Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/398

 ed than those of the Magnet, which are more grosse, impure, and rare. From whence it followeth, that the superficies of two Irons that are to touch, by being exquisitely plained, filed, and burnished, do so exactly conjoyn, that all the infinite points of the one meet with the infinite points of the other; so that the filaments, if I may so say, that collegate the two Irons, are many more than those that collegate the Magnet to the Iron, by reason that the substance of the Magnet is more porous, and lesse compact, which maketh that all the points and filaments of the Loadstone do not close with that which it unites unto. In the next place, that the substance of Iron (especially the well refined, as namely, the purest steel) is of parts much more dense, subtil, and pure than the matter of the Loadstone, is seen, in that one may bring its edge to an extraordinary sharpnesse, such as is that of the Rasor, which can never be in any great measure effected in a piece of Magnet. Then, as for the impurity of the Magnet, and its being mixed with other qualities of stone, it is first sensibly discovered by the colour of some little spots, for the most part white; and next by presenting a needle to it, hanging in a thread, which upon those stonynesses cannot find repose, but being attracted by the parts circumfused, seemeth to fly from * those, and to leap upon the Magnet contiguous to them: and as some of those Heterogeneal parts are for their magnitude very visible, so we may believe, that there are others, in great abundance, which, for their smallnesse, are imperceptible, that are disseminated throughout the whole masse. That which I say, (namely, that the multitude of contacts that are made between Iron and Iron, is the cause of the so solid conjunction) is confirmed by an experiment, which is this, that if we present the sharpned point of a needle to the cap of a Magnet, it will stick no faster to it, than to the same stone unarmed: which can proceed from no other cause, than from the equality of the contacts that are both of one sole point. But what then? Let a * Needle be taken and placed upon a Magnet, so that one of its extremities hang somewhat over, and to that present a Nail; to which the Needle will instantly cleave, insomuch that withdrawing the Nail, the Needle will stand in suspense, and with its two ends touching the Magnet and the Iron; and withdrawing the Nail yet a little further, the Needle will forsake the Magnet; provided that the eye of the Needle be towards the Nail, and the point towards the Magnet; but if the eye be towards the Loadstone, in withdrawing the Nail the Needle will cleave to the Magnet; and this, in my judgment, for no other reason, save onely that the Needle, by reason it is bigger towards the eye, toucheth in much more points than its sharp point doth.