A Letter from Stephen Gray, F. R. S. to Dr. Mortimer, Secr. R. S. Containing SomeExperiments Relating to ElectricityAuthor(s): Stephen GraySource: Philosophical Transactions (1683-1775), Vol. 39 (1735 - 1736), pp. 166-170Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/103991 .

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( 166 )

VJ. X Letter frotn Stephen GrayX F: t. S. to Dr. MortimerX Secr. 4 S, co?tvining Jome Experiments relating to ElecAricitar.

T fl E following Lines contain an accollnt of

1 uZhat Eledtrical E:xperiments I llave made fince

tllofe I laR communicated to tlle Society which xvas in Febraar.y laR.

Febr?zary the 1 8th I tried what EfEed:t would be produced on feveral Sorts of Wood with reSpeEt to

tlae luminous Part of Eledricity : the Wood svas made into Rods of the Eame Form with tllofe Iroll Ones mentioned in nny former Letter upon this Subjed ; the Woods made uSe of were Fir, A{h and

Holly, theSe being fucceEvely difipofed upon Elec_

trick liodies, afrcr the fame nzaI:ner as the Iron Rods

llal l)een, the Tube beingapplied tO otze End, there

appeared a Light on itX but not with fo great a

Force, nor did the Light extend to fo great a length ;

ntitlzer svas tlle Form of it Conical, but rather Cy_

lindrical; btlt the Extremity of it Seemed to confiR of a {hort Frltnge of Light ; when the Light, that was

given to the Rod by the application of the Tube, did ceaKe, Upon a motion of my Hand tov; ards the

Poirlt of tlle Rods the Light came out agaill, as has

been mentioned of the lron Rods; but when the Harld or Firger uas 11eId near tlae Point of theSe xveoden Rods, there was no pricking or puShing of

the Finger felt, as wherlthe IronRods were tmade uSe

of I had fome of thefe Rods male much bigger at one

J£nd thaIl tbe others and now applyil}g my Finger tQ

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( 167 ) to the larger End, there nor only appeared a Ligllt, but the Finger was pufhed, more eSpecially whetl the Holly Rod was nzade uSe of, and the Cheak wwas a little prick'dX but tlle Smart xlras rlot near fo greats as when the Iroxl Rods were uSed; the great EI<d of the Rod was pornted with a much larger lNngie then the leScr otle, yet there was very littleX if a- ny diSerences in the fbrm, or bigneSs of the Light tllat proceeded from either Endv

Having procured me tro pair of Litles ulade of Worlled Yarn, one of them of a Mazareen Blexxt tbe other of a Scarlet Colour; orl tlle 3d of Xfrit J SuEpended the Boy firft on the Blexv Lilacs> avld found that all the Ededrs were the lame7 as sYhen 1ic xnras fufipended on Lilles of iE3lexv Silk. I then fuli pended lzim upon the Scarlet Lines, 1)ut now though the Tube were as well excited, alld the Exw periment often repeated, yet tllere xvas no PJffied produced on hinl, either of attradion of a pendulou.< W^hread, llor of prick;ng or burning, by applying one's Hand near him; I tllen laid one of the trQz

Reds Srft upon the Blew Lines, and all the fame Effieds srere exhibited, as when the lame Rod had been laid on Silk Lines of that Colour; but upon laying the fame Rod *pon the Scarler Lines, no slanner of attrs&rion, eic. was perceived.

In the PhiloNophical Tranfadions, l@>nb. 422*

1 gave an LAccount of tbe Experiments 1 rxlade UpOtl

the communtcative Ejledricity of MsTater) and tbat Water is attrad;ted bytlle Tube, together xzrith feve ral remarkable CircumRances Witll ^71lich this ato trad;tion is attended; bllt I have now found, that ^rhen tlae Stand with thofe little ISQIY CUPS there

Y tnci.4%

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( 168 3 mennoned, be fet upon any Eledrick Body, thx tame Phznomena are produced, not only by hold- ing the Tube near the Water, but when that is re- moved, and the Tip of ehe Finger placed over theWater, vi=. tire is a littleHill, or })rotubev rance of NV<ater of a Conical Form from the Ver- tex of which proceeded a Light: and a fmall Suapping

May the 6th, ̂ e madJe the following ExperimeiltO

The Boy being fuEpended on the Silk Lines,, and ttle

Tube being applied rlear hisFeet asuiual; upon llis holding the End of his Fillger near a Gentlernan's Halld, that Rood on a Cake made of Slhell Lack and black Rofin; at the fame time another Gentieman Rood at th-e other fide oftheBoy xvith the petldulous Thread; then the Boy nvas- bid to- hqld his FiI)gf:

near the firll Gentlemans Hand) upon W hich it % aS

prick'dX and the fllapping Noife ras heard; and at the fame time7 the Thread hich uSas by its atj

tra&ion going towards the Boy fell back, thc Boy having loft a greae part of has attradtiou, UpOtl a Se- cond Illoving his Finger to the Gentleman's SIandX the attradtion ceafcd: then the lShread being held near tllat Gentleman, he was isud EO attrafl: very tErongly; buet having fi1nce repeated this Experiu ment, I find that thowh the attraerion of the Boy i5

much diminiffied, yet he does BOt quite lore it9 tiu " 3 and fometimes 4 applications of his Finger to the hand of hizl that Rands on the EleEtrick Bodys but without torzching him At another time I cauSed three Perfons tO [tand, one of them UpO11 a CalQe of Shell Lackt bv. the other upon one of Sulphur, the third upon a Cake of beesWax and Ro§1n; th$ PtrEens a11 holding HandsX the Boy applying h:z

.

t 1Dgft

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( 69 ) NFinger near the firft Man's Hand, they all three be^ came Eled£tical, as appeared by the attradion of the ThreadX when heid near to ally of them.

P O S T SC Et I P T.

X Repetition of J^ome of the.J^e i xperiments9 and Sdditiog of rome others snaaSe June the I oth

7-W^ee the Ioth in the Morning, I repeated thc- Experimerlts with the Wooden Rods, the moR ma- terial Ones of which xvere made with the Holly Rod: This being laid on the GlaSs Cylinder, alld a Fir Board about a Foot Square and three tenths of an Inch thick being placed ered upon a Stand, that was fer on another Glafs Cylinder, lo that the Center of the Board was placed near the Poirlt ofthe Rod, but not to touch it l)y Ilear half an Irlch ; thell the Tube being held near the great End of the Rods there iued out a Light from the little End of the Rod, which was that next the Board; and, as the Boy told me, it came along With a hiffilng NoiKeX and Itruck againll the Board : When he touched the Board, there was a Light; arld, at the fame time, a- nother oll the End of the Rod, but he heard ll-o Inap- ping rlor pricking of his Finger, as when £he BraSs plare and Iron Rod were made ufe of. Experiexts titlv the Scarlet axd Blue ATorJ?ed

rarZ reSeated. VN herl the Boy utas furpendcd upon the zScdrler

Lines, he attraded the xvhite Thread at a very fsllall DifEance but the Attrad;tion ceaKed in about 6 or 7 Seconds of Time. Then the Boy being taken oR an Iron Rod vvas laid on the Lines) bllt there sras

X 2 .na

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( 170 )

no attradion of the Thread by the Body of the ltod ; but vIzen the Thread was held near ciiler of the polnted Ends of i* there was a fmall Repul fioll of it, and in the Dark a sery Emall Llgilt was Seen at each End of the Wod.

VV7hela the Boy was fufipended UpOA the Blue Lines, he attraded the Thread tO him when it was held at leaft a Foot dillance froln him, and COntillUt

his attrad;tion to near 75 Seconds the Iron Rod £OntinUtd itS atttaaioN not more than 36 Seconds

Etperiznenn made the Xfternonew spoX the Boy

when he qwas @eaded gpon Silk Lines Qf Ieveral CQ10UrS. WVhen he was fiuended on the Blue Lines, he

centinued his Attradvion 50 MinutesX ou the Scarw et tines zS Minates>oD the Orange colollred Lines hI Minutes.

By thefe Experiments we fee the Efiicacy oa EleEtricity upon Bodies fufpended upon lLines ofthe fame SubRances but of diffierent Colours) and alfo rlaat the Attradriori continues much lollger upon E;IIk tharl upon WJaru3 and conSequeutly Siik is the PrOPereI} BOdY xse Can ma]ie USC Of tO 1USPend thOSC lSOdieS UPOnX tO Wh;Ch We WOUId COmmUNiCate aN E1eDriC;tY : BUt Of th1S SUbje2;E mOre When 1 }1al1 Tea«Ume the EXPer jmPntS COnCerning the I£UeaCC Of CQ1QUrS UPOR E1ee[iCitY i xvho am,

S>I R5 harter Ho:fe 87] 1 t 2 35* rNXS and the- Soviet2s wo-

bleand obedieat Servant,< Stephen Graars

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