1000000030

cireJe; whieh done, turn the globc wenlVaro umil ' t5

degrees of Ihc

c~lIawr

pa(s IInuer Ihe hralcn me,idiall,

ami Ihen Ihe l;uur·i'IJcx lVill be at I (Ior thc

(UII

mO.es

15 dewe,s el'ery hOllr) and the lirlllllcridi.1II "di

ellt the hOl ;zuu in the nUlllber of de::rees (roOl Ihe

nlll'lh point,

lil.lt

is dillant froOl

XII.

T urn

UII,

uIHil olh, r 15 ,kgrees 01 Ihe

e~lIalor

pArS IInder Ihe hra·

len Ill<l Hhan,

,"d

the hOllr·inJex will dieo be at

!l,

.nd

Ihe firlllllcridian wi ll CUl Ihe horizun in Ihe nlllllher o(

oeg,ces Ih.1I 1l is. din.111I from

XII :

and (o, by nlAh ing

5Jegrccs u( the

e~u'uor

pa(s under Ihe hra(en men,han

for el'C, yhour, Ihe litll OIeriJi.,n of Ihe globe \ViII CIlI Ihe

horilon in Ihe dill.nces 01' alllhe hOllrs (rom XII 10

VI,

which is dillanl jun 90 deRrces; and Ihen yuu needgo no

fmherJonhedillaneeso(

XI, X, IX, VIII,

VIl ,

and

VI ,

in Ihe lorenoon, are the famefrom

Xli,

as Ihe dif!ances of

11, Ill,

m[,

and

V[,

in Ihe a(mnoon: aud

Ih& hour·lines conlinued Ihrollgh Ihe center, wil! give

Ihe cppofile hour·lines on Ihe olher hal( o( Ihe di.1.

Tbus, 10 m, ke a horizom.1 dial (or the I.titude of

London, whieh is 51 {

de~rees

north, elevate Ihe oonh

pole of the globe 51

degrees .bove the nonh poinl o(

Ibe horizon, aod theo tum Ihe globe, unlil the firU me·

ridilo (which is Ibat 01' LooJon 00 Ihe EogliOI ler·

renrial globe) eUls Ihe nonh poiot of Ihe horizoo, aud

fet Ihe hour·index

XII

nooo.

TOen luming Ihe globe wellward umil the iodex poinlS

fueceffirelyto [,

11,

111,

IlII, V,

aod

VI,

io Ihe afler·

0000, Or umil 15, 30, 45, 60, 75, and 90 degrees of

the equator pafs under Ihe braCeo meridian, you will fiod

Ihat the firl! meridian of the globe CUIS Ihe horizon io Ihe

following oumbers of degrees from Ihe oorth towards Ihe

eall,

viz.

li ,

4~,

38T'T' 5

!{,

'r,

.aod 90; which

are tite re(peaive dillaom of the aboye hours froOl

Xli

upon the plane of the horizoo.

To trans(er thefe, and the rel! of the hours, 10 a ho·

rizontal plane, draw the parallel right lines

a e

and

d b,

(P~Rle

LXIX. fig.3.) upoo that plane, as far fromeachother

equal to Ihe imended tlllcknefs of the gnomoo or

nl.le

of the dial, and the fpace included betweco Ihem

will be Ihe meridiao or twclve o'dock line on Ihe di.1.

~r~(s

tbis meridian

right angles with the

'fix

o'dock

!lDe

Ii h,

and fening one fool of your compalfcs io the

Inter(eaion

as a cemer, de(eribc Ihe quadrant

with

aoy.conveniem radius or opening of the compafles: then,

fetung one foot in the inlerfeaion

as a eentcr, \Vith

the (.me radius de(cribe Ihe quad ranl

[J.,

and divide

eaeh quadraol imo 90

e~ual

pans or degrecs, as in the

figure.

Becaufe the hour·lines are lefs dillant (rom each olher

abouloooo, thao in . ny other pan 01' the J",I, it is bdl

lOhave the ccnters of tbefe

~lIaJnllHS

al a little Jillance

from the eemer of Ihe dial 'planc, on the fide oppofi lc

XlI,

in order 10

enlarg~

the hour dill.lI1ees tllere·

aboulS, uoder Ihe (ame aogles 00 the pl,ne. T hus, Ihe

center

tbe plane is

bUI Ihe centers of Ihe

~U.I·

d..ou are

and

Laya rlller Over the poiO!

(and kLeping it Ihere ("r

Ihe ceoter of all the aflelnoon Itour. inlite '1":IIlr.u1I

iJ)

draIV IhehOllr·)ine uf 1 througlt II

id"2rcL~

in thc 'IUA '

drant; the huur·lino uf

Il ,

through 2'1 : dl'gll'LS; uf

. Il. No..

¡j.

[1 1, Ihrol'r.h

3S ,',.

dl'grees ;

fllI,

Ihroll~h

53:;

¡rd

lhroll¡:h 71,', : _ud

b~c.l\I(e

Ihe li:n rif, s ab')llt fWlr in

the IIII11'UlIlg. on the lungdl d.,y' al Lundun, e'lOli lile

d,e hour· lill" of 1111 alld

in Ihc a(ternoon t¡uuugh

the " 'nter

the oppofite fide of Ihe di.I.--Thil done.

I.ly

Ihe ruler

Ihe cellta

of Ihe

~uadranl ' .~'

and

thruu¡:h the like divifionl ur

degrr.es

o( that

~ uadl

ant,

viz.

Il j,

24.1 1

33,-\-, 53},

antl,t,'r'

d rawth ~

fop>

00011 Ituur lin,s uf

XI,

[X,

VIII , and VII; _nd be·

caufe the lun (ets not befure eight in Ihe evelling

th.:

IOllgell d.I)'S, cuotinue the hour·liocs o(

VII

and \'111 in

Ih~

(u'CnIJOII, Ihrough Ihe cemer

VIl

.n.1 VIII ill

th~

aftemoon; ami all the hour lincs will be finil1' ed 00

this dial; 10 which the hours Olay be fet, as io the

figu re.

Laflly, IhfGugh 51.} degrees of eilher quadrant, ao,1

froOl ilS center, draw the Iight line

for the hypo·

thenu(e or axis of the gnoOlon

aod from

lel fall

the perpeodicular

upoo the meriJian line

and

therc will be a

i,ngle OIdde,

\Vho(~

liJes are

g, g

and

lf a

pl.te

limilar

this triarlgle be m,de as

lhiek as the d,llaoee bellVeen the lines

a e

and

h d,

aod

fet uprighl

b~tween

them, touching at

aoo

its hl'po·

lheoufe

\ViII be parallcl

the axis of the \VodJ,

when tlle dial is Huly fel; aod \ViII can a Ol.dow 00

the hOllr of the day.

T he tl'ouble of dividing Ihe tlVO qua¿raols

may be faved, if you have

fcale lVilh a line of ehordf.

upoo it, fllch as Iltat on the top of Pl.lIe LXX.: ("r if

you eXlend Ihe comp.lfes (rom 010 60degrecs of the lint

of chords, and lVith thal eXtenl, as a rAJius, defe,ibe

the t\VO quadrants upon lheir re(peaive centers, the a·

bo"e Jillaom may be taken \Vith the compalfes upoo

th~

Ime,

and (et ofT "pon the

~uadranlS.

To waie nn ma "irea [outh dial,

Plate LX[X. fig. 4'

Elevate the pole to the eo·latitude o( )'our place, Hn I

pro.:eed in all refpeéls as abo"e taughl (or the horizoplal

dial, from

in the .morning tO

in the afternoJo,

only the hours mun be

reverl~d,

as in the figure ; and

Ihe hypothenufe

Gf the gnoOlon

mulllllAke ar

aogle with the

dial.pl.oe

equal tO lhe co·IAlituoe of Ihe

plm. As the (un can flline no longer on this Ji,1 thln

fwm fix in the OIorniog unlil fix in the eveniog. there is

no oecauoo for having any more lhao l\Velve hours upon

it.

",o~e

011

erea dial, dulilli."g [rol/'

In:

¡¡lIlh lo·

'WordJ

ti"

elljl

,vrJI.

Elevate tite role to tite IJlilllde

of your place, anJ (crelV the qu.,dr.lnl of a"itude

Ihe

zenllh . Then, if you !' dial oedines 10wArJs the

e.dt

(\Vhieh \Ve fllall fuppofe it 10 Jo al pr&m) eouot in the

horilon the degrecs of ,kclioation, 1'1 0111 Ihe call poillt 10·

w.lrds the nonh, and bring the 10'l'er end of the 'luaJr,nt

thal degree of Jeclin.tlion at whieh the rcckoning ends.

T his done, bring auy

Pdllicul.lr

OICf1di.111 oí y"'''

~Iobc

(as luppok

11t~

lirllllleridian) direitly under Ihe s

,a.lu:

!·

ted edge of the uppcr pHI 01the br.llcnlllcri.!i,", .Ind fel

the hum In,kx

XII

.11 1100n. 1'hcu, ke<ping the

~U.I ·

,ham 01' ,¡( Iitude at the ,k¿ree o( dcdlll.ltion in 11t,·h," i·

Z'ln.

turu the

gl"J,c

eall

\V.II

(lO

iti .I\is, a"d "bLTI <Ihe

,k~recs

Cllt

dll' lidl uH"

idi.ln

in 1"<

'1".,dr.1.1I~,

. hi·

tudé

(~íJ¡!I\tl:d

(1 0m

du.:

l~·.\ilh )

.IS

dh:

hour

II.III! \

ú'Illl'S