Now although in this rank but two were commonly mentioned by the Ancients, Gilbertus discovereth many more; as Diamonds, Saphyrs, Carbuncles, Iris, Opalls, Amethysts, Beril, Crystal, Bristol-stones, Sulphur, Mastick, hard Wax, hard Rosin, Arsenic, Sal-gemm, Roch-Allum, common Glass, Stibium, or Glass of Antimony. Unto these Cabeus addeth white Wax, Gum Elemi, Gum Guaici, Pix Hispanica, and Gipsum. And unto these we add Gum Anime, Benjamin, Talcum, China-dishes, Sandaraca, Turpentine, Styrax Liquida, and Caranna dried into a hard consistence. And the same attraction we find, not onely in simple bodies, but such as are much compounded; as in the Oxycroceum plaister, and obscurely that ad Herniam, and Gratia Dei; all which smooth and rightly prepared, will discover a sufficient power to stir the Needle, setled freely upon a well-pointed pin; and so as the Electrick may be applied unto it without all disadvantage.
But the attraction of these Electricks we observe to be very different. Resinous or unctuous bodies, and such as will flame, attract most vigorously, and most thereof without frication; as Anime, Benjamin, and most powerfully good hard Wax, which will convert the Needle almost as actively as the Loadstone. And we believe that all or most of this substance if reduced to hardness, tralucency or clearness, would have some attractive quality. But juices concrete, or Gums easily dissolving in water, draw not at all: as Aloe, Opium, Sanguis Draconis, Lacca, Calbanum, Sagapenum. Many stones also both precious and vulgar, although terse and smooth, have not this power attractive: as Emeralds, Pearl, Jaspis, Corneleans, Agathe, Heliotropes, Marble, Alablaster, Touchstone, Flint, and Bezoar. Glass attracts but weakly, though clear; some slick stones and thick Glasses indifferently: Arsenic but weakly, so likewise Glass of Antimony, but Crocus Metallorum not at all. Salts generally but weakly, as Sal Gemma, Allum, and also Talke; nor very discoverably by any frication, but if gently warmed at the fire, and wiped with a dry cloth, they will better discover their Electricities.
No Metal attracts, nor Animal concretion we know, although polite and smooth; as we have made trial in Elks Hoofs, Hawks-Talons, the Sword of a Sword-fish, Tortois-shells, Sea-horse, and Elephants Teeth, in Bones, in Harts-horn, and what is usually conceived Unicorns-horn. No Wood though never so hard and polished, although out of some thereof Electrick bodies proceed; as Ebony, Box, Lignum vitæ, Cedar, etc. And although Jet and Amber be reckoned among Bitumens, yet neither do we find Asphaltus, that is, Bitumens of Judea, nor Sea-cole, nor Camphire, nor Mummia to attract, although we have tried in large and polished pieces. Now this attraction have we tried in straws and paleous bodies, in Needles of Iron, equilibrated, Powders of Wood and Iron, in Gold and Silver foliate. And not only in solid but fluent and liquid bodies, as oyls made both by expression and distillation; in Water, in spirits of Wine, Vitriol and Aquafortis.
But how this attraction is made, is not so easily determined; that 'tis performed by effluviums is plain, and granted by most; for Electricks will not commonly attract, except they grow hot or become perspirable. For if they be foul and obnubilated, it hinders their effluxion; nor if they be covered, though but with Linen or Sarsenet, or if a body be interposed, for that intercepts the effluvium. If also a powerful and broad Electrick of Wax or Anime be held over fine powder, the Atoms or small particles will ascend most numerously unto it; and if the Electrick be held unto the light, it may be observed that many thereof will fly, and be as it were discharged from the Electrick to the distance sometime of two or three inches. Which motion is performed by the breath of the effluvium issuing with agility; for as the Electrick cooleth, the projection of the Atoms ceaseth.
Cabeus his way for attraction in bodies Electrick.
The manner hereof Cabeus wittily attempteth, affirming that this effluvium attenuateth and impelleth the neighbor air, which returning home in a gyration, carrieth with it the obvious bodies unto the Electrick. And this he labours to confirm by experiments; for if the straws be raised by a vigorous Electrick, they do appear to wave and turn in their ascents. If likewise the Electrick be broad, and the straws light and chaffy, and held at a reasonable distance, they will not arise unto the middle, but rather adhere toward the Verge or Borders thereof. And lastly, if many straws be laid together, and a nimble Electrick approach, they will not all arise unto it, but some will commonly start aside, and be whirled a reasonable distance from it. Now that the air impelled returns unto its place in a gyration or whirling, is evident from the Atoms or Motes in the Sun. For when the Sun so enters a hole or window, that by its illumination the Atoms or Motes become perceptible, if then by our breath the air be gently impelled, it may be perceived, that they will circularly return and in a gyration unto their places again.
The way of Sir Kenelm Digby.
Another way of their attraction is also delivered; that is, by a tenuous emanation or continued effluvium, which after some distance retracteth into it self; as is observable in drops of Syrups, Oyl, and seminal Viscosities, which spun at length, retire into their former dimensions. Now these effluviums advancing from the body of the Electrick, in their return do carry back the bodies whereon they have laid hold within the Sphere or Circle of their continuities; and these they do not onely attract, but with their viscous arms hold fast a good while after. And if any shall wonder why these effluviums issuing forth impel and protrude not the straw before they can bring it back, it is because the effluvium passing out in a smaller thred and more enlengthened filament, it stirreth not the bodies interposed, but returning unto its original, falls into a closer substance, and carrieth them back unto it self. And this way of attraction is best received, embraced by Sir Kenelm Digby in his excellent Treaty of bodies, allowed by Des Cartes in his principles of Philosophy, as far and concerneth fat and resinous bodies, and with exception of Glass, whose attraction he also deriveth from the recess of its effluction. And this in some manner the words of Gilbertus will bear: Effluvia illa tenuiora concipiunt & amplectuntur corpora, quibus uniuntur, & electris tanquam extensis brachiis, & ad fontem propinquitate invalescentibus effluviis, deducuntur. And if the ground were true, that the Earth were an Electrick body, and the air but the effluvium thereof, we might have more reason to believe that from this attraction, and by this effluction, bodies tended to the Earth, and could not remain above it.
Our other discourse of Electricks concerneth a general opinion touching Jet and Amber, that they attract all light bodies, except Ocymum or Basil, and such as be dipped in oyl or oyled; and this is urged as high as Theophrastus: but Scaliger acquitteth him; And had this been his assertion, Pliny would probably have taken it up, who herein stands out, and delivereth no more but what is vulgarly known. But Plutarch speaks positively in his Symposiacks, that Amber attracteth all bodies, excepting Basil and oyled substances. With Plutarch consent many Authors both Ancient and Modern; but the most inexcusable are Lemnius and Rueus, whereof the one delivering the nature of Minerals mentioned in Scripture, the infallible fountain of Truth, confirmeth their vertues with erroneous traditions; the other undertaking the occult and hidden Miracles of Nature, accepteth this for one; and endeavoureth to alledge a reason of that which is more then occult, that is, not existent.
Now herein, omitting the authority of others, as the Doctrine of experiment hath informed us, we first affirm, That Amber attracts not Basil, is wholly repugnant unto truth. For if the leaves thereof or dried stalks be stripped into small straws, they arise unto Amber, Wax, and other Electries, no otherwise then those of Wheat and Rye: nor is there any peculiar fatness or singular viscosity in that plant that might cause adhesion, and so prevent its ascension. But that Jet and Amber attract not straws oyled, is in part true and false. For if the straws be much wet or drenched in oyl, true it is that Amber draweth them not; for then the oyl makes the straws to adhere unto the part whereon they are placed, so that they cannot rise unto the Attractor; and this is true, not onely if they be soaked in Oyl, but spirits of Wine or Water. But if we speak of Straws or festucous divisions lightly drawn over with oyl, and so that it causeth no adhesion; or if we conceive an Antipathy between Oyl and Amber, the Doctrine is not true. For Amber will attract straws thus oyled, it will convert the Needles of Dials made either of Brass or Iron, although they be much oyled; for in these Needles consisting free upon their Center, there can be no adhesion. It will likewise attract Oyl it self, and if it approacheth unto a drop thereof, it becometh conical, and ariseth up unto it, for Oyl taketh not away his attraction, although it be rubbed over it. For if you touch a piece of Wax already excitated with common Oyl, it will notwithstanding attract, though not so vigorously as before. But if you moisten the same with any Chymical Oyl, Water, or spirits of Wine, or only breath upon it, it quite omits its attraction, for either its influencies cannot get through, or will not mingle with those substances.