26 M E M O IR S of the 
*he Tortiiguez-e gave it that name 5 in 1522 there were 2° weft 
variation^ in 1^75 it was 8^ 00' to the weft; and in 16^1 it was 
caricufly cblervcd to be no lefs than 1 1° to the weft : At St. He- 
lena^ about the year i6oOy the needle declined 8° to the eaft; in 
1^23, it was but 6'^ 00' to the eaft; in 1^77, when Mr. HaUey 
was there, he accurately obferved it on fliore to be o" 40' eaft^ 
and in 1^92 it was found about 1° to the weftward of the north : 
At Cape Comorin in 16 zo, there were 14° 20' wefterly variation ; 
in 1^80, there were 8° 48', but in i588> it was no more tlian 7° 
50' 5 io that here, the needle has returned to the eaft about 7° in 
70 years: From thefe and many other obfervations it is evident, 
that the direction of the needle is in no place fixed and conftant, 
tho' in fome it changes fafter than in others 5 ?ind where for a long 
time it has continued, as it were, unalterable, it is there to be 
vinderftood, that the needle has its greateft deflexion, and is be- 
come ftationary, in order to return, like the fun in the tropics y 
this at prefent, viz. 1(^92, is in the Indian S§a^ about the ifland 
Mauririus^ where is the higheft wefterly variation, and in a 
tract tending fi'om thence to the N. N. W. towards the Red Sea 
and E^^^yft 5 and in all places to the weftward of this tra6t, all 
over Africa and the adjoining leas, the wefterly variation will be 
found to have encreafed 3 and to have decreafed to the eaftward 
thereof, as in the cxsim^h o^ Cape Comorin y all over the JEaJl- 
Jfidies and the ilknds near it : In like manner, in that fpace of 
call:crly variation, which, beginning near St. Helena, is found all 
over fouth America, and which at prefent is higheft about the 
mouth of Rio de la 'Plata, it hath been obferved, that in the 
eaftem parts thereof, the variation of the needle gradually de- 
creafcs , and by analogy we m.ay infer, tho* we have not expe- 
rience enough to afcertain it, that both the eafterly and wefterly 
variations in the 'Pacific Sea, do gradually encreafe and decreale 
after the fame rule: Thefe pho^nomena, being well underftood, 
2nd duly confidered, do fufficiently evince, that the whole mag- 
netical iyftem hath one, or perhaps more motions; that the mov- 
ing force is very great, as extending its effe£is from pole to 
pvole; and that the motion thereof is not per fait iim but by a 
gradual and regular motion: Now, confidering the ftrufture of 
our terraqueous globe, it cannot be well fuppolcd that a very 
great part thereof can move within it, without notably changing 
iis centre of gravity and the equilibrium of its parts, which 
would produce very wonderful eftefls in changing the axis of di- 
urnal rotation, and occaiion ftrange alterations in the furface of 
the lf"^s, by inundations and rccefles thereof, liich as hiftory never 
yet 
