Extract of a Letter from Dr. Brook Taylor, F. R. S. to Sir Hans Sloan, Dated 25. June, 1714.Giving an Account of Some Experiments Relating to MagnetismAuthor(s): Brook TaylorSource: Philosophical Transactions (1683-1775), Vol. 31 (1720 - 1721), pp. 204-208Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/103423 .

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E. ExtraS of ffi Ietter gr-own Rtr. 13rook Taylor, F R. S>. to- Sir Hans Stoan, dated 25 . Tunes 67 l 4. Gllnsg a;-Sc.coxnt of lome Exper.,ixlent&

re1-atng ta Magnetif7n

^ Fterc 11auing gisen. an Account of an Experi-

ment made vuith tlle large {agnet in the Re-

pofitory of the Ro.bal Socsery, (whicllw Ex jp-eriment i54 defcribed in PJalofop2. Tra?yRES..No 344. Article 4!)

The Letter goas on with the fame Subjgci as followsO "- If it were kno.wn vwl1at point witlain the Ston-e, and what point in -the Needle are t-lae Centers of tlae Magnetical pover, it svould be eafy to find: the true powers of the Magnet at al-ll the diIlan£es obEerx.redO For want of tha£ Knowledge, I have conaputed the Eurcei from tho -Ce-nter of- -thev Need-1e, andtt°he Ex- tremityN of the LoadIlone, arld find, that at the diC- tance of none Fects tlle Power altersfaRer, tllan as^ the Cubes of the diCancess whereas at the diCances of one and tvve Feer, the Power aIters; nearly as; their Squares. To try wither the Law, by which- tIze Magnetifin alters, could be reduced ato all diS- 2ances too any one certaill power of tIzofe dilltees, I fought thofe points-in the Needle and Stone, WlliClt beillg ufed? as the Center5 of thef power; migllt have thatproperty... Butintllatcafe; I bund.theCerter of the Scone muPc be carried quite out of-its; Figure, to. nake the- diItances- large- enougla for this- pllrpofe Pro1n wencn it fecmus ta app car, that the power of

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( 2°5 ) NIagnetirze does not alter according to any partir.uiar power of the diliances3 but decreates- mucll faRer in the greater dilhncess tllan it does in the near Ql1XS..

This Cceons toyb> confirlned by other Experunents Tmade. The firI} Experiluent was tllusj I made a I!Teedle -; of an Incll longs of very fine-Steel wire (a Foot length of wllich weigh'd but a Grain) wllich 1 le.ngthen'd by llicking a ilight piece of Ru{}1 to lt, fo tllat 1 could obferve tlle Diredion of the Aieedh ill all ltlle trials- witll aXRaGlius oftwo InclaesX Italtead of a Magnet. I ufed. a touch'd N1eedle of Steel wire which I ler on a ?erpend jcular to the Horizontal Plane t made the ObEervations onX by tneans of a Fralne I made to tranrport it from orle placttoianotller > the Nnorth end of the Needle being pIaced dowru wards9 and Inade a lit-tle Iharp, that it might mark tlle Paper it was fet. upon in esrery pofition, by pref- fing the top of the N7eedle g¢ntly utstlll the FingerO The Obfor.srations were luade in this manner ) after liaving takerl notice of tlae natural diredionoftheb fmall CompaEs Needle, I brought the perpendiclllar Needle as ntar to it as I conlreniently £ouldf fettiag it in fucll a manneh tllg a Line from the uprigbt Needle to tlle Center of the Compafs migllt be perw pendicular to the CompaSs Needle. Then obfervillg tlle fame caution (wIlicll waseanvenierle to make the Center of the Cotnpafs fersre. iflicisntly well to be eReeln'd its Center of Povzer) l placed the upright Ntedle at feveral greater di0£ances3 trery tinle luark ing the place in the manner already clefcribed,nd obZ fersring the Vatiation of the Compafs. Bystllis means 1 got a Cllrare pretty regularly and fairlZ drawn lijr points orl the paper. And by- examllll;ng thls

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( 206 ) Curve, compared with the Variations of the Cotnpafs correfponding to its refpedive points7 I found that tlle; Magnetscal power dWecreafed fatier at the greater diIRances than at tlle nearer It is of lit- tle ute to be very particular in the account of the feveral ObCervatlons. I nlall only take notice} that at about two 5nc1les and a quarter diEtance, the Force did not alter fo fi{} as tlle Squares, and at ten Inches dEance Swhere tlle lTariation was one degree only) it alter'd filler than the Cubes, tlle Index or the Pow- er being about 34. The Needle of the CompaSs was fo fllort, rllat to fAppofe its Center of Force to be ei- tller in the middle or at the extremity of it, would not alter -the lndex of the Powers of tlle diIlances 2 r

of an Unite. 1 Inade another- Experiluent to the fame purpofe,

with a CompaMs Needle tnade of a fight piece of Straw,- with a ftnall piece of :Steel-wire-faRen'd to one end of it, -wllich was aIways kept in the fa-1ne pofition, being lDalanced betwee*tl two perpendicular Needless otle of which was moveable, and the o tIzer fix'd. The U;vent was mucll tlle fame as in the former Experiment.

Endeavouring to find the trllt Poles, or Centers of t,he magnetical Power in touch'd Needles, I made a Needle of two Inches long, of the fine Steel-wire, which I touch'd witll the South poillt of a fmall capt LQadRotie, applying tlle point of the Gp only to the Extrelnity of the SNeedle, withollt drawing it along. The Needle fo toucb'd, being Iasd gently on the Surface of a iRagnant WaterX floated. I then -applied to it fucceIElvely-the two ends of a touch'd

Needle,

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( 207 ) Needles -as- near as I couldX without lettmg thE Need-les touch. The refult w-aS, tlaP th8 fiDating Needle wRed under the refpedive Po;les of -tmhe o- ther Ncedle mark'd witll the f£lall Lelters N r a ¢# s. nX s SQ that by one Touch w;ith tlle N .F N S

, s * s L - * _

Loa( ttone, waic 1 gave tlle Needie a- ]!Jortll- :1N s N t N pole at NX where itt -- was touch'd, i£acquir'd N S _$_ three otber Poles) $5

sX whicll we rnsy not N T n S _

tlaertfore tuproperly ca11 its conCequential Poles. HavingzdiCcover'd tllefe conCequential--Poles, I mZade fome other Experiments +n difcover more of the Nature of them as- they are defcribXd in the Selletne annexed. T-he-Needles were all of theIn tsro Inches lotag,tnadeofthe falne firle Steel- wire, and the Letters X, or nX an-d S, or sX derlote the CharaAer ot Nortll or South belonging to tlle points tnark'd; the great Letters fignifyirlg the points the LoadRone was applied to, and the finall Letters Illewing zthe canSeq-luential Poles

Ther@ are two other Experiments defcribed in the falne Letter, relating to the Attradion-*of Fluids,, one of whic!h (t7it that of the iperbaltzs made by t-lle Surf of the Water between two GlaSs-planes ) bbmg already deferibed tn thefe 1ranJaEZions (NoO

336.) we ia11 only tranfcribe r-he Account given g tle other.

I took feveral arery thin pieces of Fi+>boadX and haxring hung stllem fucceElvely in a consrenient lnan- ntr tQ a nSce pair- of ScalesX I tried what Weight

.

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( 208 ) was neceffiryX (over and above their own, after they had been well foak'd in wttater) to ieparate thern at once froln the Stiiface of flagnating tater. found 50 Grains to feparate a Surface of one Inclr fquare i Nand the Weigl1t in- every trial being exadly prKoportional -to theSurfaceX I was encourag'dto tllink tSe Experitnent well lnade. The difiance of the

.. . .. ... ..S, 1 . . . 0 , . ^ z

tunc ler Surtace ot tj ile i foarc troan the :>urtace or t le RaRgnating Water, at tlze time tlley feparatedX I found to be X r o6 0f an Inch i tl10ugtll I believe it would be found greater, if it could be 1neafured at a greater dif- tance trom the Edge of the Board, than I could do it, the Water rilzing a little before it came quite un- der the Edge of the Board.

F I N I S

-

l O ND O N: Printed fer W and g. InX7S, Printers tO the RO7AI

Soviet; at the Princ'sSrms, tha WeIlEnd of S; P4XMht6br4rd.

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