And now ‘tis time to advance to one of the main Considerations I had to propose to you concerning the Subject of this Letter, and it is this; That when we are to judge, whether a thing be contrary to Reason or not, there is a great deal of difference, whether we take Reason for the Faculty furnish’d only with its own innate Principle, and such Notions as are generally obvious, (nay, and if you please, with this or that Philosophical Theory;) or for the Faculty illuminated by Divine Revelation, especially that which is contain’d in the Books commonly call’d the Scripture.
To clear and inforce this the better, I shall invite you to take notice with me of the two following particulars.
We may then in the first place consider, That ev’n in things meerly Natural, Men do not think it at all Irrational, to believe divers such things upon extrinsecal Proofs, especially the Testimony of the skilful, as, if it were not for that Testimony, a Man, though born with good parts, and possibly very Learn’d in the Peripatetick or some other particular Philosophy, would look upon as Irrational to be believ’d, and contrary to the Laws of Nature.
Of this I shall give you some Instances in the Phaenomena of the Loadstone, and particularly such as these; That the Loadstone, though (as was above intimated) with one part it will draw, yet with another the same stone will repel the same point of the same excited Needle; and yet at the same time be fit to attract either point of another Needle that never came near a Loadstone before: That though it be the Loadstone that imparts an attractive virtue to the Iron, yet when the Loadstone is cap’d, as they call’d it, and so a piece of Iron (and consequently a distance) is interpos’d betwixt the stone and the weight to be rais’d, it will take up by many times more than if it be it self apply’d immediately thereunto, insomuch that Mersennus relates1, that (if there be no mistake,) he had a Loadstone that of it self would take up but half an Ounce of Iron, which when arm’d (or cap’d) would lift up ten Pounds, which (says he) exceeded the former weight three hundred and twenty times: That a Mariners Needle, being once touch’d with a vigorous Loadstone, will afterwards, when freely poiz’d, turn it self North and South; and if it be by force made to regard the East and West, or any other points of the Compass, as soon as ‘tis left at liberty, ‘twill of its self return to its former Position: That a Loadstone floating on water, will as well come to, and follow a piece of, Iron that is kept from advancing towards it; as, when it self is fix’d, and the Iron at liberty, ‘twill draw that Metal to it: That without any sensible alteration in the Agent or the Patient, the Loadstone will in a trice communicate all its virtues to a piece of Steel, and enable that to communicate them to another piece of the same Metal: That if a Loadstone, having been markt at one end, be cut long-wise according to its Axis, and one Segment be freely suspended over the other, the halves of the markt end, that touch’d one another before, will not now lie together, but the lower will drive away the upper; and that which regarded the North in the markt end of the intire Loadstone, will join with that extreme of the lower half, which in the intire stone regarded the South: That (as appears by this last nam’d Property) there are the same Magnetical Qualities in the separated parts of a Magnet, as in the intire stone; and if it be cut, or even rudely broken into a great many parts or fragments, every one of these portions, though perhaps not so big as a Corn of Wheat, will, if I may so speak, set up for its self, and have its own Northern and Southern Poles, and become a little Magnet, sui juris, or independent upon the stone from which ‘twas sever’d, and from all its other parts: That, if a Loadstone be skilfully made Spherical, this little Magnetick Globe, very fitly by our Gilbert call’d a Terrella, will not only, being freely plac’d, turn North and South, and retain that Position, but have its Poles, its Meridians, its Aequator &c. upon good grounds designable upon it, as they are upon the great Globe of the Earth. And this will hold, whether the Terrella be great or small.
I might not only much encrease the number of these odd Magnetical Phaenomena’s, but add others about other Subjects: But these may suffice to suggest to us this Reflection, That there is no doubt to be made, but that a Man, who never had the opportunity to see or hear of Magnetical Experiments, would look upon these as contrary to the Principles of Nature, and therefore to the Dictates of Reason, as (accordingly) some Learned Aristotelians, to whom I had occasion to propose some of them, rejected them as Incredible. And I doubt not, but I could frame as plausible Arguments from the meer Axioms of Philosophers, and the Doctrine of Philosophick Schools against some Magnetical Phaenomena, which Experience hath satisfi’d me of, as are wont to be drawn from the same Topicks against the Mysterious Articles of Faith; since among the strange Properties of the Loadstone there are some, which are not only admirable and stupendious, but seem repugnant to the Dictates of the received Philosophy and the course of Nature. For, whereas Natural Bodies, how subtile soever, require some particular Dispositions in the Medium through which their Corpuscles are to be diffus’d, or their Actions transmitted, so that Light it self, whether it be a most subtile Body, or a naked Quality, is resisted by all opacous Mediums, and the very effluvia of Amber and other Electricks will not permeate the thinnest Glass, or even a sheet of fine Paper; yet the Loadstone readily performing his Operations through all kind of Mediums, without excepting Glass it self.