1000000031

.rollotlce between I<not and knot; thcn it i. plain, tbat

.,hatev<r Durober of fecoDd. the gl.f. conGn. of, and

'WhateJer nu¡nber of

rCel

is contained between knot and

knot; yet the dinaDce ¡¡iveo by th.e log liDe, wil1 b, the

true d¡(bDce in mile• .

12.

Tllougll !he method of me.furing tbe lbip'.

II"'Y

by the log.liDe, defcnbed in the fo<egoing .nicle. , be

«hit

whica is

DOW

commooly made ufe of

yet

Cubo

jell

feveral erron, and chefe very confida.blo. For

firn, lhe halfminu,e or quarler miou,e gl.lfes (by which,

,he log, lbe fhip's w'y is determined) are feldom or

aever true, becau'fe dry and wct weather have a great

.¡n8ucnce

meO!; fo thac at oae

time

~hC'y

may

rUD

more, and at another time (cwer t'ban 30 Cecond" and

ót

is e.idenl ,bal a

(",.11

errdr in ,he glar. will caufe a

fe , fible one io thefhip's way . A¡ain, Ihe chid properly

of ,he log is to h>ve il fwim upright, or perpendicul.r 'o

the horizoD: bUI

this

is to:) olten wa nting iD log5. bec3u(e

(ew reamen examine whethcr

(o ar notoal1d generally

cake il upon trun, being fati,6ed if il weigh a Iiule

n,ore at the nern Iban ,he head: and from Ihis ,here

flows

a.n

error io the rtckoning ; .for

(he 10g daes not

fwim opright, it

will

no'

hold

WOler, nor rema;n f1eady

in ,he .place wbere it i.

hea.ed

, Gnce Ibe le.n cheek io

,he hand iD veering Ihe line will make it come op (e.

nral

feel: tbis repeated will make the errors become

{.Ihom" and perhaps !toots, which, how inGgnihcanl fo–

~.er

tbey ippear, are miles and parl'!! of miles. and amount

to • good deal in a

long

.oyage, Ano,h.r inconvenieneo

.mndiog Ihe 10g.line is itl nretching and Otrinking; for

",hen a ocw line is 6rn yfed, lel il be over fo

\Vell

Orctch·

upoo Ihe deck, and meafured as Irue as pollible, yet

af,er wetting il fhrink. confiderably ; and confeqÍle.ntly

belhebetter .

lfur.ed

of ,h. !hip's way by Ihe log.line, we

ooght to meafure and alter Ihe knolS on il every time be·

fore we ufe it; bUI this i. feldom done oftner Ihan once

a week,

and fometimes

oo~

above

once or

(wice io a

"bole vOY'ge1 alfo \VheD th. Jine i, meafured to i..

ere..en d:gree of lbrinkine, it i. ¡¡enerally Idl ,here;

and when,

much ufe,

comes

C1:retch

again, it is

feldom or Dever mended. Ihough il \ViII n re,ch b'yond

what it

lira

íhrunk . Thtfe, and many other eHOfS

too

"'ell

koo\Vn, att"nding that melhod of meafuring ,he

lbip'. way by Ihe

10g.line.

plainly aoClVe,", for a great

m~Dy

errors commincd

reckonings.

So it

witbed, that e.ithe.r this method were improved or amend·

.d, or Ihat [ame o,her ",elhOO

I,C.

fubj<él to error were

fou.d OUI.

13.

Tbe meridian and prime vertical of aoy place

CUl!

\he horizon in

poinu,

degrees dil1ance

from one

Inolher, viz.

N orlb, Sou/h, J;:aj/.

and

W'j/;

thOl pa"

of the

mtddian

wbic.h

exlfodJ

i,Celf fronl Ihe place

1he

nor/h

poiot of the

horiun

is called the

nor/h lin"

\hat wh;ch tends to ,be

¡'ulh

poi", of ,he horizon, is

~alled

Ihej,ulh

lint;

and ,hal part of Ibe

prilf" vulital

'\Yhieh eX1<nd. tOIVard, Ihe right hand of Ihe obferver.

when his face i. lurned

Ihe

nor/h,

is called the

toj/

¡in, ;

.od laOly, ,hat part of ,he

prime vtr/icl1l

whích

toods 'oIVards lbe leCI hand, i,

c.lled

Ihe

'Wtj/line;

,he

four

poiou in which tbcre

tilles

Oleet (he

horizon,

are

CA/led ,he

tardinal , .inl/.

VOl., 1Il, N° , 84 ,

14.

order to determine the eourfe of Ihe wind.,

and

difco'Ver rheir various alteraríons or fh ift ings ; each

quadraru of the

horizoo interc..epted be[wecn

lhe

rneridiact

aDd prime venical, is ufu.lly di.ided io,o eig,ht e'lllal

parts, and confequeotly the ",hole horizoD into thirty:

two ; and [be line!a drawA. fro.m (he place on \fr'hich the

obferper llaodeth,

tO the

poinu

divj(jon

inhis

horiz.on,

are called rumb Jines, !he four principal of which are

,hofe defcribed in the precediog artide, ..eh of ,hem

having its name

fTom

the

cardinal poiot

in che

horizon

rowards which it

tcnds; (be f ea:

of lhe

rumb liDes

have

the~r

nam!!s

comounded of (he

princi pl l Jines

on each

Gde of them, as in Ih: figure;

(fee Na.iga/ion Pla/er,

No.

J.)

and over wh. ch·(oever of Ihefe lines ,he cour(e

the wind

direBed,

th..

1Vind

ukcs in

Dame ac.

cordingly.

The ionrument commooly ufed

fea for direlliog

the lhip's way, ¡s caBed the mariner's compars; which

conroO. of a cird .nd two boxes. The card i.

cirde

made

tO'

repreCcnt

the horiZon, whofe circumfercnce

'luanered aDd di.ided iOlo degrees, aod alfo in,o thiny–

two

equal

parts, by lines drawn from the ceotte ro

the

feveral poin.. of d¡viGon, caJled poin.. of Ihe compa(.,

On Ihe back fide of Ihe card, and jun below the foutR

.nd north line, is fixed a íleel needl. ",ílh a braf. cupola,

or bollow center in Ihe middle, wllich i. pl.ced upon !he

end

a fine pin, upon which Ihe card may

Gly

lurn

ab""t; ,he o«dle i. touched ",ilh • load none, by whieh

a ceruio

virtue

iofufed

ioto it, that malees

(andeon.

fequently the foo,h and nonh line on ,he card above il)

h. ng nearly io ,he plane of ,he.meridian, bywhich means

'Re fou th and north lin.. on the card produced \Vould

mee' the

~orizon

the

fouth and

north poinu; and con.

[equemly all Ihe olher lines

Ihe card produced

,"ould

mc:et

the

horizon. in

the refpeltive

poinu.

J6.

c.rd

i, reprefen,ed in No.

in \Vhieh you

may ob <lve, Ihallhe capitalle"ers N, S, E,

deoole

the four cardinal poinlS,

"iz.

~he

Nor/h,

S ,be

S. u/h,

Sec.

aod Ihe CmaJl letler

Ggol6e, Ihe word

by:

Ihe

Rhomb,

in the middle between any

t\\',

of the

cardio.ls

are expre/fed by'he letlers deooling thefe cardinal., ,hat

which denotes ,he poiol Iying in Ihe Oleridian having Ihe

precedence; thus lhe

rh om b

in the middJe

bClween

the

north and e.n is exprelfed N E. ",hieh i,

be read

N9T/h. Eojl

;

alCo S

denoles Ihe

So"ih.W,j/

rhomh,

&c.

tbe

otherrhombs

are exprdfed

according

lheí r

(¡.

luation wilh refpeél 'o Ihefe

middle

•

hOOlb., and the

oearen cardinals,

i5 plain

from the

rorcraid

figure.

17.

The card

put

iDIO

round

box, mIde

for

¡t,

h..ing apio ereélt:d in theOlidJle, upon whieh ,he boJlow

centre of lhe needle is 6xed, fo as Ihe card may lie ho–

rizontal,

iimd eafily vibrate

according

tbe

motion of

the

needle: the box is covered over with a

fmooch

gl ...fs , aod

¡s hung in a brafs

hoop

upan two cylindrical pios, diame.

trically oppo(ite to one another; and lhis hoop is hung

within

another brafs c¡rele,

UpOD

two

píos

righc

anglc::s

with

the

former.

There

t\Vo cirdes,

and

che:

box,

41ft

placed in ano,her fquare \Voodeo box, fothal Ihei onermon,

box, and confequently Ihe card, may

k«p

horizon, . 1

whieh way (oever Ihe Ihip heels.

18.

Sioce Inemeridian. do all mee' al the polc., and