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1725
E Š S À Y
TOWARDS
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S O L U TION
OF Í HE
Horizontal MOON
By Hans De Vert, A.B. Eman, Coll.
Wequrucnc Luna rubens nitet Vultu. Hor,
5
I
NORTHAMPTON
Printed by WILLIAM DICEY; 1725
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Τ T HE
EPISTLE Dedicatory
.
TO THE
Ladies of Northampton. .
unuwunuwa nenouocowww.00 un
Te GLORIES of Tour County!
As That is of ENGLAND:
N order to alledge fome
Reaſon why this minute
Piece of PHLOSOPHY
crouds itſelt under your
Hoop-Petticoats for Shel-
ter, 'twill be requiſite to ſhew the
Connexion betweeri Aſtronomy and the
Fair.
A 2
iv Epiſtle Dedicatory.
Fair-Sex: And ſure 'tis no Wonder
that, after having reach'd the Moon,
I ſhou'd ambitiouſly fly to Stars of
the greateſt Magnitude. Indeed ev'ry
Scribler has prefer'd the Ladies to
the Stars in Point of Luſtre---- But
give me Leave to ſay that Northamp-
ton exceeds the Firmament in the
Number of its Conſtellations; for
ſuch every Beauty there is, as being
a Complication of Charms: Beſides
this, a certain Wag informs me there
is a Poſture as well agreeable to the
Female Part of Human Kind as to the
Pra&tice of Stargazing ; not to men-
tion the peculiar Charms of Femi-
nine Converſation when the Sun has
reſign'd his divided Dominion to the
Stars and Ladies. How pleaſing is it
alternately to view the Fair One's
Eyes and the Coeleſtial Lamps, and to
draw
>
Epiſtle Dedicatory.
V
1
draw a Parallel between her Boſom
and the Milky-Way ?
As my Book was originally de-
fign'd as an Account of the Moon,
I ſhall inform you, Ladies, of ſome
Adventures of mine in the Cæleftial
Bedlam : But my firſt Admiſſion
there, firſt claims
your
Attention.
About a Twelvemonth ſince, I
had accidentally caſt my Eyes upon a
blooming Beauty, and having been
once before in Love, my Heart,
Tinder- like, catch'd Fire at the
Spark, and I crawled Home very
light-headed and ſick of an intellec-
tual Fever. It happen'd, at that
Juncture, to be the Full of the Moon :
But, to ſhorten my Story, while I
was walking with my Arms a.croſs,
and courting the diſtant Fair One in
Soliloquy, ſomething inſenſibly drew
me
.
vi Epiſtle Dedicatory
me upwards, till the Moon and I be-
came contiguous. I need not men-
tiọn how fimple I look'd when, pul-
ling out my Key to go into my Cham-
ber, I found my felf loſt. I wan-
der'd about ſome little Time, but
being a familiar Puppy, I foon got
Acquaintance with the beſt Families
there, and at preſent I maintain a
conſtant Correſpondence with her lu-
nar Majeſty ; however, I wou'd not
have you ſuſpect that I'm of her Pri-
vy Council : Tho' I may juſtly chal-
lenge ſome Intimacy with her, yet is
ſhe true to her nocturnal Truſt, and
inviolably conceals the numerous In-
trigues committed to her Charge : In
general indeed, ſhe calls herſelf a Con-
fidant to Amours in great abundance
within the Verge of your County, but
always waves the Communication of
Particulars.
SHOU'D
Epiſtle Dedicatory. vii
SHou'd the great Empreſs of the
lunar Territories, upon a due Con-
fideration of the Merits of this Trea-
tife, conſtitute me her Secretary of
State ; don't let it make you uneaſy,
Ladies, for I ſhall fill be a Man of
this Workl, nor do I propofe ever to
deſert my preſent Method of Corre
ſpondence, which is tranſmitting Let-
ters by the String of a Paper-Kite :
But I ſhall be oblig'd to pay a month-
ly Attendance, viz, in the Full of the
Moon, for then the Grandees ſit, jolly,
fiery.faced Fellows; and (by the by).
the Full of the Moon is nothing but
the united Beams of ſo many Car-
buncle Noſes.
I'm ſorry, Ladies, I can ſay but
little detracting upon the Female In-
habitants of the Moon : Their Beauty
falls prodigiouſly ſhort of yours, tho?
not
viii Epiſtle Dedicatory.
not in ſo great a Degree as their Sta-
ture ; for her preſent Majeſty's purple
Robe ſweeps the Ground, and is but
ſeven Inches three Quarters long, tho'
ſhe is one of the talleſt Women there.
The frequent Depredations they ſuf-
fer from formidable Swarms of Mice,
is the greateſt Calamity they lie un-
der : To redreſs which, I innocently
carried thither a Cat, like Whitting-
ton, for a Venture; but the ſilly Ani-
mal miſtook her Majeſty's Life-Guard
Men for Rats, and had devour'd thir-
teen of 'em before I cou'd interpoſe.
This unhappy Accident abated ſome-
thing of the Royal Favour towards
me, but I foon retriev'd it by preſent-
ing 'em with a Ring of Bells; the
Tenor was a Dram-Glaſs, and ſound-
ed very melodioully, but it prov'd a
little too heavy. Their Canals are
excel-
Epifile Dedicatory. ix
excellently well ſtor’d with Fiſh, and
the Inhabitants are pretty good An-
glers; but, not long ſince, the Queen's
eldeſt Son had inevitably been drown'd
by an overgrown Gudgeon, if I had not
plung'd in (almoft Knee-deep) to his
Reſcue. I know you Ladies will dil-
believe theſe Stories, or at leaſt affect
a Disbelief of 'em ; (your uſual Me-
thod of treating Young Men) but to
ſhew the Probability of my Afferti-
ons, at my next Return from the
Moon, l'll bring, ty’d to my Watch-
String, Curtail Spanbigh, their famous
Bear-Garden Champion.
They have excellent Tea, I muſt
own, but I cou'd never like it, as
not being recommended by a Daſh of
Scandal ; tho’ I have ſome Hopes of
weaning 'em to the Faſhion ; for they
can cheat at Cards already, and not, a
B
few
X Epiſtle Dedicatory
few of 'em have kept a Cordial in their
Cloſets this three Months. I have
made foie few Profelytes to Play-
Books, and laid a Scheine to make
'em reliſh what they don't underſtand
a Word of; for I have taught one of
'em to fing Italian equal with Cutzoni.
But lier Majeſty's Obſtinacy in ſome
Particulars, is really very provoking ;
for in ſpite of all my Remonftrances to
the contrary, ſhe obſtinately perfifts in
waſhing her face with nothing but
fair Water : Nor will all my Elo.
querce perſwade her Grandınother to
the Uſe of falſe Teeth. They are ſo
far from admitting the Spleen and
Vapours among 'em, that I can never
make 'em underſtand the Terīns. To
inſtance once inore how ill-bred they
are, ihey never ſhew the leaſt Affecta-
tion or Coquettry to a Lover, but
iinme-
Epiſtle Dedicatory. xi
immediately diſcloſe their Sentiments
at the firſt Time of asking. They
have an odd Way of ſaying their
Prayers too in Church; ſo that, in
the Time of Divine Service, a Maņi
can ſee no more of their Eyes than
the Whites. They are ſurprizingly
puritanical, and infiſt upon it, that
Tea and Bread and Butter turn as
much to Nouriſhment as Roaſt Beef,
and conſequently may as reaſonably
clairn a Grace. I have Orders to pro.
ceed no farther, upon Pain of her
Majeſty's Diſpleaſure ; wherefore, as
I have great Views there, I hope you
Ladies will excuſe my future Silence
upon ſuch dangerous Topicks : Since
then I'm oblig'd to lay afide Lunacy,
be perſwaded, Ladies, nothing ſhall
eſcape me but what You may claim a
Share in ; and if I meet with your
B 2
Appro-
}
xii Epiſtle Dedicatory.
Approbation, undaunted, I'll ſtand
the Shock of critical Thunder ! I
have endeavour'd to pleaſe both
Sexes; but if Applauſe can be gain'd
but on one Side, give me (at leaſt)
my Choice: Then Smile, ye Fair
Ones, and I'm happy. But if I
ſhou'd unlappily meet a ſevere Cen-
fure from both Parties !----- Well; I
won't think on't, becauſe I don't ex-
pect it ; for you muſt know I'm a
very pretty Woman's Man: So that
you may juſtly conclude I am, and
ever ſhall be (till I fink into the
Gout, old Age, or the Grave)
Right beauteous Ladies,
Tour most bumble Vaffal,
HANS DE VEIL.
A N
[1]
A W **** W 28
Series
BOEN
*
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32 發​羅密​晚 ​避​露露 ​♡♡
AN
E S S A
SA Y
TOWARDS A
S O L U TI O N
OF THE
Horizontal MOON
wisuusvaununununununununueservewiesesuar
ហហហហ
INTRODUCTION.
BELIEVE no Treatiſe ever
appear’d under greater Diſad.
I
vantages than this does: I have
pitch'd upon a Subject which
has foild abler Pens than mine,
and tho? I treat of it in a new Method, I
may probably meet the old Fate. A Scep-
tick in Philoſophy is indeed an odious Cha-
racter;
[21
racter ; but it's many a Man's Misfortune
to be branded with the Name of one before
his Works have appear'd beyond an Adver-
tiſement in the News-Paper : Wherefore I
Ihall have two Comforts under the Sentence
of Condemnation. 1. The Cenſure may be
unjuſt; and 2dly, Shou'd the Imputation
prove agreeable to Truth, I ſhall be degra-
ded in this Reſpect) no lower than to a Le-
vel with Wallis, Gafſendus, &c.
METHINKS I want ſomething which
might prove a Counterpoiſe to Prepoſſeſſi-
On: The Subject of this Treatiſe has al-
ways been number'd among the greateſt
Difficulties, and as ſome of the greateſt
Men have fail'd in attempting an Expli-
cation of it, 'cis no wonder if my Solution
of it is deſpiſed before it's read : But ſurely
this is not like the ſquaring of the Circle,
the Impoſſibility of which will admit of a
Demonitration; whereas ?ris undeniably
certain that this phænomenon muſt be the
Effect of ſomething natural. You'll here
ſee my Sentiments of the Matter, and I
really think my Arguments concluſive; the
World indeed muit judge of that; but I
ſhall ſtick to this Opinion till I ſee Demon-
ſtration again't it. But perhaps Nobody
will think me or my Book worth their No-
tice: Whercas in my opinion, when a Per-
fon
[3]
ſon innocently attempts to propagate an
Error, any Body that can ingenuouſly con-
fute his Depoſitions, ought to reclaim him:
Beſides, the worſt grounded Opinions never
want their Votarics; wherefore a Demon-
ſtration againſt me wou'd probably be of
Service to many; tho' I ſhall never believe
there is Demonſtration againſt me till I
ſee it.
AMBITION was what Influenc'd me
moſt to the printing this; and That, I fancy,
will, upon mature Deliberation, he found
the greateſt Spurr to Learning, and ſcarcely
wou'd a Revolution of Saturn produce a
Philoſophical Treatiſe, were Writings con-
demn'd to appear anonymous.
..
It is certain (as I faid before) that the
Phænomenon of the horizontal Moon muſt
be the Effect of ſome natural Cauſe; and if
any Perſon, by a lucky Gueſs, bids fair for
a Solution of it, his Arguments ſhou'd be
ſubmitted to a candid Scrutiny, and his
Reaſons fairly weigh'd : But let no Man
condemn this Opinion till he has examin'd it
in propria Perſona: A Man may then con-
demn it ſafely when his Reaſon points out
to him an Abſurdity; but to diſapprove it
upon Hearſay, is only thinking by Proxy, and
reſigning one's Soul to another's Juriſdiction.
BE-
[ 4
-
BEFORE I proceed directly to the Pur-
poſe, viz. the Solution of the horizontal
Moon by the Refra&tion of the Atmoſphere,
'twill be neceſſary to look into another Hy-
potheſis which has very much obtain’d of
Iate ; I mean that of Rerum Longinquarum :
Thoſe of leſſer Note (as the Dilatation of
the Pupil, Mr. Hobbs's Scheme, &c.) I ſhall
paſs by ſince they have been ſo throughly
confuted: To the Queſtion then in Hand,
viz. Whether the Phanomenon of the horizontal
Moon is folv'd by the Interpoſition of diſtant
Objects
Sect. 1. This Hypotheſis is grounded up-
on the Diminution of the horizontal Moon's
apparent Magnitude when ſeen through an
empty Tube : for, as the Affertors of this
Opinion tell you, the diſtant Objects, exhi-
bited by the Horizon, make the Moon ap-
pear more diftant in the Horizon than in
the Meridian, and conſequently larger :
wherefore, as an empty Tube intercepts all
thoſe diſtant Objects, the Moon ſhou'd (as
indeed it does) appear leſs through ſuch a
Tube than when ſeen by the naked Eye.
If I underſtand the Hypotheſis, I have
ftated it fairly; wherefore I ſhall proceed
to object againſt it.
Sr2 The
[ 5 ]
$. 2. The meridional Moon appears leſs
through a Hole prick'd in a Piece of Paper,
than when ſeen by the naked Eye; as will
any luminous Body: I ſhall account for this
in §. 17. But let it proceed from what Cauſe
it will, if the meridional Moon is lefſened
by a fine Bore as well as the horizontal
Moon, 'rwill be evident that the horizontal
Moon does not appear leſs becauſe the diſtant
Objects are intercepted by the Tube, and
conſequently that the Encreaſe of apparent
Magnitude in the horizontal Moon does not
depend upon the Interpoſition of diſtant
Objects.
§. 3. A SHEET of Paper rightly placed
wou'd intercept diſtant Objects: But thoa
Sheet of Paper be ſo placed as to intercept
diſtant Objects, yet the Moon remains un-
alter'd; therefore the Encreaſe of the hori-
zontal Moon's apparent Magnitude cannot
be owing to a Compariſon between the
Moon and choſe Objects, ſince the Moon
appears equally large, whether the Objects
are ſeen or not. To this the Longinquiſts
anſwer; that when you look at the horizon-
tal Moon by ſuch a Plan as a Sheet of Pa-
per, you are ſtill certain that the Objects
are in Statu quo, and by Means of that Pre-
judice the Moon ſtill retains it's apparent
C
Magni-
1
[ 61
Magnitude. The Reply to this is almoſt
too plain to be inſerted; for ſurely the di-
ftant Objects leave as great an Impreſſion on
me, whether I direct my Eye-light by a
Sheet of Paper, or an empty Tube.
9. 4. THES E diſtant Objects bound our
Horizon, and conſequently all the celeſtial
Objects in the horizontal Circle, ſuch as the
Moon, Stars, &c. muſt appear contiguous
to thoſe terreſtrial Objects; there is chere-
fore evidently a vaſt Interval (viz, that be-
tween the Moon and the diſtant Objects)
cover'd or cut off when the Moon is in the
Horizon: Whereas, when it is in the Me-
ridian, the whole Diſtance lies open to us :
Whence, I conclude that thoſe very Objects
make the horizontal Moon appear nearer to
us rather than more remote: All the Per-
ſons, unacquainted with Philoſophy, whom
I have conſulted, and who are certainly the
beſt Judges in this caſe, have anſwer'd me
agreeably to what I have laid down. If
then the Moon appears nearer in the Hori-
zon than in the Meridian without an En-
creaſe of Angle, it ought, according to the
Rules of Opticks, to appear leaſt when hori-
zontal
§. 5. THE
[7]
6.5. THË Moon appears differently
large at different Times in or near the ſame
Horizon. If this Affertion is true, I think
the Hypotheſis muſt fall; for 'cis á Maxim
in Philoſophy, that the ſame Effects will
flow from the ſame Cauſe: But this Objec-
tion is too ſtrong to be admitted ; and they
that eſpouſe the Opinion of Rerum Longin-
quárum,always have and always muſt, either
directly or indirectly maintain, that the ap-
parent Magnitude of the horizontal Moon
is unalterably the ſame in the ſame Horizon.
Mr. Mollineux has averr'd the contrary; and
what Views could he have in ſtriving to im-
poſe a Deceit upon the World ? I'm ſure (if
I can truſt my Senſes) I have obſerv'd a
great Difference in the apparent Magnitude
of the horizontal Moon, when I cou'd per-
ceive none in the Horizon : But Men bigot-
ted to an Opinion, ſhut their Eyes againſt
the Truth Accordingly the Longinquiſts
tell you, “ You are miſtaken ; you forget
“ what Bigneſs the Moon appear'd of laft
“ Night : tho’ you fancy the Moon ap-
pears at leaſt five Times greater or leſs than
it did the Night before. Again, ſome that
have more Conſcience than to deny the Evi-
dence of their Senſes, tell you the Moon
changes her Horizon every Night. True,
The does ſo: Bur cho' the Horizon is chang’d,
the
C2
[8]
the ſenſible Extent of it may remain unal-
ter'd; and 'tis properly the Length of the
Horizon which muſt influence the apparent
Magnitude of the Moon: Beſides, is it pro-
bable that a ſmall Change in the Horizon
(for it can't be a great one in two ſucceſſive
Nights) ſhou'd encreaſe the Moon appa-
rently to five Times it's uſual Diameter ?
'Tis plain then, theſe are only Quibbles in-
vented to ſerve an ill-grounded Hypotheſis.
9.6. To ſum up theſe Objections in ſhort.
« If the meridional Moon is leſſen'd as
" well as the horizontal, by being view'd
" through a fmall Aperture.
« If the horizontal Moon retains its ap-
parent Magnitude, tho' the diſtant Ob.
“ jects are intercepted by a Plan or a Sheet
« 'of Paper.
« If diſtant Obje&ts diminiſh the appa-
rent Diſtance of the horizontal Moon.
And laſtly,
“ If the Moon appears differently large
16 when view'd at ſeveral Times in or very
“ near the ſame Horizon;" what Reaſon,
what Shew of Argument is there which
may inducę us to imagine that the Encreaſe
of
[ 9 ]
of the Moon's apparent Magnitude has a
Dependance on her being compar'd with
diſtant Objects ?
So much againſt thys Hypotheſis : Now
for my own Opinion, viz. The Phænome-
non of the horizontal Moon is owing to the
Refraction of the Atmoſphere : To make it
evident,
Firſt, I SHALL prove that the Atmo-
ſphere colle&s the Rays of Light, or makes
'em converge.
Secondly, FROM this colle&ing Property
of the Atmoſphere, I ſhall account for the
Encreaſe of the Moon's apparent Magnitude
as ſhe approaches the Horizon.
Thirdly, I SHALL prove that the Angle
ought to ſuffer no Alteration from Re-
fraction.
un
PART
[ 10 ]
inunununununununununununun menununununun
wuwunucncrcnucunwiwtcanviccininis
PAR TI.
The Atmoſphere colle&ts the
Rays of Light, or makes
'em converge
Sel. 7.
·T
HE Sun generally appears in
the Horizon while it is yet
four Degrees below it. (That this is Matter
of fact, may be ſeen in Derham's Phyſico-
Theology, Page the 13th, Edition the ſixth,
in the Notes.) This Phænomenon is un-
doubtedly the Effect of the Refraction of
the Atmoſphere. Now if the Sun appears
in the Horizon when it is four Degrees be-
low it; the sun will alſo appear four De-
grees (or thereabouts) above the ſenſible
Horizon when it is in the rational Horizon:
for the Sun has no Parallax, as ſeen from
different Points of the Earth; or, which is
all one, the ſenſible and rational Horizons
coincide with Reſpect to the Sun.
But
when
[ 11 ]
when we conſider the Moon, we find that
her horizontal Parallax is rather more than
one Degree ; which muſt be ſubſtracted
from the four Degrees of refracted Elevati-
on: But was the Moon as diſtant from us as
the Sun is, She wou'd likewiſe appear four
Degrees above the ſenſible Horizon while
ſhe is yet in the rational Horizon; becauſe
the two Horizons wou'd then coincide :
Wherefore, after having fubftracted the
Quantity of the para Hactic Angle, The
Moon appears (nearly) three Degrees above the
ſenſible Horizon, when ſhe is really in the ratio,
mal Horizon.
9.8. The rational and ſenſible Horizons
are parallel; wherefore, did the Moon appear
exactly in the ſenſible Horizon when ſhe is
in the rational Horizon, her Rays wou'd be
exa&tly parallel ; and conſequently the Moon
wou'd enlighten exactly half the Earth: For
a right Line interſecting two parallel Tan-
gents in the Points of Contact, muſt go
through the Centre of the Sphere, or biſect
it: If therefore the Moon ſhou'd appear in
the ſenſible Horizon while ſhe is in the
rational Horizon, the Plantof the Circle in-
terſecting Light and Darkneſs wou'd go
through the Centre of the Earth; that is,
juſt half the Earth wou'd be enlightned by
the Moon : But if the Moon (as ſhe really
does)
[ 12 ]
does) appears three Degrees above the fen-
ſible Horizon when the is in the rational
Horizon, ſhe muſt enlighten a conſiderable
Part of the Earth beyond the Plane which
biſects the Earth : Therefore, The Moon
enlightens more than half the Earth.
§. 9. If the Moon enlightens more than
half the Earth, 'tis evident that the Rays
muſt come in a converging Direction: For,
(as I ſaid before) if the Rays were parallel,
no more than half the Earth'cou'd be en-
lighten'd : And if they came diverging,
they could not enlighten ſo much as half the
Earth, as will appear by the Scheme. If
two Lines (or T
Rays) are drawn
from the Point
X
A as Tangents
A
to the Circle X,
'tis evident they
S
can never touch the Extremities of the Line
TS, which biſects the Circle, unleſs the
two Lines firſt interfect the Circle : Since
therefore the Moon enlightens more than
half the Earth, The Rays muſt come to the
Eye (as well as to the Earth) converging.
9. 10. If the Rays come to us converging,
they muſt tend to a Focus----But this will
beſt appear by a Scheme. Let the Moon be
at
[ 13 ]
at L, let the outer Circle be the Atmoſphere,
the inner the Earth: Now 'tis plain that the
two refracted Rays which touch the Earth
R
P
L
N
beyond the bife&ing Line R. N, meet at the
Point or Focus P. To ſum
To ſum up theſe Asgua
ments in ſhort.
§. 11. WHEN the Moon is horizontal, ſhe
appears three Degrees above the Horizon-
Therefore ſhe muſt enlighten more than half
the EarthTherefore the Rays muſt come
to us converging--Therefore there is a Fo.
cus behind us, and, The Atmoſphere. colle&ts
the Rays of Light. Quod erat demonſtrandum.
2.12. PERHAPS, it will be deny'd there
is a Focus, becauſe the Earth interpoſes:
But if the Rayscome to my Eye converging,
it will produce the ſame Effect, as if they
really did converge.
2
See
D
PART
[ 14 ]
hotel
PART II.
The Difference of the Moon's
apparent Magnitude is om
ow-
ing to our Change of Diſtance
fromthe
Focus of the Moon's
Rays
Sect. 13
T has been already prov'd that
Rays of Light are collected by
the Atmoſphere, or infected to a conver-
ging Direction: This collecting Property
mult proceed from the ſame Cauſe, (viz.
Attračtion) in Air as in Glaſs: We may
therefore juftly compare the Atmoſphere to
a convex Lens in this point. But an Object
ſeen through a Lens encreaſes in apparent
Magnitude, as the Eye recedes from the
Lens towards the Focus of it's Rays. (N. B.
I always mean a convex Lens.) This Pro-
perty of a Lens is taken Notice of
Rohanlt, (Part 1. Cap. 33. §. 10.) and the
Reaſon, which he alligns for it is, in my
humble
[ 15 ]
S
F
bumble Opinion, entirely agreeable to the
Laws of Opticks. The Reaſon is this
" As the Rays paſſing through a Lens-åré
more or leſs refra&ted, as they are more or
leſs remote from the Axis or middle Ray,
'cis plain that the Eye will intercept Rays
conſtituting a larger Angle as it recedes to
the Focus" But to make it more evident,
ſee the Scheme, where A. B. is the Lens,
and 0. N, 0.
A.
N, the Eye
in two diffe-
rent Scitua.
tions: Now X4
'cis plain by
che Figure,
cliat where
the Eyo is
B.
neareſt the Focus, it receives the Rays AX
and B X, which conſtitute a larger Angle
than the Rays Þ X and Q X, which it
intercepts in the other Poſition. If then a
greater Inclination of converging Rays, or
( which is all one) a nearer Approach to the
Focus will occaſion an Encreaſe of apparent
Magnicude in an Object ſeen through a col-
lecting Medium, and if the Atmoſphere
collects or renders converging the Rays flow.
ing from the Moon, 'tis plain that her En-
creaſe in apparent Magnitude mult proceed
from our Approach to the focus of het Rays,
if
D 2
[ 16 ]
if it can be prov'd that her Focus is neareſt
Us when the Moon is neareſt the Horizon
i
which is plain, becauſe,
.
14:
THE Focus muſt be on that Side
the collecting Medium which is oppoſite to
the Object : Beſides, as the Rays come to
us converging, 'riş clear, even to Demon-
ſtration, that there muſt be a Focus (at leaſt
an imaginary one) behind us when the
Moon is horizontal : But if the Focus is
behind us when ſhe is horizontal, It (the
Focus) will be remov'd almoſt a Semidiame-
ter of the Earth more diſtant from us when
ſhe is meridional. Laſtly, Was the Focus
between us and the Moon, by the Rules of
Opticks, the horizontal Moon muſt appear
much the leaſt : For the Focus wou'd be
moſt diftant from us when the Moon is hori.
zontal, and conſequently we ſhould receive
Rays conftituting a leſs Angle than when
ſhe is in any other Scituation. The Argu-
ments then, for 'the two. laſt Propoſitions,
run thus
15. WHEN the Moon is in the Hori.
zon, ſhe appears three Degrees above it-
Therefore ſhe enlightens more than half the
Earth-Therefore the Rays come to us
converging - Therefore there is a Focus
behind us An Obje& appears largeſt
through
( 17 )
through a collecting Medium when the Eye
is neareſt the point of Convergence : But
the Eye is neareſt the focus of the Moon's
Rays when ſhe is horizontal-Therefore,
The Encreaſe of the horizontal Moon's apparent
Magnitude is owing to our Approach to the Focus
of her Rays. Quod erat demonſtrandum.
Now I have given a demonſtrative Solu.
tion (for ſuch I think it) of the Encreaſe of
apparent Magnitude in the horizontal Moon,
'twill be requiſite to give ſome Reaſon why
her Angle ſhould remain unalter’d; for I
ſhall ſuppoſe it to do ſo, ſince the Diminu-
tion of her Angle has been found proportio-
nate to the Encreaſe of her Diſtance: The.
beſt Reaſon which I can aſign for this
Phænomenon, is a Proof of my third Propo.
ſition, viz.
*
ucunciunion
unusurans
TATA
EX
incuruanos
mission
ninus
PART
[ 18 ]
號​盤​發​器 ​路​路​發
​PART III.
The Angle ought to ſuffer
no. Alteration from Re-
fraction.
A
Séct. 16. LENS interpos'd between
the Obje&t and the Eye (pro-
vided the Eye is between the Lens and the
Focus) protrudes the Objed, and makes it
appear as a Portion of a more diſtant Circle :
This is not a bare Aſſertion of my own; as
may be ſeen in Rohault, (Part I. Cap. 33.
9. 7.) However it may eaſily be prov'd as
chus. There are but two Reaſons why the
Magnitude of any Object appears encreas’d.
ift, When the Object is brought nearer,
and conſequently fubtends a greater Angle.
2dly, When, under ſome particular Circum-
ſtances, the Object appears more remote,
and nevertheleſs fubtends the fame Angle.
Refraction certainly encreaſes the apparent
Magnicude of Objects one of theſe two
Ways; but that it does not augment the
Angle,
[ 19 ]
Angle, I thus prove. Let us ſuppoſe a Circle
mark?d with 360 equal Diviſions; each Di.
viſion will ſubtend an Angle of one Degree:
Inſtead of the ſurrounding Atmoſphere, let
us ſuppoſe within that Circle a concentrick
one compps'd of 360 equal Lenſes : In the
Centre of theſe Circles let an Eye be plac'd.
This Eye will perceive each of the Diviſions,
as it ſeverally turns to 'em, magnified by
Refraction to perhaps ten Times their unre-
fracted apparent Magnitude : But can any
reaſonable Man ſuppoſe their reſpective
Angles equally enlarg’d? For, was it ſo,
how many Degrees wou'd there be in a
Circle! If a Circle cou'd be ſuppos’d to
contain as many right Angles as ſuch an
Augmentation would occaſion, where wou'd
be the Truth of the Mathematical Maxim?"
" No more than four right Angles can be
" drawn about a Point." A Circle will be
a Circle ſtill, be it's Area never ſo much
encreas'd ; nor will a right Angle expand
itſelf, tho’ it's Arc or Subtenſe is made.a
Portion of a larger Circle. Allowing that
the Eye can ſee through but one Lens 'ac
once ; (as it has been objected to me) yet
ſhould an Angle of one Degree be magnified
to that of two Degrees, the other Diviſions
might reaſonably expect the ſame Favour;
and wou'd not the Symmetry of the Circle
be as much violated by the Admittance of
one
)
L
20 )
one new Degree, as by the Addition of a
Thouſand ? Beſides this, I know an Inſect
whoſe Head is encompaſs’d with a tranſpa-
rent Humour, deſign'd probably for Viſion;
and was this Creature placed in the Centre
of the abovemention's Circles, it wou'd cer-
tainly perceive the ſeveral Diviſions equally
magnified, that is, the whole Circle wou'd
appear to it as farther remov'd; or (which
is all one) encreas'd by Refraction; for the
Enlargement of a Circle can have no Effect
upon the central Point. The Epitome then
of this Proof runs thus : If Refra&tion cannot
alter the Angles contain'd in a whole Circle,
or drawn about the Centre, neither can it
alter the Angle ſubrended by any Arc or
Part of a Circle: But ev'ry Obje&t (or rather
'the Diameter of it which we meaſure)
appears as part of a Circle, whoſe Radius
is a Line drawn from the Eye to the Object.
Therefore, Refraction does not alter the Angle.
Quod erai demonſtrandum.
Now (tho' I think my Solution of the
horizontal Moon fully proy'd,) I ſhall pro-
ceed to corroberating Circumſtances, ſuch
as, if fairly attended to, will carry with
'em fufficient Evidence (almoſt) excluſive
of the Proofs already laid down.
§. 17. WHEN
[ 21 ]
ſ. 17. When the Moon (I ſay the Moon
in general) is view'd through an empty
Tube, I have obſerv'd that its apparent
Magnitude is (cæteris paribus) direaly as the
Bore of the Tube, unleſs the Bore is too big
or too little to cauſe any Difference. This
I have hinted at ſ. 2. and to give a true and
rational Account of this, we muſt conſider
that Light is attracted by all Dodies : But
the ſmaller the Bore is, the ſtronger will
that Attraction be; (viz. to the Sides of
the Tube) and the exterior Rays of that
Pencil which comes to the Eye of the Ob-
ſerver, will be more inflected from their
Inclination, and conſequently form a leſs
Angle with each other; upon which Angle
the apparent Magnitude depends. Graveſend
(Book 3d. No. 613.) ſays, agreeably to what
I have ſaid, “ It is alſo prov'd that that
" Action (viz. the Inflection of Light) is
" encreas'd as the Diſtance is diminiſh'd."
Wherefore we may with Juſtice impute the
Diminution of the Moon's apparent Magri-
tude (when feen through an empty Tube)
to this Inflection of the Rays. How miſe-
rably this Diminution, &c. has been miſap:
ply'd, may be ſeen Q. 1.
22
§. 18. The Moon's apparent Magnitude
decreaſes as her Elevation encreaſes. This
Phænomenon of the Moon is perfectly con-
E
liſtent
[ 22 ]
,
fiftent with my Opinion, and, with Men of
Candour and Ingenuity, will evince the
Truth of it: For as the Moon's Diſtance
from the Horizon gradually encreaſes, ſo
does our Diſtance from the Focus, till, when
the Moon becomes meridional, the Point
of Convergence is fartheſt remov'd from us,
and therefore the Moon ſhou'd then, as it
really does, appear leaft. What can be
plainer than this? If Men are in the leaſt
willing to admit the Truth, they can't avoid
it here.
$. 19. The Moon's apparent Magnitude
is different ac different Times in or near the
fame Horizon. Now this is a Phænomenon
which cannot poſſibly be folv'd any other
way than by my Hypothefis : I my ſelf am
convinc'd of the Truth of it, if our Senſes
my Word for it (as I'm a prejudiced Perſon)
may take Mr. Mollineux's. My Principles
will eaſily account for this extraordinary
Appearance. For, our Diſtance from
the focus of the Moon's Rays will be
inverſely as the Convexity of that part of
the Atmoſphere which is perpendicularly
under the Moon : Therefore, as that Con-
vexity is, ſuch will be the apparent Magni-
tude of the Moon directly, and it's too
evident to be den 'd, that a great many
Acci-
[ 23 ]
Accidents will encreaſe or diminiſh the Con,
vexity of the Atmoſphere. If theſe Proofs
are inſufficient, I muſt patiently ſubmit to
abſtinate Prepoſſeſſion: Tho' in my Judg-
ment, Euclid's Demonſtrations are not clear.
er : And I'll venture to argue as Sir Iſaac
Nepton did for Gravitation. If the Phæ-
nomenon of the horizontal Moon de-
" pended on the Refra&ion of the At-
“ moſphere, ſuch wou'd be the Effe&ts ;
“ ſince therefore ſuch are the Effects, the
“ Refra&ion of the Atmoſphere muſt be the
“ Medium whereby to ſolve che Phænome-
“ non of the horizontal Moon.” I ſhall
now endeavour to take off ſuch Objections as
I have heard ſtarted againſt this Opinion.
9. 20. It has been objected to me, that,
when the Moon is horizontal, the Rays
which we receive are ſo far diſtant from the
Axis or Perpendicular, as to be unfit for
optical Uſes.
Anſwer. 'Tis true, thoſe Rays, by which
we perceive (or rather fancy) The Moon to
be in our Horizon, are the most diſtant from
the central Ray of the Rays which are regu-
larly refracted; otherwiſe we ſhou'd ſee the
Moon ſooner : But as thoſe Rays give us a
diſtinct View of the Moon, they muſt be
fit for optical Uſes. I have ſeveral Times
cover'd
E 2
[ 24 ]
cover'd a Lens all buc the very Edge, and
yet obſerv'd as great an Encreaſe in the
Obje&t's apparent Magnitude, by drawing
my Eye toward the Focus, as if my Eye
had been placed in the Centre of the Glaſs :
Indeed the farther the Eye is remov'd from
the Axis, the more diftant will the Object
appear from it's true Place.
6. 21. It has been objected to me, that
the Convexity of the Atmoſphere is too
ſmall (i. e. the Atmoſphere is too flat) for
ſuch a Refraction.
Anſwer. Let it be conſider'd that, if the
Earch was taken away, and it's Place fill'd
with Atmoſphere, an Object (as far diſtant
from us as the Moon is) ſeen from the Focus
through the whole Globe of Atmoſphere,
wou'd appear as large as the Atmoſphere.
I therefore think that ſo conſiderable an Ap-
proach to the Focus as (nearly) a Semi-Dia.
meter of the Earth, may reaſonably be
allow'd ſufficient to ſolve the Encreaſe of
the Moon's apparent Magnitude.
22. It has been objected to me that,
as the Atmosphere reaches beyond the
Moon, the lunar Rays can meet with no
retracting Surfaces.
Anſwer.
[ 25 ]
...
-------
Anſwer. I SHALL not loſe Time in con-
futing the Minor of the Propoſition ; but I
muſt give a ſmall Hint about Retardation of
planetary Motion : But if we look into the
Conſequence, we ſhall find it as unphiloſo-
phical as the Minor : For as the Atmoſphere
encreaſes in Denſity as it is nearer the Earch,
every Ray at any Diſtance from the Axis
(i. e. the Ray which points to the Centre
of the Atmoſphere) will deſcribe a Curve,
and impinge upon perpetual refracting Sur-
faces.
9. 23. It has been objected to me that,
as an Object ſeen through a Lens with both
Eyes appears double, To ought the Moon
through the Atmoſphere, ſince I have ac-
knowledg’d ($. 13.) that the refracting
Power proceeds from the ſame Cauſe in Air
as in Glaſs.
WHEN I firſt learn'd this Phænomenon
of a Lens, I own it ſtartled me; but I
thought my Opinion too well eſtablish'd to
fear any Objection, unleſs it was Demon-
ftration, againſt mé: For an unanſwerable
Difficulty is no Proof that a Man is in the
wrong, tho' it may put him to a Stand.
I have now two Solutions of this Difficulty;
either of them fufficient to take off the
Objection.
Anſ.
[ 26 ]
Anfo 1. THe Moon (ſay my Adverſaries)
ought to appear double: True, it ought ſo,
nue becaule we ſee it through a convex
Medium, but becauſe we ſee it with both
Eyes; nay, more, it really does fo; but by
Prejudice we judge it Gogle. I have good
Reaſon to believe this: For a very eminent
Surgeon inform’d me, that a Patient of his
by an Accident had one of his Eyes fo much
diſtorted, that he could not fee with it; but
upon the Reſtitution of his Eye, ev'ry Thing
appear'd to him double, till by Degrees Ob-
jects became familiar to him, and at laſt
exhibited ſeverally but one fimple Appea-
tance. The Gentleman farther inform'a mę,
that he had never met with a Body (tho’hę
diſſected ſeveral) in which the opcick Nerves
met; wherefore he juſtly concludes that
Prejudice is the fole' Cauſe why the two
Images on the Retinas produce but one
Senſation. I'my ſelf have obſerv'd, that the
longer I look at an Objed with both Eyes
through a Lens, the two Repreſentations
draw nearer and nearer.
Anſ. 2. The ſingle Appearance of the
Moon is owing to the ſingle refracting Supe
face of the Atmoſphere: By this I mean,
that the Rays, in paling through the Ace
moſphere to the Eye, luffer no Refrađion
but on that Side of the Atmoſphere next
the
[ ging 1
the Moon: The other Side which is next
the Eye, is contiguous to the Eye, and the
Rays, when they emerge from the Air, do
not alter their Dire&tion before they reach
the Eye: Whereas Rays of Light, in paſſing
through a Lens, are refracted by both Sur-
faces : But if a Lens was ſo contriv'd as is
repreſented in the following Scheme, I.dare
be bold to ſay an Object ſeen through it
wou'd appear ſingle. Let
A. B. be a concave-convex
А.
Lens, and C the Focus. I
have made the focus to
be the Centre of the
Sphere of which the con-
cave Surface is a Portion,
ſo that ev'ry Ray which
B
tends to the Focus, falls
perpendicularly on the concave Surface, and
confequently ſuffers no Refra&ion by.it.
Thar à Lens refracts on both sides, and the
Atmoſphere but on one is the only material
Difference I could find between the Armo-
ſphere and a Lens; to that therefore I impute
the different Appearances of Obje&s ſeen
through’em : Beſides, there is ſome Analogy
between their reſpective Surfaces, and the
Appearances which they generally exhibit.
F I N 1 S.
[ 28 ]
1
So
E
R RATA
AGE 6, Line 14, leave out the Word as. P. 9. l. 47
inſtead of thy, read this. P. II. 1. 26, inſtead of Plan,
read Planes" P. 12. 1. 4. dicro. P. 13. I. laſt but fpo, for
Ray, read Rays.
P
Northampton chercury
906. Jumeist
NORTHAMPTONSHIRE LADIES.
Mr. C. A. Markham has shown me an ex-
tremely interesting, and in some ways enigma-
tical publication printed at the " Northampton
Mercury” Office in 1725 by William Diray. The
title page reads :-
An Ersay towards a Solution of the Horizonal
Moon. By Hans De Veil, A.B. Eman. Coll
Northampton : Printed by William Dicey, 1725.
In the hiatus above is a Horatian versi and a
woodcut. The first refers to the moon, the second
contains a representation of the sun. It is a
scientific work of forty pages, twelve of which
are occupied with "the Epistle Dodicatory to
the Ladies of Northampton,” who are thus
apostrophised :-
* Ye Glories of Your County! As
That is of England.
The scientific essay, illustrated with cuts, seeks
to explain why the monn appears larger when
rising than when high in the heavens. The pre-
face is an attempt to explain why “ this minute
Piece of Philosophy crouds itself under your
Hoop-Petticoats for Shelter." The compliments
to the ladies and some bacchanalian allusions I
cannot very well repeat in a modern newspaper,
and one is inclined to fancy that the Essay
when first published failed to sell, so a broad
and witty preface was written in the hope that
where science failed a suggestion of licentious-
ness would be successful. There are parts wonder-
fully suggestive of Swift's Gulliver's Travels,'.
which was not published until the following
year.
The author says he visited the moon. The
lunar ladies were not beauties; and all the
humans were dwarfs. The robe of the queen,
one of the tallest of women, although it sweeps
the ground, is but seven inches and three-quart-
ers long. The people suffered from formidable
swarms of mice, and he therefore innocently
carried thither a cat, like Whittington, for a
venture; but the silly animal mistook her
majesty's Life Guard Men for rats, and had
devour'd thirteen of 'em before I cou'd interpose.
This unhappy accident abated something of the
royal favour towards me, but I soon retriev'd it
by presenting 'em with a ring of bells." The
tenor was a dram-glass, and was a little too
heavy." Again :
Not long since, the Queen's eldest son had
inevitably been drown'd by overgrown
gudgeon, if I had not plung'd in (almost knee-
deep) to his rescue.
There is some excellent satire. "The lunar
inhabitants have an odd way of saying their
prayers in church, so that, in the time of divine
service, a man can see no more of their eyes
than the whites.''
There is much more in similar strain. Mr. J.
S. Shepard believes that Hans de Veil was a
Northampton apothecary or something of the
sort: but it is suggested that the name is
fictitious. Whichever is the case, is it possible
that Swift. wrote the epistle dedicatory to help a
friend to sell his book, which one would fancy
must have otherwise been a drug in the market?
an