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m ELECTRICITY.

ductor is removed : so that the fly abed may lie about the heightof the centre of the cylinder. r riie latter being then put m mo-tion, the electricity from it proceeding to the fly, will cause it to-turn round and the clapper attracted by each of the bells alter-nately in its rotation ; winch, if they are properly tuned, will pro-duce a pleasing and harmonious sound.

^ Experiments exhibiting Electric Light and Fire.

The following experiments require to be made in the dark: foralthough the electric light in several circumstances may he seen inthe day-light, yet its appearance in this manner is very confused ;ami that the electrician may form a better idea of its different ap-pearances, it is absolutely necessary to perform such experimentsin a darkened room.

The Star and Fkncii. of Electric Light. 'When the elec-trical machine is in good order, and the prime conductor is situ-ated with the collector sufficiently near the glass cylinder, turn thewinch, and you will see a lucid star at each of the points of the col-lector. This star is the constant appearance of the electric fluidthat is entering a point. At the same time you w ill see a stronglight proceeding from the rubber, and spreading itself over thesurface of the cylinder; and if the excitation of the cylinder is verypowerful, dense streams of fire will proceed from the rubber, and,darling round almost half the circumference of the cylinder, willreach the points of the collector. If the prime conductor is re-moved, the dense streams of fire will go quite round the cylinder;reaching from one side of the rubber to the other. If the chain ofthe rubber is taken off, and a pointed body, for instance the pointof a needle or a pin, he presented to the back of the rubber, at thedistance of about two inches, a lucid pencil of rays will appear toiroceed from the point presented, and diverge towards the rubber,t another pointed body be presented to the prime conductor, itwill appear illuminated" with a star; but if a pointed wire or otlierpointed conducting body be connected with the prime conductor,it will throw out a pencil of rays.

Drawing Sparks. Let the prime conductor be situated in itsproper place, and electrify it by working the machine; then bringa metallic rod with a round knob at each end, or the knuckle of a•finger, within a proper distance of the prime conductor, and a-park will be seen between that and the knuckle or knobbed wire.Tlie longer and stronger spark is drawn from that end of the primeconductor which is farthest from the cylinder, or rather from theextremitv of the knobbed rod fixed at its end. This spark appearslike a long line of tire, reaching from the conductor to the opposedbodv, and often (particularly when the spark is long, and differentconducting substances are near the line of its direction) it will havethe appearance of being bended to sharp angles in different placesresembling a flash of lightning. It often darts brushes of light side-wise in every direction.

The Artificial Lightning. Let two persons, one standingupon an insulated stool, and communicating with the prime con-ductor, and another standing upon the floor, each hold in one ofhis hands a metal plate, so that the plates may stand back to hackin a parallel situation, and about two inches asunder. Let thewinch of the machine he turned, and the flashes of light betweenthe two plates will appear so dense and frequent, that one ntayeasily distinguish any tiling in the room. By this experiment theelectric light is exhibited in a very copious and beautiful manner,And bears a striking resemblance to lightning.

To Fire Inflammable. Spirits. The power of the electricspark to set fire to inflammable spirits, may be exhibited easilythus: Hang to tiie prime conductor a short rod having a smallknob at its end ; then pour some spirits of wine, a little warmed,into a spoon of metal; hold the spoon by the handle, and place it insuch a manner, that the small knob on the rod may be about oneinch above the surface of the spirits. In this situation, if, by turn-ing the winch, a spark be made to come from the knob, it w ill setthe spirits on fire. It will generally lie found more advantageous tofix the dish containing the spirits upon the prime conductor, as re-presented fig. 1(5, Plate LX I If. This experiment may be varieddifferent ways, and maybe rendered very agreeable to a companyof spectators. A person standing upon an electric stool, and com-municating with the prime conductor, may hold the spoon withthe spirits in his hand, and another person, standing upon the floor,mavset the spirits on fire by bringing tiis finger within a small dis-jauce of it. 'Instead of his finger, he may fire the spirits with .a

piece of ice, when the experiment will seem much more surprising.

If the spoon is held by the person standing upon the floor, and theinsulated person brings some conducting substance over the sur-face of tlie spirits, the experiment succeeds as well.

The Luminous Conductor. Fig. 17, Plate LXIII. repre-sents a prime conductor invented by Mr. Ilenly, which shewsclearly the direction of the electric fluid passing through it, from,whence it is called the luminous conductor. The middle part E Eof this conductor is a glass tube about 18 inches long and three orfour inches in diameter. To both ends of this tube tlie hollowbrass pieces ED, BE, are cemented air-tight, one of which has apoint C, by which it receives the electric fluid, when set near theexcited cylinder of the electrical machine, and the otlier lias aknobbed wireG, from which a strong spark may be draw n ; andfrom each of the pieces F D, C E, a knobbed «ire proceeds withinthe cavity of tlie glass tube. The brass piece I<’D, or lift, is com-posed of two parts ; i. c. a cap E cemented to the glass tube, andhaving a hole with a valve, by which t-he cavity of the glass tubeis exhausted of air ; and the ball D, which is screwed upon the capE. The supporters of this instrument are two glass pillars fastenedin tlie bottom board 11, like the supporters cl the prime conductor.W hen tlie glass tube of this conductor is exhausted of air by anair-pump, and tlie brass ball is screw ed on, as represented in’thefigure, then it is fit for use, and may serve for a prime conductorto an electrical machine. If the point C of this conductor is setnear tlie excited cylinder of the machine, it w ill appear illuminat-ed with a star; at ilie same time tlie glass tube will appear all illu-minated with a weak light ; but from the knobbed wire that pro-ceeds within the glass tube from the piece ED, a lucid pencil wiltissue out, and tlie opposite knob will appear illuminated w ith a slar,which, as well as the pencil rays, is very c lear, and discernibleamong the other light, that occupies tlie greatest part of tlie cavityof the tube, if the point C, instead of being presented to the cy-linder, be in contact with tlie rubber of the machine, the appear-ance of light within the tube will be reversed ; the knob wliicUcommunicates with the piece ED appearing illuminated with a starand the opposite one with a pencil of rays; because in tills case thedirection of the electric fluid i-s just the contrary of what it was be-fore; it then going from 1) to 15, and now coming from B andgoing to D. If the wires within the tube EE, instead of being lur-nislied with knobs, be pointed, the appearance of light is the same ;but it seems not so strong in this as in the otlier case.

The conducting Glass Tube. Take a glass tube of abouttwo inches diameter, and about tw o feet long ; fix to one of its endsa brass cap, and to tlie otlier a slop-cock ora valve; then exhaustitof air by an air-pump. If this tube be held by one end, and its otherend be brought near the electrified prime Conductor, it will appearto he full of light whenever a spark is taken by it from tlie primeconductor, and much more so if an electric jar be dischargedthrough it. This experiment may also be made with the receiverof an air-pump. 'Fake a tail receiver, clean and dry, and througha hole at its top insert a wire, which must be cemented air-tight.The end of tlie wire within the tube must be pointed, hut not verysharp ; and the other end must be furnished with a knob. Put tinsreceiver upon tlie plate of the air-pump, and exhaustit. If nowthe knob of the w ire at the top of tlie receiver be touched withthe prime conductor, every spark will pass through the receiver ina dense and large body of light, from the wire to the plate cf tlieair-pump. When the air-pump, or any tiling not very portable,is to be touched with tlie prime conductor, the communication be-tween them may. be made by means of a rod furnished with an elec-tric handle.

'Flic artificial Aurora Borealis . 'Fake a phial nearly ofthe shape and size of a Florence flask ; (fig. 18, Plate LXI11.) fix astop-cock or a valve to its neck, and exhaust it of air as much aspossible with a good air-pump. If this glass be rubbed in tlie com-mon manner used (o excite electrics, it will appear luminous with-in, being full of a flashing light, which plainly resembles tlie au-rora borealis or northern light. 'Phis plnal may also he made lumi-nous, by holding it by either end, and bringing the otlier end to tlieprime conductor; in tins case, all the cavity of tlie glass .will in-stantly appear full of flashing light, which remains in it for a con-siderable lime after it lias been removed from the prime conduc-tor. Instead of tlie glass phial a glass tube exhausted of air and.hermetically sealed may be used, and perhaps with more advan-tage. The most remarkable circumstance of this experiment is,* tlu.t