(455) 
The Particulars tliemfelves follow : 
I • To obf wve th e T^eclinatms andVariaims of 
the^mpajs or ^h(eedk from the Meridian 
exaBly , in as many T laces as they can^ and 
in the fame T lace every fever al Voyage. 
AT La^d^ where by the help of good fixt Dials 5 and other fit 
Inftruments , the precife Meridian of the place may be 
known , it is eafie to find the Variation of the Needle^ divers 
wayes: As, by applying of the Needle, cJ^r. toth^ Shadow of a. 
rhred hanging perpendicular , when the Sun is in t\\Q Meridian % 
or to the Meridian Line 5 or the Side of a fixt Horizontal 
Dial y drc. 
But at Sea , in regard the Meridian is not fo eafie to be found to 
any tolerable exadnefs 5 to know the Variation of the Needle y is 
much more laborious and difficult. The Height of the Pole ^ and 
the Suns Beclinatton being known , a large Ring-Dial , truly 
wrought , having a Box with a Compafs or Needle fixt to its Me- 
ridian below J may go as near as any other Inftrument , to /hew the 
Variation required. For, when it is fet to the jail hour and minute 
of the day , the Meridian of it fl:ands juft in its due place 5 and fo 
fliews bow far the Needle varies from it , as exadly as the largenefs 
of the Card will permit. 
Eut becaufe thefe Dials are fo rarely juftj &c, though they may 
be ufed and taken noticeof, yet are they not to be relied on. The 
thing therefore is to be performed;, as fdlloweth : 
Vindomth^ Suns Az^imuthal Difance from the Meridian ^ fome 
hours before^ or after noon , and then its Magnetical Azimuth^ 
or Diftance from the Mm^i^;^ pointed at hy tht Needle^ and the 
Difference of thefe two Diflances , is the Variation of the 
Needle. 
Tofind the Suns true Azimuth^ or by how many Degrees ^&c. 
ok thtHorizon\il%d^i9imtixomx.\\Q Meridian I its Declination^ its 
Altitude i zndthQ Elevation of tfeTok , muftall three be known, 
L 1 1 2 For 
I 
