I N T R 0 D U C T I O N.
O a th e F ra ii/ it LT,elejcope.
' , i Si'. A fenflt-Telefcope Is.a telefcbpe ©oveabl^about
.Rn horizontal axis,,r.and Ip' ^djuftep, that its axis may-
move exactly hi the plane o^the rneridian^ The aimex-
ed figure reprefents th]stin®iiiment; T L r^pjefents the
telefcope, lA B tHe ^is^qQut.^hieh ^t^ms?i^ c | it ,en'd
o f which is made c^'Endrical; thefe are' <each laid
m an angular nptcfi^cut^ih a piece:©£%r|us; ana each o f
jh e fe pieces o f brafs. are moveable in a/brafs frame fixed
in firm ftone pillars'; each_piece is move^l by-a fcrew;
that at one; encLa6isf again ft the under 'fide p f one- o f
the b„rals p^92Si, and gives that end o f the axis rA B "df
teleicope, a motion perpendiejilar \ to the horizon ;
'and tn,e?-othe^ fcrew a£b 'againft one o f the fi'des o f J:he
other brafs pieee,* add^gives the axis A B ' a motion parol-
leLtp Jthe horizon.; b y means o f Inefe two fiTrews tHere-
fpre the .te^^pue Gampe brdught into any pofition. In
- the fp cus jf o f the | Q^jeft igiafs there jare fixra'fwa' firife
/wires perpendicular to each?otk^;$iifd the line joinin'g
.their interfi.£tion and tfiei center o f the object glafsj Is
called tht^axis o f t/he tube 'v i i i qr ^the <ltne of collirnafion
bjTthp telefcope. .One o f thefe wires is adjufted,perpendicularly
to the horizon,, and p f C.ourfe the.other
will then be parallel to it. A f te r all /the £adjuftmen ts o f
^^nmrOmentare made', lftfieinftrument be turned' about;.
the’hjtis AB ^th e perpendicular wire moves exadfly in
the plane o f /the meridian;;^fp that when any obje^b
tomes to this wire, b y means--pf a c lo c k properly regulate
dj/you get'this time o f its pafiage over the meridian, .j
-Sometimes there are fixed cine or two more perpendicular
wire’s, equidiftant from this nftddle perpendicular
wire. For an explanation o f the methods o f makmgytfidfd
adjuftments, we muft refer to the work' before- mentioned.
This inftrument is ufed to find the right aftenfions
M the heavenly bodies, as we lhall afterwards explain.
: 15 I
Explanation of hf&ymi.,
* ‘’ip . d;na fight
Jinn /|?^!fre'he^ve[r;v .iomcS, hly \\ in' fiepre we proceed
explain thefe and' fomeother teiinl,lwhich we (Kail have
occafiqn to make life W t
tm lyh^xofThe.iir// f ’’ d rtyfifc
oijt'“ 'cirt.lfe'tthlclri, 1 l>"d tile tjjnhioi»;1 aiyd if
jffieaxis o f diSearth he e x ten d ed^ 4fflC,B©vi'nt, Afe
r f 'ih e
Yelelmr eqilarok'^!rhsus the heavens are.1 biviSid 3ift&
~nortfS/rn zrttxftmtitrh hemitpheresj corrfefoSna tag to airilfe
mMh. I
i.t TnSt'on o f
VRe'flm nit 1 liWrf tlft? it ! l,m‘otion o f't'lfW * i^ I^ b oV
r‘8ilie' fun.. in the /pace of td’^year •" ft is'toeref^iVi'if fidt,
1 ’t'h'at *deretffi4s,'^(ft*?cff^5c.' V’THgi^qfiator 'and
‘a S ' f ^ fM d w eadh
Jj^!!T.t8 tni atigfi o y^ o®
'&&• »ppuiit. u l l i i t |li t | l <y«ggxa a ij,rfiKl|^>
angle is called' ^■
' L e t AEL§>^^eRicfcn£,A6 chfeiiiaj“e lu a S J r h f f iP
the ecliptic, inclined to, a S ' «UjBm; la -ff l<a1ie^!W)‘()-'
p file joflits , L , f i r 'n l l '^ r t it^ c rV v -d ile -t/lrti
■ olhet into two ttph'.-ji'-frf.. I ht-tCIiptie is ‘d njed ni-o‘
1) ^qSal parts,.called^®.;-ar/ej <y, If«;/« y , -gemini
n , cancer ho p /itorgtT f%, tibia i orpin rrl; f«.'
ightariun~f>j ^ v* . T h e
■ order o f thefe;is accoiidingito the-apparent motioni'of:
the-Wn.1 Th6-"firltpoint of,- arfeshfcokrtdeV with One
o f ElieV ecfriiiioxes, as A , 1 and I'eonfe^Cffedy ’ thV'ftrft
point o f libra coincides with thc-ofher'eqjunox I ,. The
firft & ’fignsrate called norfkernlying;, oh '-tW■ hortS fide,
o f the equator; and tfidiSft fix* Aft 'cwte&Toutherny lying
on the Joulb fide- When the-' -motion o f the heavenly,
bodies is according to tire :prder o f the figns, it is called
direSt and whefe the motion is in a contrary1 direftioh, it
is according to
tr.otfofi'is; lometinies in a contrary direction, for retfons
r N T R- & D U C I I ON.
wh xh will aftcrvar-K inpe-” -. The eij lirioftia f'ipoi|ts
A , L , are not fi 1
' about 50" in a yeai ; this is called the precejjion 1/ tie
equinoxes. "I In 20 h c, is a i < 1 extei d ig'8°.on each
" £ lc o f th< ;ediptic, w ithin which-the-,jno io 1 o f all the
plapets hre-pcrformed.. ,
I f r be the .p la ctpf a ftar, mj ml a great cird:e-
'T i fB ^ ^ c#'i''';to the equator, then' ^m is called the
MtBUJcenptm o f the (far, and rm is called' ts decimation.
I f «/'he- -a great cirplfe perpendic l^ i tn lh ecliptic,
. ■ •.then .jfn is called the /on^r«^ o f the ftar, and m.isicalled
t o f w If'therefore we know tile right, afeenlion
■ 'Am, and declination ms < f an heavenljrbody, we know
its place r ; or ifiive-kn ow its longitude A , and lati-
t n # » . it? glace is known. I f hilt.the ecliptic A('.1‘
% „ V half in P , then C and
P are the bfigii ningsjif.eancer 1 id 1 it 'k o
^‘ .i called points. Two fmall circles, drawn
Ihion h thefe tw|p' pbiiits,up rallek'to he 1 e
c lied r p . tl at pafii i j thro igh <jJ i called the t ipic
of.cancer, s S f t lr a t ■ |h^|igh i f , W 1 n or.)
i2:1^ i n ccnjtinSi «.. with the *fun, when, it
Jf has theffame lon'gifdde; and in the differ
nee o f their.lon'gitudes is -180°. , 4
1 .- 22...The p ^nfioa o f .a b o d y i s it an p h r diliiince
. | i 111 tliL^uJijjwJleSftip b u n tin. ttr th fi'u
-1 23. T he to ajTpeftato.r upon the:tarth.’ s^ffir-
* h tjjr is|tbatgp9ipS^n|the fu i^ t e i^ q k lis w ^ in d& a lr
* r A ’BPSfrUjOTlM'-t^e
; f f a body in the heavens 'be .referred-;to the.hori
201 b ' i vertical circle,, by drawing a vertic ,1- c ircle
through ,it, the diftance o f tha point o f . the lfofizon
irom the nb'r|i; or lonth points, 5 called.its azimuth ;
‘ “ r ta f - . the eall or weft points, is:called
p.^amplitude. iThefe four points are caUdd the cardinal
Jjfj* ? y The t ,u 70 planets are the ft wl ch revol e
about the fun , tl d tlijjp lets i 1 thofe which
revolvf about the prinidry, and thefe. are alfo calle 1 r tel•
lites, or mmmr. ,
' 26- T h e nodts'lre the jo in t s where £ o f the
primary planets cut the ecliptic and where the orbits
o f the ft-piidary plarrl^i c^ 'illy orbits ,of:4heir prima-r
ries. T h a t node'is ''caftcd1 ■ afcending. 'Miere. the planet
pafies fiom the fouth to the n-utli fide o f khe ech’ptic;
■ and.;' is-'marked thus, a ; theiiodjer node is called de-
;/sending, and is mirked thus, fty.
' 27. T he aphe/ton^i that point in the,orbit o f a planet
which i f fm thew fromLthe fun ; and the perihelion is
that point which-is neareft.to the fun. •
28. T h a hpogee is! .that point o f the earth’ s orbit
.which is fur theft, from the- fun, or that point o f the
' moon’s oidut which is fuftBeft from the earth and the
perigee is that .point o f each ts-hit which is nearetl to the
fiiH, or eart%f i
■ 29- The- apfis 'ofrr,ifi~ot'bit.is' either its 1 apogee or-
perigee, aphelion o f petihelipn;. >
’-'j. \s3PJ ’A fidereal day’ is th e ’ interval between two fucceffiye
paflages of,the fame fixed ftar, over the meridian.
Thefe days are; all equal. - ;
3 1- A >%;da y- is.the interval between two fucceffive
pafiages o f the fun over the meridian. . Thefe' days are
o f the fun in
ng n S w s 11 Tf th^-fPr<' we' compare a clock with
% Tun, and adjuft it lo go 24 hours from tlie time the
the
i R W f i r T 5y | | ihdtrcpntintie.to agree'with the
Iun> that is, i't,w'ilfndfecontiniie-:to (how 12 when the fmt
comes to; khe meridian ; as will afterwards more fu lly '
32- ^ « r a /m p o n is the time when the fan, comes to
1? er'^ i-^. 5' mem- -noon is .12 ©tbiock, by 3
watch adjufted to go/24 h o its in a An d '
flu difft 1-ence hetwffe apparent and tnian noon is tha
equation yjjftpm'ei* - '
when it rifes '
and feta at fun n-fing ; and when it nfes or fets at fun
fetting,. .i.tts faid to rife dylftt achromcaliy.
3+- A ftar is faid to rife j&e/iarotfj,, when after having
| f o near to emerges out
?* ,? y s.’ and.juft appears, ip.the teprning j and '
■1.t ? v “ * 0 ,‘.-t Idiacally, when the 1'fiiri' approaches fo
near to it, that ij «S?»j. into the fiin7«
rays, and to beepmi 'ihvifiM'e tu 'the evening
35-‘ ^ f e i s a twelftlfpart o f ’t'heMiameteo'of the
,36.- is a cOlieaion o f ftars contained
within fome affuined'figure,'as a ram, a dragon, an Her.
rt//«yj&c. whole- heatens lsi-hus divided into con-
'fbellations. \
37- I f ™ ;eye be in,the plane o f Meitcle, that circle
appsars as itraigbt lin e th e r e fo r e in the. reprefentation
o f the circles o f a fphere upon a plane' furface, thofe
circles, whofe^ planes pafs through the * eye, are repre-
iM e d by ftraightlin^s.f-^^
3^. Charadtcrsr ’ n(cyl).,fori.;'thc fun, moon, and
planets.
W^fSfel-h&fin’n1- | Mar's
IgMfif fh'e-Moou I ip- Jupieet*
■ g Mercury j -Saturn ’ >
vf ¥ ViKras ~ . • 1 1 j H Georgian,
• © the Earth < | . ? f
u&4 for the days o f the week.
Shnday -- I 11 Thurfday
. -,;j D > Monday 1 j 1 Exiday;'. ,-
d - Tuefda^ f - I . b Saturday,
g Wedneiday. ^tjj j ^
O n - th e 0 0 rm e ' o f . th e Sphere. r
- i f 39- A fpeiftator upon the furfece o f the-earth, conceives
lnmfelf to be placed in the center o f a cohcave
fphere, in which all. the heavenly bodies areifituated -
and,by conftantly obferying them,the perceives that for
khei!gi;eater.,number o f them never change their relative
Situations, each rifing and fitting at the fame interval
W M S K S m S sstim ■ >'8 <: ’o f