( t76 ) 
By this it appears, that at about 250 or 300 
Leagues Weft from the South-head of Calefornia , 
the Baft Variation diminifties to about 4 of a degree } 
That for 1300 Leagues from thence, the fame Eaf- 
terly Variation gradually encreafes to about 12 de- 
grees, where it becomes greateft. And that at the 
llleof Guam, five hundred Leagues (till more Wefter- 
ly , it is again decreafed to 5 degrees 40 minutes. 
As far as this fingle Inflance can dired us, I am 
inclinable to think, that in all that fpace of Sea which 
lies to the Northwards of our T rack, between Japon 
and Calefornia , there reigns an Eafterly Variation , 
which is ftill greater and greater as the North Lati- 
tude encreafes. But that to the Southward of our 
Track, and efpecially to the Southward of the 
Equinodial, a Wefterly Variation arifes, of no great 
extent or quantity, but which is greateft about 1000 
Leagues Weft from the Coafts of Peru and Chili, 
about the fame Meridians where Capt. Rogers found 
the Eaft Variation fmalleft. This is agreeable to the 
Theory of the Variation I laid down in No. 148. of 
thefe Tranfaclions , about 40 Years fince*, and I then 
exprefly mentioned, in my feventh Remark on the 
Obfervations there cited, that there was undoubtedly 
fuch a Trad of Weft Variation in the Southern 
Parts of the South-Sea , it being the neceftary Con- 
fequence of the Site of the four Magnetical Poles 
there fuppofed, though at that time I wanted Expe- 
riments, to prove it. 
IV. A 
