( 03 y 
frieretov the whole nauft neeeflarily move together. 
So then the^External Parts of the Globe may well 
be reckoned as the Shell, and the Internal as a NncUtts 
or inner Globe included within ours, with a fluid me- 
dium between Which having the fame common Cen- 
tre and Axis of diurnal Rotation, may turn about with 
one Earth each 24 hours , only this outer Sphere ha- 
ving its turbinating Motion fome fmall matter, either 
fwifter or flower than the internal Ball. And a very 
minute difference in length of time, by many repetiti- 
ons becoming (enfible 5 the Internal parts will by de- 
grees recede from the External, and not keeping pace 
with one another will appear. gradually to more either 
Eaftwards or Weft wards by the difference of their Mo- 
lions. 
Now fuppofing fuch an Internal Sphere having fuch a 
Motion, we fhall folve the two great difficulties we 
encountred in my former Hypothecs. For if this ex- 
terior Shell o£Earth be a Magnet having its Poles ?t a 
diflfance from the Poles of Diurnal Rotation 5 and if 
the Internal Nucleus be like wife a Magnet, having its 
Poles in two other places diftant aifo from the Axis, 
and thefe latter by a gradual and flow Motion change 
their place in refped of the External 5 we may then 
give a reafonable account of the four Magnetical Poles 
I prefume to have demonftrated in No. 148. of thefe 
Tranfa&ions* as likewife of the changes of the Nee- 
dles Variations, which till now hath been unattem- 
pted. 
The Period of this Motion being wonderful great, 
and there being hardly an hundred Years fince thefe 
Variations have been duly obferved, it will be very 
hard to bring this Hypothefis to a Calculus, efpecialljr 
fince, tho the Variations do increafe and decreafe regu- 
larly in the fame place, yet in differing -places, at no 
great dfftance, there are found fuch cafual Changes 
thereof 
