The Works of Sir Thomas Browne, Volume 1

by Sir Thomas Browne

The magnetical vertue of the Earth diffused extra se and communicated to bodies adjacent.

Nor is the vigour of this great body included only in its self, or circumferenced by its surface, but diffused at indeterminate distances through the air, water, and all bodies circumjacent. Exciting and impregnating Magnetical bodies within its surface or without it, and performing in a secret and invisible way what we evidently behold effected by the Loadstone. For these effluxions penetrate all bodies, and like the species of visible objects are ever ready in the medium, and lay hold on all bodies proportionate or capable of their action, those bodies likewise being of a congenerous nature, do readily receive the impressions of their motor; and if not fettered by their gravity, conform themselves to situations, wherein they best unite unto their Animator. And this will sufficiently appear from the observations that are to follow, which can no better way be made out then by this we speak of, the Magnetical vigour of the Earth. Now whether these effluviums do flye by striated Atoms and winding particles as Renatus des Cartes conceiveth; or glide by streams attracted from either Pole and Hemisphere of the Earth unto the Equator, as Sir Kenelm Digby excellently declareth, it takes not away this vertue of the Earth, but more distinctly sets down the gests and progress thereof, and are conceits of eminent use to salve Magnetical Phenomena's. Apparencies observations. And as in Astronomy those hypotheses though never so strange are best esteemed which best do salve apparencies; so surely in Philosophy those principles (though seeming monstrous) may with advantage be embraced, which best confirm experiment, and afford the readiest reason of observation.The doctrine of effluxions acknowledged by the Author. And truly the doctrine of effluxions, their penetrating natures, their invisible paths, and insuspected effects, are very considerable; for besides this Magnetical one of the Earth, several effusions there may be from divers other bodies, which invisibly act their parts at any time, and perhaps through any medium; a part of Philosophy but yet in discovery, and will, I fear, prove the last leaf to be turned over in the Book of Nature.

First, Therefore it is true, and confirmable by every experiment, that Steel and good Iron never excited by the Loadstone, discover in themselves a verticity; that is, a directive or polary faculty, whereby, conveniently placed, Point to the North.they do Septentrionate at one extream, and Australize at another.Point to the South. This is manifestable in long and thin plates of Steel perforated in the middle and equilibrated; or by an easier way in long wires equiponderate with untwisted Silk and soft Wax; for in this manner pendulous, they will conform themselves Meridionally, directing one extream unto the North, another to the South. The same is also manifest in Steel wires thrust through little sphears or globes of Cork and floated on the water, or in naked Needles gently let fall thereon; for so disposed they will not rest, until they have found out the Meridian, and as near as they can lye parallel unto the Axis of the Earth: Sometimes the eye, sometimes the point Northward in divers Needles, but the same point always in most: Conforming themselves unto the whole Earth, in the same manner as they do unto every Loadstone. For if a Needle untoucht he hanged above a Loadstone, it will convert into a parallel position thereto; for in this situation it can best receive its verticity and be excited proportionably at both extreams. Now this direction proceeds not primitively from themselves, but is derivative and contracted from the Magnetical effluxions of the Earth; which they have winded in their hammering and formation; or else by long continuance in one position, as we shall declare hereafter.

It is likewise true what is delivered of Irons heated in the fire, that they contract a verticity in their refrigeration; for heated red hot and cooled in the Meridian from North to South, they presently contract a polary power, and being poised in air or water, convert that part unto the North which respected that point in its refrigeration, so that if they had no sensible verticity before, it may be acquired by this way; or if they had any, it might be exchanged by contrary position in the cooling. For by the fire they omit not onely many drossie and scorious parts, but whatsoever they had received either from the Earth or Loadstone; and so being naked and despoiled of all verticity, the Magnetical Atomes invade their bodies with more effect and agility.

Neither is it only true what Gilbertus first observed, that Irons refrigerated North and South acquire a Directive faculty; but if they be cooled upright and perpendicularly, they will also obtain the same. That part which is cooled toward the North on this side the Equator, converting it self unto the North, and attracting the South point of the Needle: the other and highest extream respecting the South, and attracting the Northern, according unto Laws Magnetical: For (what must be observed) contrary Poles or faces attract each other, as the North the South; and the like decline each other, as the North the North. Now on this side of the Equator, that extream which is next the Earth is animated unto the North, and the contrary unto the South; so that in coition it applies it self quite oppositely, the coition or attraction being contrary to the Verticity or Direction. Contrary, If we speak according unto common use, yet alike, if we conceive the vertue of the North Pole to diffuse it self and open at the South, and the South at the North again.

This polarity from refrigeration upon extremity and in defect of a Loadstone might serve to invigorate and touch a Needle any where; and this, allowing variation, is also the readiest way at any season to discover the North or South; Some conceive that the figure of the Tree or Spread-eagle in the root of Brake or Fern stands North and South, but not truly. and surely far more certain then what is affirmed of the grains and circles in trees, or the figure in the root of Fern. For if we erect a red hot wire until it cool, then hang it up with wax and untwisted Silk, where the lower end and that which cooled next the earth doth rest, that is the Northern point; and this we affirm will still be true whether it be cooled in the air or extinguished in water, oyl of Vitriol, Aqua fortis, or Quicksilver. And this is also evidenced in culinary utensils and Irons that often feel the force of fire, as Tongs, Fire-shovels, Prongs, and Andirons; all which acquire a Magnetical and polary condition, and being suspended, convert their lower extreams unto the North; with the same attracting the Southern point of the Needle. For easier experiment, if we place a Needle touched at the foot of Tongs or Andirons, it will obvert or turn aside its lillie or North point, and conform its cuspis or South extream unto the Andiron. The like verticity though more obscurely is also contracted by Bricks and Tiles, as we have made trial in some taken out of the backs of chimneys. Now to contract this Direction, there needs not a total ignition, nor is it necessary the Irons should be red hot all over. For if a wire be heated only at one end, according as that end is cooled upward or downward, it respectively acquires a verticity, as we have declared in wires totally candent. Nor is it absolutely requisite they should be cooled perpendicularly, or strictly lie in the Meridian; for whether they be refrigerated inclinatorily or somewhat Æquinoxially, that is toward the Eastern or Western points; though in a lesser degree, they discover some verticity.

Nor is this onely true in Irons, but in the Loadstone it self. For if a Loadstone be made red hot, it loseth the magnetical vigour it had before in it self, and acquires another from the Earth in its refrigeration; for that part which cooleth toward the Earth will acquire the respect of the North, and attract the Southern point or cuspis of the Needle. The experiment hereof we made in a Loadstone of a parallelogram or long square figure; wherein onely inverting the extreams, as it came out of the fire, we altered the poles or faces thereof at pleasure.

It is also true what is delivered of the Direction and coition of Irons, that they contract a verticity by long and continued position: that is, not onely being placed from North to South, and lying in the Meridian, but respecting the Zenith and perpendicular unto the Center of the Earth; as is manifest in bars of windows, casements, hinges and the like. For if we present the Needle unto their lower extreams, it wheels about and turns its Southern point unto them. The same condition in long time do Bricks contract which are placed in walls, and therefore it may be a fallible way to find out the Meridian by placing the Needle on a wall; for some Bricks therein by a long and continued position, are often magnetically enabled to distract the polarity of the Needle. And therefore those Irons which are said to have been converted into Loadstones; whether they were real conversions, or onely attractive augmentations, might be much promoted by this position: as the Iron cross of an hundred weight upon the Church of St. John in Ariminum,De miner. l. 1. or that Loadston'd Iron of Cæsar Moderatus, set down by Aldrovandus.

Lastly, Irons do manifest a verticity not only upon refrigeration and constant situation, but (what is wonderful and advanceth the magnetical Hypothesis) they evidence the same by meer position according as they are inverted, and their extreams disposed respectively unto the Earth. For if an Iron or Steel not firmly excited, be held perpendicularly or inclinatorily unto the Needle, the lower end thereof will attract the cuspis or Southern point; but if the same extream be inverted and held under the Needle, it will then attract the lilly or Northern point; for by inversion it changeth its direction acquired before, and receiveth a new and Southern polarity from the Earth, as being the upper extream. Now if an Iron be touched before, it varieth not in this manner; for then it admits not this magnetical impression, as being already informed by the Loadstone, and polarily determined by its preaction.

And from these grounds may we best determine why the Northern Pole of the Loadstone attracteth a greater weight than the Southern on this side the Æquator; why the stone is best preserved in a natural and polary situation; and why as Gilbertus observeth, it respecteth that Pole out of the Earth, which it regarded in its Mineral bed and subterraneous position.