tis now known to be
very comfortably ſo: Tho', no doubt, warm
enough to thoſe Inhabitants of it to whom
the
Aftronomical Dialogues.
43
the Sun is fucceffively vertical, or directly
over their Heads, as you cafily fee by the
Globe he will be.
YES, yes, faid fhe, I underſtand that
very well; but I can't help reflecting
upon the Arrogance, as well as Ignorance,
of the Ancients, in fuppofing their Know-
ledge to be the Bounds of all things; and
glad I am that we know fomething which
they did not; for I have heard them fo
much cried up, now and then, by Authors,
that I could almoſt wiſh myſelf to have
lived among them; but I will, at laft take
Comfort, and thank God that I am a Mo-
dern, and alive now.-But pray go on
about your Zones.
THESE two Spaces of the Earth, ſaid
I, Madam, which lie between the Tro-
picks and the Polar Circles, each Way
North and South, the old Geographers
called the Temperate Zones; and as theſe Temperate.
Oriental Sages, and the Learned
Greeks and Romans, lived (as you
(a) fee here) in one of them, fo
they did allow the other to be ha-
bitable alſo.
Terreftrial Globe I
(a) Here on the
fhewed her the chief
Places of the Gracian
and Roman Empires.
THAT was pretty good-natur'd, faid
fhc, for I fuppofe they never faw the
South-
44
Aftronomical Dialogues.
Frigid.
Southern Temperate Zone, any more than
the Torrid one.
NOT that we can find by Hiftory,
faid I, Madam: But to proceed; Thefe
fmall Spaces of the Earth, between the
Polar Circles and the Poles, they called the
Frigid Zones, and did pretty juſtly ſup-
poſe them not to be habitable, upon the
account of their Coldness; for tho' we
have fince diſcovered, that 'tis poffible to
fubfift, and ſeveral of our Ships do yearly
go within the Northern Frozen Zone, yet
I can't recommend it to you as a Place much
worth your Enquiry after.
O! don't speak any more about them,
faid fhe, you make me fhiver all over
with the Thought of them, and my Blood
is juſt going to curdle in my Vcins; no
Lapland or Spitsburghen; no Whale-
Fishing Voyages for me.
You ſeem to be really a-cold with the
Thought of it, Madam, faid I; let mac
warm you a little with this Defcription
of thefe Zones given by Mr. Dryden.
From VIRGIL and OVID.
Zones. Five Girdles bind the Skies: The Torrid Zone
Glows with the paſſing, and repaſſing Sun ;
Far
Aftronomical Dialogues.
45
Far on the Right, and Left the Extreams of Heaven,
To Frofts, and Snows, and bitter Blafts are given;
Betwixt the midft, and theſe the Gods affign'd
Two Habitable Seats for Human Kind;
And cross their Limits cut a floping Way,
Which the twelve Signs in beauteous Order fway:
And as five Zones the Ætherial Regions bind,
Five correfpondent are to Earth affign'd;
The Sun with Rays directly darting down,
Fires all beneath, and frys the middle Zone :
The two beneath the diftant Poles, complain
Of endleſs Winters and perpetual Rain :
Betwixt the Extreams two happier Climates hold,-
The Temper that partakes of Hot, and Cold.
WELL, faid fhe, thefe Verfes have a
little recovered my Spirits, as well as re-
freſhed my Memory, and will, I find, fix
in the latter, the obliging Pains you have
taken to inftruct me: But pardon me,
Good Sir, if I ftop you a Minute: Mr.
Dryden here mentions the Word Climates; Climates.
Pray what are they?
MADAM, faid I, you will find a deal
of uſeleís Stuff in fome Introductions to
Geography, &c. about thefe Climates;
but all that is neceffary to know of them,
is, that the Ancients fuppofing two Circles
to be fo drawn parallel to the Equator, on Parally,
the Terreſtrial Globe, or at that Diſtance
3
one
46
Aftronomical Dialogues.
one from another, that to fuch as inhabit
the leffer, the longest Day, would be a
Quarter of an Hour longer, than it is to
thoſe who dwell in the larger: Then the
Space on the Globe, between thefe two,
they called a Parallel, and the Double of
fuch a Space a Climate; you will eafily
fee therefore, that theſe Climates muft
leffen as you go each way from the Equa-
tor to the Poles, and must be 24 in
Number.
WELL! faid fhe, I fhall not trouble my
Head about reckoning theſe Climates ;
but I think I underſtand what is meant by
fuch a Place lying in fuch a Climate, as
well as what the Navigators mean by
failing in fuch a Parallel, and that will be
enough for me at prefent; but I will tire
you no longer now, I'll get the Book you
adviſe me to, which I believe I have above
among my Brother's things; and after I
have conned my Leffon well over, you
muft expect that I fhall ask you abundance
of Queſtions more.
WITHIN a fhort Time after this, the
Ingenious and Inquifitive Lady got her
Globes fet out again, and began with me
thus:
I
Aftronomical Dialogues.
47
I have been looking over the little Book
you recommended to me, Sir, faid fhe,
which I think is very plain and concife,
and I fancy I am now got to be fuch a
Proficient, as that I am qualified to go thro'
the Problems, as the Book calls them, Problems.
tho' what that Word fignifies I don't un-
derſtand.
THAT Greek Word, Madam, ſaid I,
fignifies fomething to be done or practifed,
and I queſtion not but you have ſo well
confidered this Affair, as to be able to
work or perform any of thefe Problems
the Globes yourſelf.
upon
I don't know that, faid fhe, but I'm
reſolv❜d to try, and with a little of your
Help, perhaps, I may get thro' them:
Come, pray, let's begin; and, first, fhew
me how to rectify each Globe, as he calls Rectify-
it, and what I fhall learn by that.
Rectifying the Globes, Madam, faid I,
is reducing them to fuch a Pofition, as that
they fhall truly reprefent the Situation of
the Circles of the Sphere of the fixed Stars,
and Plancts; and of the Pofition of the
Earth itself at any Time afligned.
ز
3
VERY
ing the
Globe.
48
Aftronomical Dialogues.
Sun's
Place.
VERY well, faid the Lady, let us then
take his Time of the Year; ſuppoſe May
10, 1719; How muft we begin?
MADAM, faid I, for common Ufe,
look firft for the Sun's Place, against the
Day of the Month, in the Calendar, on
the wooden Horizon (tho' if you would
proceed to greater Exactneſs, you muſt
find the Sun's Place in fome good Tables,
fuch as thoſe which Dr. Harris hath given
in the ſecond Volume of his Lexicon,
or fuch as Parker's Almanack, which I have
here in my Pocket, gives you every Year,
or elſe you muſt determine it by Calcu-
lation, &c.) and then finding that Place,
or what Degree of any Sign of the Zo-
diac the Sun appears to be in that Day at
Noon, which you will find to be then in
the firſt Degree of Gemini, look it out on
the Ecliptic on the Globe, and there make,
either with a Pencil or with Ink, a Mark to
repreſent the Sun for that Day.
BUT, faid fhe, won't that ſpoil the
Globe?
No, Madam, faid I, that being var-
nifh'd, the Ink will cafily come out again,
if you rub it with your Handkerchief a
little
Aftronomical Dialogues.
49
little wetted; as foon as this is done, you
may alſo, if you pleafe, by the Help of
Parker's or fome fuch Ephemeris or Aftro-
nomical Diary, place all the Planets on
your Globe, after the fame manner, al-
lowing for their Latitude, either North or
South of the Ecliptic.
}
Thus the Moon being then in 24° 33′
of Cancer, and having about 4° 41′ of
South-Latitude, take, with
with a Pair of
Compaffes, thofe Degrees and Minutes of
Latitude from the Meridian, or any great
Circle, and placing one Foot in 24° 33′
of, turn the other directly towards the
Equinoctial, and there make this Mark >
to repreſent the Moon.
me
After the fame Method you may
place ↳ Saturn in 8° 42' of Virgo ;
and Jupiter in 26° 35' of Leo &:
Then make alfo this Mark 3 for Mars
in 16° 32′ of Aquarius : And this
Character for Venus in 28° 18′ of Ge-
mini II: Laftly, placing Mercury
II° 4' of the fame Sign, you will have
adorn'd your Globe with the Characters.
of the Seven Planets, all appearing in
their proper Place as they are in the
Heavens.
in
THIS is mighty Entertaining, faid ſhe;
here take this Pencil quickly, and let me
E
fee
50
Aftronomical Dialogues.
ſce you juſt now place all your Planets
upon the Globe according as they ought
to be done, that I may learn how to range
them another Time: For I fancy their very
Characters or Figures fo much, that I could
almoſt wiſh our Patches were cut into fuch
pretty Forms; but that I fear 'twill revive
the foolish Notions of Aftrology again,
which you have taught me to defpife. But,
pray, continued fhe, how do you know
the Planets from the fixed Stars when you
ſee them in the Sky?
PRETTY eafily, faid I, Madam, as to
Saturn, Jupiter, Mars, and Venus. And
Mercury is fo near the Sun, as to be very
rarely feen at all.
THAT puts me in mind, faid fhe, of
what Sir Richard Blackmore faith of him
in his Poem call'd Creation, in thefe Lines:
Mercury, nearest to the Central Sun,
Doth in his oval Orbit circling run;
But rarely is the Object of our Sight,
In Solar Glory funk, and more prevailing Light.
WELL remember'd, Madam, ſaid I.
But to our preſent Point, the Knowledge of
theſe Planets from the fixed Stars: The
former, you must know, don't twinkle as
the
Aftronomical Dialogues.
51
the fixed Stars do; befides they are al-
ways and all of them in or near this Line
here called the Ecliptic: Which you may
eafily learn to trace out in the Heavens, by
theſe Conſtellations which compofe the
Twelve Signs; and if you ſhould, at laft,
doubt about the Planets, if you fee them
change as they will do, in fome Time,
their Diſtance from any fixed Star that
you know; you may eafily diftinguiſh
them to be Erraticks or Planets.
I think, faid fhe, you reckon'd feven
Planets juft now; fure I have read fome-
where, that there are more.
And nets.
IN that Account above, faid I, Ma-
dam, I followed only the vulgar way
of Computation, for in Reality the Sun
is no Planet or Wanderer, but a fixed
Star placed in the Center of our Syftem, Number
and in all Probability like the rcft of of Pla-
thoſe that we fee in the Heavens.
round him, as a Center, Mercury, Venus,
Mars, the Earth, Jupiter, and Saturn,
do revolve, and are now called Primary
Planets; becauſe they revolve round the
Sun, as their Center: While the others
we call Secondary Ones or Satellites, `i. c.
Guards or Attendants, becauſe they re-
volve round ſome one of the Primary Pla-
E 2
nets,
52
Aftronomical Dialogues.
nets, as their Center, and together with it,
move alſo round the Sun.
Thus the Moon is a Secondary Planet,
whofe Center of Motion is our Earth, on
which ſhe conſtantly attends, and her Circle
round us the performs in about a Month's
Time, while at the fame time, fhe re-
volves together with the Earth round the
Sun in its Annual Courſe. Jupiter hath
Satel- four fuch Moons or Satellites; and Sa-
lites. turn five, revolving round him: But it
doth not yet appear that Venus or Mars
have any Satellites at all.
.
As for Mars, faid the Lady, I fhan't
trouble my Head about him; tho' one
would think, the God of War, or Cap-
tain General of Heaven, might command
a few Guards or Followers: But I will
never forgive the Aftronomers, nor be-
lieve at all in Teleſcopes, if they don't
find out that Venus hath fome Attendants;
that is ſuch an Affront to our Sex, as we
must never pass by. But to be ferious,
I ſuppoſe, Mercury and Venus being fo
near the Sun, have no occafion to be
lighted in the Night by Moons, as the
more remote Planets have; tho' why our
Earth fhould have one, and yet Mars
none, is not, methinks, fo eafy to be ac-
counted
Aftronomical Dialogues.
53
counted for. But we have made a long
Excurfion from our Globes; pray let's re-
turn to them: And let me ſee what I fhall
be the better for knowing how to rectify
the Globes, and to patch on the Planets,
as you juſt now have fhewed me the way
of.
MADAM, faid I, bring the Sun's Hour-
Place, for May 10, to the graduated Side Circle
of the Meridian, and then turn or fet the and In-
dex.
Index of the Hour-Circle (placed here as
you fee upon the Brafs Meridian about
the Pole) to Twelve at Noon; and then
your Globe will be fitted to fhew you
the State of the Heavens. As it now ftands,
the Mark for the Sun reprefents his being
on the Meridian, as he is every Day at
Noon; and there it will fhew the Sun's
Meridian Altitude above the South Part
of the Horizon to be 58 Degr. 42 Min.
Then if you will bring that Mark to the
Eaſtern Edge of the Wooden Horizon,
you will fee there what Point of the
Compass the Sun rifes upon, and your In-
dex will fhew you the Time of it; and if
you bring the Sun's Place to the Weſtern
Edge, you will find how far from the true
Weft Point the Sun fets, and what a-clock
it is when he goes down, as we call it :
Thus, May 10, the Sun rifes about
E 3
3
of
an
54
Aftronomical Dialogues.
an Hour before 5 a Clock; and ſets of an
Hour after 7.
WELL, faid fhe, I fancy I fhall be able
to make an Almanack in a little Time.
THAT you may foon do, this way,
faid I, Madam, and much better than
moſt of thoſe who publifh them: But
if you have a mind to know the Stars
and Planets, how they will appear, and
are fituated at any particular Time, ſuppoſe
to-night at Eleven a-Clock; you need only
turn the Globe about till your Hour-Index
points to Eleven at Night; and then putting
a little Piece of Paper under the Brafs Me-
ridian, to ſtay the Globe in that Poſition,
pleaſe to turn the Frame, and Globe and
all, about, till the North-Pole here point up
towards the Pole-Star in the Heavens; and
then you will have all you can wifh for
fhewed you: for, by comparing the Pic-
tures and Marks of the Stars and Planets
with the real ones, at that Time in the
Heavens, you will find them exactly to
anfwer to one another; and theſe on the
Globe will make thofe eafily and fufficiently
known to you.
S1R, faid fhe, after abundance of
Thanks, I muft beg you to break off
here;
Aftronomical Dialogues.
55
'here;
we must defer this till Night:
When with the Stars we'll be familiar,
As e'er was Almanack Well-willer.
And in the mean time, I'll con my Leffon
in the Book, that my Ignorance may not
give you too much Trouble. The Tea
waits us; will you pleaſe to move, Sir?
THE Evening of this Day proved one
of the fineft I ever faw, and the Night
fucceeding it was fo very clear and bright,
that the Moon being then not above our
Horizon, there appeared many more Stars
than uſual. As we were walking to a
Summer Houſe, placed on a Mount in
the Garden, where the Lady had order'd
the Celeſtial Globe to be ſet out, ſeveral
Poctical Deſcriptions of fuch a Night oc-
curred to our Thoughts, and were recited.
The Lady cloſed all with that famous one
of Mr. Dryden,
All things are hushi, as Nature's felf lay dead,
The Mountains feem to nod their drowzy Head,
The little Birds in Dreams their Songs repeat,
And fleeping Flowers beneath the Night-dew fweat:
Even Luft and Envy fleep-
I was going to fay-But Love denies, &c.
when
E 4
56
Aftronomical Dialogues.
when the interrupted me, and ſaid, I'll
have nothing of Love mention'd nor talk'd
of to-night; the Opportunity is too fo-
lemn, and I'm afraid I fhall grow in car-
neft and ſerious about it: We will both
make our Court now only to Urania, and
every gay thing fhall give place to Aftro-
nomy: Let's enter the Summer-Houfe, and
fee whether I have rectified the Globe as it
fhould be, and ſet it right to repreſent the
preſent Time, which is juft half an Hour
paſt Ten,
MADAM, ſaid I, you have done it with
Accuracy: And I fee you have mended
the hafty clumfey Figures, that I had
made, of the Planets, and have placed
very beautiful oncs, of your own, in their
Room.
BUT, faid fhe, I don't know how to
place the Globe due North and South, as
my Book directs, unleſs there were a little
Compass here, placed on the Frame.
MADAM, ſaid I, there ufually is fuch
a Compaſs made on purpoſe to be placed
on the Globe; but I can fhew you how to
fet the Globe right enough without it; you
Charles- ſee theſe 7 large Stars here, that are painted
Jain. within the Figure of the greater Bear, 3
in
Aftronomical Dialogues.
57
Theſe
in the Tail, and 4 in his Body:
our English Country-People call Charles-
Wain, and fancy the four to be the 4
Wheels of the Waggon, while, forsooth,
the three are to repreſent the 3 Horſes
that draw it. But as to the prefent Con-
cern, pleaſe to take notice, that as this
Conſtellation, in our Horizon, never ſets,
but ſeems to revolve round the Pole in
24 Hours; ſo theſe two Stars of the 7,
that are nearest to the Pole Star, or the
two hinder Wheels of the Wain, do al-
ways point up pretty nearly to the Pole
Star; and are therefore fometimes called
the Pointers; and confequently, if you
carry your Eye on in a Right Line from
them, they will direct you to the Pole
Star, which you fee is here, on the Globe,
placed in the End of the Tail of the Leffer Leffer
Bear, a Conftellation of 7 pretty large Bear and
Stars, much in the fame Figure of thoſe in PoleStar.
the Great Bear or Charles-Wain.
I SEE them on the Globe, faid fhe,
let us now look out of the Window and
obferve them in the Heaven; O! I fee
them yonder very plain, faid fhe, and
now I fhall know in the Night as well as
the Day, how to find the four Points of
the Compaſs, Eaft, West, North, and
South.
WE
58
Aftronomical Dialogues.
WE muſt then return again to the
Globe, Madam, faid I, and by opening
the North Window, direct its Pole to
point up to the Pole Star, and ſo ſet it as
near as we can due (a) North and
South.
(a) Here the
Brafs Meridian
of the Globe was
placed due North
and South.
There is no need of great Accu-
racy for our preſent Purpoſe; and
I think it ſtands pretty true now,
Before we look or go out again, pray,
Madam, pleaſe to obferve this Situation
of the Globe, and then you will eafily
fee how the Pofition of the Stars do at
prefent correſpond with it: There is, in-
deed, now not any very eminent Star, or
one of the firſt Light or Magnitude, exact-
ly on the Meridian, either North or South:
But you will fee this great Star, which is
Spica
called the Virgin's Spike, becauſe painted
Virginis. on an Ear of Corn which fhe holds in her
Hand, a little to the Weftward of the
South, and about 28 Degrees high above
the Horizon; as you fee, appears by
bringing this Quadrant of Altitude fcrew-
ed in the Zenith, to it; which is an Arch
of 90°, and being moveable, ferves to
fhew the Altitude of any Star or Planet.
I SEE that, faid the Lady, here on
the Globe: But how fhall I be able to find
and count Degrees in the Heaven?
YOU
Aftronomical Dialogues.
59
You know, Madam, faid I, that it
hath been before obferved to you, that the
Aftronomers have Inftruments made on
purpoſe for it, which do it with great Ac-
curacy: But as for your preſent Enquiry,
how high any Star or Planet appears to
be above the Horizon, you may gueſs at
it nearly, thus: The Diſtance you fee here
between the two Pointers of the Great
Bear before-mentioned, is nearly five De-
grees; and this being a Diftance always
ready, and in view, will ferve you very
well to gueſs at the Height of any Star
above the Horizon; or at the Diſtance of
one of them from another; fo as to en-
able you to find out any of them in the
Heavens by the Help of the Globe, or any
Planiſphere, or Map of the Heavens: Ufe
will make this ealy to you; and when
you come alfo to confider, that from the
Zenith to the Horizon, being 90°, half
that Diſtance must be 45°; one third of
it 30°; a fixth of it 15°; a ninth part of
it 10°, &c. you will, by Degrees, cafily
gain a practical Knowledge of thefe Di-
ftances.
But if you pleafe we will go on Al-
moſt South-weft, at this time, and about
43° high, will appear another Star of the
firft Magnitude, called Deneb, which is in Deneb.
the
ba
Aftronomical Dialogues.
the Tip of the Tail of the Lion I fee
it yonder fimpering thro' that Weſtern
Window; if you will let me lift up
the Safh, you may fee it without going
out.
O! I do, faid fhe, and the Virgin's Ear
of Corn too, very plain: But what are
thoſe two great Stars that appear together
almoft nearly Weft, and let me fee!
don't tell me
about, about- I muſt
look out at the Pointers again to get my
Meaſure—why, they are about 25 De-
grees high.
VERY well guefs'd, faid I, Madam
you will come to meaſure the Diſtance of
Stars by your Eye, in a little time, as
accurately as the good Houſewives and
Work women can meaſure Cloth or
Ribbons, by the length of their middle
Finger.
WELL, faid fhe, Mr. Obfervator, and
fo I can too, for all I have a mind to be
an Aſtronomer, as well as the beſt of them;
and I don't deſign, Sir, that my Studies
ſhall ſpoil my Houſewifry: But pray tell
me quickly, who thoſe two famous Stars
are.
THE
Aftronomical Dialogues.
61
THE uppermoft, Madam, faid I, is Cor Leo
called the Lion's Heart, and is, you fee, nis.
drawn here on the Globe: And the other
is Jupiter; you remember you have
drawn the Character of him here your
felf.
BLESS me! faid fhe, is that Jupiter-
well, I have many Queftions to ask you
about that Planet another time, but I will
not ſtop you now; pray go on, and fhew
me how to know more of theſe Stars and
Planets; for I begin to grow mighty fond
of their Acquaintance.
DON'T you fee, Madam, faid I, here
on the Globe, two Stars, about 15 or 16
Degrees high, and within two Points to
the Weftward of the Northern Edge of
the Horizon: Theſe two are called the
Shoulders of Auriga, and the lowermoft
and moſt Northern is called Capella, and Capella.
is a Star of the first Magnitude; there are
very conſpicuous Stars, and you may fee
them in the Heavens very plain out of that
Northern Window.
I Do, faid the Lady, very clearly, and
I fee, faid fhe, alſo another pretty re-
markable Star, about the fame Height
with
62
Aftronomical Dialogues.
with Capella, about a Point to the North-
ward of the Weft, under the Great Bear;
pray, what Name do you give him?
THAT is called Pollux, Madam, ſaid
I, and his Brother Caftar, you ſee, ſits
here cloſe by him on the Globe; and be-
tween them they make up one of the
Signs of the Zodiac, which they call Ge-
mini, or the Twins.
Is that, faid fhe, the Deity that the
Countrywomen fwear by, when they cry
O Gemini!
But don't look grave, or
give me any Return: For tho' I trifle, and
am impertinent, I won't allow you to be
fo. Let us go on and fee what noble Stars
we can find to the Eastward of our Me-
ridian.
MADAM, faid I, if you will look out
at that North Window, and direct your
Eye along by the Pointers of the Great
Bear, till you fee paft, or beyond, the
Pole Star, and continue it down till you
come within 20 or 30 Degrees of the
North North-Eaft Part of the Horizon,
you will fee an eminent Conftellation
which is called Caffiopeia's Chair: This is
the Figure of it here on the Globe; 'tis
always
Aftronomical Dialogues.
63
always oppofite to the greater Bear, either
above or below the Pole Star.
I SEE it, faid fhe, very plain, and a
very notable Collection of Stars it is; but,
pray, faid fhe, what do you mean by cal-
ling it Caffiopeia's Chair? Who, or what Caffiopain.
was that Caffiopaia? fure I have read
fomething about her, in fome Books of
the Heathen-Gods.
No doubt of it, Madam, ſaid I, and
the Company you will fee fhe is in, will
refreſh your Memory. This Caffiopaia, the
Poets tell you, was the Wife of Cepheus, Cepheus.
who was, once upon a time, King of
Æthiopia; and here the good old Mo-
narch ftands upon the Globe, with his
Scepter in his Hand, just above Caffiopata ;
and below her, at the very Edge of the
Horizon, you fee, you are to look for her
fair Daughter Andromeda, who had the Andro-
Vanity to think herſelf handſomer than meda.
the Nereides or Sea-Nymphs, which put
them into fuch a Rage, that they imme-
diately applied to old Neptune, the God
of the Sea, to revenge the Indignity.
On this, the obfequious Deity fent a
huge ugly Monſter up into the Country,
which did great miſchief there: The poor
People, who in thofe days were always
puniſhed
I
64
Aftronomical Dialogues.
puniſhed for the Sins of the Great Ones,
apply'd to the Oracle for Relief, and were
told that the only way to appease the Gods,
who were all on the Side of the Nereides,
was, to expoſe the audacious Andromeda
to be devoured by a Sea-Monſter; which
I fuppofe Neptune undertook to get ready
for that purpoſe. This was done, but the
Perfeus. gallant Perfeus, whom you fee here on
the Globe, juft behind her, as her Cham-
pion, deliver'd her and kill'd the Monſter,
and I hope carried off the Lady; and to
reward the Mother of fo beautiful a Crea-
ture, he got Jupiter to place her up here
among the Stars, and they form the Ce-
leſtial Chair in which he fits in State :
And thus, Madam, I have given you
the Hiſtory of one of the Conſtellations,
and if you pleaſe, I can tell you as long
and as true a Story of many of the
reft.
I THANK YOU, Sir, faid fhe, but you
fhall not, this is enough for a Sample;
and now I remember all this Stuff about
Perfeus and Andromeda, as well as if I
had ſeen the whole Affair, as I believe I
did once, or at leaſt good part of it, fhewn
upon the Stage: And have much oftener
feen it in Pictures and Prints. But drop-
I
ping
Aftronomical Dialogues.
65
ping all Fables, let me go on with my Lef
fon; I fhall know Caffiopaia again, when-
ever I fee her.
BUT, faid I, Madam, I have a Story
to tell you of Caffiopeia's Chair, that is no
Fable, but a certain Truth, and yet is e-
qually ftrange with the other fabulous Re-
lation. About the Year 1572, there ap-
peared a New Star in this Conftellation,
which at firſt was as big as Jupiter appears
now to be, and was fix'd to one Place like
the reſt of the fixed Stars; but leffen'd by
Degrees, and at laft, at the End of 18
Months, went quite out, and appear'd no
more.
THAT indeed is a very unaccountable
thing, faid the Lady; but as I have met
with ſome fuch Relations of other fix'd
Stars, fo I fhall leave my Surprize, and
my Queries about it, till I come to trou-
ble you about the Nature, Ufes, and Di-
ftances of the fixed Stars in general: for
I muſt have a deal of Talk with you
about that and other things in Aftrono-
my, before you get quite rid of me, and
you muſt thank your ſelf, if my Curio-
fity be teazing and impertinent, for you
have wound it up to a very great Height
I'll affure you. But, pray, Sir, let us now
F
go
66
Aftronomical Dialogues.
nor.
go on and make an end of our Stars, it
grows late and the Air cold.
MADAM, faid I, we fhall difpatch the
reft, as faft as you pleafe, for the way I
have fhewn you, of finding and diſtinguiſh-
ing the Stars above-mentioned, will teach
you to do fo, by any others in the Hea-
vens: Thus you will fee here above, the
Pole-Star, and about 14 Degrees from him,
and a little to the Eaftward of the Meri-
Urfa Mi-dian, the Conftellation, called the Little
Bear, confifting, alfo of feven pretty emi-
nent Stars, of which the lowermoft, now,
or that in the Tip of his Tail, is the Pole-
Star: You fce here, almoſt due Eaſt, a
fine bright Star of the first Magnitude,
Lucida which is called Lucida Lyra; and under
Lyra. it, a little to the South of the Eaft, as
Lyra is to the North, another great Star
of the firſt Light, about 12 Degrees high,
Alcair. which is called Alcair: And you can't
but take notice of theſe four Stars here
all of the fecond Magnitude, placed in the
Form of a Lozenge, which is called the
Dolphin. Dolphin. About 8 Degrees high, and a-
1
I
bout 2 Points and to the Eastward of
the South, you fee alſo a famous Star, of
Scorpion's the firft Light, in the Body of Scorpio, one
of the 12 Signs.
Heart.
I
ALL
Aftronomical Dialogues.
67
ALL thefe Stars I fee, faid the Lady,
and I think diftinguiſh very well; and I
fancy I fhall be able, by degrees, by the
Help of fuch eminent Stars as that, which
I fee here on the Globe, are placed pretty
near the Ecliptic, to trace out, as you
faid a while ago, that Circle in the Hea-
vens. But, pray, firſt tell me, what you
call that Star, or rather Planet, (for I fancy
'tis one of thoſe wandring Lights) which
appears yonder, almoft upon the South
Part of the Meridian, and about 25 De-
grees high.
You have gueffed very right, Madam,
faid I, 'tis a Planet, and the moft remote
one of all, Saturn.
·
Is that Saturn, faid fhe? I'm heartily
glad to ſee him, I ſhall know him again
another time; I long to pecp at him thro'
a Teleſcope, and to ſee his famous Ring :
But of this, more fome other time, when
the Teleſcope, you have promiſed me, is
fitted up. Is there any thing else worth
obferving, before we remove to our
Sleep?
ONLY pleaſe, Madam, faid I, to take
Notice of that Track of Light, yonder in
F 2
the
Saturn.
68
Aftronomical Dialogues.
the Heavens, and here drawn upon the
Milky Globe, which is called the Milky Way. You
Way. fee here by the Globe, as the Pofition of the
Heaven's is now, that it begins at the North
Part of the Horizon, about Perfeus, takes
in Caffiopaia, and after that the Swan, and
then runs on toward Scorpio, and towards
the South Pole, and takes in the famous
Conſtellation called the Cross; then it
turns Northward again, thro' the Ship, a
little above the Great Dog-Star, or Sy
rius, and above the Right-Shoulder of
Orion, and thence taking in Capella, runs
on towards Perfeus, where we began to
trace it.
I'm glad you thought to fhew me this,
faid fhe, before we finiſh our Night's Ob-
fervations; I fee it plain in the Sky, and
perceive that its Figure, on the Globe,
correfponds exactly with it: I won't ftay
now to ask you what it is, becauſe that
may be one of my many Queſtions to you
another time; we will only remember
what Mr. Milton faith of it:
A broad and ample Road! whofe Duft is Gold,
And Pavement Stars, as Stars to us appear,
Seen in the Galaxy, that Milky Way,
Like to a circling Zone powder'd with Stars.
MR.
Aftronomical Dialogues.
69
MR. Milton, Madam, faid I, alludes
to the Notion that the Poets had of it;
that it was the Path which the Gods uſed
in the Heavens, which Mr. Dryden, from
Ovid thus alfo defcribes:
A Way there is in Heaven's extended Plain,
Which when the Skies are clear, is feen below,
And Mortals, by the Name of Milky, know :
The Groundwork is of Stars ; thro' which the Road,
Lies open to great Jupiter's Abode.
SIR, faid the Lady, a thoufand Thanks
to you for the Pains you have taken to
inſtruct me, and I wish you a good Repoſe.
THE next Day my Affairs called me
away, for fome time; but at my Return,
as I found the Teleſcopes and other In-
ftruments, I had ſent for, in perfect good
Order, fo I found the Lady had been clofe
at her Aftronomical Studies: She was ex-
actly ready in all Problems upon either
Globe, and had gotten fuch an intimate
Knowledge of the Stars, that fhe had alfo
acquired a very tolerable Knowledge in the
feveral Systems of the Univerſe, or Hypo-
thefes to folve the Celeftial Appearances,
as they are called by Aftronomers; and
long'd with great Impatience to ſee the
Uſe
F 3
70
Aftronomical Dialogues.
Ufe of the Telescopes and Quadrant &c.
which I had fent down to her Country-
Seat.
Where foon after I arrived, fhe put me
upon beginning our Obfervations, and had
methodized the Enquiries and Queſtions
ſhe defigned to make, with great Addreſs
and Dexterity.
LET us begin, faid fhe, to talk a little
Sun. about the Sun; I think you agree, that
his Center appears to move always in the
fame Line, or in the Ecliptic; but I
think you fay his apparent Motion is un-
equal there.
t
'TIS true, faid I, Madam, for when
the Earth is nearest the Sun, as fhe is in
Winter, then fhe, in reality, and the Sun,
Seemingly, moves faſter than in the Sum-
mer, when the Distance between the Earth
and the Sun is greater; and accordingly
the Sun's Diameter appears bigger in Win-
ter than in Summer.
BUT, Sir, 'tis ftrange, methinks, faid
fhe, that the Sun's nearer Approach to us
in Winter than in Summer, doth not
counterchange thofe Seafons: Have not
we the greateft Heat from the Sun when
we are nearest to him?
No,
Aftronomical Dialogues.
71
+
No, Madam, faid I, for the diffe-
rent Heat of our Seaſons of the Year, do
not depend upon that, but upon the Sun's
Rays falling more directly, or more ob-
liquely upon us; together with the length
of his ftay above the Horizon, which is
a great deal longer every Day in Summer
than in Winter: For in the Diſtance of
70,000,000 of Miles, a little Approach of
the Earth to, or its Recefs from the Sun,
will make no fenfible Alteration as to Heat
or Cold. But there is another thing a-
rifing from this Inequality in the Earth's
Motion round the Sun, which is pretty
confiderable, and that is, that the Sun will
appear to tarry about 8 Days longer in the
Northern Part of the Ecliptic than he doth
in the Southern; the Reaſon of which is,
from the Figure of the Earth's oval or el-
liptic Orbit: [See Lexic. Techn. Vol. II.
under Sun.] And thus having given you
fome general Ideas of theſe things, I wait
your further Commands.
WHY, then, faid the Lady, pray give
me now, for it ſeems to be a proper Place,
fome little Knowledge about the Equation
of Time, which I have read a good deal
about, and Tables of which I have ſeen
hanging by Clocks, and put upon Dials
F 4
and
72
Aftronomical Dialogues.
and Watches; pray, can our Sun be in
the wrong, don't he meaſure Time equal-
ly?
{
MADAM, ſaid I, the daily Revolu-
tions of the Earth's Equator round its
Axis, are exactly equal in Time to one
another; and yet the Time from the ap-
parent Noon of one Day to that of the
next, is unequal, and fometimes greater
and fometimes leffer.
WELL, faid fhe, I'm glad however, 'tis
not our Earth's Fault, and that he is fo
regular in her diurnal Whirls: But, pray,
let me then know, where the Error, or
Inequality, lies?
THERE is, faid I, Madam, a double
Cauſe of this Inequality; the former is,
that the Earth's Annual Orbit is not an
Exact Circle; and the other is, that the
Earth's Equator, about which the Diur-
nal Motion is made, and the Ecliptic, or
the Circle fhe deſcribes round the Sun,
are not co-incident, or in one and the fame
Plane, but make an Angle, as you know
they do, at their Interfection, of 23° 30'
of which when your Curiofity, and fur-
ther Knowledge of theſe Affairs, leads
you to make more full Enquiries, you
will
Aftronomical Dialogues.
73
will receive a plain and ſatisfactory Ac-
count, from Mr. Whifton's Aftronomy,
P. 116, 117, &c.
I thank you, Sir, faid fhe, but, pray,
let us now get all things ready to look
on the Sun, with your Glaffes, that I
may know, by my Eyes, as much as I
can of that wonderful Luminary, the
great Center of all the Planets Motions.
OUR Teleſcope was about 14 Foot
long, and had a plain Glaſs ſmoaked with
a Candle, fcrew'd on before the Eye-Glafs,
to defend the Eye from receiving any In-
jury from the too intenfe Light of the
Sun.
AFTER fhe had look'd upon him 2 or
3 times ; It appears plainly, faid fhe, to
be a great Globe of Fire, or rather, as
Butler faith,
A Piece
Of red-hot Iron, as big as Greece.
and ſo no doubt it muſt be, by the great
and conftant Heat which it gives: But,
pray, tell me, as fully as you can, what
the late Aftronomers and Philofophers
have
1
Aftronomical Dialogues.
74
Solar
Spots,
have diſcover'd about this vaft World of
Light. I perceive you fuppofe him fix'd
and immoveable, as to Place, in the
Center of what you call the Solar System;
but doth he turn round his own Axis or
not? how much bigger is he than our
Earth how far is he from us? and how
can his Heat continue fo long as it hath
done, without any fenfible Waſte or Di-
minution?
MADAM, faid Ì, by obferving careful-
ly the Spots, which often appear in the
Sun's Face, tho' there happen to be none
now, they have difcovered, that the Sun
revolves round its own Axis, in about 25
Days.
SPOTS! faid fhe, What, are there
Spots in the Sun, which fometimes ap-
pear there, and fometimes not; for God's
fake what are thoſe Spots ?
THERE are various Opinions about
them, Madam, faid I; but the moſt
probable one, is, that they are a kind of
Drofs or Scum which fometimes gathers
upon his Face, as is the Cafe of melted
Metals; for I have feen feveral Spots,
which for a time appeared diſtinct, at
laft ſome of them quite vaniſh'd, and
others
Aftronomical Dialogues.
75
others run together into one, and ſo com-
poſed a much greater Spot, as was the
Cafe at the Time of the laft famous E-
clipfe of the Sun; and fome of theſe
Spots muſt be immenfely large, to appear
fo big as they do, fometimes, to us, con-
fidering the prodigious Diſtance of the Sun, Diſtance
which probably amounts to about 70 or 80 of the
Millions of Miles.
EIGHTY Millions of Miles! faid fhe,
Why you fright me, my Head turns round,
and I'm giddy with the very Notion of
it!
AND yet, Madam, ſaid I, as great as
this Diſtance is, a Ray of Light runs it
in about 7 or 8 Minutes Time; while
ſuch a ſwift Traveller, as a Cannon-Ball,
fuppofing it to move all the way as faſt
as when it juſt parts from the Gun, can't
arrive there in 25 Years. Theſe things
muft needs appear wonderful and fur-
prifing to you, but we have very good
Reaſons to conclude, that they are very
near to Truth; which I forbear to men-
tion, becauſe perhaps at prefent, you may
not be qualified fully to comprehend
them.
I
Sun.
76.
Aftronomical Dialogues.
I doubt indeed, I am not, faid fhe,
which I heartily lament, and I envy you
Men and Scholars, as much as I dare,
the Pleaſure of knowing the Reaſons of,
and inquiring into the Natures of theſe
amazing things. But, pray, Sir, is not
the Bigness of the Sun anfwerable to this
vaft Diſtance that he is from us?
YES, Madam, faid I, according to
thefe Ways of Computation, the Sun's
Diameter, or his Breadth from one Side
to the other, is about 800,000 Miles,
which is above 100,000 times greater
than the Diameter of our Earth; and
therefore his Bulk, or rather the Quan-
tity of Matter in the Sun, muft exceed
that of the Earth above 10,000,000
times.
And this Confideration of the Vaſtneſs
of the Sun's Magnitude will account for
the Query you rightly enough ſtarted,
how he can ſo long continue his Heat
without any fenfible Diminution? For
we take the Sun and the fixed Stars to
Sir Yaac be only very great Bodies of Earth,
Newton's vehemently hot, whofe Heat is preferved
Opticks,
P318. laft by their Greatneſs, and by the mutual
Edition. Action and Re-action between them and
the
Aftronomical Dialogues.
17
the Light which they emit, and whofe
Parts are kept from burning out and fu-
ming away, not only by their being of a
fixed Nature; but also by the Weight
and Thickneſs of the Atmospheres which
are round about them, and which do
ftrongly comprefs them, and condenſe the
Vapours and Exhalations which would
otherwiſe fly away from them; but are
now by this Means made to fall back
again upon his Body. And as to the daily
Expence of his Light and Heat, the Par-
ticles of Light are fo infinitely ſmall, that
out of a Body fo big as the Sun, they
may be fent for many hundred thouſands
of Years together, without any fenfible
leffening of his Bulk, Weight, or Mag-
nitude.
I believe, I comprehend the main of
your Reaſoning, faid fhe, but I am got
a little out of my Depth; let me re-
cover firm Ground again, and then I
would ask you farther, whether, fince
you take the Sun to be an immenfe Globe
of Earth, thus fet on fire, and the fixed
Stars to be Suns, or Bodies of the fame Fixed
Nature, you don't think the Stars, feve-Stars fo
rally, to have the fame Ufe, and to be the many
Centers each of them, of Systems of Pla- Suns.
nets revolving round them, as ours do
I
round
78
Aftronomical Dialogues.
round the Sun, to whom they afford fuch
all-chearing Light, and enlivening Heat, as
our Sun doth to us? For methinks 'tis a
mean Uſe of them, and below the Wif
dom of our Great Creator, to place them
in the Sky only to twinkle and divert us;
whereas, all of them put together, don't
afford us the 10th Part of the Light of
the Moon; but if we ſuppoſe them all to
be Suns to ſome other Systems of Planets,
becauſe of their vaft Magnitudes, and be-
cauſe of their fhining, as I think you.
agree they do, by their own Light, and
not with one borrowed, like that of the
Planets; what a glorious Idea doth it
give us of the Almighty Power! of the
Wiſdom and Goodneſs of the Divine Na-
ture? And what a poor contemptible
Opinion ought it to make us entertain
of our felves, who perhaps may bear as
little a Proportion in Wisdom and Know-
ledge, to fome of the Beings that inhabit
the Starry Regions, as we do in Magnitude
to them all; for I can eafily conceive infi-
nite Degrees of Knowledge and Perfection,
with as great a Variety, that may be in a
Series in Creatures between us and the
Deity; and perhaps there may be alſo a
confiderable one below us.
1
Aftronomical Dialogues.
79
I AGREE intirely with you in that
Speculation, Madam, faid I, but we muſt
touch it tenderly, or elfe the old Divines
will be angry,
Ay, ſaid ſhe, fuch of them as imagine
all things made for the fake of Man only;
but I have no fuch lofty Notions of the
Dignity of our Species: and I think
Mr. Oldham's is a very juft Satyr upon that
narrow Notion, when, with regard to the
very Point before us, he faith, that Man
belieyes,
That turn-Spit Angels tread the Spheres for him.
But now I'm talking about the Stars, pray
tell me once for all, have theſe Stars and
the Planets no real Influence upon us Mor-
tals?
W
No T. at all, Madam, faid I, fo as by
any Phyfical Power to influence our
Wills, Lives, and Actions; that kind of
Effect is certainly more true with re-
gard to what the Stars have often been
unequally compared, the Eyes of a fine
Lady of good Senſe and Virtue; for Thofe
do certainly, like the Eyes of a good Ma-
giftrate, ſcatter and difperfe all Evil be-
fore
80
Aftronomical Dialogues.
fore them: They heighten our Genius, and
infpire us with Wit, and yet keep our
Converſation as chaſte and modeft as they
make it entertaining and inſtructive.
I ALWAYS take your Compliments
for Inftructions, faid fhe, and have no
Excufe to make for the Vanity of being
pleaſed with them, but that I will en-
deavour to be as good as you reprefent us,
and we ſhall have a much better Reaſon
than ever to value the Power we may have
over your Sex, if we can make it help us
to reform it: But you will not allow
me then to believe any Aftrologic In-
fluences?
NoT any at all, faid I, Madam, for
they ſerve only to nurfe Superftition, to
fill us with falſe Fears, deceive us with
vain Hopes, and to excite a dangerous
Curiofity, and an unreasonable Inquifi-
tiveness into Futurities; and it is indeed,
in effect, either making the Stars ſo many
Deities, and confequently running into
ſome of the worst Sorts of the Idolatry of
the Heathens; or elſe 'tis introducing the
Notions of a Phyfica Fatality, and ba-
niſhing out of our Minds all Religious and
Moral Notions.
SIR,
Aftronomical Dialogues.
8x
SIR, faid fhe, I acquiefce; and to tell
you the Truth, I never had much Faith
in things of that Nature: But let us leave
this Sun of ours for the prefent;
This Sun, of our poor World both Eye and Soul :
This Sun, that with ſurpaſſing Glory crown'd,
Looks from his fole Dominion like a God;
That by magnetick Beams thus gently warms
The Universe, and to each inward Part,
With gentle Penetration, tho' unſeen,
Shoots genial Virtue even to the Deep:
As I think Milton expreffes it; and give
me leave to ask you a few Queſtions about
his Brethren, the Stars. If the Sun and
they be nearly of the fame Bignefs, as Fix'd
they appear to be of the fame Nature, Stars.
what an infinite Diſtance muſt they be
from us?
'Tis very juftly obſerved, Madam,
faid I; for indeed, whatever their Bignefs
be (and much less than the Sun we have
no reaſon to ſuppoſe any one of them to
be) their Diſtance is fo great, that the Their
Diameter of the Earth's yearly Orbit or immenfe
Circle round the Sun, which you know Diftance.
muſt be double to his Diſtance from us,
and therefore about 160 Millions of
Miles: This I fay, according to all the
G
Obfer-
82
Aftronomical Dialogues.
་
Obſervations we can make, and the Rea-
fonings we can form, bears no manner of
Proportion, and is but a Point, in com-
pariſon of the Diſtance of the nearest
fixed Star; for we have no reaſon to ſup-
poſe them all equally remote from us.
And could we advance towards thefe Stars
99 Parts in 100 of the whole Diſtance,
and that there were but one hundredth
Part of the prefent Diſtance remaining,
they would appear very little larger to us
than they do now. The Diſtance of Sy-
rius or the Dog-Star, Mr. Huygens takes
to be about 27000 times as far from us as
the Sun is; ſo that I believe we are not
much out of our Computation, when we
conclude, that a Ray of Light cannot come
from thence in leſs than 6 Months time,
nor the Cannon-Ball, above-mentioned, in
soooo Years.
GOOD God! cry'd fhe, how immenſe
and wonderful are the Works of thy Hands!
Why then, faid fhe, if all the Stars were
to be extinct or annihilated this next Night,
we ſhould not miss them till about 6
Months after !
No, Madam, faid I; that Stream of
Light now flowing from them to our
Eyes, fhould the Fountain be ſtopped,
would
Aftronomical Dialogues.
83.
would be half a Year before it would be
run quite out; tho' it run after the rate of
above 10 Millions of Miles in a Minute;
a Motion almoft as quick as Thought it-
felf, as we ufually fay.
S.S. Pro-
WELL, faid fhe, this hath made an ex-Vid. Ac-
travagant Notion of Mr. Whifton's about comp. of
the Diſtance of Heaven, or the Region phecies,
appointed for the Bodies of the Bleffed, p. 288.
its not being by any means fo far off as
the fuppofed Empirean Heaven of the
Divines, much eafier to me than it at first
appeared; and which then I thought a
very new, wild, and unaccountable Opi-
nion. But, pray, let's go on; Is not the
Number of theſe fix'd Stars as wonderful
as their Diſtance?
YES, in truth is it, Madam, faid I;
for as the naked Eye diſcovers immenſe
Numbers of them in a clear Night, (above
1000 of which are diſtinguiſhed and taken
notice of) and many more in the Nor-
thern cold Countries than we can do
here; fo when affifted by a Teleſcope of
any great Length, it fees amazing Crouds
of other Stars, which becauſe they are
inviſible without thefe Helps, the Aftro-
nomers have called very properly Telefco-Telescopic
pical Stars. Such a Glass as this which Stars.
G 2
we
84
Aftronomical Dialogues.
Milky
Way.
we but now uſed to obſerve the Sun with,
will diſcover to you many Thouſands of
Stars, before invifible to the naked Eye;
and I think I have told above 70 within
that little Bunch of Stars, which we call
the Pleiades, or the 7 Stars; tho' now
ther appear but 6 to the bare Eye. The
Milky Way is crouded with infinite Num-
bers of fmall Stars, from whence, as is
uſually thought, its Whiteness appears;
which is a Diſcovery entirely owing to
the Teleſcope; but whether the White-
ness proceeds from the Smallness of thoſe
numberless Stars, their Nearness to one
another, or their immenfe Distances, we
can't yet certainly determine, but muft
leave to Time and future Obfervations.
How endleſs is the Extent of the Di-
vine Power and Goodneſs, ſaid ſhe, and
how far are we yet from knowing the
Bounds of the Starry World! But, Sir,
your hinting, that formerly there were fe-
ven where now there appear but fix Stars
in the Pleiades, reminds me of your Pro-
mife, to acquaint me with the Hiftory of
fome Appearances of New Stars, and
Diſappearance of others, in Caffiopeia's
Chair, and in fome other Places in the
Heavens.
MADAM,
Aftronomical Dialogues.
85
MADAM, faid I, the Milky Way, in
which Caffiopaia is placed, hath been fa-
mous for theſe Appearances; many new
Stars having been diſcovered in the Swan,
Andromeda, the Ship, Eridanus, and
Aftron. in
other Conftellations within that Tract:
Some of which have, after fome time
diſappeared, and then re-appeared again.
Of theſe things you may fee feveral In-
ftances collected by the Author of Lexi-
con Technicum (a Book which your La-
dyfhip hath) under the Title of Fixed
Stars, in the fecond Volume. But 'tis
difficult to determine, what theſe new
Stars are; fome fancy them to be Planets Ricciol.
Almageſt
revolving round fome of the Stars in the Hevelij.
Galaxy, and which therefore become vi- Prodrom.
fible only in that Part of their Circle Mercator
which is next to us; others take them Append.
to be Comets, and others think that they Philofoph
are really fixed Stars, whofe Light and Mifcellanea
Vapours expire, but are again recruited Berlin.
and enkindled by the Accefs of Comets Aftron.
towards them: But thefe Hypothefes can't Derham,
well folve all the Phænomena; for befides.
the Appearances of thefe New Stars,
it hath been obferved of the known
fixed Stars themſelves, that fome of them
have much changed their Magnitude and
their Light; fome of them have quite
G 3
diſap-
Tranf.
Whifton's
86
Aftronomical Dialogues.
diſappeared for a Time, and then come
into fight again; and this at certain Times
and determined Intervals. And when
you come to read what Mr. Huygens
obſerved of the Stars in Orion's Sword,
you will meet with what will very much,
and I believe very agreeably, ſurprize you;
but let it be which way it will, 'tis a
wonderful Phenomenon, and perhaps will
never be thoroughly known, if ever, till fu-
ture Ages have increaſed our Obſervations,
and improved our Reafonings upon them.
I THINK, faid the Lady, I have
enough for this time, about the Sun and
the fixed Stars; I will confider of it, and
have recourſe to the Books you recom-
mend to me, and trouble you the next
time about the Planets, in the Order as
they are in, with refpect to the Sun;
only give me leave to break in upon it,
with regard to our own Planet, the Earth,
and her Attendant, the Moon. With
which, out of Self-love, or rather Inclina-
tion to the Place of our Birth and Abode,
I would fain begin, if you don't judge it
to be improper.
By no means, Madam, ſaid I; for many
things will occur in our Difcourfes about
the Moon and Earth, which are very com-
mon
Aftronomical Dialogues.
87
mon and obvious Appearances, and which
thoroughly accounted for, and explain'd,
will render the Knowledge of the other
Planets much more eafy, and intelligible.
NOT long after this, the curious Lady
attack'd me again, thus: I have been con-
fidering, faid fhe, the amazing Subject we
difcourfed upon the laft time, and am pre-
pared now to talk with you about the
Earth and the Moon, and the different
Magnitudes, and Motions of each; and of
this I find it previouſly neceffary to have
fome Knowledge, or elſe my Enquiries in-
to those of the other Planets, will not give
me fufficient Satisfaction: Pray, Sir, how
many Miles is the Diameter of our Earth
reputed to be, by the Aftronomers?
SOMETHING lefs than 8000, Ma-
dam, faid I; and becauſe I know you
will expect it, I muft tell you, that we at-
tain this Diſcovery thus: Both in England
and in France, a Meaſure in Length hath
been taken upon the Earth's Surface, un-
der one and the fame Meridian, or, in a
right Line running exactly North and
South, till by accurate Inftruments it was
found, that the Pole was raiſed or depref-
fed exactly one Degree. This, the Mathe-
maticians of both Nations agreed in to be
almoſt
G 4
88
Aftronomical Dialogues.
almoſt 70 Miles, English: And there being
360 Degrees in every Meridian, that Num
ber, multiplied by the former, gives you the
Number of Miles in the whole Circum-
ference of a great Circle on the Earth, or
how many Miles it is round our Globe;
and then, by the Principles of Geometry,
they know, that ſomething more than one
Third of that muſt be the Earth's Diame-
ter. I don't trouble you, Madam, with
the exact Numbers, nor the Multiplication
and Divifion, but you may depend upon
it, that the round Number of 8000 Miles,
is pretty nearly the Earth's Diameter, tho'
fomething too much: And the half of
Earth's this, viz. 4000 Miles, is the Semidiameter,
Semidia-or the Diſtance from the Surface to the
Earth's Centre, a Number, or Meaſure,
much uſed by Aftronomers.
meter.
}
I THANK You, Sir, quoth fhe, for
this; the Knowledge of this fingle Point,
will, I fee, carry me a great way, when I
come to read Aftronomical Authors: But,
pray, Sir, go on and oblige me with a
further Account of this Earth: Do you
think it really turns round its Axis, as
you have found the Sun to do by its Spots?
YES, Madam, faid I, and as there is
nothing more eafy and fimple than this
Motion,
Aftronomical Dialogues.
89
Motion, ſo it accounts for the Appear-
ances of Day and Night in an eaſy and Caufe of
natural manner; for as this Earth revolves Day and
from Weft to Eaft in exactly 24 Hours Night.
Time, it makes the Sun appear to do ſo
from Eaſt to Weft in the ſame time; and
makes it Day to thofe Places on its Sur-
face, which are turned towards the Sun,
and Night to fuch as are in the oppofite
Parts ; as you fee, Madam, if I fet this
Globe into the Sun's Light, it will illumi-
nate but one Half of it, and the other
Half will lie in the Shadow; but as I turn
the Globe round its Axis, all Parts of the
Earth's Surface painted upon it, will come
fucceffively into the Light, as the oppo-
fite Parts go, after the fame manner, into
the Dark.
I GRANT you, Sir, faid fhc, this is a
very natural and eaſy way of accounting
for the Viciffitudes of Day and Night; and
fo ſhort and unembaraffed in compariſon
of the other wild Notion, which makes
the Sun, and all the Region of the fixed
Stars, to revolve round us in 24 Hours,
that it recommends itſelf to us, at firſt
fight, as agreeable to the other Proceed-
ings of Nature, if we could but get rid
of our Prejudices, fo as to conceive
it poffible to be done, without our per-
ceiving
90
Aftronomical Dialogues.
ceiving it. But can we travel above 1000
Miles in an Hour, and not be fenfible of
it ?
As cafily as 10 in a Ship, Madam,
faid I; where, let the Veffel move never
ſo faſt forwards, if it were not for the
Toffings and Shocks which the Refi-
ftance of the Water and Waves make, and
for the Ruftling and Buftle that the Wind
makes in the Sails, you would perceive no
Motion at all in the Ship, but judge it to
be perfectly at Reft; and if another Ship
lay at Anchor by you, you would judge
that to move backwards, and not your felf
forwards. And much more will this ap-
pear plain, if you confider that with the
Earth's Motion round its Axis, the Air,
and all the Atmoſphere moves along with
you, and doth not refift you, as is the
Cafe in the Motion of a Ship. But in-
deed, the greateſt Wonder in this Cafe is,
that we are not all whirl'd off into the Air,
like Dirt from a Wheel, or Drops of Wa-
ter from a twirling Mop, or Stones part-
ing from a Sling.
YOUR talking of the Twirl of a Mop,
faid fhe, puts me in mind of a whimfi-
cal Deſcription of that Action, which a
Friend of yours made to ridicule fome
I
Verbofe
Aftronomical Dialogues.
91
Verboſe Verfes then repeated: But tho' I
have almoft forgot them, I hope you have
not.
MADAM, faid I, your Ladyfhip's think-
ing of them now is proper enough; for
tho' made to expoſe another Matter, they
will illuftrate what we are upon :
See how Culina with hard adverfe Wrifts,"
The dreary Radii of her Mop untwifts ;
Swift twirling round, the oblong Planet rolls,
With Axe produc'd thro' the Meridian Poles;
The Stiff'ning Threads their rigid Form preferve,
While dirty Drops fly off in Tangents to the Curve.
WHY this is very true, faid fhe, of thoſe
dirty Drops, and I can't imagine why 'tis not
fo with us; for I don't know any thing that
faftens us down to the Earth, but our firm
Inclinations to this World, which I believe Centripe-
yet hath no Phyfical Power to keep ourtal Force.
Bodies annexed to its Surface. Pray, how
do you account for this Difficulty?
By that Will of the Creator, Madam,
which we call the Law of Gravity, or
Gravitation; whereby all heavy Bodies
have a Tendency towards the Center of
our Earth, in fuch an Over-Proportion,
that the Centripetal Force, by which Bodies
tend
92
Aftronomical Dialogues.
tend thither, is almoft 300 times greater,
than that by which they are forced off by
the Earth's Motion round its Axis, or the
Centrifugal Force, as they call it; and 'tis
this All-wife Provifion that keeps all things
together on the Surface of the Earth; and
which, when exactly adjusted, keeps alfo
every Planet in its proper Circle, and at
its due Diſtance from the Sun, or from its
Primary one: And this is fo univerfal a
Law, that it prevails every where. And
if a Cannon-Ball could be diſcharged from
any confiderable Height, in the Air, parallel
to our Horizon, and with à Velocity equal
to that of the Earth's Attraction, or the
Force of Gravity towards the Earth's Center,
it would then neither fall to the Earth at
all, nor go quite off from it, but would
revolveround it, like our Moon; and this
is the very Reaſon why ſhe doth fo
WELL, faid fhe, a new World of
Knowledge opens and dawns upon me! I
begin to fee a thouſand Things, of which
I had no Notion before; and I believe the
Motions of the heavenly Bodies, after this,
won't appear fuch abftruſe unintelligible
Things as I imagined them to be: But,
pray, Sir, explain this a little further, with
regard to the Moon.
You
1
Aftronomical Dialogues.
93
You muſt know, Madam, ſaid I, that
this Gravitation of a Planet towards any
Central Body, decreaſes as the Square of
the Diſtance from that Center increaſes;
therefore the Moon being about 60 of the Moon's
Earth's Semidiameters, or 240000 Miles Diftance.
diſtant from us; her Gravitation towards
the Earth, will be 3600 times leſs than
that of a Cannon-Ball ſhot out of a Gun
on or near the Surface of our Globe; for
the Moon's diſtance from the Earth, 60 of
the Earth's Semidiameters being ſquared,
that is, multiplied by itſelf, makes 3600;
and if he were but 2 Semidiameters re-
moved from the Earth, the Square of 2 is
4, and as much as 3600 exceeds 4, ſo much
does the Attraction of the Earth, or any
Central Body exceed at 2 Semidiameters
above that of its Attraction at 60 Semi-
diameters. And the Great Creator hath ſo
wonderfully contrived it, that her Centri-
fugal Force, or her Endeavour to fly off
from the Earth, is exactly equal to her Gra-
vitation thither; and this keeps her in her
Orbit, as it doth all the Planets in theirs,
as I faid before.
、『
O wonderful and happy Adjuſtment!
faid fhe; for I perceive, if the Moon's
Gravity towards the Earth were much
I
abated,
94.
Aftronomical Dialogues.
*
abated, he would run out of her Orbit,
and leave us; and if the oppofite Force
were much leffen'd, fhe would in a little
time, tumble down upon us: Am I right,
Sir, in this Conclufion?
EXACTLY, Madam, faid I, and I per-
ceive I need not ſay much more to you
upon this Head, except it be to tell you,
that if the Centrifugal Force were taken
away from the Planets, and that only the
Power of Gravitation towards the Sun re-
main'd, they would all foon fall down to
him, and our Earth would get down thither
in about 64 Days and 10 Hours time.
But I think, Madam, we are gotten to
the Moon a little too foon, having not yet
quite done with the Earth, whoſe Annual
Motion round the Sun therefore, let us next
confider By which all Increaſe and De-
creaſe of Day and Night, and the Changes
and Seaſons of the Year are made.
AND can you give me any good Reaſons,
that I can understand, to believe this An-
nual Motion of the Earth, ſaid ſhe?
I think, Madam, faid I, there is in Aftro-
nomy a plain Demonftration for the Motion
of the Earth round the Sun; but it will be
too remote for your prefent Knowledge of
theſe
Aftronomical Dialogues.
95
theſe Matters: However, I think 'tis a very
good Argument for its being ſo, that this
way there is a Parity and Agreement with
the other Proceedings of Nature, which is
very ſuitable to the Wiſdom, Eaſineſs, and
Conciſeneſs obferved by the Divine Being:
For it being now agreed, that the Sun is
the Center of all the other Primary Pla-
nets, and that we are placed in ſuch a due
Diſtance from the Sun, between the Or
bits of Venus and Mars, as anſwers to the
Time of thoſe Planets Revolution round
the Sun; and fince 'tis alfo agreed, that
the other primary Planets, as well as Mars,
Venus, and Mercury, do, in their ſeveral
Orbits, revolve round the Sun; what
Reaſon can poffibly be affigned, why the
Earth fhould not do ſo too? fince they
are Earths likewife, as our Planet and the
Moon are, and confequently our Earth muft
be as capable of moving round the Sun, or
any other Center, as they or fhe are.
זי
I own, faid fhe, that tis much more
natural, orderly, and harmonious to ſuppoſe
it fo; and therefore I will lay afide all Pre-
judice, and believe it with a good Aftrono-
mical Faith.
MAD-A M, ſaid I, if you will obſerve
what Fontenelle faith, very juftly, of Na-
ture,
96
Aftronomical Dialogues.
Moon.
ture, that She is always magnificent in the
Defign, but frugal in the Execution of it,
you will never believe that the Sun and
fixed Stars turn all round us in 24 Hours ;
when you reflect, that the bare Motion of
the Earth round its Axis will answer all
your Ends that are to be ſerved by the other.
That would be juſt as abfurd, as for a great
Architect to contrive, with vaft Expence
and Machinery, a Kitchen-rate, that
ſhould revolve round a Spit, in order to
roaft a Wheatear, or a Wren; but never
fo much as dream of a way to turn the
Spit round.
'T 18 monftrous, faid fhe, as well as ri-
diculous, and, as I told you before, I won't
believe one word about it: I ſee, that the
more plain and intelligible things are, the
more they are valuable; and that Obſcurity
and Mystery are ufually the Effects of Ig-
norance, and want of Skill either in the
Operator, or the Explainer. But, Sir, will
you give me leave then to ftep to the
Moon, and ask you a few Queſtions about
her, for I can't put thoſe fine Lines of
Butler out of my Head :
The Moon put off her Veil of Light,
Which hides her Face by Day from Sight;
Myfte
Aftronomical Dialogues.
97
Myfterious Veil of Brightnefs made,
That's both her Luftre, and her Shade;
And then indeed as freely fhone,
As if her Rays had been her own :
For Darkness is the propher Sphere,
For borrow'd Glories to appear.
And I know a good deal of his Meaning
in them; as that the Moon borrows her
Light from the Sun, &c. but I could be
glad if you would explain a little upon
that Matter, and upon her Motion round
the Earth; after we have at Night exa-
mined her Face by the Teleſcope: Is this
a good Time to look at her?
YES, Madam, faid I, a very lucky one,
for the is now increafing, and not quite
full;
we ſhall fee her Mountains more
diſtinctly, and the Light of the Sun move
from one Hill to another.
THE Evening, according to our Wiſhes,
proved very clear and fair, and the Lady
was mightily pleafed with the Face and
Appearance of the Moon thro' the Glafs;
and having alfo the Day before been read-
ing a little in Mr. Huygens's Cofmotheoros,
or his Celeſtial Worlds difcover'd, or Con-
jectures about Worlds in the Planets; and
in Mr. Whifton's late Book, called Aftrono-
H
mical
98
Aftronomical Dialogues.
mical Principles of Religion; he was
prepared to ask me fome very proper
Queſtions, and began thus:
PRAY, Sir, faid fhe, is not our Earth
a Moon to the Lunar People, as well as
She is to ours?
YES, Madam, ſaid I, and a moſt uſeful
and a glorious one too; and we may, in
fome meaſure, perceive that our felves,
by the Light which our Earth reflects upon
the Moon before fhe is juft new, and for
fome time after; for doubtless that is the
only Light that then renders her viſible to
us: And when you confider that the Light
of our Earth, confider'd as a Moon, will
be thirteen times greater than that of the
Lunar Light to us, it won't appear
ftrange, that its Reflection on the Moon
fhould render her then dark Body viſible
to us. However, this Terreftrial Light,
when the Earth appears at Full to the Peo-
ple in the Moon, is not above a 3600th
Part of the Sun's Light there, as the Light
of our Full-moon to that of the Sun, fhi-
ning upon us, is about as to 48000..
I THANK YOU for this, Sir, ſaid ſhe,
and am heartily glad we can be fo ufeful
to the Lunar World. But, pray, go on:
I
Aftronomical Dialogues.
99
I perceive, faid fhe, you agree that the
Moon as well as all the reft of the Planets,
turns round her own Axis, which, me-
thinks, in her is very ftrange; for we feem
tô diſcern always the fame Face of her,
without any Variation: Pray in what time
is that Motion perform'd?
UST
Just in the time, Madam, faid I, that
ſhe is revolving round the Earth; which
I will explain to you preſently: But, firſt,
it will be proper to inform you, that the
Figure of the Moon not being exactly glo-
bular or ſpherical, but a little oval, or
like that of an Egg, her longeft Diameter
(which exceeds her ſhorteſt by about 200
Foot) would, if you fuppófe it extended
fo far, paſs thro' the Centre of our Earth :
And hence it is that we fee always the fame
Face of the Moon- obverted towards us;
and that this is not hinder'd by her Mo-
tion round her Axis, this familiar Inftance
will fhew you. Pleaſe to fit ftill, without
turning your felf, while I walk round you;
you will then fee plainly, that if I keep
my Face always towards one and the fame
Point of the Compafs, while I am moving
round you, when I come à Quarter of my
Circle, my Right-fide, and not my Face,
will be towards you; when I have gone
half way round you, my 'Back; and when
H 2
·
I'm
100
Aftronomical Dialogues,
I'm gotten three Quarters, my Left-fide
will be turned towards you; but if, as I
move in my proper Orbit round you, I al-
ways keep turning towards you, as indeed
I can't help doing, you will then always
obferve me beholding you with the fame
Face of Respect and Eſteem.
You Men, faid fhe, are not like thofe
conftant Celeſtial Lovers; for you ſeldom
continue your Refpect for above a Revo-
Jution or two: However, you may now
ſtop in your Circular March, continued
fhe, for I fee the thing plain, and that the
Reaſon why we fee always the fame Face
of the Moon, is becauſe fhe moves round
her Axis in the fame time that the per-
forms her Circle round the Earth: But,
pray, let me know fomething more of the
manner of her Motions.
MADAM, faid I, the Moon revolves
continually from Weft to Eaft, and that
pretty nearly in the fame Circle which
we call the Ecliptic; but not exactly ſo,
fometimes running 5 or 6 Degrees above
it to the North, and fometimes below it
to the Southward: She doth not alſo keep
always the fame Diſtance from the Earth ;.
as appears by her Diameter, which when
we come to measure, we find fometimes
con-
Aftronomical Dialogues.
ΙΟΙ
*
confiderably larger than at others; fhe
moves ſwifter in the Syzygies, as they call
them, that is in their Conjunctions with,
and Oppofitions to the Sun, than fhe doth
at her Quadratures, or when fhe fhews
juſt half of her Face.
WELL, faid fhe, I perceive now that
her Motion is fo irregular, that fome Com-
pariſons, which have been made with her,
are not quite groundleſs: But this Part I
fancy I fhall get over by my Books, and I
think I know alfo, that the Reaſon why
fhe appears full, is, becauſe the is then op-
pofite to the Sun, who fhines full upon
her; and we lofe Sight of her in what we
call the New Moon, becaufe fhe is then
between us and the Sun, or in Conjunction
with him; and 'tis eafy to fee alfo that all
her other Changes and Appearances, or
Phafes, as I remember you call them,
are accountable from her being in fome
intermediate Pofition between new and
full. But, pray Sir, why have not we an
Eclipfe of the Sun at every new Moon,
and one of the Moon at every full?
THAT is Owing, Madam, ſaid I, to the
Moon's Latitude, by which the runs fome-
times 5 or 6 Degrees from the Ecliptic,
(in which the Earth always moves) both
North-
H 3
102
Aftronomical Dialogues.
Northward and Southward. But if her
Orbit, and that of the Ecliptic, were all
in one Plane, there would be total and
central Eclipfes at every new and full
Moon.
{
I CONCEIVE what you ſay, faid
fhe; fo that there can be no Eclipfe of
either Sun or Moon, unless the Moon, be
in the Ecliptic as well as the Earth, be
caufe the Sun's Light will go by or befides
the Earth or Moon.
1
}
You have it exactly right, faid I, Ma-
dam, in general; all that I need tell you
further is, that if the Moon have but a very
little Latitude, an Eclipfe may happen.
or if fhe be at the time of the Conjunction
with, or Oppofition to the Earth, in or
near the Nodes, as they call it, that is, :
the Points where the Moon's prefent
monthly Circle croffes the Ecliptic. And
this falling out commonly twiçe in every
Synodical Month, or Lunation, as we call
it, there would be an Eclipfe of the Sun
every new Moon, and an Eclipfe of the
Moon every full, if the Earth could ſtay
about the Nodes, and did not proceed on
in her Orbit all this while, or change her
Place in the Ecliptic forward on. How-
ever, within the Compaſs of the Year.
there
Aftronomical Dialogues.
103
there happen ufually four notable and al-
moſt total Eclipfes, fomewhere or other,
two of the Sun and two of the Moon.
But your Ladyfhip will pleafe to confider,
that there is in the Nature of the thing a
great deal of Difference between thefe two
kind of Eclipfes: For in the Lunar Eclipfe
there is a real Lofs of the Moon's Light;
for the Moon being immerfed in the Earth's
Shadow, receives none of the Rays of the
Sun, and therefore can reflect none of
them to the Earth: and it is alfo over the
whole Earth the fame, from whencefoever
it is feen, not being changed by the diverſe
Poſition of the Spectator on any Part of
the Earth's Surface, whether he be in the
Equator, or at the Poles.
But in an Eclipfe of the Sun, there be-
ing no real Lofs of the Sun's Light, but
only an Interception of part of it, from
coming to our Eyes, by the Interpofition
of the Moon's Body; this Eclipfe muit
appear different according to the different
Places on the Earth, from which a Spec-
tator may obſerve it: for tho' to that
Part of the Earth to which the Centre of
the Moon is then interpofed between the
Obferver's Eye, and the Sun's Centre, it Fig. III
will be total, yet it will be but a partial
one to all other Places, and none at all
H 4
to
104
Aftronomical Dialogues.
to the remote ones, as you will eaſily fee
by Plate III.
I THANK you for explaining the
Nodes to me, faid fhe, and theſe Phæno-
mena of Eclipfes; and by it you have now
faved your felf the Trouble of anſwering
many Queſtions: And I perceive, for the
future, I fhall get to underſtand thefe kind
of Things and their Terms of Art, pretty
well: My Lexicon Technicum is a ready
Help to me in time of need, and I bc-
lieve the Doctor compofed it out of a
peculiar Regard to our Sex; I'm fure we
are very much obliged to him for it. But
have we any thing further to ſay about
this Vagrant, the Moon, of whom Dry-
den fpeaks a little coarfely, methinks, in
his Tranſlation of Ovid:
Nor equal Light the unequal Moon adorns,
Or in her wexing, or her waneing Horns;
For every Day he wanes, her Face is lefs,
But gathering into Globe, fhe fattens at Increafe.
MADA M, ſaid I, happy is your Tafte
in every thing! A piercing Judgment,
great Memory, fedate Confideration, and
fine Luxuriances of Wit, feldom unite in
one Perfon; but you are adorn'd with all.
PRAY,
Earth
Fig. III.
the Earths
¡
he Moons Orfie
Moon
Annual Orbit
1
2
104
Sun
A Lunar Eclipfe
Earth
A
1
A Solar Edipfe
**
}
:
the Moons Orbit
the Earths Annual Orbit
Aftronomical Dialogues.
105
PRAY, Sir, faid fhe, ceafe your high
Strains, or elfe I fhall begin to think, as
Hudibras expreſſes it, That
The Queen of Night, whofe vaft Command
Rules all the Sea, and half the Land;
And over moist and crazy Brains,
In high Spring-Tides at Midnight reigns,
had laft Night fome Effect on my Teacher's
Head.
MADAM, faid I, between you both,
I own I am now and then a little flutter'd.
But your laſt Verſes mentioning the
Tides, put me in mind of another great
Influence and Ufe the Moon hath over this
Earth, befides the great Light fhe gives us;
and that is, that he is the principal Cauſe of
our Tides, which are ſo beneficial to us, in
keeping our Ocean ſweet by their Motion;
and in helping the Navigation of our Ships
in Rivers, and Places of the Sea, near the
Shores. But I will refer you to the Lexicon
Technicum, under the Word Tides, for an
Account of it, where you may receive full
fatisfaction, with regard to this Affair;
formerly to very unaccountable, but now
very clear and intelligible.
I
·∙100
Aftronomical Dialogues.
I CAN'T leave, faid fhe, this inconftant
Planet, whom your ill-natur'd Wits have
ſo often made the Refemblance of our Sex,
without asking you a Question or two
more; What is that you call the Hunter's
Moon? I have heard the jolly Fox-Chacers
talk much about it.
MADAM, faid I, what they mean by it,
I don't underſtand; but I fuppofe it muſt
be fome very long Moon, which fhines a
great while about the Hunting-Seaſon, and
fo hath become eminent that way, tho' this
can't always fo happen: But if you will
pleaſe to go to the Globe yonder, you will
eafily fee, that when the Moon is in Cancer,
her Sweep, or the Ark which ſhe makes
above our Horizon, will be vaſtly larger
than when he is on the other oppofite
Side of the Equator in Capricorn; and if
it then happen to, be full Maon, or pretty.
near it, (as will be the Cafe next October)
the enlighten'd, Ark of her Motion above.
the Horizon will be very large and con-
fpicuous, in comparison of what ſhe will
run when her full fhall happen to be in
Capricorn. Alfo, fhe will rife for feveral
Nights nigh the fame Point of the Com-
pafs, becauſe 13. Degrees on either fide of
the Tropick has very nigh the fame Decli-
nation with the Tropick: But the Moon's
Lati-
Afixqvainicák Dialogues.
107
<
Latitude won't much help, to account for
this Phenomenon for that is greater at
her Quadratures, i, e. when he appears an
Half Moon, than, at the Syzygies, as we
call them, 2. e. at Nege or Full Moon of
when the Sun, Moon, and Earth are all
nearly in one Right Line.
I THINK I apprehend this, faid the Lady;
and now for the reft of my, Queftions.
What is the Diameter and Magnitude of
this Planet? What is her Motion? What
Proportion, doth the bear to our Earth &
And do you think ſhe is inhabited as we are?,
•
HER Diameter, Madam, faid I we
reckon to be almoſt 2200 Miles; in De-
grees, when taken with an Aftronomical
Inftrument, it is about 32 Min. 12 Seconds,
which is nearly, the fame with the Sun's
apparent Diameter, for that is but 31 Min.
27 Seconds; her Magnitude, or rather
her Mafs, or the quantity of Matter in her,
with regard to the Earth, is about part;
but then the Denſity of her to that of the
Earth, Is as 9 Tos; fo that if the hath any
Inhabitants, as I take it to be highly pro-
bable, all the Planets have, they can't be, of
Such Conflitutions as we are. And tho
fome of our Aftronomers have
cluded: from fome Obſervations made in
lately con-
Eclip-
108
Aftronomical Dialogues.
J
!
Eclipfes of the Sun, that fhe hath an At-
mosphere, or Air about her like our Earth;
yet 'tis probably of a very different Nature
from ours, without any Clouds, Rain, Hail,
or Snow; becauſe, whenever our Air is
clear, we can always difcern the Moon's
Face, with, as well as without a Teleſcope,
to be bright, clear, and diſtinct: Which I
think could not well be, if her Atmoſphere
were like ours.
The exact time of her Periodical Revo-
lution round the Earth, is in 27 Days,
7 Hours, and 43 Minutes, and this is call'd
her Periodical Month; in which Courſe ·
ſhe runs about 2200 Miles in an Hour.
But her Synodical one, as they call it, or the
Time from New Moon to New Moon, is
29 Days, 12 Hours, and of an Hour.
PRAY, faid the Lady, what occafions
this Difference of above 2 Days and s Hours,
between theſe two kinds of Lunar Months?
THE Reaſon, Madam, faid I, you will
eafily apprehend; and 'tis this: While the
Moon is revolving round the Earth in her
Periodick Month, the Earth itſelf is moved
on in her Orbit round the Sun almoſt an
entire Sign, or one twelfth part of the
Ecliptic: and therefore that Point in the
Moon's Circle or Orbit, where the laſt
Con-
Aftronomical Dialogues.
109
Conjunction with the Sun was made, will
now be gotten too far to the Weftward:
for the Sun being got forward 27 Degrees
from the Place where the laft Conjunction
was, the Moon must move forward till fhe
overtake the Sun, which will take about
the Space. of two days: fo that although
the Moon come to the fame place of the
Ecliptic again in 27 Degrees, 7 Hours, 43
Minutes, yet ſhe takes 29 Degrees, 12 Hours,
and from the time fhe feparates from the
Sun till the time fhe overtakes him again,
which is the Synodical Moon; in which
time the Moon exhibits all her Phaſes.
I hope, faid fhe, I fhall get to conceive
this a little better by degrees; but pray
let me go on now, and ask you a Queſtion
or two more: I have been thinking, that
the Inhabitants of the Moon muſt have one
thing very odd and ftrange; and that is, that
to one half only of their World our Earth,
which I am appriſed muſt appear as a Moon
to them, can be viſible: So that their
other Hemiſphere will be for ever deprived
of the Advantage of a Moon's Light.
O! MADAM, faid I, if your Specula-
tions lead you into fuch Depths, we have
you ſafe for an Aftronomer; and I don't
doubt but that will lead you alfo into the.
Study
ITO
Aftronomical Dialogues..
See
Study of fuch other Parts of Mathema-
ticks, as, the more you know of them, the
more you will find them neceffary. And
I could now tell you a great many furpriſing
things about the Appearance of our Earth
to the Inhabitants of the Moon; but I will
not deprive you of the Pleaſure of reading
them yourself: you will find them fully en-
larged upon at the End of Dr. Gregory's
Aftronomy, which is lately tranflated into
English which you will find among thofe
Books,that, according to yourCommands, my
Bookfeller fent you laft Night from London.
:
VERY well, Sir, faid fhe; I fhall be
impatient till I get fome further Know-
ledge of that Matter. But we will now
take our Leave of Mrs. Moon; and, if
you pleafe, go down, as you call it, to-
wards the Sun: and from thence afcend
Fig. IV. again; taking the reſt of the Planets in
their Order, according as this Diagram
here repreſents them; which you have
kindly drawn for me; and which you call
a Scheme of the Solar Syſtem. Pray there-
fore, good Sir, tell me as much as you
Mercury, think I can underftand, about Mercury,
the nearest Planet to the Sun.
A
MERCURY, Madam, faid I, is a Planet
whofe Diameter we reckon to be about
2700
Aftronomical Dialogues.
IFT
2700 miles; and therefore he is about two
thirds of the Earth's Magnitude. His
Distance from the Sun is about 32 millions
of miles; and his mean Diſtance from us,
about 22000 of the Earth's Semidiameter,
or 88000000 miles, according to Caffini's
Numbers. He revolves round the Sun in
fomething less than 88 days, with the Ve-
locity of 100000 miles in an Hour; which is
almoſt as faſt again as the Earth travels: for
we don't go above 56000 miles in that time;
and yet that is making pretty good ſpeed
too; for that don't want much of 1000
Miles in a Minute, or 15 miles in a Second;
or in that ſpace of Time in which you can
diftinctly pronounce one, two, three, four.
And yet however amazingly ſwift this may
feem, 'tis crawling like the American Ig-
navus, or Beaſt called the Sluggard, in
compariſon of the Velocity of the Ray's
of Light, which certainly move about
180,000 miles in that time.
WHAT! in a Second? ſaid ſhe: Let me
fee-why, that is almoft soooo miles
while I can fay the word Light. For god-
fake flop a little, or you will make me per-
fectly giddy: my Head will turn quite
round. What! have you and I then been
travelling almoſt 2000 miles together this
Morning, and I knew nothing of the matter?
3
'TIS
ม
112.
Aftronomical Dialogues.
'Tis even fo, Madam, faid I; and you
fee we move cafily: But if you pleaſe, I
will go on.
The Heat of the Sun there,
is probably 7 times (Mr. Huygens faith 9
times) as great as with us in the hotteſt
Summer; which is, I believe, cnough to
make Water to boil. You will easily fee
therefore that his Inhabitants cannot be
fuch as we are; for our Bodies could by no
means bear fuch a Degree of Heat.
[
OUR Ancestors Bodies, faid fhe, I be-
lieve could not: but by our drinking fo
much fcalding Tea and Coffee as we now
do, I fhould think we are preparing our-
felves to go and live there: And I ſuppoſe
our famous Fire-Eater came from thence.
There can be no Fluids fure in this Fiery
Planet, much leſs denfe, than that which
bears his Name; and no doubt all things
elfe are denſe there in the fame Propor-
tion, or clfe the Sun would rarify him,
and fend all his Furniture off in Fume,
Smoak, and Vapour,
Well! faid the Lady, as much as I hate
frozen Zones, and bitter cold Weather, I
think this Mercurial World to be worſe
in the other Extream; fo I will never wiſh
for a Voyage thither.
3
No,
Aftronomical Dialogues.
113
No Madam, faid I, you will find this
Earth to be a much more eligible Place
of Abode for People of our make, than
any other which we yet have diſcover'd in
the beſt Planet of them all. As for this
we are talking of, Mercury is ſo near the
Sun, that he is very rarely ſeen by any
but Aftronomers, who know how to look
after him. But about St. George's Day laſt
he was at his greateſt Diſtance from the
Sun, and then about 8 in the Evening
might have been ſeen very plainly.
WELL, faid fhe, I fhall not much
trouble my felf to enquire after him; but
I remember I faw him very plain and di-
ftinct, during the Total Darkneſs, in the
laft Eclipſe of the Sun; and that ſhall fa-
tisfy my Curiofity, till fome other Op-
portunity offers it felf. But pray, Sir,
doth the Teleſcope fhew us any thing re-
markable about him?
ONLY, Madam, that he hath Phafes,
as we call them, like thoſe of the Moon,
and ſometimes appears full, and ſometimes
horned, like her, which you will eaſily
conceive muſt be the Cafe of any Globe
of Earth illuminated by moving round
the Sun, and changing its Pofition, with
I
regard
114
Aftronomical Dialogues.
regard to him, and to our Eyes. It hath
not been yet difcovered by any Spots or
Marks upon him, that he revolves round
his Axis, nor confequently what the Po-
fition of that Axis is, tho' 'tis probable
he performs that Motion in a certain and
determinate Time, as the reft of the pri-
mary, and I believe all the fecondary. Pla-
nets do. Venus and our Earth muſt needs
appear very bright and large to the Inha-
bitants in this Planet, and the former will
ſeem 6 or 7 times larger than fhe doth to
us, which will help to fupply the want of
a Moon to him in the Night. But there
is one more very remarkable Phænomenon
of him, and that is, that as his Orbit is
within ours, he muſt ſometimes get be-
tween us and the Sun, and then he ap-
pears like a little black Spot in the Face
of that Luminary, and may very eaſily be
obſerved and diftinguiſh'd by a Teleſcope.
O, I am mightily pleafed with this,
faid the Lady, and fhall I ever ſee him in
that Pofition?
I HOPE you will many a time, Ma-
dam, ſaid I, for he will be there in April
1720, and in October in 1723, which is
but a little while hence; and he will alſo
be there again in May 1761.
WELL
Aftronomical Dialogues.
115
WELL, faid the, I will then have a
full look at him, if I live fo long; and
in the mean time let this Herald of the
Gods ramble on as he pleaſes; and let us
talk next about Venus.
Beneath the fliding Sun, who runs her Race,
Doth fairest ſhine, and beft become the Place:
For her the Winds their Eaftern Blasts forbear,
Her Month reveals the Spring, and opens all the
With Smiling Afpect the ferenely moves!
(Year.
Adorns with Flowers the Meads, with Leaves the
(Groves.
The joyous Birds her Welcome first expreſs,
Whofe Native Songs her Genial Fire confefs.
But whither am I running? Pray, Sir,
ftop me a little, and tell me fome ferious
Aftronomical Things about this celebrated
Planet.
THE Diſtance of Venus, ſaid I, Madam,
from the Sun is about 60 Millions of
Miles; and by fome Spots which the Te-
leſcope hath diſcovered in her Face, fhe
appears to have a Revolution round her
Axis: The Time of which feems to be
about 23 Hours. But neither Caffini at
Paris, nor our Mr. Hook here, tho' they
I 2
plainly
Venus.
Dryden's
Lucretius.
116
Aftronomical Dialogues.
plainly faw the Spots to move, were able,
pofitively and expreffly to determine the
Time of her Diurnal Rotation round her
Axis; tho' the former takes it, as I faid
before, to be in about 23 Hours; and
therefore that will be the Length of her
Natural Day. Her Motion in her Orbit
round the Sun, is perform'd in a little
above 224 Days, and her Motion in an
Hour is about 70000 Miles.
THAT's pretty fair, faid fhe, too for a
Lady; but I am glad fhe doth not fly quite
fo faſt as the laft Whirlegig Mercury,
however: But pray, Sir, go on.
THIS Planet, Madam, faid I, Mr.
Huygens takes to have a large Atmoſphere
which reflects fo ftrong and glaring a Light,
that her Body is rarely feen clear and di-
ſtinct. She also hath Phafes like the
Moon; as was before obferved of Mer-
cury; fhe hath no Satellites, Attendants,
Moons, or Secondary Planets moving
round her, becauſe, as you very juſtly ob-
ferved a while ago, Mercury and fhe be-
ing fo near the Sun, have no occafion to
be enlightned by Moons, as our Earth,
Jupiter and Saturn have. Indeed Caffini,
in the Years 1672, and 1686, with a Te-
leſcope of 34 Feet, fancied he faw a Sa-
tellite
Aftronomical Dialogues.
117
tellite moving round her, whofe Diame-
ter was about a quarter part of that of
Venus: And Dr. Gregory thinks it not
improbable, that this might be really a
Moon to this Planet, and takes the reafon
of its not being uſually ſeen, to be, the un-
fitness of its Surface to reflect the Rays of
Light: But as no fubfequent Obfervations
have confirmed this, I look upon it no
more than a Conjecture. Neither fhe nor
Mercury ever come fo much as into
Quadrature with the Sun, much less to
an Oppofition to him; and indeed, their
utmoſt Elongation from him, as we call
it, or greatest Distance Eaft or Weft from
the Sun, never amounts to above 2 Signs;
Mercury not going above 28, and Venus
never above 48 Degrees from the Sun.
She is much about the bigness of our Earth:
And the Light and Heat of the Sun, is a-
bout 4 times as great as it is with us.
I'm heartily forry, faid the Lady, that
'tis fo; for I would fain have had this
beautiful Planet to have been inhabited
by juft fuch fine Gentlemen and Ladies as
we have here; but I find 'twon't do; the
Women wou'd be there all as fwarthy as
Gipfies, and fry and fweat like Negroes
in Africa: Out upon it! I'm afraid I
I 3
fhall
118
Aftronomical Dialogues.
fhall find never a Planet fit to be inha-
bited by fuch People as you and I are.
MADAM, faid I, take care; you are
falling in with the Aftrologic Whimfies;
one would think you had read Athan.
Kircher's Iter Extaticum, which agrees
with your Wiſhes as to Venus, Mercury,
and Jupiter; but he makes Mars all
Smoke and Fire, and Saturn nothing but
dull Lead, Dirt and Naftineſs, as jou will
find when you come to look over Mr.
Huygens's Planetary Worlds, which I have
ordered the Bookfeller to fend you.
You are always cautioning me againſt
Aftrology, ſaid ſhe, and I muſt thank you
for it. Bur I have heard that their beginning
with that Study, hath made fome Men be-
come good Mathematicians, and even Aſtro-
nomers; Shall I name them to you, Sir?
you have forgot what you have told me of
fome of your Friends. But enough, let us
proceed, and before we have quite done
with this warm Dame, will you pleaſe to
tell me, why ſhe is fometimes our Morning,
and ſometimes our Evening Star?·
✔
THAT depends Madam, faid I, on her
Pofition, with regard to the Sun and us;
when fhe is in that part of her Orbit which
is
Aftronomical Dialogues.
119
is below the Sun, or between him and us,
then ſhe is the Morning Star; but when
fhe gets into the oppofite part of her Orbit
above the Sun, then ſhe becomes our
Evening Star.
AND under both thofe Denominations,
faid fhe, I think the Poets make her change
her Sex, and turn He-Thing, as if ſhe could
not be as useful when of our Gender, as
of yours; for thus, forfooth, Mr. Dryden
Compliments the Changeling:
So from the Seas exerts his Radiant Head,
That Star, by whom the Lights of Heaven are led,
Shakes from his Rofy Locks the pearly Dews,
Difpels the Darkneſs, and the Day renews.
And fo that blind Creature Milton cries,
Bright Hefperus that leads the ftarry Train, &c.
Marry come up indeed! Can nothing but
Men ſerve you? Sure we have had Women
every way as well qualify'd to be Morning
or Evening Stars as any bearded Tyrant of
you all.
MADAM, faid I, this is only owing to
Cuſtom, which hath made it the Mens
Province to write Books and make Verſes,
and fo they compliment themſelves: But
however, you may be pretty eafy, when
I 4
you
120
Aftronomical Dialogies.
Venus in
you reflect, that we ufually call the most
ufeful things She's: Our Saxon Anceſtors
and our plain honeft Country Folk, now
call the Sun himſelf, that Father and Go-
vernor of all the Planets, She; and fo we
agree to call Guns and Fowling-Pieces;
nay, our Sailors are ſo well bred, and fuch
Lovers of your Sex, that they call a Ship
She, tho' fhe be a Man of War.
WELL! faid fhe, this is fome kind of
Atonement and Satisfaction; and there-
fore at your defire, I will for this time for-
give the Goffips of Phoſphorus and Heſper ;
but if they ſhould attempt to make a Man
of the Moon, I will never paſs it by, for I
can hardly be reconciled to thoſe that place
a Man in that Planet. But have you any
thing further to tell me about Venus?
ONLY, Madam, that She alſo fome-
the Sun. times, like her Neighbour Mercury, hath
appeared like a Spot in the Sun; as you
will eafily conceive fhe may, when you
confider that the Orbit of the Earth in-
cludes her's within it; and that therefore
fhe muſt be ſometimes, tho' very feldom,
between our Eye and the Sun, and then ſhe
will appear like a Spot in the Sun's Disk.
The next time that Venus will be ſeen in
the Sun, will be May 26. 1761. a little
before 6 in the Morning; I wish your
Ladyfhip
Aftronomical Dialogues.
121*
Ladyfhip Health and Happineſs till the time
of that Obfervation, and that you may be
then well enough to get up to fee it.
O! Sir, faid fhe, I can rife betimes in a
Morning, for a leffer Occafion than this:
and I defign to fee that furprizing Appea-
rance, if it pleaſe God I live fo long: But
methinks 'tis a little ungratefully done of
the Moon, and theſe lower Planets, faid
fhe, thus to eclipfe him, or deprive him
of any of his Light, when they receive all
theirs from him; tho' I'm almoft afraid
our Earth doth fo too: for fince fhe is a
Moon to the Moon, it must often be inter-
poſed between the Sun and Moon, and
therefore for a time deprive the latter of
the Light of the former.
UPON my word, Madam, faid I, you
begin to run great Lengths, and go deep
into the very Heart of Aftronomy: And
if you will pleaſe to read Dr. Gregory's
Comparative Aftronomy, in the Place I
before recommended to you, you will be
glad to ſee how rightly you have reaſoned.
Shall we proceed next, Madam, to talk
about what they call the Superior Planets ;
and in particular about Mars, who next Mars,
Occurs in Order?
YES,
122
Aftronomical Dialogues.
YES, faid fhe, we must take him in his
way; but I hope you Aftronomers han't
fuch terrible ſhocking things to ſay of him
as the Poets have. Mr. Dryden, I re-
member, gives fuch a Defcription of Him
and his Temple, as when I read it, chill'd
me with Horror; and what is worſe ſtill,
after he had enumerated all manner of
Slaughters, Famines, Plagues, &c. he adds
this:
f
Theſe and a thouſand more the Fane adorn,
Their Fates were written e'er the Men were born;
All copied from the Heavens, and ruling Force
Of this Red Star, in his revolving Courſe :
The Form of Mars, high on a Chariot flood,
All fheath'd in Arms, and gruffly look'd the God.
No, Madam, faid I, we give him no
fuch Power of doing Miſchief in our Hy-
pothefes; but make him as calm and as
gentle as any of the Planets.
1
VERY well, faid fhe, then begin, and
fay what you pleaſe of him.
THEY account the Diameter of Mars,
Madam, faid I, to be about 4400 miles,
and therefore he muſt be much less than
our Earth: And his Diſtance from the Sun
1
is
Aftronomical Dialogues.
123
is about 123,000,000 miles; he revolves
about the Sun in 687 Days nearly, and runs
at the rate of 45000 miles in an Hour,
WELL! faid fhe, that is pretty good
marching too, for a Man in Armour. Sir,
praygo on.
MADAM, faid I, by fome Spots which
have appeared in him, the Time of his
Diurnal Revolution, is by Mr. Huygens
fettled exactly at 24 Hours 40 Minutes;
and the Motion of thofe Spots hath alfo
diſcovered that this Axis hath very little
or no Inclination to the Plane of his Orbit;
and therefore the Martial Inhabitants will
have no fenfible difference between Sum-
mer and Winter. Huygens thinks that
the Colour of the Earth in him is blacker
than that of Jupiter, or the Moon. His
Light and Heat is twice, and fometimes
thrice, as weak as what we receive from
the Sun. When he is in his Quadratures,
as they call it, that is, in the middle be-
tween his Conjunction with, or Oppofition
to the Sun, he appears a little gibboſe, and
to a good Glaſs almoſt biffected; but when
at Full, perfectly round and diftinct. The
Teleſcope hath not yet been able to diſtin-
guiſh any Moon, or Satellites moving round
him; but that will not be a demonſtrative
Rea-
124
Aftronomical Dialogues.
Jupiter.
Reaſon that there are none at al for as
they are at a great Diſtance from us, fo they
may be but ſmall, and reflect but a weak
and ſmall Light, and therefore may not be
vifible. The Proportion of Heat and
Light in this Planet, in compariſon of ours,
is not much above half.
O! faid fhe, for all he looks ſo red,
then I perceive the Planet is not fo fiery
as the Poets feign the God of War to have
been. Pray, Sir, let us go on to Jupiter.
THIS, Madam, ſaid I, is the largeſt of
all the Planets, and you fee by the general
See Fig. Scheme, that he is much more remote from
IV. the Sun, than any of the Inferior Planets
we have already been difcourfing of, and
therefore Heaven hath granted him a ſupply
of Light, by 4 Moons or Satellites, which
revolve round him as our Moon doth round
us; and theſe Moons, like the Satellites of
Saturn, are ſo much less than their primary
Planets, that they are not vifible without
long Glaffes, and therefore were perfectly
unknown until the laft Age.
Theſe ſecondary Planets fuffer four kinds
of Eclipfes. (1.) When they are within
the Shadows of their Principal. (2.) When
the primary Planet is between them and us.
(3.) When they are between their Primary
one
:
The Orbit of
The
Line of the Comet
which appear 1662 (ans
Fig. II.
6941 CF
Fig. IV.
Figs II x TV
weddy
The bit of Saturn, with his Ring, and 5 Moons
Jupiter and his 4 Moon
The Orbit of Mari
The
Orbit of y Earth
The
Orbit of Venus"
of
Mercury
Moon,
will appear again A.D: 1758
豐
​124
which
the Year 1660. and 1681. Its Period is 575 Years
"The Trajectory of the Comet
Aftronomical Dialogues.
125
one and us; for then 'tis difficult to diſtin-
guiſh of two Luminous Points one from
the other. (4.) When they interpoſe be-
tween one another and our Eye, fo as to
hide one another from our Sight; which
indeed happens but very rarely. And all
thefe Attendants or Satellites, as well as
Saturn's, like the Moon, the Earth's moſt
obfequious humble Servant, do always turn
their Faces towards their Lords the primary
Planets, about whom they revolve, and on
whom they wait.
THIS, faid fhe, exhibits a good Image
of reſpect and regard in Servants and At-
tendants; I wiſh our Earthly ones would
imitate the Celeſtial.
MADAM, faid I, the Times of the Pe-
riodical Revolutions of Jupiter's Moons
round about him, are as follows:
The innermoft moves round him in
1 Day and 18 Hours, the fecond in 3 Days
13 Hours, the third in 7 Days and almoſt
4 Hours, and the outermoft in 16 Days
and 16 Hours. In the Lexicon Tech-
nicum, you will find a good deal more
about this Planet, and how the Eclipfes of
his Satellites are calculated; and thence
ariſes an eaſy way to find the Longitude on
Shore: But I doubt it is not practicable at
K
Sea.
126
Aftronomical Dialogues.
Sea. If this Evening happen to be clear,
(as it promiſes well) I will fhew you the
Planet with his Attendants about him.
I SHALL long to ſee that Sight, ſaid
fhe; but pray go on, and tell me more
about this noble Planet.
HIS Diameter, Madam, faid I, is above
80,000 Miles; and the Quantity of Matter
in him is about 220 times greater than that
of our Earth; and his Diſtance from the
Sun about 424 millions of Miles: He re-
volves round his own Axis in 9 Hours and
56 Minutes, and about the Sun in 11 Years
and 10 Months: And fo large is his Orbit,
that he moves after the rate of about 24,000
Miles in an Hour.
THIS Planet, faid fhe, makes a great
Figure by the largenefs of his Bulk, and
the grandure of his Attendants; but pray
what kind of Temperament hath the Air
of Jupiter? I doubt it must be much
colder than ours, and then I fhall never te-
fire to be a Jovian.
MADAM, ſaid I, the Heat and Light of
the Sun can't be above a 27th Part of what
we enjoy here, and therefore it muſt be
very dark, diſmal, and cold living there;
and
Aftronomical Dialogues.
127
and the weight of all Bodies will be double
to what they are on our Earth.
•
NAY, faid fhe, if the People be twice
as heavy, and almoft 30 times as cold as
we are, even let them live by themſelves
for me; I'll never hanker after going thi-
ther, but content myſelf with ſome jovial
Friends here in our dirty Planet, as
Dr. Burnet call'd it; but I fhall never have
much value for his Judgment any more,
that reprefented Jupiter as the Pattern of
the fine Antediluvian World. But pray,
Sir, What Diſtance may theſe 4 Moons of
Jupiter be from his Body?
نے
THE neareſt, Madam, faid I, is about
130,000 Miles from that Planet; the fe-
cond about 364,000; the third 580,000;
and the fourth or outermoft is about a
million of Miles diftant from him.
WHAT a fine Appearance muſt theſe
four Moons make, faid fhe, and what fre-
quent Eclipſes of the Sun, and of one
another, do they produce! And if Jupiter
hath any Ocean, and it ben't always frozen
up like the Baltick in a hard Winter, what
whisking Tides muft they produce there,
fince our own Moon hath ſo great an Effect
here, in that refpect!
I
MADAM,
128
Aftronomical Dialogues.
MADAM, faid I, I fee you don't only
advance in Aftronomical, but even in Phy-
fical or Natural Knowledge: That Specu-
lation about the Tides of Jupiter is cu-
rious and new, and will be worth a further
purfuit. But if you pleaſe, we will now
go on with our Planet's Phenomena. You
fee by the Figure of Jupiter, that befides a
famous Spot by which his Diurnal Motion
was determined, there are Appearances in
him like Swathes or Belts, as they call
them: Theſe they take to be moveable,
and to be formed by the Clouds of this
Planet, which feem, like our Trade-Winds,
to lie in Tracts parallel to the Equator of
Jupiter.
AND if theſe are really Clouds, fays
fhe, won't it be a proof of Jupiter's
having a vaporous Atmoſphere about him,
like that of our Earth.
IT will doubtlefs fhew, faid I, Madam,
that he hath ſomething round him like
our Air: but its Texture, Gravity, and
Elaſticity may notwithſtanding be vaftly
different from that of Ours; but if by it
you mean to infinuate that he is inhabited,
I entirely agree with, you; for I take it,
that fuch an Apparatus as the making four
Moons
Aftronomical Dialogues.
129
Moons to revolve about, and to enlighten
him; (as five fuch there are alſo moving
round Saturn, befides his Ring) I take this,
I fay, to be a demonſtrative Proof of both
theſe Planets having ſome kind of Inha-
bitants, who have Eyes to ftand in need
of Light, as well as other Senfes proper
for their Naturcs: For we never find Na-
ture doing any thing in vain, but order-
ing all things with the most confummate
Wiſdom, and we must never believe the
would form Moons, where there are no
People to be lighted by them.
Do you think, faid the, that our Earth
can be ſeen by the Jovial Inhabitants ?
No, Madam, faid I, by no means.
LORD! What vain Creatures we arc,
faid the, in this Earthly Planet? What a
bustle do we make to extend our Power
and Empire over it? But I'm mighty glad
the impertinent and destructive Ambition
of an Alexander or a Louis le Grand, can't
be heard of in Jupiter; and I hope the
Hetoes there are always exerting them-
felves for the good of their People. How
vain is it alfo in fome of our Divines, to
fuppofe Jupiter, as well as the reft of the
Heavenly Bodies, to be made only for
K
the
}
130
Aftronomical Dialogues.
the uſe of Mankind? When yet, neither
in him nor in Saturn, can the Place of
our Habitation be feen. But pray, Sir,
go on.
THIS, Madam, faid I, I think is all
that is very remarkable about this famous
Planet, except one thing more, which is
indeed very confiderable and furprizing:
And that is this; that by the Eclipfes of
Jupiter's Satellites, made by the Interpo-
fition of his Body between them and our
Eye, it hath been diſcovered that Light is
in its Motion Progreffive, and not Inftan-
taneous, but that it takes up a determinate
Time to come from Jupiter to our Eyes:
For they have obſerved that theſe Eclipſes
happen sooner than they ought to do, by
Calculation, when Jupiter is neareft to
the Earth; and when Jupiter is fartheſt re-
moved from our Earth, then thoſe Eclipfes
do not happen fo foon as they fhould do
by Calculation. The difference between
Jupiter's neareſt and fartheft Diſtance from
our Earth is the Diameter of the annual
Orbit, and the Difference of the Eclipfes
of Jupiter's Satellites appearing fooner or
later than the Time by Calculation; and
thoſe Differences being ftill the fame, ac-
cording to the Diſtance of Jupiter from
our Earth, it is therefore exactly found by
Obfer-
Aftronomical Dialogues.
ІЗІ
Obfervation, the Time that Light takes to
move the length of the Diameter of the
annual Orbit of our Earth. And by thoſe
Obſervations it is found that Light moves
from the Sun to us in 7 Minutes of Time :
And on this Calculation it was, that what
I told you before about the prodigious
Velocity of the Rays of Light, was foun
ded.
I SHALL look a little further, faid
fhe, into this Affair fome other time; but,
pray, let us now go on to talk about Sa-Saturn.
turn:
THAT outermoft Planet in our Sy-
ftem, Madam, faid I, is at a very great
Diſtance from the Sun, about 777 millions
of Miles; and the Time of his Revolu-
tion round him, is about 30 Years, or
more exactly ſpeaking, in 10759 Days,
6 Hours, and 36 Minutes: And yet fo
very large is his Orbit, that he moves at
the rate of about 18000 Miles an Hour;
his Diameter is about 61000 Miles; and
with regard to the Quantity of Matter in
him, 'tis about 94 times as great as that
of our Earth; but his Denfity is not much
above a 7th part of that of the Matter of
our Planet. And as to Light and Heat,
tis probable that he hath not above a 90th
K 2
part
132
Aftronomical Dialogues.
1
part of what we enjoy by the Sun. In
deed in order to fupply this great Defect
of the Sun's Light, occafion'd by fo great
a Diſtance, our All-wife Creator hath fur-
niſh'd him with Five Moons or Attendants;
the largeſt of all which, and which is the
only one that is commonly feen, is the
4th in order from his Body; and he bears
the Name of the Huygenian Satellite, be-
cauſe firſt diſcover'd by Mr. Huygens.
Theſe Satellites of Saturn revolve round
him in the Plane of his Ring (of which
Ring I ſhall ſpeak prefently) and fo their
Circles make the fame Angle with his
Orbit, that the Plane of his Ring doth,
which is about 31 Degrees. But the
Orbit of Saturn himſelf is nearly coinci-
dent with the Plane of our Earth's Eclip-
tick, as are indeed the Orbits of all the
primary Planets. It doth not yet, I think,
appear, that Saturn hath any Diurnal Re-
volution round his own Axis; the Time
of his Periodick Motion round the Sun,
I gave you before; and thofe of his Sa-
tellites are as follows: The Innermoft of
thefe Moons revolves round Saturn in one
Day, 21 Hours and 20 Minutes, and is
diftant from him about 146,000 Miles.
The ſecond is diftant from him about
187,000 Miles, and performs his Revolu-
tion in 2 Days, 17 Hours and 40 Minutes.
The
Aftronomical Dialogues.
133
The third's Revolution takes up 4 Days,
13.
Hours and 45 Minutes, and he is di-
ftant from the Centre of Saturn about
263,000 Miles. The Huygenian Satel-
lite is about 600,000 Miles from him,
and moves round him in 15 Days, 22
Hours and 40 Minutes. The laft is
1,800,000 Miles diftant from Saturn, and
takes up 79 Days, 22 Hours, in revolving
round him.
'Tis highly probable that there may be
more Satellites than theſe five moving
round this remote Planet; but their Di-
ftance is fo great, and their Light may
be ſo obſcure, as that they have hitherto
escaped our Eyes, and perhaps may con-
tinue to do fo for ever; for I don't think
that our Teleſcopes will be much farther
improved.
But the most furprizing and unparallel'd
Phænomenon of all, in this Planet, is that
which we call his Ring; which appears
nearly as the Figure reprefents it, in an Vid. Fig.
ordinary Telescope: 'Tis a vaft Body of of Saturn.
Earth, as is moſt probable, of perhaps 7
or 800 Miles in thickneſs, which at the
Diſtance of about 21000 Miles from Sa-
turn's Body, and with just as great a
breadth, is placed in a circular Arch,
round about the Planet, in figure much
like the great wooden Crane-Wheels, in
K 3
which
134
Aftronomical Dialogues.
which Men or Horfes walk, to raiſe Goods,
or to draw Water. 'Tis placed exactly over
the Equator of Saturn, and is not any
way contiguous to his Body, nor fupported
by any thing. The Surface of this Ring
is not rough and full of Hills and Protu
berances, as that of the Moon in moft
places is; but even and plain, as it is in
rhofe Regions of the Moon, which.fome,
becauſe of their great. Evenneſs, have
judged to be Seas.
་
THE Thickness of the Ring, comes
not into Aftronomical Obfervation, ap-
pearing but as a Line. And tho' the two
broad Surfaces of the Ring reflect a good
deal of ftrong Light, yet the marginal Sur-
face of it, or its Edge or middle Part be-
tween the two eminent Surfaces, reflects
hardly any at all. The Plane of the Ring
is inclined to that of the Ecliptic, with
an Angle of about 31 Degrees; and this
Inclination in the Courfe of one entire
Revolution of Saturn round the Sun, hath
fome Variation; being twice greatest,
and twice the leaft of all. And this oc
cafions the Planet fometimes to appear
without any Ring at all, as when the
Sun happens to be in the Plane of the
Ring; and at other times, with Anfa, as
they call them, or Handles only; when
♣
but
Aftronomical Dialogues.
135
but little of the Surface of the Ring can
be ſeen And at all other times the Ring
will appear in an Oval Form, which fome-
times will be more, fometimes leſs ob-
long.
I fuppofe, faid the Lady, it is at that
critical Time when the Anfa only appear,
that Saturn puts on the Figure which Hu-
dibras makes Sydrophel give him, that is,
that 'tis like a Tobacco-Stopper.
THAT is but a mean Ridicule, faid I,
Madam; but I perceive it hath ſome Uſe;
for it impreffes itſelf, and the Thing,
Stronger on the Memory, than perhaps
a more juſt and ſerious Deſcription would
have done. But your Ladyfhip will foon
be above theſe little Helps: And you will
receive a great deal of Pleaſure, Madam,
by reading what Dr. Gregory hath writ-
ten about this Ring, in his Diſcourſe of
Saturn, and in his Comparative Aftro-
nomy, ſo often recommended to you;
where the moft confiderable Phænomena
of this Ring, and of the Satellites, as
they appear to an Eye fuppofed to be
placed in Saturn, are explained and ac-
counted for; or you may confult the
Lexicon Technicum.
1
K 4
1
136
Aftronomical Dialogues
I WILL, faid fhe, attach my ſelf hear-
tily to that Book, as foon as I can: And
after we have view'd this Planet with
our Teleſcope, which I will fit up any
time of the Night to do,
ford me your Affiftance.
if you can af-
For thefe two
fuperior Planets have fo many Wonders
attending them, that I grow ferioufly
amazed; and long to underſtand a little
more of them, and to contemplate theſe
wonderful Works of our great Creator.
And indeed what a vaft Field of Thought,
what a new World of Speculation, do
theſe new Difcoveries open to us!
How
empty and ſtarv'd is a Mind unfurnifh'd
with fuch glorious Ideas!
What a rich Fund of Images is treaſured
up here to embellifh our Poetry? And yet
I don't remember to have met with many
Allufions taken from thefe Things; ex-
cept in a late Copy of Verfes preſented
to her Grace the Dutchess of Bolton,
where after the Poet had faid a great many
fine and juſt things of her, I now remem-
ber thefe Lines; the Beauty and Propriety
of which, did not at firft ftrike me fo
much as they do now, fince I have been
converfant with thefe Speculations.
·
BOLTON'S
Aftronomical Dialogaiss.
137
BOLTON's the Centre of Respect and Love ;
Round her, like Planets, we at Distance move's
From her receive our Light, derive our Fleat,
And ftill tow'rds Her we tend and gravitate,
Juft in Proportion to our Senfe and Weight.
But now, Sir, ſaid ſhe, if you pleaſe
we will leave off, unbend, and go to our
Tea.
THE Lady plied her Teleſcopes, and
gurfued her Aftronomical Studies with
great Application and Succefs; and after
fome time, when I had the Honour to wait
upon her again, fhe took me out into the
Summer-houſe in the Garden, and then
began thus with me.
SIR, faid fhe, you have already taken
a great deal of pains to gratify a Woman's
Curiofity; but I muft beg you to indulge
me yet a little further, and to afford me a
Lecture upon another Point; about which,
as I am afhamed to trouble you, ſo I ſhould
be afraid to ask you, but that you have
been ſo kind already, as to help me to get
rid of many Fears and Terrors, too inci-
dent to our Sex: And if you can eaſe my
Mind of this remaining Dread, I fhall think
you can do me a fignal piece of Service.
You
138
Aftronomical Dialogues,
You must know I have been tumbling
over thoſe Books of Aftronomy, which
you have bid me read; and tho' there be
very many Things that I don't underſtand
fully at prefent, yet there are fome alfo
that I know enough of, to be put into the
Vapours by them.
The Affair of Comets, Sir, with their
grifly Beards and horrid Tails, fright me
almoſt out of my Wits: For god-fake
therefore, tell me, as plainly as you can,
whether my Dread is well-grounded; Do
they really forebode all manner of Miſchief
to Mankind, as well as do a great deal,
when they come among us? What are
they? Are their Motions natural, and ac-
countable by Mathematical Calculation, as
thofe of the Planets? Or are they miracu-
louſly fent hither as the Meffengers of God's
Wrath, and as the Executioners of his
Judgments upon finful Mankind ?
MADAM, faid I, as to their Prefages,
I take them to be entirely groundleſs;
but they may be made (as almost any
other of the Heavenly Bodies may, if
God pleaſes) to become the Inftruments
of Evil and Deftruction to any of the
other Planets: but indeed it doth not
plainly appear, fince their Motions and
Appearances have been of late more fully
en-
Aftronomical Dialogues.
139
enquired into, that they have any fuch
deftructive Ufe, or that they have actually
done any real Mifchief in the Planetary
World. There have indeed been fome
fuch Conjectures; but as I take them to
be no more, I will not trouble you with
them now; becauſe I believe they will
occur to you in your future purfuit of
thefe Studies.
I'm glad to hear you fay fo, faid fhe,
and I begin a little to be comforted: But
pray go on, and compleat my Cure; for
I don't care to be drown'd or burnt up
by one of theſe extravagant Ramblers, a
Comet, before I am aware.
O MADA M, faid I, I perceive where
you have been dipping; I will therefore
give you the moſt fatisfactory Account I
can.
THE Ancients, you muſt know, ge-
nerally believ❜d Comets to be only Meteors,
like our Firedrakes, &c. and that they
were no higher than our Regions of the
Air; while fome modern Writers placed
them among the fixed Stars. But fubfe-
quent Obfervations, with good Inftru-
ments, and the Application of the Laws
of Motion and Geometry, to Aftronomi-
I
cal
140
Aftronomical Dialogies.
"
1
cal Enquiries, have now fatisfied us almoft
to a Demonſtration, that they are a kind
of Planets revolving in determinate Pe-
riods round the Sun: But indeed the Ors
bits of many of them are fo very ob-
long, excentric or oval, as well as large
and extended, that they can appear to us
but very feldom; and when they do be-
come viſible, they exhibit Appearances
which are very furprizing; for the lower
ends of their Orbits are fo very near the
Sun, that when they come down into
that part, or into their Perihelion, as 'tis
call'd, they are actually heated and fet on
fire by him to fuch a degree, as not to
get off again, without fuch dreadful Beards
and Tails, as would really fright ſuch as
don't underſtand and confider how they
come by them.
BLESS me! faid fhe, why then if our
Earth moved in ſuch an Orbit, I fee we
might be eaſily deftroyed and burnt up,
by that very Sun, who now gives us
cheering Light and kindly Heat!
'Tis very true, Madam, faid I; for
that great Comet which appeared here
in the Year 1680, (and which I faw,
and very well remember, tho' then but
a Boy) went fo near to the Sun, as to
ac
Aftronomical Dialogues.
141
acquire a Degree of Heat above zooo
times as great as that of red-hot Iron :
And if its Body was about the Size of
our Earth, as it was judged to be, it
won't be cool again this Million of Years.
And yet it pleafed God, that that Comet
went away from us, without doing us
any fenfible Harm, that I know of; and
fo little do I fear being hurt by any of
them, that I could almoft with another
would appear, to help us to compleat the
Theory of their Motions.
1
NAY, faid fhe, if you that know fo
much of them are not afraid of them,
I'm ſure I won't be fo for the future :
Pray therefore, Sir, proceed, and tell me
what you can of the Number, Motions,
and Appearances of thefe Comets, how
their Beards and Tails are formed, and
how you account for the moſt eminent of
their Appearances.
MADAM, faid I, there have within
this laſt 400 Years appeared to this part of
the World but 24 Comets, (how much
greater a Number there may be, God
knows, and perhaps fubfequent Obfer
vations may difcover more.) And of
thefe, according to the Obfervations of
Dr. Halley and other Aftronomers, three
3
of
142
Aftronomical Dialogues..
The Orbits
of them have had their Orbits and Appea
rances fo very like, and the Times of their
Appearing ſo very equal, that they have
judged it very probable that thoſe three
Comets, which fucceffively appeared as
three, were in reality but one or the fame
Comet appearing at three feveral times.
And the like they are inclined to judge
of two others; that they alſo are but one,
appearing at two different times.
That great Comet that appeared here
in the Years 1680, and 1681, was feen
before in our Hemiſphere, A. D. 1106;
once before, about the Year 532; and
alfo 44 Years before our Saviour's Birth:
And therefore they conclude the Time of
its Periodick Revolution round the Sun to
575 Years.
The Time of the Revolution of another
of theſe Comet, which they judge will appear again
defcribed in A. D. 1758, is 75 Years: Another, which
Fig. IV. probably may be ſeen here again, A. D.
three are
1789, makes its Ellipfis round the Sun in
129 Years.
WHAT Bignefs do you take thefe
Comets to have been of, Sir? faid the
Lady.
MADAM, faid I, they are generally
of the fize of the rest of the Planets, and
have
Aftronomical Dialogues.
143
have Atmoſpheres about them like our
Earth: But then as all our Planets move
pretty nearly in the Plane of the Earth's
Ecliptic, thefe Comets are tied to no ſuch
Rules; for the Planes of their Orbits have
very different, nay, almoſt all manner of
Directions and Pofitions, and their Mo-
tions are all manner of ways; fome from
Eaſt to Weft, others from Weft to Eaſt,
fome from South to North, and others a
quite contrary way, &c. And yet their
Motion is equable enough, and fhews us
this great Point; that as there can be no
fuch folid Orbs as was imagined in the
Ptolemaic Syftem; ſo there can be neither
any fuch thing as a Plenum, and no fuch
fubtile Matter as the Cartefians have in-
vented, to folve their Hypothefes: But
we may fairly conclude, that all the vaſt
Spaces both between and beyond the Pla-
netary Syftem, are filled with no Matter
capable of making any confiderable Re-
fiftance to their Motions, but rather are
an immenfe Void, or Vacuity.
}
I think that is a very probable Conclu-
fion, faid fhe; for if there were any quan-
tity of refifting Matter, 'it muft always ob-
ftruct a little, and by degrees muft make
very fenfible Alterations in the Planets
Motions; which I don't find to have been
in
144
Aftronomical Dialogues.
in Fact diſcovered; but fure, Sir, thefe
Comets muſt go off to vaft Diſtances from
the Sun ?
YES, Madam, faid I, and therefore
they are ftill more unfit than any of the
other Planets, to be inhabited by fuch
kind of Beings, as thoſe of human Race;
for the middle Diſtance of the Great Co-
met that appeared in 1680, was more
than 5000 millions of Miles from the
Sun; as its greateſt Diſtance was above
twice as much; and yet its leaſt Diſtance
was not above a 20,000th part of its
greatest: fo that in its whole Revolution,
it would be fubject to fuch Extremities,
as that its greatest Degree of Light and
Heat to its leaft, were above 400 millions
to one. And yet notwithſtanding this
immenfe Extenfion of its Ecliptic Orbit,
the Great and All-wife Architect of the
Univerfe hath probably fo adjusted the
Centrifugal and the Centripetal Forces,
that it doth not quite leave the Sun, the
it go fo far from him, but returns again
towards him, and revolves round him in
a determinate Period of Years. None of
the Orbits of any of thefe Comets yet
known, are in or near the Plane of the
Earth's Ecliptic; and therefore in their
Afcent from the Sun, tho' heated never
fo
Aftronomical Dialogues.
145
fo much by him, yet they won't come
near enough to our Earth to burn us, or
affect us with any fenfible Heat; and
therefore, Madam, your Fears of being
burnt in your Bed by a Comet, I hope
will vanifh for this time.
WELL, faid fhe, and fo they will; but
I love to know the Reaſons of things as
well as any Man of you all. But pray,
Sir, what are the Heads, Beards, and
Tails of theſe Comets?
MADAM, faid I, the Bodies of Co-
mets are probably in Subſtance like our
Earth; fixt, folid, and compact: Their
Tails are probably long and very thin
trains of Smoak and Vapours, emitted
from the heated or enkindled Body, Head,
or Nucleus, as fome call it, after their
Perihelion, or after their having been at
their neareſt Diſtance to the Sun; for then
it hath been obſerved, that the Tails of
all Comets have appeared largest and
longeft. In the Lexicon Technicum, un-
der the word Comet, you will find a great
deal ſaid about the Phenomena of Comets,
their Beards, Tails, &c. from Sir Ifaac
Newton, and other Authors; and there
you will likewife find Conjectures about
their Ufe in the Planetary Syftem.
L
SIR,
146
Aftronomical Dialogues.
}.
SIR, faid fhe, I fhall have recourfe to
thoſe Books with a great deal of Pleaſure,
and will trouble you no farther now with
my Enquiries: I fee Company appearing,
let us forget our Aftronomy a while, and
trifle with them as agreeably as we can.
ABOUT a Month after our laft Con-
ference, I waited on the Lady in London,
who after the ufual Compliments, began
thus with me.
THO" you might be justly afraid to
meet fuch a queftionary Creature as I am,
I will own, I'm glad to ſee you in this
Place; for I have a great many things to
enquire of you, with relation to our late
Conferences in the Country. Ever since
that, I have been tumbling over Aftrono-
mical Books with the utmoft Application;
I have dipt a little alfo into the New Phy-
ficks, and I have been running over your
Geometry, your Trigonometry, and your
Spherick Projection, in order to uſe my
felf to Figures, and to get clearer Ideas of
what the Aftronomical Writers fay: And
tho' I believe I fhould have been frighted
and deterred from beginning with Geo-
metry, and the abftracted Mathematicks,
yet I now find them fo neceffary, that I
am
Aftronomical Dialogues.
147
am refolyed to try at them, and will beg
your help, when your Leiſure will permit.
But in the mean time pray tell me, Don't
you think that the Elementary Mathe-
maticks, and the Newtonian Phyficks, or
Natural Philofophy, might be taught to
Gentlemen, or even to our Sex, in the
eafy and delightful way you have inftruct-
ed me in Aftronomy?
DOUBTLESs, faid I, Madam, there is
no one really Maſter of any Science, but
he can communicate it to another in plain
and eafy Words, and render it intelligible
to any common Capacity and inquifitive
Genius.
WHY then, faid fhe, if I have any
Power or Influence over you, which fome-
times you compliment me with believing,
I would defire you by all means to attempt
that, as your Leifure will occafionally per-
mit you, and in the Intervals between
your Leverer Studies; for I really think it
would be of the greateſt Ufe and Advan-
tage, not only to our Sex, but even to
your own: And I'm fatisfy'd too, that many
of our young Gentlemen grow vicious
chiefly becauſe they are idle, and having
been taught nothing to improve their
L 2
Minds,
148
Aftronomical Dialogues.
Minds, can have no Notions of the Rap-
turous Pleaſures of Science.
I ENTIRELY agree with you in your
Notions, Madam, faid I, and your Com
mands fhall be my Delight as well as my
Duty; in the mean time, can I ſerve your
Ladyfhip in any thing now?
You are very obliging, faid fhe, to
anticipate your Trouble; but we will
loſe no time in Compliments: What I
want at prefent, is, to be inftructed farther
by fome Diagram or Figure, how by the
Earth's revolving round the Sun in her
Annual Motion, together with that round
her Axis, the different Seafons of the
Year, Length and Decreaſe of Day and
Night, &c. are accounted for. Have you
drawn me fuch a Scheme as you once
promiſed me, for this purpoſe?
I HAVE, Madam, faid I, and here it
is; I took it chiefly from Mr. Flamstead's
Doctrine of the Sphere; a Book, I dare
fay, your Ladyfhip will one time or other
dip into.
I HAVE feen it, faid fhe, in Sir Jonas
Moor's Mathematicks, and perhaps may
confider it further; for tho' I never de-
fign
Aftronomical Dialogues.
149
fign to attempt the Calculation or Con-
ftruction of Eclipfes, yet I fhall be glad to
know how the. Aftronomers do it. But,
pray, Sir, go on, and explain the Figures
to me.
L
An Explication of Fig. V.
ET the Circle A B C D reprefent
the Earth's Annual Orbit round
the Sun, whofe Centre is fuppofed to de-
ſcribe that Periphery, as it moves round
the Sun from A towards B, in the Na-*
tural Order of the Signs, and from Aries
to Taurus, &c.
THE Line r, o,, repreſents the
Equinoctial Colure, and the other, ©, V,
ſtanding at right Angles to it, is the Solfti-
tial Colure.
The 4 leffer Circles doti reprefent
the Earth's quadruple Pofition in the 4
Cardinal Points, as they call them, i. e.
at the 2 Equinoxes, and the 2 Solftices,
and the Line dt at right Angles to the
Colures, may fitly enough be called the
Horizon of the Earth's Disk, becauſe it
ſeparates that half part of the Earth which
the Sun fhines on, from the other which
lies behind in the Dark.
L 3
BUT
150
Aftronomical Dialogues.
BUT, pray, faid fhe, what do you
mean by the Earth's Disk?
I USE the Word, Madam, faid I, be-
cauſe you will frequently meet with it in
your reading; it fignifies that round ap-
pearance of the Sun, Moon, or Earth,
which we fuppofe to be the Object of any
Spectator's View; and therefore the Earth's
Disk is the appearance of that half of it,
which becauſe it is enlightened by the
Sun, is ſeen by any remote Beholder.
VERY well, Sir, faid fhe, pray go on.
IN thefe 4 Figures of the Earth, the
Spectator's Eye is fuppofed to be below
under the Earth's Centte e, which Cen-
tre always moves in the Circle A B C D,
To an Eye fo placed, the Circle do ti,
which divides the Earth's Upper Hemi-
fphere from the Lower, will appear to
lie in, or be coincident with the Plane of
the Ecliptic; and therefore that may bę
called the Ecliptic on the Earth's Globe.
THE North Pole of the Earth, or the
upper End of the Axis, about which her
Diurnal Motion is made, will then ap-
pear to be at P, 23° 30' diftant from e to
the
Aftronomical Dialogues.
151
the Pole of the Ecliptic; and if you
draw a Line thro' thofe Points connecting
the two Poles, that may be called the
Line of Direction of the Earth's Axis;
and if produced, it will be coincident with,
or parallel to the great Solftitial Colure,
and therefore will defcribe fuch a Line
on the Earth, to which, when the Sun's
Rays run parallel, or whenever the Earth's
Centre is in the Points w or %, then will
the longest, in the latter, and the ſhorteſt
Days, in the former Cafe, happen to all
the Inhabitants of the Earth.
This Line of Direction Pe, is always
found parallel to the Line %, 0, w, du-
ring the whole annual Revolution of the
Earth.
PRAY, faid fhe, what occafions this
Parallelifm of the Earth's Axis? which
I have read much of.
MADAM, ſaid I, 'tis not any new Mo-
tion, fuperinduced into the Earth, but
only her keeping to the firft Pofition or
Direction of that Diameter about which
The revolves; which fhe muft always do,-
without it be chang'd by the Will of the
Great Creator, who at first appointed it
to be fo as it is. But if you pleaſe, I will
go on.
L 4
A
152
Aftronomical Dialogues.
A Line drawn perpendicular to the
Earth's Axis, will reprefent on the Earth
the Equinoctial Colure, and will always
be parallel to the Great Equinoctial Co-
lure, r, O, ; and whenever the Sun's
Rays run parallel to this Line, which they
will do, whenever the Earth is in r or,
then will the Days and Nights be equal
all the Earth over: For you ſee that as the
Earth revolves round its Axis t Ped, all
Circles defcribed on the Earth, from the
Pole P, i. e. fuch as are the Equator and
all its Parallels, will be juft one half in
the Light, and the other half in the
Dark.
The Angle made between the Earth's
Axis and that of the Ecliptic, may be
Fig. VI. learnt beſt from Fig. VI.
In which the Ecliptic Liner C = C
repreſents the Earth's Annual Orbit, as
view'd by the Eye, at a vaſt Diſtance,
and when the Eye is placed a little above
its Plane: Here let e be the Pole, and ed
be the Axis of the Earth's Ecliptic, which
you muſt fuppofe to be every where at
right Angles to the Plane of the Great
Orbit; and let P be the Earth's North
Pole, Pm the Earth's Axis, about which
the Earth turns from Weft to Eaft in 24
Hours; and fuppofe the Angle P Ce to
be always the fame, viz. 23° 30′.
→
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Fig. VI...
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153
m
Aftronomical Dialogues.
153
Theſe things being fuppofed, it will
be plain, that every Point on the Earth's
Surface, will, as the Earth revolves in
her Diurnal Motion, deſcribe a Circle about
the next Pole: And when you confider,
that every fuch Point is Vertical to the
Earth's Centre, and anſwering to what hath
ufually been called the Zenith, or Vertex,
in the Ptolemaic Projections, the Circle ſo
deſcribed, is very properly called the Path
of the Vertex, becauſe 'tis a Track or Line
made by the Motion of that Point,
I FANCY I fhall conceive this right,
faid fhe, when I get to my Globe; for then
if I bring London into the Zenith, the
Point on the Globe reprefenting London,
is, I ſuppoſe, what you call the Vertex;
and if I turn the Globe round its Axis,
I fee that Point will defcribe a Circle, pa-
rallel to the Equator; and fuch a Parallel,
Į take it, you call the Path of London.
EXACTLY right, faid I, Madam, and
no one could have explained it better. I
think then, we ſhall now go on with
pleaſure.
In fuch Projections as theſe four Figures
of the Earth in Fig. V. a Circle equally
diftant from both the Poles, muſt be the
Earth's Equator; and the Diſtance of any
Place
154
Aftronomical Dialogues.
Place from that Circle, will be the Lati-
tude of that Place; and therefore half the
Diameter of any Path will be the Sine
Complement of the Latitude of any
Place, defcribing that Path.
If you take any Place on the Earth,
and make a Circle paſs thro' it, and the
two Poles, that will be the Meridian of
that Place.
That Point in the Earth's Periphery,
which is oppofite to the Sun, or which is
found by a right Line drawn from the
Earth to the Sun, is called the Sun's Place
in the Ecliptic.
i P o, and t Pd in Fig. V. repreſent the
Earth's first Meridian, in each Pair of
the oppofite Circles.
ma zl, reprefents the Circle made by the
Vertex of London; as that within doth
the Northern Polar Circle; and the next
without it, the Northern Tropick.
By the Figure it will appear plain, that
fince the Sun enlightens but one half of
the Earth's Globe at a time, if the Earth
be in or, the Horizon of the Disk
will then coincide with the Solftitial Co-
lure; and therefore as the Earth turns
round her Axis, which now is coincident
with the Line dt, the Paths of the Ver-
tices,
Aftronomical Dialogues.
155
tices, or the Equator and all its Parallels
will be biffected by the Line dt: and
while any particular place on the Earth, or
any Vertex is in the Light Part t id, the
Inhabitants of it will fee the Sun; and
therefore to them it will be Day: And
while it is in the Dark Part, it will be
Night to them.
But when the Earth is moved on, either
from v to, or from to, the Line of
Direction will coincide with the Solftitial
Colure, and the Horizon of the Disk will
become at Right Angles to it on the Pole
of the Ecliptic e. Wherefore, when the
Earth is in w, all places between the two
Poles of the Earth and the Ecliptic, and
the entire Artic Circle, will, now you ſee,
be illuminated in their whole Revolutions,
as the Earth revolves round its Axis ¿P o.
The Vertexes therefore will fee the Sun,
each one longer than 24 Hours, according
as it is more or leſs diſtant from the Polę
of the Globes; and thofe that lie under
the Artic Circle, touch the Horizon of
the Disk; and confequently at this time
of the Year, viz. June 10, they will fee
the Sun 90 Degrees from the Vertex, both
on the North and South of their Meridian
ſo that as ſoon as he is Set, he will imme-
diately Riſe again; and conſequently they
have no Night: But all Paths without
this,
;
156
Aftronomical Dialogues.
this, you fee, do cut, or get within the
Horizon of the Disk; and fo will have
their Days longer than their Nights, in
proportion to the Quantity of the en-
lightned part of their Path, to the dark
one; ie. at London, As the Ark n v mlf,
is to the Ark n zf; which is above Two
to One: and therefore the Days will then
be above 16 Hours long, and the Nights
fcarce 8.
Again, while the Earth moves from
thro', and fo on to r, you ſee the
North Pole of the Earth is all that time
in the Light part of the Disk; which
fhews you that to fuch as live under that
Pole there will be 6 Months Day. But
while the Earth runs on from thro' s
to, that Pole will, you fee, be in the
dark part of the Disk; which fhews that
then, under the Poles, there will be fix
Months Night, For indeed, when the
Earth is in, all things will be the very
reverſe of what they are when fhe is in
w; i. e. the Nights longer than the
Days, &c.
But when the Earth is in Yor, the
Axis of the Earth's Revolution being dt,
(the Horizon of the Disk) juſt one half
of the Equator, and all its Parallels will
be enlightened, and the other half in the
Dark;
Aftronomical Dialogues.
157
Dark; and therefore the Days and Nights
muſt be equal all the World over.
SIR, faid the Lady, if you can part with
this Figure, I will look it over more care-
fully another time, when I am by myſelf.
In the mean time I have another trouble to
give you, if you will oblige me in it; and
that is, to get me a fight of the famous.
Orrery, which I have heard you and others
ſo often ſpeak of; and which I think was
made by Mr. Rowley, the famous Mathe-
matical Inſtrument-Maker, and Maſter of
the Mechanicks to the King; and whom I
find you have always recommended in your
Books, as the beſt Workman of his Pro-
feffion.
I ſhall ſtay in Town about a Week longer,
and will enlarge my time a day or two,
rather than miſs feeing fo inftructive and
curious a Piece of Ingenuity.
MADAM, faid I, the fine Inftrument of
that Name, which Mr. Rowley made for
the East India Company, is now luckily
in a Place where I can come at it; I will go
thither to-morrow, and then appoint you a
day when I will wait on you to fee it.
The
158
Aftronomical Dialogues.
The Defcription of the Famous In-
ftrument called the ORRERT;
made by Mr. John Rowley,
Master of the Mechanicks to the
King.
W
ITHIN a day or two, I obtained
for the Lady a fight of the Orrery
fhe defired we might have no other Com.
pany but one young Lady more of her Ac-
quaintance; becauſe, faid fhe, I ſhall ask
fo many Queſtions, as perhaps will fhew
my Impertinence to thoſe who are not ac-
quainted with Things of this Nature, and
my Ignorance to thoſe who are.
As ſoon as the Inſtrument was taken out
of its Cafe and fet upon the Table, fhe
expreſſed herſelf mightily pleaſed with the
cleannefs and cleverness of the Workman-
fhip of it; for indeed the Outfide of it
is very rich and beautiful. The Frame
is of fine Ebony richly adorned with
twelve filver Pilafters, in the form of
Cariatides; and with all the Signs of the
Zodiack, caft of the fame Metal, and pla-
ced between them; the Handles were alſo
of Silver finely wrought, with the Joints
as
○ The Sun.
E The Earth.
Q
¥
The Moon.
Venus.
Mercury.
75
r
The Orrery
The Eccliptick.
E
Made by Mr. Iohn Rowley M of Mechanicks to His Maj-
1
ty
159
Aftronomical Dialogues.
159
and Zo-
diac.
as nice as ever were ſeen in the Hinges of
any Snuff-Box: On the Top of the Frame,
which was exactly Circular like the Horizon
of a Globe, is a broad filver Ring, on Ecliptic
which the Figures of the twelve Signs are
exactly engraved; with two Circles ac-
curately divided; one fhewing the Degrees
of each Sign, and the other the Sun's
Declination, againſt his Place in the Eclip-
tic, each Day at Noon.
The Nature and Uſe of theſe Circles the
Lady perfectly underſtood, from what ſhe
had before learned; and therefore in her
pleaſant way, ſhe began thus:
IF fo much Art and Expence be be
ftowed upon the Outfide of this curious
Machine, I don't doubt but the Infide of
it is at leaſt equally curious and uſeful:
And therefore I must defire you, Sir, faid
fhe, to begin quickly, and to fhew it all
to me, as the Man doth the Tombs at
Westminster; tho' I hope you won't be
always in the ſame hafte, nor imitate his
precipitant Manner, and aukward Tone of
Speech: but do it flowly and diftinctly,
allowing me time to think and confider
about it, and to ask you all the Queſtions I
have a mind to.
MADAM,
3
160
Aftronomical Dialogues.
MADAM, faid I, you know, you
can determine and command me, as you
pleaſe.
This Silver Plate on which the Signs
of the Zodiac, &c. are drawn, repre-
fents the Plane of the Great Ecliptic of
the Heavens; or that of the Earth's An-
nual Orbit round the Sun; which as it
paffes thro' the Sun's Centre, fo its Cir-
cumference is made by the Earth's Centre's
Motion; and which for the better advan-
tage of View and Sight, is here, you ſee,
placed parallel to our Horizon.
The large gilded Ball which ſtands up,
you fee, here in the middle, not upright,
but making with the Plane of the Eclip-
tic an Angle of about 82 Degrees, is fo
placed to reprefent the Inclination of the
Sun's Axis; and which being pretty near
the Centre of this Orbit, repreſents the
Sun.
PRETTY near, faid fhe; why is not
the Sun then exactly in the Centre of
that Circle which you call the Earth's
Orbit ?
No, Madam, faid I, nor is that Orbit
exactly a Circle; but an Oval or Ellipfis.
3
As
Aftronomical Dialogues.
160
As in this Figure which I will now draw
with my Pencil and fhew you: Let the
Curve Line POTR
repreſent the Orbit of
the Earth revolving
round the Sun, which
is placed not in C the
Centre, but in S, a
Point in the longer P
Diameter, which they
call the Focus: The
Distance between C
:
S
T
R
and S is what in the Ptolemaick System
was called the Eccentricity, and expreffes
how much the Earth's Orbit differs from
being a true Circle. And the Contri-
vance of this Inftrument is fo admirable,
that you will fee by and by, when I fet
ita-going, this Eccentricity, and that of
the other Planets will be plainly fhewn to
your Eye, in the fame Proportion as they
are in the Heavens. '.
PRAY, Sir, faid fhe, go on; I find I
fhall come to underſtand this better, when
I come again to read Dr. Gregory, and
Mr. Whiston
mi
MADAM, faid I, you fee here two
little Balls ftanding upon two Wires, at
different Diſtances from, but pretty near
M
!
the
?
ड
162
Aftronomical Dialogues.
the Sun; the innermoft of theſe is de
figned to repreſent Mercury, the other
Venus.
BUT why are they placed, faid fhe;
upon thoſe two Wires; they ftand perk
ing up like the Traitors Heads upon Tem-
ple-Bar; I hope Mr. Rowley hath not
difcovered that they have committed any
late Treaſon against their Sovereign the
Sun.
No, no, Madam, ſaid I, they are very
Loyal Planets; the Contrivance is only
to bring their Centres to be, fometimes
in, and always pretty near the Plane of
the great Ecliptic, (and, by the by, the
Plane of their Orbit always paffes thro
the Sun, and interfects the Ecliptic in
two Points, which they call Nodes) and
this Pofition is contrived in order to fhew
us what Appearances they do really exhibit
in their feveral Revolutions round the
Sun. For the fame Reaſon you fee the
Earth and Moon here placed likewiſe on
Wires or Pins, that their Centres may
get fometimes actually into, and always
be pretty near this Plane of the great
Ecliptic; for fo the Orbits of all the
Planets are really placed in the Heavens..
I
Aftronomical Dialogies.
163
I LIKE that pretty Ivory Earth very
well, faid fhe, as I do the Golden Sun:
But, pray, why doth the Earth's Pin ſtand
inclining fo, and not upright?
MADAM, faid I, that is to reprefent
alfo the Angle that the Earth's Axis, or
that of the Equator, makes with the Axis
of the Ecliptic, which latter, in this In-
ftrument, being perpendicular to the Ho-
rizon, the Earth's Axis is placed fo as to
make an Angle with the Plane of the
Horizon of 66°½; or dipping down from
the Zenith juſt 23° 30', which you know
is the Angle made by the two Planes of
the Equator and Ecliptic. And as the
Earth in each of her annual Revolutions
round the Sun, always keeps her own
Axis parallel to its felf; fo you will fee,
by and by, when the Inftrument moves,
that this Terella, or little Ivory Earth,
will do fo too, as it takes its Tour quite
round the Golden Sun in this Inftrument.
I LONG to fee that, faid the Lady,
very much; but I fuppoſe I muſt fufpend
my Inclinations, till you tell me 'tis fit
they should be gratified.
M 2
MADAM,
164
Aftronomical Dialogues.
See Fig.
of the
Orrery.
MADAM, faid I, 'tis beft to confider
the ſeveral Parts of the Inftrument, firft
ſeparately or fingly, and then the feveral
Motions and Phenomena will appear in
the better and more inftructive Light:
Therefore if you pleafe, we will go on.
You obferve, Madam, ſaid I, another
Wire here, ftanding cloſe to this Silver
Circle, and which hath a Ball upon it,
whoſe Centre is in the Plane of that Cir
cle: This is defigned to repreſent the
Moon; and the Silver Circle reprefents
her Orbit round our Earth, the Plane of
which always runs thro' the Earth's Cen-
tre, and the Figures that are engraved.
upon it, fhew her Agc, from one New
Moon to another.
WELL! faid fhe, this is mighty in-
ftructive! I long to fee the Earth and the
Moon move, but I know I muſt have pa-
tience: I fuppofe the Moon's Globe being
black on onc fide, and filvered white on
the other, is defigned to repreſent her
Phaſes, as they call them, of which you
have fhewed me fomething before.
the
'Tis fo, Madam, faid I; and you will
fee this Machine fo admirably contrived,
that
Aftronomical Dialogues.
165
that what I told you of the Moon's month-
ly Revolution, will fhew itſelf to be in fact
true here; for the Lunula here, will turn
round its own Axis, at the fame time as it
moves in this Silver Orbit round the Te-
rella. And in reality, Madam, I can't
blame your eagerness to fee the Machine
put into Motion, when I fee how well
you underſtand it, and know what it
ought to do: And therefore you fhall be
detained no longer, than while I defire
you to take notice of this Hole in the
great Brafs Plate that covers all the Move-
ment, and of this moveable Index here
on the filver Ecliptic. You fce there
are on the former fome Figures engraved;
they are the common folar Tears: and
by taking the Inftrument to picces, it may
be fet to this prefent Time: And the Pla-
nets, by means of an Ephemeris, may be
fet to any particular Time alfo. So that
if a Weight or a Spring, as in a Clock,
were applied to the Axis of the Move-
ment, ſo as to make it move round once
in juft 24 Hours, thefe Reprefentative
Planets, which you fee here, would all
perform their Motions round the Sun and
one another, exactly in the fame Order
and regular Manner, as their Originals do
in the Heavens; and this would then be
M 3
>
166
Aftronomical Dialogues.
a truc Celestial or Aftronomical Clock,
which would fhew the Afpects, Eclipfes,
and other Phænomena of the Sun and
Planets, for ever. But becauſe this would
be inftructive only in that flow tedious
way to fuch as could have daily recourſe
to it, Mr. Rowley hath contrived, by a
Winch or Handle, to turn the Axis
ſwiftly round about, and by that means
to fhew all the Phænomena or Appearances
in a very little Time, as you fhall fee I
will now procced to do; for by turning
this Handle backward or forward, you
may ſee what Eclipfes, Tranfits, &c.
have happened in any Time paft; or
what will happen for any Time to come,
without doing any Injury to the Inftru-
ment.
I am amazed at the Thought and Con-
trivance of this Inftrument, ſaid ſhe, and
I doubt not fhall receive a prodigious
Picafure when I fee it put into its proper
Motions: But pray, Sir, let me firſt ask
you, Are all the Planets here?
No, Madam, ſaid I, (for I fee nothing
can 'ſcape your Ladyfhip's Difcernment)
here are only fhewed the Orbits of Mer-
cury, Venus, the Earth, and the Moon;
for
Aftronomical Dialogues.
167
for the others are at too great a Diſtance
to be brought into the Inſtrument, if any
tolerable Proportion be obferved between
its Parts : And indeed, by what you will
fee of the Motion of theſe three Planets,
and of the Earth's Satellite, the Moon,
you will eaſily know what the Phenomena
of the Superior Planets and of the other Sa-
tellites would be, if they could be here
fhewn; as they cannot well be without
embarraffing the Inftrument with a vaſt
number of Wheels more: And it hath
almoſt 100 already.
But now, Madam, I will fix on the
Handle, and begin to put the Inftrument
in Motion.
One entire Turn of the Handle anfwers
to the Diurnal Motion of the Earth round
its Axis, as you will fee by the Motion of
the Hour Index, which is placed at the
foot of the Wire on which the Terella is
fixed; and which
and which you perceive moves
once round, as I now with my Hand turn
the Spindle of the Machine round, after
the fame manner. You will take notice
alſo, that the Inftrument is fo excellently
formed, that I can make the Motion tend
either way, forward or backward; and
turn it about after the fame manner, till
I bring the Earth to anſwer to any Degree
M 4
or
168
Aftronomical Dialogues.
>
or Point of the Ecliptic. As for inſtance
I will move it about till I bring the Earth
to the firſt Point in Aries. Then you ſee,
to an Eye placed on the Earth, the Sun
will appear to be in the Oppofite Point,
that is, in the firft of Libra.
BUT, Sir, faid fhe, I perceive as you
turn the Earth about, the filver Circle
on which the Moon's Age is placed, and
which I think you faid reprefented her
Orbit, rifes and falls: What is the mean-
ing of that?
MADAM, faid I, you know the Moon's
Orbit is not exactly in the Plane of the
Ecliptic; but makes an Angle with it of
between 4 or 5 Degrees: And juft fo
s
much this Circle rifcs above and finks
below the great Ecliptic, according as the
Moon hath North or South Latitude,
and just as much as that Latitude is And
you will obſerve two little Studs, which
are placed in two oppofite Points of this
filver Circle; they are defigned to re-
prefent the Moon's Nodes, or the Points
of Interfection of her Orbit, with that
of the Ecliptic: Of which, more by and
by
Q!
Aftronomical Dialogues.
169
O! pray! move on, Sir, ſaid ſhe, this
is amazingly fine: I fancy myſelf travel-
ling along with that little Earth in its
courſe round the gilded Sun, as I know
1 am in reality with that on which I ſtand,
round the real one.
:
You fee, Madam, faid I, that one en-
tire Turn of the Handle is, as I ſaid before,
a Natural Day: Now, if you pleaſe to
take off one of the broadest of your Patches,
and make it a Spot upon the Golden Sun
there, you ſhall fee that your Patch will
move quite round in 25 Days, or 25
Turns of this Handle; and that will fhew Sun's Mo-
you how by the Motion of the Spots in tion round
the real Sun the Aftronomers difcover'd
he had ſuch a Motion round his Axis, as
you ſhall ſee Mr. Rowley hath given here
to his Reprefentative.
WELL, faid fhe, fince even my Patches
muſt become Aftronomical, I will ftick
one upon this Fictitious Sun; but I muſt
own I don't love thofe Spots upon the
Natural one; nor to have any of his Face
hid, or his Heat impaired: But fhew me
to what part of the Sun this Patch is to be
preferred.
PLEASE
his Axis.
Spot
170
Aftronomical Dialogues.
PLEASE to ſtick it, ſaid I, Madamı,
juſt againſt the first Degree of Aries, and
in the middle of the Sun's Body,
Very well! Now you will fee that as
365 of theſe Turns of the Handle will
carry the Earth quite round in the Ecliptic;
Mercury. fo 88 will make Mercury perform his Re-
Venus. volution, and 244 Turns will make Venus
move quite round the Sun.
Twenty feven Turns and a little more
than a quarter of one, you ſhall ſee, will carry
Moon's Pe- the Moon round in her Orbit; in which
time you will obferve fhe always turns the
fame Hemiſphere towards the Earth.
riodic
Mouth.
Take notice alfo, Madam, that now I
have just made 12 Turns and an half,
which hath carried your Patch to the op-
pofite part of the Sun.
AND fhall I ever fee it again, ſaid
fhe; fhall I ever recover the Solar Tra-
veller ?
YES, Madam, faid I, you may have
it again; bur pray keep it for hereafter
only for fuch Uſes, and don't replace it
on your Face; for I am as angry at
Patches in a good Face, as you are at
Spots in the Sun; and for your Reafon,
becauſe
Aftronomical Dialogues.
171
becauſe I would not have any part of it
hidden from me.
But the Handle goes on; a Turn or
two more will have carried the Moon half
round in her Orbit; obferve how fhe
moves: 'Tis now 25 Turns, you ſee,
your Patch is come ſafe about to you; off
with it.
No, faid fhe, there it fhall ſtick till
we have done, fince you won't have it be
on my Face any more: I love dearly to
fee it turn round; and perhaps fhould
I put it on, it may make my Head turn
quite round too, as I think it begins to do
already without it: but pray turn on your
Handle however.
MADAM, faid I, at the end of 27
Turns and a Quarter, you ſee I have
made the Moon perform her Revolution
round the Earth: Mercury is got about a
third part of his way; and in 17 Turns
more will have finiſhed juſt half his Revo-
lution. And Venus, you fee, will then
have advanced a fifth part of her way, in
proportion to the Magnitude of her Orbit:
And the Earth alfo hath traverſed in the
Ecliptic the Diſtance of above three
Signs.
And
172
Aftronomical Dialogues:
And by thus revolving the Earth and
Planets round the Sun, you may bring
the Inftrument to exhibit Mercury, and
fometimes Venus, as directly interpofed
between the Earth and the Sun, and
then they will appear as Spots in the Sun's
Disk; as I hinted to you before, p. 114.
And this Inftrument fhews also very clearly
the Difference between what they call
Geocentric and Heliocentric Aſpects, ac-
cording as the Eye is placed in the Centre
of the Earth or Sun.
WELL, faid fhe, I have no words to
exprefs the Pleaſure and Satisfaction I
receive from this moft curious Engine,
nor the Amazement the wonderful Con
trivance of it gives me. Were my For-
rune but half as great as my Curiofity,
I would have one of theſe Inftruments as
foon as poffibly I could get it, and then
without being beholden to any of you
He-things, I would turn it about myself,
till I made it do all I had a mind to. And
I wiſh now, that I could ſee the Inſide of
it; and underftand what Numbers of
Teeth and Pinions he hath made uſe of,
to produce theſe various Motions.
MADAM,
Aftronomical Dialogues.
173
MADAM, faid I, that can't be done
without the Hand of Mr. Rowley himself:
But our moſt Excellent King having the
fame Defire and Curiofity as your Lady-
fhip, he took it all to pieces before his
Majesty, and to his great Satisfaction
fhewed him every Part of the Contri-
vance.
WELL, faid fhe, fince I can't have
that Satisfaction now, pray proceed to
let me know as much of it as you
can.
*
MADAM, faid I, you will, next be
pleaſed to ſee the Difference between the
Moon's Periodic and Synodic Month, Periodic
and the Reaſon of it, very plainly here and Sy
fhewn to the Eye: I have. now turned Months.
the Handle round till
juſt ſuch a Period, as
I have fhewn you,
the Time between
•
our first New Moon, when the Earth
was in the firſt Point of Aries, and the
prefent one: And at the Earth's Place in
the Ecliptic, where this happens, I will
ftick this bit of Paper; and turning 27
Turns of the Handle more, you fee I
have brought the Moon again to be ex-
actly interpofed between the Earth and
•
the
nodic
174
Aftronomical Dialogues.
་
the Sun; and then you know it will be
New Moon to us; but you fee the Line
of the Syzygy is not right againſt the bit
of Paper, but behind it; and it will re-
quire two days time, or two Turns more,
before it will get thither.
I THINK the Reaſon of that, faid fhe,
appears here very plain; becauſe in this
27 Days the Earth advances fo far for-
ward in her annual Courſe, as is the quan-
tity of the Difference in Time between the
Moon's two Months. But pray, Sir, faid
fhe, won't this naturally carry you to fhew
me how the Eclipfes are formed?
YES, Madam, faid I, and that is all
which is material, that I have left to fhew
you.
You know, Madam, the Aftronomi-
cal Books tell you there can be no Eclipſe
of either Sun or Moon, but when the
Moon is in or near the Nodes: And this
will be here very plainly fhewn to you
by the means of this Thread, of which
if you pleafe to take that End, we will
extend it fo as to reprefent the Line of
the Syzygies: I will turn the Handle
about till the next Conjunction of the
Moon comes to be in or near the Node,
or
Aftronomical Dialogues.
175
or in the Plane. of the Ecliptic; and
then you ſhall ſee there will be an Eclipfe
of the Sun. You fee I have turned the
Handle about 27 times; but now the
Centres of the Sun, Earth, and Moon
are not near in a Right Line, as the
Thread fhews you; and therefore there
will be no Eclipfe of the Sun: But you
fee now at the (a) Full Moon, the Line
connecting the three Centres, is very
near the Node; therefore there will be
an Eclipfe of the Moon: And (a) now, (a) After I
you fee, there is an Eclipfe of the Sun had turned
which is Central, when all the three feveral
Centres above mentioned come into this times till
it hapued
Thread thus ftretched in the Plane of the
Ecliptic; and Total, when the Moon is
in her Perigaum, at the greateſt Diſtance
from the Sun, and neareſt to us.
1
;
But in order yet farther to fhew the
Solar Eclipfes, and alfo the ſeveral Sea-
ſons of the Year, the Increaſe and Decreaſe
of Day and Night'; and the different
Length of each in different Parts of our
Earth, Mr. Rowley hath this further ele-
gant Contrivance.
f
He hath provided this little Lamp to
put on upon the Body of the Sun; which
dafting, you fee, by the means of a Con-
vex Glaſs, and the Room made a little
3
dark,
it round
#76
Aftronomical Dialogues.
dark, a ftrong Light upon the Earth s
will fhew you at once all theſe things:
first how one half of our Globe is always
illuminated by the Sun, while the other
Hemifphere is in the dark; and confequent-
ly, how Day and Night are formed, by
the Revolution of the Earth round her
Axis; for as fhe turns from Weft to Eaft;
The makes the Sun appear to move from
East to West. And you will pleaſe to
obferve alfo, Madam, that as I turn the
Inftrument about in order to fhew you
the feveral Seaſons of the Year, and the
Length and Decreaſe of Day and Night,
how the Shadow of the Moon's Body
will cover fome part of the Earth, and
thereby fhew you, that to the Inhabitants
of that part of the Earth there will be a
Solar Eclipfe.
THAT is exceeding plain and in-
ftructive, ſaid the Lady; I have taken
notice of two or three already, as you
have whirled the Earth and Moon round
the Sun. But pray for what other End do
you thus turn it now?
ONLY to bring it to fhew you the
Autumnal Equinox, ſaid I, Madam! and
then you will plainly fee the Reaſon
I
of
Aftronomical Dialogues.
177
*
of the Equality of Days and Nights all
over the Earth, when fhe is in that Po-
fition.
But
O! SIR, faid fhe, I thank you; this
explains the Figure you drew for me be--
fore, by which alone I could not get fo
dictinct and fo clear an Idea of the Earth's
two Motions, as thus fhewn me.
now I fee, that as the Earth turns round
her Axis, just one half of the Equator
and all Parallels to it, will be on the
Light, and the other half in the Dark;
and therefore the Days and Nights muft
be every where equal: For I fee the
Horizon of the Earth's Disk now lies
parallel to the Plane of the Solftitial Co-
lure.
EXCELLENTLY well remembred and
´expreffed, ſaid I, Madam. Your Lady-
ſhip, I fee, hath ftudied hard fince I faw
you laft in the Country, and we are now
fure of you for an Aftronomer.
I DON'T know that, faid fhe, 'tis pro-
bable I may never take pains enough to
go into the Calculatory Part; but I think
every one ſhould be defirous of knowing
the Reaſon of thefe common Things we
N
are
178
Aftronomical Dialogues.
are now upon, and which happen to us
every Year. But pray, Sir, go on, and
ftop when the Earth comes to be in
Cancer.
'Tis now got thither, faid I, Madam;
and you will obferve that the Horizon
of the Disk, or that Plane which di-
vides the Earth's two Hemifpheres, the
Enlightened from the Dark one, is now
no longer parallel to, but lics at right
Angles to the Plane of the great Solſti-
tial Colure: The Earth being now in
Cancer, the Sun will appear to be in
Capricorn; and confequently it will be
our Winter Solstice. And you fee plain-
ly, that as I keep turning the Earth round
its Axis either way, the entire Northern
frigid Zone, or all Parts of the Earth
lying with the Artick Circle, are in the
Dark Hemiſphere; as you ſec by this
little bit of Wafer, which I ftick upon
the Circumference of that Circle.
Your Ladyfhip will obferve alſo, that
now I remove that bit of Wafer, and
place it in the Circumference of that Cir-
cle which exhibits the Path of the Ver-
tex of London, how much Longer, in a
Diurnal Revolution of the Earth, that
will be in the Dark, than in the Light:
Juft
Aftronomical Dialogues.
179
Juſt ſuch is the Difproportion of our Days
to our Nights at that time; fcarce a third
Part.
I SEE this thing, faid fhe, exceeding
plain; and alfo that the Inhabitants of
our North Pole, if any fuch there are,
have not ſeen the Sun fince the 12th of
September.
No, nor can't again, faid I, Madam,
till the Vernal Equinox; for all this fix
Months they must be condemned to per-
petual Darkness: Only the Sun never be-
ing above 23 Degrees below their Ho-
rizon, and the moſt of the time not a-
bove 10 or 12; the Sun, by his fhining
on their Atmoſphere, reflects them fuch
Light as we have about half an Hour af-
ter Sun-fet: Alfo they have Moon-Light
for half of the time, fo that both theſe
added together, it is not fo very Dark
with thoſe at either Pole, during the Ab.
fence of the Sun, as at firft you imagined.
But pray obferve, Madam, that as I move
the Earth along in its Orbit, till it come
thither, how the Nights shorten, and the
Days lengthen, by Degrees, till they come
then to an Equality again on the 10th of
March; when our Earth being in the
N 2
firft
180
Aftronomical Dialogues.
firft of Libra, the Sun muft appear to be.
in the firſt Degree of Aries. And now the
Earth's Axis, which you fee always keeps.
parallel to it felf, will come again to be
in the Plane of the Horizon of the Disk,
and conſequently the Equator, and all its
Parallel Paths will be biffected by that
Horizon in every Diurnal Revolution of
the Earth; or there will be an univerfal
Equinox all over the Globe.
THIS, faid the Lady, is indeed ſeeing
into the very bottom of the Matter, and
underſtanding it from its Caufes and Ori-
ginal. But pray, Sir, turn about your
Handle again; and get me our dear Nor-
thern Pole out of the Dark, as I fee it will
foon be, and then I hope it will enjoy the
Benefit of fix Months cheering Day, as it
hath had a melancholy half Year's Dark-
nefs.
THAT it will, Madam, faid I; and
now you will obſerve with pleaſure, how
the Days Encreafe, and the Night's De-.
creafe, as the Earth moves on towards
Capricorn, where now I will ftop it;
while you obſerve that all the Polar Cir-
cle is got into the enlightned Hemiſphere;
as alfo above two parts in three of the
Path
3
Aftronomical Dialogues.
18
Path of London, (h Lm f) in Fig. Vi
and therefore now our Days are at Longest,
this is our Summer Solstice, or Midfummer.
1
YES, faid fhe, I fee it, and under-
ftand it perfectly well: But I fee withal,
that our Days, now at their greateſt ex-
tent, are going to ſhorten again, which I
will bear as fong as I can, that is, till
you wheel, the Earth about again into
Aries: But then, if you pleaſe, we will
leave off, having attended upon the Earth
in one entire Revolution round the Sun;
and moſt demonſtratively and delight-
fully feen, how thereby all the Pheno-
mena of the different Seafons of the
Year,, and the, Varieties and Viciffitudes
of Night and Day are folved and accoun
ted for.
Pray, when you fee Mr. Rowley, thank,
him from me, for this moſt noble and in-
tellectual Entertainment.
Claudiani Epigr. xiii. In Sphæram
Archimedis.
Jupiter in parvo cum cerneret Æthera Vitro
Rifit, & ad Superos talia dicta dedit :
Huccinè mortalis progreffa Potentia Cura?
Jam Meus in fragili. luditur Orbe labor!
Jura
182
Aftronomical Dialogues.
Jura Poli, rerumq; fidem, Legefq; Deorum
Ecce Syracufius tranftulit arte Senex !
Inclufus variis famulatur Spiritus Aftris,
Et Vivum certis Motibus urget Opus!
Percurrit proprium Mentitus Signifer Annum
Et fimulata novo Cynthia menfe redit!
Famq; fuum volvens audax Induftria Mundum
Gaudet, & humanâ fidera mente regit,
Quid falfo infontem tonitrue Salmonea * miror.
Emula Natura parva reperta Manus.
Thus imitated and applied to Mr. Rowley's
ORRER Y.
When lately Jove the ORRERY furvey'd,
He Smiling thus to Gods in Council faid;
How shall we stint prefuming Mortals Pow'r?
The Syracufian Sage did, once before,
The heavenly Motions fhew in Spheres of Glass,
And the Erratick Orbs and Stars exprefs:
But
* Salmoneus King of Elis, by driving a Chariot over a
Brafs-Bridge, dared to imitate Thunder, for which Jove
flew him with a Thunderbolt; for thus Virgil, Æn. 6,
ſpeaks of him,
Vidi
Crudeles dantem Salmonea pœnas,
Dum Flammas Jovis, & fonitus imitatur Olympi.
Aftronomical Dialogues.
183
But his Machine by one fixt Pow'r and Weight,
Mov'd, and was govern'd, as we are, by Fate.
While the bold Rowley in his Orrery
Keeps his firft Pow'r, juft like his Genius, free:
He knows the Secret Springs; and can impart
Laws to the whole, and to each fingle part ;
His daring Hand, or brings or hinders Fate,
Makes Mercury fly, or Saturn walk in State:
He makes the Earth thro' filver Zodiac run
Fuftly obfequious to the Golden Sun :
While the bright Moon fhining with borrow'd Light,
Marks out the Months, and rules the Sable Night.
And all obedient to his fole Command,
Turn round their Axes, as he turns his Hand:
Their Phaſes and their Afpects all difplay,
And at his beck, exhibit Night or Day:
He makes Eclipfes, as he will, appear,
For any paft, prefent, or future Year;
Shews their true Caufe, and roots out vulgar Fear.
Guiltless Salmoneus at your Suit I flew,
Shall I, to pleaſe you, take off Rowley too?
O! no! all cry'd ; the glorious Artiſt ſpare ;
Tranſplant him hither, and make him a Star.
2
This
*184
Aftronomical Dialogues.
This famous Sphere of Archimedes ´is
mention'd by Cicero and by Ovid : and
the former faith, that it fhewed the Mo-
tion of the Sun, Moon, and Planets.
Pliny tells us, that Atlas and Anaximan-
der, both made fuch a Sphere; as Dio-
genes Laertius faith Mufaus alfo did.
Sextus Epiricus faith it was, made of
Wood; and Calus Rhodiginus, that it
was of Braſs.
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