XVIII. A letter from Thomas Ronayne, Esq; to Benjamin Franklin, LL. D. F. R. S. inclosing an account of some observations on atmospherical electricity; in regard of fogs, mists &c. with some remarks; communicated by Mr. William Henley. 1 w 3 XVIIT. A Letter from Thomas Ronayne, Efq\ to Benjamin Franklin, D . F. & $- inclofng an Account of fome Qbfervations on A tm ofpherical ; in regard of Fogs, Mifts, with fome Remarks i communicated by Mr*: William Henley* S I R , Kiad April w ^conform ity. to the delire o f fome 1 J l friends, I have drawn up the folJow- ihg obfervations on atmofpherical ele&ricity, w hich I beg leave to lay before you y and fhall think the trouble-I have had, in profecuting the neceffary ex­ periments^ fufficiently compenfated, if it fhall appear to you that they contain any thing new or curious;; in which cafe, you are at liberty to difpofe o f them in whatever m anner you fliall think proper, . I am, s i r ;; W ith very refpe&ful confideratidn, Your moft obedient fervahL Cecif-Street,.. Sf Thos Ronayne. T q l. L X I t . 1 S O M E . D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 C * 3 8 ] ' * S O M E years ago I difcovered, by M r. Canton’s tled ro m eter, defcribed in the. Philof. Tran&dionsf m X L y n i : p-V 783. that the' air o f Ireland is ̂ during the winter ietifcn, m almoft a , c6fift/nt'r ftate o f pofitive eledricity y which, however, is* fo weak, that, in order to obferve itfatisfad o rily , I have al­ ways found it ncceflary to have the cork-balls fuf- :pended from threads o f a middling finenefs, fix or feven inches in length, quite fre ig h t, and to avoid, as m uch as poffible, any interruption from the wind. I have like wife had frequent recourfe to the fol­ low ing contrivance, by which I was enabled, within doors, to puffue my inquiries with greater accuracy and advantage: having procured a flender tapering piece of wood, about five feet long, to the fmaller *end o f which an eledrom eter was affixed, by means ~9f a finall hook j I placed it out from an open garret w indow , and fattened the other end with a fmall hafp to one of the ja m b s : I had alfo at hand another piece of wood, in the ends o f which, a fmall glafs tube and a ttick o f fealing-wax had been inferted. "Either o f thefe was occafionally excited, and applied near the cork-balls, in order to determine more pre- 4 > ] Having, on the contrary, obferved that bodies, ‘infulated with dried filk, had loft their electricity in a very fhort time, I attempted to render it a non­ conductor, by having varnifhed it over w ith oil o f turpentine, balfam o f fulphur, and fuch like, but did not fucceed j for filks fo treated foon became a condu&or, and increafed confiderably in weight, if th e air happened not to be very * dry f fo m uch indeed, that I think ordinary filk, from its power o f abforbing moifture from the air, may well ferve an occafional hygrometer, either by being put*'mtp a balance, or by having an ele&rified body infulated w ith it. W hen the denlity o f fogs, floating near the earth, increafes confiderably, the balls always approach $ but when they are fituated high in air, the reverfe generally happens. I had an opportunity o f rem ark­ ing a ftruggle between breezes from the north-well and fouth-eall at the fame time, in which the one feemed fometimes to prevail, and afterwards the other. T his contention was fucceeded by a frnoaky. hazinefs, which, like a fog, occafioned the balls to open : as the hazinefs •f* thickened, they opened * Even glafs attracts moilture to its furface, which makes it a conductor of eleCtricity, and, confequently, not fo convenient as fealing-wax. f An eleCtrical body, when contracted in its dimenfion, will have its eleCtricity increafed, as appears by D r. Franklin’s cu­ rious experiment with the chain and filver can. I alfo have dif- covered, from repeated trials, that a piece of flannel, filk, &c. excited, and fuddenly twifted, not only (truck at a greater di- ftance than before, but fometimes emitted pencils of fire into the air. May we not hence infer why the eleCtricity of vapour, &c. (when not in contaCt with the earth) increases by condenfa- * tion? wider, D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 f 142 ] wider, and frill wider when it diffolved into rain • but- V S j X S S t - * , Tt^ e k a ro m e te r placed out from a garret window- (p* 130.), has been frequently ufeful to m e, in de- e S r W t ! the|fnKtUrei,0 f a“ aPPfoaching c lo u d , whole eleftricity, although generally ftrong, was for the m o ftp art uncertain, having been fometimes poBtive and at other times negative.But, as the Z d ov ram were frequent impediments to the accuracy of m v e x p e r i m e n t s , t h e f o ll o w i n g m e th o d s o f m a k i n g .o b f e r - va 10ns,.with fuccefs,. under fhelter, occurred to me. I have fometimes flood, in an upper, room, on a cake_of w ax,, holding in my right hand, out at th e Window, a long (lender piece o f wood, round w hich a wire projedting a few inches had been tw illed and ” 7lf r h a n d -an elearo m e ter:. an affiftant had ex - cited glafs or wax in readinefs. A t other times, I have-, made ufe o f a tapering •• tube of tin, twenty feet long,,ending-in-a p o in t^ the S e? n d a f ° f l t K? i d ° Ut h i S f e i n t h e a ir> a n d t h e h i c k e n d , f r o m w h i c h a n e l e d r o m e t e r h u n ? w a s* fupported. infide the window,: fometimes wifh frlk1 cords, _and_at other times w ith ftrong flicks, o f Bv 5£ S " I 6!-*6' Cnd % hooks of. iron,w ire? 7 K f ? ° f ' means 1 have often dilcovered, 3 ^ h a t feemed to m e a Angle cloud, produced, in ’ ts paffmg over, feveral fucceflive changes, from ! ' u i 6 t v ° t h T b T *^a h d f t 0 m n̂ /ivei<0 P J ith e J tc mainms, r ^̂ Ĉ min| fogethet each Ume, and re- . D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 t m ); T h e permanence of either kind o f d ed ricity iti "the clouds, or the length o f time in which neither can be difcovered, is uncertain ; fomdimes the fame eledricity has returned, and at other times has been fucceeded by the contrary *; whilft either generally came on, and went off gradually. Rut changes were often made, very fuddeniy, by a flafh of lightning, efpecially if the thunder-ftorm happened to be in th e zenith. A branch o f it, over-head, has fre­ quently occafioned Wronger electricity than I could difcover, when the greateft part of the fky had been overcaft; which, perhaps, m ight be accounted for, from this consideration, that one kind of electricity idling alone, mufl: exert more powerful effects than when counteraded by the other. I once obferved in a thunder-ftorm , during which I faw no lightning, that the halts, which hung from the tin tube, repelled and attraded each other, very rapidly, for the ipace of ten or twelve feconds ; at the fame time, M r. Canton’s eledrom eter, w hich I held at fuch a diftance from the tube, as to have its balls opened to the diftance o f an inch, continued quiet in that ftate, and were not affeded convulfively like, the others. Hence I imagined, that the fame kind o f eledricity went off, and came on, without being changed incontrarium; for when that circumftance happened, they were very evidently affeded in the fame manner. And here I muff obferve, that I have found it more eafy to difcover the kind of eledricity prefent in the tube, by approaching ex­ cited wax to the balls of an eledrom eter, which I held at a proper diftance from the tube, than by ap­ plying it near the balls which hung from the tu b e ; for D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 [ r 4 4 J % t h e y ,, in tlie^general, diverged To much, that I found it very difficult' to have in readinefs a final! them ° f g afs’ ° r wax 1'uffieienHy excited to affedt I t has fometimes happened th a t the balls o f the o f a f e * n : r M l y at reft> have> in confequence o fa flaih .o flig h tn in g j fuddenly repelled each other an d imm ediately after clofed. As this circumftance d l o l T % i aP P r d ’ t he- ai r , was in a p ltate, I have fometimes imagined that th e b S »»d clouds t S the h.V W 7 d ° ri ’ 0n ^ e i v i n g the eleftricity o f the higher ones. a n d . at other times, have fuppofed 5 p lo fio n .,gb be ° Wing the lateral effe