Experiments, notes, &c. about the mechanical origine or production of divers particular qualities among which is inferred a discourse of the imperfection of the chymist's doctrine of qualities : together with some reflections upon the hypothesis of alcali and acidum / by the Honourable Robert Boyle ...

EXPER. XIII.

AS for the Abolition of the Magneti∣cal vertue in a body endow'd with it, it may be made without destroying the Substantial or the Essential Form of the body, and without sensibly adding, dimi∣nishing, or altering any thing in reference to the Salt, Sulphur and Mercury, which Chymists presume Iron and Steel, as well as other mixt bodies, to be composed of. For it has been sometimes observed, that the bare continuance of a Loadstone it self in a contrary position to that, which, when freely placed, it seems to effect, has either corrupted or sensibly lessened the vertue of it. What I formerly observed to this purpose, I elsewhere relate, and since that having a Loadstone, whose vi∣gor was look'd upon by skilful persons as very extraordinary, and which, whilst it was in an Artificers hand, was therefore held at a high rate, I was careful, being

by some occasions call'd out of London, to lock it up, with some other rarities, in a Cabinet, whereof I took the key along with me, and still kept it in my own Pocket. But my stay abroad proving much longer than I expected, when, being re∣turned to London, I had occasion to make use of this Loadstone for an Experiment, I found it indeed where I left it, but so exceedingly decayed, as to its attractive power, which I had formerly examin'd by weight, by having lain almost a year in an inconvenient posture, that if it had not been for the circumstances newly related, I should have concluded that some body had purposely got it out in my absence, and spoiled it by help of the fire, the ver∣tue being so much impaired, that I cared little to employ it any more about consi∣derable Experiments. And this corruption of the Magnetical vertue, which may in tract of time be made in a Loadstone it self, may in a trice be made by the help of that Stone in an excited Needle. For 'tis observ'd by Magnetical Writers, and my own Trials purposely made have assured me of it, that a well pois'd Needle, being by the touch of a good Loadstone, excited and brought to turn one of its ends to the North and the

other to the South, it may by a contrary touch of the same Loadstone be deprived of the faculty it had of directing its de∣terminate extreams to determinate Poles. Nay, by another touch (or the same, and even without immediate Contact, if the Magnet be vigorous enough) the Needle may presently have its direction so chan∣ged, that the end, which formerly poin∣ted to the North pole, shall now regard the South, and the other end shall instead of the Southern, respect the Northen pole.

Notes

• EXPER. XIV.