An BxtraSi 
Ofa Letter, mitten by D. B. to the Publifier, concerning the f re* 
fent Declination of the Magnetick Needle, and the Tydes , 
May 23. 166$. 
Sir., I here prefent you with a Scheme of the MagneticalVari- 
atiom^lt was fent me by Gapt. Samuel Sturmy, an experi- 
enced Seaman, and a Commander of a Merchant Ship for many 
years 5 who (as he affures 
observed June 13. 166$. 
Sun's Obferv'd 
Altitude. I 
Magne- 
tical 
Azimuth. 
Suns [Variat. 
true jWefter- 
Azimuth.! ly. 
Gr. 
44 
n 
M.Gr. M.,Gr. M.G. M. 
23 
0070 
c»78 
381 22 
20 103 
oc|8s 
26 
I 
00 
93 
I 
— 4 i 
00 
101 
23 
r 
23! 
1 
— 1> 
me) took the Obfervati 
ons himfelfin theprefence 
of Mr. Staynredy an antient 
Mathematician, & others, 
in Row nham-Meadowes by 
the water-fide, in fome 
fuch approach, I think, to 
Rriftol , as Lime*houfe or 
the Fields ad joyning are to 
London. This (as the 
"Table fhews ) was taken 
June 15.1666. They ob- 
served again in the fame day of the next year, 'viz. June 13. 
16.67$ and then they found the Variation increaTd about 6, mi- 
nutes Wefierly, 
Now he promifeth to take the Obfet vations in the fame Com- 
pany and Place, on the i$thl June next following, with a Qua- 
drant of 6 foot radius .> accurately divided into minutes, and with 
a very good Needle about 8. inches long -, and he doubts not, 
hut the Obfervations fhall be as exaftly .made, as can be done by 
any Men in any place of the World. 
He adds, that he has found in feveral places or Meridians, upon 
his own Obfervations, from 2. min, to 7. minuts fome difference,, 
In this 7 able he notes thegreateft diftance or difference to be 14. 
minutes > and fo taking the mean for the true Variation^ he con- 
cludes it then and there to be juft i # deg. 27. min. triz>. June 13. 
1 666-; 
The fame perfon promifeth an exa£i accompt concerning, 
Tydes 
