(considering the compact hardness of that Substance) can it easily be suppos'd; though the Matter of Fact be too notorious and universal, not to be accounted for.
These Difficulties had wholly made me despond, and I had long since given over an Inquiry I had so little hopes of, when in accidental Discourse, and least expecting it, I stumbl'd on the following Hypothesis; in delivering whereof, if I shall seem to advance any thing that looks like Extravagant or Romantick, the Reader is desir'd to suspend his Censure, till he have consider'd the force and number of the many Arguments which concur to make good so new and so bold a Supposition.
Though it be sufficiently known and allow'd, that the Needles Variation changes, it will be necessary however to give a few Instances, whereby it may appear that this Change is gradual and universal, and the effect of a great and permanent motion: For which take the following Examples.
At London, in the Year 1580, the Variation was observ'd by Mr. Burrows to be 11° 15' East. In Anno 1622, the same was found by Mr. Gunter to be but 6° 0' East. In the Year 1634, Mr. Gellibrand found it 4° 5' East. In 1657, Mr. Bond observ'd that there was no Variation at London. Anno 1672, my self observ'd it 2° 30' to the West; and in the Year 1692, I again found it 6° 00' West. So that in 112 Years the Direction of the Needle has chang'd no less than seventeen Degrees.
At Paris, Orontius Finæus about the Year 1550, did account it about eight or nine Degrees East Variation. Anno 1640, it was found three Degrees East. Anno 1660, there was no Variation there, and Anno 1681, I found it to be 2° 30' to the West.
At Cape d' Agulhas, the most Southerly Promontary of Africa, about the Year 1600, the Needle pointed due North and South without Variation, whence the Portugueze gave its name. Anno 1622, there