MAGNETISM.

0/1

10. To Improve Naturae Magnets.

This may be done by the same methods which are used to com--,llu mcate the virtue to steel-bars or to iron-ores ; but the natural11; 'gnets being generally very short, we can seldom do more thanK<tce them between two strong magnetic bars: however, whenk'oy are 0 f sufficient length, they must be rubbed with other barses tdes those between which they are put; using the same precau-' 0lls as in making artificial magnets. When subjected to tiiistla? 1 ''* 1011 ’ ’*■ "‘H always be proper to remove the armature from

11. To Arm Natural or Artificial Magnets.a T>nd out the poles of the magnet; then shape it in the form of^ I’^aHelopipedon; care must lie taken to let the poles fall about* middle-of two opposite surfaces; in this direction the magnetj u Sht-to have the greatest length possible: for a natural magnetth'^A^'ied much more by having a part cut off from its lengthiii 'l' 1 hieadth. This done, provide two plates of soft iron, equala ,.^'eadth to those surfaces where the poles stand, and projecting: 1 ,* e on one side of the stone, as shewn bv fig. 20. The pro-tli tlons marked DD must be much narrower than the breadth ofl;ir p,atc5 > f ro m a quarter to half an inch being sufficient for theI^S e r magnets, and about one-tenth of an inch for small ones, for'hi ,P Ur P° 3c °f applying to them the surface of the iron F. Thestl ck »ess of the plates CD, CL), must be proportioned to the°* tbe magnet Al) ; and tills proportion cannot easily' bethgjimicd without an actual experiment. The best method,filii ° re ’ is to make them somewhat thick at first, and then keepthem down as long as the power of the magnet increases;

''which the 'filing is to be discontinued. The” armature mayTij e Pt on, either by tying or by a box; which last is preferable,and annature of spherical magnets must be adapted to their shape,")av eac !’. I ar g e enough to cover a quarter of it. In like mannerrnA artificial magnets he armed, and thus a compound magnetI)f A e .Produced much more powerful than any single one. Thusttij' , , n 'ght constructed two very powerful artificial magnets, ortile p lnes 9^ magnetic bars, which are now in the repository offou r ^°yal Society. Each of these consists of 240 bars disposed intji n i eil S.tfis, so as to form a parallelopipedon, each length con-ai>d “8 s 'Nty bars. They are all kept together by iron-braces,c ni'i ' e w I*°l e suspended on pivots, with a wooden pedestal orwhich they may be easily placed in any required po-sh 0e ‘ I* the artificial magnets be made in the shape of a horse-illg s ’ 2, r a semi-circle, they have no occasion for armature, it he-llo*. * lc >cnt to join them either by rivelting or by means of aai 'fi indeed even when straight bars are''used, a compoundCannot llla y * ,e made without armature ; but then as the poles (■ti 0t( j act m the same plain, it is necessary to have two magazines jThe er to give magnetism the more conveniently to other bodies, jthe sam' Ver a magnet is rather augmented by being armed, fori ' s a 1 rRas . on tliat it is increased by a piece of iron affixed to it. :* l cri n ‘ ra js-ring, by which it may be suspended with the iron ad- ;° 0 d, which is the best method for preserving its virtue.

F the Time required by Magnetism to Penetratepp . through Iron .

a ' J1, g placed a bulky piece of iron, suppose one weighing

forty or fittv pounds so near a magnetic needle as to draw it alittle out of its direction, apply one cl' the poles of a strong mag-,net to the other extremity of the iron, and it will require some se-conds before the: needle can be affected by it. The interval isgreater or less according to the size of the iron and the strength ofthe magnet.

13. To Explain the. Appearances of the Dipping-Needle.

Take a globular magnet, or, which is more easily procured, :moblong one, like SN, fig. 2! ; the extremity N of which is thenorth pole, the other extremity S is tlie south pole, and A is itsmiddle or equator; place it horizontally upon a table CD: thentkke another small oblong magnet n .? (viz. a bit of steel-wire, or asmall sewing-needle magnetized) and suspend it by means of a linethread tied to its middle, so as to remain in an horizontal position,when not disturbed by the vicinitv of iron, or other magnet.Now if the same small magnet, being held by the upper part ofti'.e thread, be brought just over the middle of the large magnet,'within two or three inches of it, the former will turn its south poles, towards the north pole, N, of the large magnet; and its northpole il, towards the south pole, S, of the large one. It will befarther observed, that- the small magnet, whilst kept just over themiddle A, of the large one, will remain parallel to it; for sincethe poles of the small magnet are-equally distant from the con-trary poles of the large magnet, they are equally attracted. Butif the small magnet be moved a little nearer to one end than to theother of the large magnet,, then one of its poles, namely, thatwhich is nearest to the contrary pole of the large magnet, will beinclined downwards, and of course the other pole w ill he elevatedabove the horizon. It is evident that this inclination must in-crease according as the small magnet is placed nearer to one of thepoles of the large one, because the attraction of the nearest polewill have more power upon it. If the small magnet be broughtjust opposite to one of the poles of the large magnet, it will turnthe contrary pole towards it, anti will place itself in the samestraight line with the axis of the large magnet. This simple expe-riment will enable the reader to comprehend easily the pheno-mena of the magnetic inclination, or of the dipping-needle, uponthe surface of the earth; for it is only necessary to imagine thatthe earth is a large magnet (as in fact it appears to be), and thatany magnet, or magnetic needle, commonly used, is the smallmagnet employed in the above-mentioned experiment; for, sup-posing that the north pole of the earth is possessed of a south mag-netic polarity, and that the opposite pole is possessed of a northmagnetic polarity, it appears evident, and it is confirmed by ac-tual experience, that when a magnet, or magnetic needle, pro-perly shaped and suspended, is kept near the equator of the earth(since neither the magnetic equator, nor the magnetic poles of theearth, coincide with its real equator and poles), it must remain ina horizontal situation: if the magnet is removed nearer to one ofthe magnetic poles of the earth, it must incline to one of its extre-mities, namely, that which is possessed of the contrary polarity;and this inclination must increase in proportion as the needle re-cedes from the magnetic equator of the earth. Lastly, when theneedle is brought exactly over one of the magnetic poles of theearth, it must stand perpendicular to the horizon of that place,

'k^M GNE TISM, Animal, a sympathy' which "Ail1 con 10 subs,st '"-'tween the magnet and the hurna b° e \-apable« ^quence of which, the former was opposed to be^cHall-A m 8 '"'most every disease. T lus fanciful )- , . fought

C>‘ ,lv ented by Fatter Held, of Vtenna, a

f lal notice ’ ia 177t5 > by M- M e ^m er > ' t he fsna-tip a \ C a '> f ° rtane in France , by imposing his doclunes _ ,, -

."'■‘t r*|* j ]t — '-J j jinj/uuiiig ihj uummvJ v»* •” —

*y‘®tely de v i ' ° us: 'ds pretended mysteries were at length com-Vi’ejv,- elo P.ed by a committee of learned and ingenious men,Ppointed to investigate his pretensions. Although this

successful juggler refused to explain the principles of his art, yetfrom the account of one of his most eminent pupils, it appears, t.That animal magnetism is an universal fluid, pervading the wholecreation, and forming a medium of mutual influence between theplanets; and also between the earth and animal bodies. 2. [t ijthe most subtle fluid in nature, being capable of flux and reflux ;and of receiving, propagating, and continuing', all kinds of mo-tion. 3. That the animal body is subject to the influence of thisfluid by means of the nerves which are immediately affected by it.4. It operates at a distance, without the intervention of any person.-.

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