hath no bottom; and Thales Milesius, to make it swim in water.9

Nor is the vigour of this great body included only in itself, or circumferenced by its surface, but diffused at indetermi nate 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, than by this we speak of, the magnetical vigour of the earth. Now, whether these effluviums do fly 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 equa tor, as Sir Kenelm Digby excellently declareth, it takes not away2 this virtue of the earth; but more distinctly sets down the gests and progress thereof, and are conceits of emi

9 water.] The first edition continues thus :- "Now whether the earth stand still, or moveth circularly, we may concede this magnetical stability for although it move, in that conversion the poles and centre may still remain the same, as is conceived in the magnetical bodies of heaven, especially Jupiter and the sun; which, according to Galileus, Kepler, and Fabricius, are observed to have dinetical motions and certain revolutions about their proper centres; and though the one in about the space of ten days, the other in less than one, accomplish this revolution, yet do they observe a constant habitude unto their poles, and firme themselves thereon in their gyration."

1 the magnetical vigour of the earth.] Having stated, in the preceding note, in what sense we are not to regard the earth as a magnet, we may now admit that in the sense of a body permeated by the magnetic fluid (whatever that may be) the earth may be regarded complex magnet, or rather as a collection of substances, many of which, under certain circumstances, are susceptible of the magnetic influence, and display accordingly magnetic phenomena.-Br.

as a great

2 it takes not away.] Read, "they take not away, &c." viz. "Neither of these opinions takes away, &c."—Wr.

nent use to salve magnetical phenomena. And, as in astronomy, those hypotheses (though never so strange) are best esteemed which best do salve appearances, 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. And truly the doctrine of effluxions,3 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, they do septentrionate* at one extreme, and australiset at another. 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

* Point to the north.

+ Point to the south.

3 And truly the doctrine of effluxions.] The remarks in the passage commencing with these words may be considered to have been made good by the discoveries of the present century, if we regard the notion of "effluxions" to result from an obscure perception of the existence and functions of those ethereal fluids, to the motions of which the united results of modern science lead us to attribute the phenomena of heat, light, electricity, magnetism, &c. It is requisite, however, to observe, that what Browne, as well as some of his predecessors and contemporaries, appears to have supposed to consist of subtle emanations from grosser bodies, must be regarded contrariwise, agreeably to the most profound researches of our time, as the principles from which all ordinary ponderable matter derives its activity-from which it takes all its force and energy.—Br.

* steel and good iron, &c.] This, in the sense in which the author intends us to understand it, is an error; unmagnetized iron or steel has no directive power; the experiments apparently alluded to must have been performed with steel plates, wires, and needles, which had, in reality, become magnetic, although they might not have been actually "excited by the loadstone." As an observation that the magnetic virtue is possessed by bodies which have not been so excited, it is quite worthy of Browne.-Br.

and soft wax; for, in this manner pendulous, they will conform themselves meridionally, directing one extreme unto the north, another to the south. The same is also manifested in steel wires thrust through little spheres 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, lie 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 untouched be 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 extremes. 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 ;5

5 They contract a verticity, &c.] The statements here made, to the end of the period, are probably true, provided the cooling takes place in a direction corresponding, or nearly corresponding, to that of the dip; but the extent to which they are true, so far as modern experiments afford us the means of verifying them, may be best seen, perhaps, by comparing them with the following observations made by Mr. Barlow, and published in the Encyclopædia Metropolitana, Treatise on Magnetism, § v. 38, 39 :-For certain purposes of research, which it is unnecessary here to state, Mr. Barlow heated in a furnace a bar of soft iron and a bar of cast-iron, nearly of equal dimensions, placing them in an inclined position, in the direction of the dip of the needle, and ascertaining their attractive effect upon the horizontal or common magnetic needle previously to the application of heat. As soon as the bars arrived at a high blood-red heat, they began to exercise an increased power of attraction upon the needle, and in a minute or two this attained its maximum, which was far greater than the attractive power of the bars when cold; the deviation produced by one of them being in the latter case 24° 20′, but in the former, 78° 30'. In the course of these experiments the following facts were observed, which bear directly upon the passage of our author now before us :—“ It should be observed here, that the great attraction produced by the heat did not subside with it, provided the bar remained in its place undis

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 amit not only many drossy 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 atoms invade their bodies with more effect and agility."

turbed; for after some days it was found that the power of the bar continued just the same as at the time of making the experiment when it had not been displaced; but then the bar upon trial was always found to possess a certain degree of fixed magnetism, its other extremity producing an opposite effect upon the needle; but if the bar was inverted, while it retained any visible colour from the heat, both ends produced exactly the same deflection: as to the magnetic effect to which we have alluded above, it was lost, or at least a great part of it, after leaving the bar for some time horizontal, or, after its being thrown about with other pieces of iron.”—Br.

may

For by the fire they amit, &c. whatsoever they had received either from the earth or loadstone; and so, &c.] This statement is true in itself, but unless viewed in connexion with other facts produce an erroneous impression upon the mind. Mr. Barlow's experiments have also elucidated this subject; his results on which will be appropriately introduced by an historical notice of it, derived from the Treatise on Magnetism cited in the preceding note, from which the comparative amount and nature of our author's knowledge respecting it may be inferred, by contrasting it with his own remarks. "The effect of temperature, in changing and destroying the magnetic power of iron bodies had been long imperfectly known, but it had never been satisfactorily established prior to Mr. Barlow's experiments. It is, for example, stated in Newton's Optics, that red-hot iron has no magnetic property, while Father Kircher asserts, that the magnet will attract red-hot iron as well as cold; Mr. Cavallo again found, that although iron at a red heat had a greater power over the magnet than when cold, yet at the white heat it had less; but he was not aware that it was entirely lost at a white heat."-(Encyc. Metrop. Magnetism, § vi. 41.) The last-mentioned fact, viz. that the magnetic action of iron is destroyed by a white heat, was ascertained by Mr. Barlow in the experiments already noticed, and he observed, on the same occasion, an extraordinary phænomenon, the consideration of which will explain some of the apparently contradictory facts which are related by our author in this chapter. It is, that "after the iron loses its entire power of attraction at the white heat, it acquires, as that colour subsides into the bright red and red, an attractive power, the reverse of what it had

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 towards the north, on this side of the equator, converting itself unto the north, and attracting the south point of the needle; the other and highest extreme respecting the south, and attracting the northern, according unto the 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 sides of the equator, that extreme which is next the earth is animated unto the north, and the contrary unto the south, so that in coition it applies itself 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 virtue of the north pole to diffuse itself, 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; and surely far more certain than what is affirmed of the been when cold; so that if the bar and needle are so situated that the north end [of the needle] is attracted when the iron is cold, the south end will be attracted during the above interval," that is, while it is passing through the high temperatures indicated by the shades of colour just mentioned; after which the usual attractive power again takes place in the increased degree stated in the preceding note.—Br.

7 but if they be cooled upright, &c.] This statement is quite accurate; and, in fact, a nearly perpendicular position is more favourable to the reception of magnetism by the iron than the horizontal. The effect depends upon the suitable position of the iron for receiving and retaining a portion of the magnetism of the earth, and the position in which the greatest effect is exerted by the earth's magnetism is when the iron is placed in the position of the dipping needle; that is, inclined to the magnetic north at an angle (in these latitudes, and at the present time) of about 693 degrees with the horizon. The subject is resumed, and with equal correctness, towards the end of the next paragraph, which has evidently been written from experiment. Both are replete with just representations of the facts.-Br.

Now on this side, &c.] Itt is certainly knowne that beyond the line the needle keeps his posture to the north, as truly as att the first setting out of England.-Wr.