in a Tract tending from thence into the N. N. W. towards the Red-Sea and Egypt . And in all Places to the Westward of this Tract, all over Africa and the Seas adjoining, the West Variation will be found to have encreas'd; and to the Eastwards thereof as in the Example of Cape Comorine , to have decreased, viz. all over the East-Indies , and the Islands near it.
After the like manner in that Space of East Variation, which, beginning near St. Helena, is found all over the South America, and which at present is highest about the Mouth of Rio de la Plata, it has been observ'd, that in the Eastern
Parts thereof, the Variation of the Needle gradually decreases; but whether on the contrary it increases in those places which lie more Westerly than that Tract wherein the highest East Variation is found; or how it may be in the vast Pacifick Sea, we have not Experience enough to ascertain, only we may by Analogy infer, that both the East and West Variations therein do gradually increase and decrease after the same Rule.
These Phænomena being well understood and duly consider'd, do sufficiently evince, That the whole Magnetical System is by one, or perhaps more motions translated, whether Eastwards or Westwards, I shall anon discuss; that this moving thing is very great, as extending its effects from Pole to Pole, and that the motion thereof is not per saltum, but a gradual and regular motion.
Now considering the Structure of our Terraqueous Globe, it cannot be well suppos'd that a very great part thereof can move within it, without notably changing its Center of Gravity and the Equilibre of its Parts, which would produce very wonderful Effects in changing the Axis of diurnal Rotation, and occasion strange alteration in the Seas Surface, by Inundations and Recesses thereof, such as History never yet mention'd. Besides, the solid parts of the Earth are not to be granted permeably by any other than fluid Substances,