experiment will not fucceed; for if you place your images on a clean dry pane of glafs, and hold this under the upper plate (firft removing the lower plate and it's ftand), you will find, that the images will not be put in motion, notwithstanding you continue to turn the machine. Glafs does not tranfmit the two electricities, and therefore no contrariety in the electric ftate of the image can be occafioned, and confequently it will not move backwards nor forwards between the two plates. But if any means be used to cause an exchange in the powers, as by holding your finger under the glafs plate, they will be driven backwards and forwards as before.

Here is a fmall apparatus, confifting of three bells with two clappers between them, fig. 6, pl. 1; they are fufpended from a ftrait piece of brafs, the two outer ones by fmall brafs chains, the middle bell and the clappers are fufpended on filk; from the middle bell there is a chain which goes down to the table; I turn the machine, and the clappers fly from bell to bell, affording you a pleafing peal by electricity. The power from the conductor is conveyed down the chains to the exterior bells; by means of the chain, the exterior bells repel the fame power with which they are electrified from the ball or clapper, which, on the powers being thus feparated, are driven to the outer bell by the contrary power which fits in from the table, &c. through the middle bell; the ball becoming electrified with the fame power as the middle bell, is driven back, and will continue going from one to the other, as long as the outfide bells are kept in an electrified state by the machine.

If you take hold of the filk cord which is tied to the lower end of the chain that comes from the middle bell, and thereby raise that chain from the table, the ringing will immediately ftop; for filk

being a non-conductor, prevents the afflux and efflux of the fluids.

As the apparent attraction and repulsion of all light bodies depend on the afflux and efflux of the Separated powers, I fhall not, in fhewing you every experiment, enter into a detail of thefe circumftances; hoping that what I have already faid, will render that point fufficiently clear. I turn the machine with one hand, and hold the other about three or four inches from the end of the conductor; drop a fmall lock of cotton upon the hand near the conductor, and the cotton immediately jumps from my hand to the conductor and back again, ftretching itfelf out both ways into a longish form, and moving fo quick that you will fcarce be able to perceive it's form.

Here is a fmall toy, fomewhat refembling a hog; I have coated it with ermine, in the hairs of which I have inferted a few pieces of cotton pulled out, fo as to be of a confiderable length; place this upon the conductor, I turn the machine, and the hairs of the ermine diverge, and the pieces of cotton are discharged and driven fome feet from the conductor. This apparatus, by thus difcharging it's quills, may be called with propriety the electrical porcupine.

*

Few branches of philofophy afford fo much entertainment as electricity; here the ufeful and the agreeable are intimately blended, and while you are inveftigating fcience, you are entertained by the variety and beauty of the experiments. It was the ftrong, attractive, and repulfive powers exhibited by electricity, that firft engaged the attention of natural philofophers; by thefe they were led on to purfue the fubjects, as it were by enchant

* Communicated by Mr. Wiffet.

ment,

ment, and have been richly rewarded by discoveries both interefting and important.

A few more of the leading experiments, which have been so advantageous to science, will not be unpleasant.

METHODS OF IMITATING THE PLANETARY

MOTIONS.

Rackstrow's òrrery confifts of small glass balls blown exceeding thin; they are placed on a wooden board, and environed with circles of brafs wire infulated with fealing-wax, or glafs, of fuch a height that the center of the balls may be nearly parallel to the wire circles. One of thefe circles may represent the orbit of Saturn, another that of Jupiter, &c. the circles being connected with the conductor of the machine by a wire, and a glass fphere placed between each, the fpheres will perform their revolutions round their orbits, and at the fame time acquire a rotation on their axes.

When the machine is fet in motion, the balls will be first attracted to the brafs circles, by which means the point that touches the brafs circle will become electrified, and be immediately repelled; other parts will in the fame manner be attracted and repelled, by which means the glass ball acquires a kind of fpinning motion on it's axis, at the fame time it must have a progreffive motion round the circle.

Provide a ball of cork about three quarters of an inch in diameter, hollowed out in the internal part by cutting it in two hemifpheres, fcooping out the infides, and then joining them together with pafte. Having attached this to a filk thread, between three and four feet in length, fufpend it in fuch a manner that it may juft touch the knob of VOL. IV.

Y

an

an electric jar, the outfide of which communicates with the ground. On the first contact it will be repelled to a confiderable diftance, and after making feveral vibrations, will remain ftationary; but if a candle is placed at fome diftance behind it, fo that the ball may be between it and the bottle, the ball will inftantly begin to move, and will turn round the knob of the jar, moving in a kind of ellipfis, as long as there is any electricity in the bottle. This experiment is very ftriking, though the motions are far from being regular; but it is remarkable, that they always affect the elliptical rather than the circular form.

Cut a piece of India paper in the shape of an ifofceles triangle, whofe fides are about two inches long and two tenths of an inch in breadth; then erect a brafs ball of two or three inches diameter on a brafs wire one fixth of an inch in thickness, and two feet fix inches long, on the prime conductor; electrify the conductor, and then bring the obtufe end of the piece of paper within the atmosphere of the ball; let it go, and it will revolve round the ball, turning often round it's own axis at the fame time.

TUMBLER AND BALLS.

Put a pointed wire into one of the holes which are at the end of the conductor, hold a glass tumbler over the point, then electrify the conductor and turn the tumbler round, that the whole interior surface may receive the fluid from the point; place a few pith balls on the table, and cover them with this glafs tumbler, the balls will immediately begin to leap up and down, as if they were animated, and will continue to move for a long time.

ELEC

ELECTRICAL FLUID UNIVERSALLY DISSEMINATED, AND IN CONTINUAL ACTION.

That the electrical fluid is univerfally diffeminated, and in continual action, has long been the opinion of those who have paid attention to it. To prove this to others, various inftruments have been contrived to detect the smallest variations, and discover the minuteft figns of it's exiftence; these have been generally named electrometers; and among these, that defcribed by the Rev. Mr. BɛnNET, of Wirksworth, ftands the foremost, as being by far more fenfible than any of the rest.--This is one of them, fig. 1, pl. 2.

The foot is made of metal, and about three inches high, that you may handle the inftrument without touching the glafs; the cylindrical glafs, in which the gold leaf is fufpended, is about five inches high, and one in diameter; the cap is made of metal, and flat on the top, that the various fubftances whofe electricity is to be examined may be conveniently placed thereon. The diameter of the cap is larger than that of the glafs, and it's rim is about an inch deep, hanging parallel to the glafs, in order to keep it clean and dry; within this is another circular rim that goes over the glafs, and is lined with a foft fubftance to make it fit close, within this rim; at the center of the cap a tube is fixed, wherein the peg is placed to which the two flips of gold leaf or filver are fastened.

If there were no glass, the gold leaf would be fo agitated by the leaft motion of the air, that it would be entirely ufelefs. To prevent the gold leaf from being attracted and torn by flying to the glafs, two pieces of tinfoil are faftened, with varnish on the oppofite fides of the glafs, where it may be expected to ftrike thefe flips and carry off the fuperY 2 fluous