ELECTRICITY.

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smelled strong v of sulphur. In making them, lie received a strokeon his arm a little below the elbow ; but lie could not tell whetherit came from the brass w ire inserted into the phial, or from theUir. lie did not attend to it at the time ; but the pain continu-ing, he uncovered his ami when he went home in the presence ofCoissier. A mark was perceived round it, such as might havebeen made by a blow with the wire on his naked skin. Dr.Franklin himself had an opportunitv, about a month after this, ofverifying his own hypothesis. He was waiting for the erection ofa spire in Philadelphia , not imagining fliat a pointed rod of a mo-derate height could answer the purpose. At last it occurred tohim, that by means of a common kite he could have a readier ac-cess to the higher regions of the atmosphere than any other waywhatever. Preparing, therefore, a large silk handkerchief andtwo cross sticks of a proper length on which to extend it, he tookthe opportunity of the first approaching thunder-storm to take awalk into a field where there was a shed convenient for his pur-pose. But dreading the ridicule which too commonly attends un-successful attempts in science, he communicated liis intention tonobody but bis son, wbo assisted him in raising the kite. A con-siderable time elapsed before there was any appearance of success.One very promising cloud had passed over the kite without anyeffect; when just as lie was beginning to despair, lie observed someloose threads of the hempen string to stand erect and avoid oneanother, just as if they had been suspended by the conductor of acommon electrical machine. On this lie presented liis knuckle toa key which was fastened to the string, and thus obtained a veryevident electric spark. Others succeeded even before the stringwas wet ; hut when the rain had begun to descend, lie collectedelectric lire pretty copiously, lie had afterwards an insulated ironrod to draw tiie lightning into liis house; and performed almostevery experiment with real lightning, that bad before been donewith t'le artificial representations of it by electrical machines. Anew and extensive field was thus opened for philosophers; but itwas soon found, that experiments of this kind were attended withdanger. In 175'J, the Abbe Nollet published some cautions tothose who tried experiments on lightning. lie had been inform-ed by letters from Florence and Bologna, that some persons inthese places had received violent shocks, while they drew sparksfrom an iron liar electrified iiy lightning. A correspondent in-formed him, that once, as lie w as endeavouring to fasten a smallchain, with a copper ball atone of its extremities, to a great chainw hich communicated wit!) the bar at the top oftiie building, therecame a flash of lightning which lie did not see, but which affectedthe chain with a noise like that of wild-fire. The observer in-stantly receivedsuch a shock, that tiie ball fell out of liis hands,and lie was struck backwards four or five paces. But the mostmelancholy proof of tiie danger of these experiments, was thedeatli of professor Richman, at Petersburg!!. This happened onthe 6tlii Aug. 1753, as he was making experiments on lightningdrawn into liis own room. lie had provided himself with an in-strument for measuring the quantity of electricity communicatedto his apparatus; and as he stood with his head inclined to it. Mr.Solokmv an engraver, w ho was near him, observed a globe of bluefire, as big as Ins list, jump from the instrument, which was abouta foot distant, to Mr. lliclmian’s bead. The professor was in-stantly dead, and Mr. Solokow was also much hurt. The latter,however, could give no particular account of the wav in which liewas affected ; for, at the time tiie professor was struck, there a:;osea sort of steam or vapour, which entirely benumbed him, and madehim sink down to the ground ; so that lie could not even remem-ber to have heard tiie clap of thunder, which was a very loud one.I he globe of lire was attended with an explosion like tliut of a pis-tol ; flic instrument for measuring tiie electricitv (called by theprofessor an electrical gnomon) was broken to pieces, and tiiefragments thrown about the room. Upon examining the effects ofthe lightning in tiie professor’s chamber, they found the door-casehalf split through, and tiie door torn off and thrown intotiie room. A vein was opened in the body twice, but no bloodfollowed; after which, they endeavoured to recover life by vio-lent friction, but in vain: upon turning the corpse with the facedownwards during the rubbing, an inconsiderable quantity of bloodran out of the mouth. There appeared a red spot on the forehead,from which spirted some drops of blood through the pores, with-out wounding the skin. The shoe belonging to tiie left foot wasVOL. II. — no. 71.

burst open, and uncovering the fool at that part, they found a bluemark : whence it was concluded, that the electric matter havingentered at tiie head made its way out again at that foot. Uponthe body, particularly on the left side, were several red and bluespots resembling leather shrunk by being burnt. Many more alsobecame visible over tiie whole body, and particularly over the.back. That upon the forehead changed to a brownish red, but tiieliair of tiie head was not singed, in the place where tiie slice wasunripped, the stocking was entire; as was (he coat everywhere,tiie waistcoat only being singed on tiie fore flap where it joined thehinder: but there appeared on tiie back of Mr. Soloksw’s coatlong narrow streaks, as if red-hot yvires had burned off'the nap, andwhich could not well be accounted for. Next day, when the pro-fessor’s body was opened, the cranium was very entire, having nei-ther fissure nor contra-iissure : the brain yvas sound ; but the trans-parent pellicles of the wind-pipe were excessively tender, andeasily rent. There yvas some extravasated blood in it, as also inthe cavities below the lungs. Those of the breast were quitesound ; but those towards the track of a brownish black colour,and filled with more of (lie blood above-mentioned. The throat,-the glands, and the small intestines, were all inflamed. The singedleather-coloured spots penetrated the skill only. In 4$ hours thebody yvas so much corrupted that they could scarce get it into acofim. Since tiie discovery of the identity of lightning and theelectric matter, long rods of iron or other metal have been madeuse of with a view to protect buildings from file danger or strokesof lightning. A considerable dispute has been carried on yilie-flier these rods ought to lie pointed or not ; but a committee oftiie Royal Society lately determined it in favour of the former.

Explanation or Terms used in Electricity.

Electric Fluid. On rubbing glass, sealing-yvax, sulphur,and several other bodies, with flannel or other proper rubber, andpresenting the hand, or any other part of file body to the sub-stance so rubbed ; a fluid passing between the rubbed body, andthe part presented is sensibly felt. This fluid lias a sulphureoussmell, and is rendered visible by its luminous appearance espe-cially in the dark. The fluid thus exhibited has received thename of the electric, or electrical fluid.

Elfctrical Appearances. It lias been known for ages, thatamber, jet, and some oilier bodies, when rubbed, attract and repellight bodies, as hairs, feathers, down, dust, See. In more moderntimes, it was discovered, that glass, resins, silk, dry wood, <xchave the same properties; and that any of these, yvlien dry, andrubbed for a short time, yvould attract light substances verv readily.On darkening Ihe room, and rubbing the glass tube again, sparksof lire will follow the hand ; present a linger to the tube, at tiiedistance of half an inch, and these sparks v ill be formed into pen-cils or brushes of light attended yyilh a snapping noise. By vary-ing the experiments other effects of the electric fluid yvill be per-ceived. Hie attraction, repulsion, sparkling, &c. are termedsigns of electricity, or electrical appearances.

Rubbers. The substance that rubs the electric to produce tiieelectrical appearances, is termed die rubber. The rubber makesan essential part of the construction of an electrical machine.

Excitation. Those bodies, w hich-by-mbbii.g are made toexhibit electrical appearances, arc said to be excited by the fric-tion or rubbing.

Electrics. Those bodies which can lie excited, or made toproduce the electrical appearances, are called electrics, ami fre-quently electrics per ,sr.

Non-Electrics. Those wliicli cannot lie excited, are callednon-electrics,

Conductors. It is found that some bodies admit the fluid topass through them on which account they are called conductin'!,,'i bis properly belongs princi;udly to the non-electrics ; hence theterms conductor and non-electric are nearly synonymous.

Nox-Conductoiis. It is found that some bodies do not admitor yvith diflicuity admit the fluid to pass through them, and theseare called non-conductors. 'This properly belongs principally totiie electrics, lienee the terms non-i oiutuctor and electric arenearly synonymous.

Insulation. When a body is placed entirely upon non-con-ductors, it is said to be insulated. Insulation prevents the dissipa-tion of the electric fluid, through.lhe surrounding bodies. A per,3 T sort