tance for the flash, they are attracted towards each other till within that distance; for the sphere of electrical attraction is far beyond the distance of flashing.

36. When a great number of clouds from the sea meet a number of clouds raised from the land, the electrical flashes appear to strike in different parts; and as the clouds are jostled and mixed by the winds, or brought near by the electrical attraction, they continue to give and receive flash after flash, till the electrical fire is equally diffused.

37. When the gun barrel (in electrical experiments), has but little electrical fire in it, you must approach it very near with your knuckle before you can draw a spark. Give it more fire, and it will give a spark at a greater distance. Two gun barrels united, and as highly electrified, will give a spark at a still greater distance. But if two gun barrels electrified will strike at two inches distance, and make a loud snap, to what a great distance may 10,000 acres of electrified clouds strike and give its fire, and how loud must be that crack?

38. It is a common thing to see clouds at different heights passing different ways, which shews different currents of air one under the other. As the air between the tropics is rarified by the sun, it rises, the denser northern and southern air pressing into its place. The air so rarified and forced up, passes northward and southward, and must descend in the polar regions, if it has no opportunity before, that the circulation may be carried on.

39. As currents of air, with the clouds therein, pass different ways, it is easy to conceive how the clouds, passing over each other, may attract each other, and so come near enough for the electrical stroke. And also how electrical clouds may be carried within land very far from the sea, before they have an opportunity to strike.

40. When the air, with its vapours raised from the ocean between the tropics, comes to descend in the polar regions, and to be in contact with the vapours arising there, the electrical fire they brought begins to be communicated, and is seen in clear nights, being first visible where it is first in motion; that is, where the contact begins, or in the most northern part; from thence the streams of light seem to shoot southerly, even up to the zenith of northern countries. But though the light seems to shoot from the north southerly, the progress of the fire is really from the south northerly, its motion beginning in the north being the reason that it is there seen first.

For the electrical fire is never visible but when in motion, and leaping from body to body, or from particle to particle through the air. When it passes through dense bodies it is unseen. When a wire makes part of the circle, in the explosion of the electrical phial, the fire, though in great quantity, passes in the wire invisibly; but in passing along a chain, it becomes visible as it leaps from link to link. In passing along leaf gilding it is visible: for the leaf gold is full of pores; hold a leaf to the light and it appears like a net, and

the fire is seen in its leaping over the vacancies. And as when a long canal filled with still water is opened at one end, in order to be discharged, the motion of the water begins first near the opened end, and proceeds towards the close end, though the water itself moves from the close towards the opened end: so the electrical fire discharged into the polar regions, perhaps from a thousand leagues length of vaporified air, appears first where it is first in motion, i.e., in the most northern part, and the appearance proceeds southward, though the fire really moves northward. This is supposed to account for the Aurora Borealis.

41. When there is great heat on the land, in a particular region (the sun having shone on it perhaps several days, while the surrounding countries have been screened by clouds), the lower air is rarified and rises, the cooler denser air above descends; the clouds in that air meet from all sides, and join over the heated place; and if some are electrified, others not, lightning and thunder succeed, and showers fall. Hence thunder-gusts after heats, and cool air after gusts; the water and the clouds that bring it, coming from a higher and therefore a cooler region.

42. An electrical spark, drawn from an irregular body at some distance is scarce ever strait, but shows crooked and waving in the air. So do the flashes of lightning; the clouds being very irregular bodies.

43. As electrified clouds pass over a country, high hills and high trees, lofty towers, spires, masts of ships, chimneys, &c., as so many prominencies and points, draw the electrical fire, and the whole cloud discharges there.

44. Dangerous, therefore, is it to take shelter under a tree, during a thunder gust. It has been fatal to many, both men and beasts. 45. It is safer to be in the open field for another reason. When the clothes are wet, if a flash in its way to the ground should strike your head, it may run in the water over the surface of your body; whereas, if your clothes were dry, it would go through the body, because the blood and other humours, containing so much water, are more ready conductors.

Hence a wet rat cannot be killed by the exploding electrical bottle, when a dry rat may.

46. Common fire is in all bodies, more or less, as well as electrical fire. Perhaps they may be different modifications of the same element; or they may be different elements. The latter is by some suspected.

47. If they are different things, yet they may and do subsist together in the same body.

the

48. When electrical fire strikes through a body, it acts upon common fire contained in it, and puts that fire in motion; and if there be a sufficient quantity of each kind of fire, the body will be inflamed. 49. When the quantity of common fire in the body is small, the quantity of the electrical fire (or the electrical stroke) should be

greater if the quantity of common fire be great, less electrical fire suffices to produce the effect.

50. Thus spirits must be heated before we can fire them by the electrical spark.* If they are much heated, a small spark will do; if not the spark must be greater.

51. Till lately we could only fire warm vapours; but now we can burn hard dry rosin. And when we can procure greater electrical sparks, we may be able to fire not only unwarmed spirits, as lightning does, but even wood, by giving sufficient agitation to the common fire contained in it, as friction we know will do.

52. Sulphureous and inflammable vapours arising from the earth, are easily kindled by lightning. Besides what arise from the earth, such vapours are sent out by stacks of moist hay, corn, or other vegetables, which heat and reek. Wood rotting in old trees or buildings does the same. Such are therefore easily and often fired.

53. Metals are often melted by lightning, though perhaps not from heat in the lightning, nor altogether from agitated fire in the metals. For as whatever body can insinuate itself between the particles of metal, and overcome the attraction by which they cohere (as sundry menstrua can) will make the solid become a fluid, as well as fire, yet without heating it: so the electrical fire, or lightning, creating a violent repulsion between the particles of metal it passes through, the metal is fused.

54. If you would by a violent fire, melt off the end of a nail, which is half driven into a door, the heat given the whole nail before a part would melt, must burn the board it sticks in. And the melted part would burn the floor it dropped on. But if a sword can be melted in the scabbard, and money in a man's pocket, by lightning, without burning either, it must be cold fusion.t

55. Lightning rends some bodies. The electrical spark will strike a hole through a quire of strong paper.

56. If the source of lightning assigned in this paper be the true one, there should be little thunder heard at sea far from land. And accordingly some old sea captains of whom enquiry has been made, do affirm, that the fact agrees perfectly with the hypothesis; for that in crossing the great ocean, they seldom meet with thunder till they come into soundings; and that the islands far from the continent have very little of it. And a curious observer who lived thirteen years at Bermudas, says, there was less thunder there in that whole time than he has sometimes heard in a month at Carolina.

• We have since fired sparks without heating them, when the weather is warm. A little poured into the palm of the hand, will be warmed sufficiently by the hand, if the spirit be well rectified. Ether takes fire most readily.

These facts, though related in several accounts, are now doubted; since it has been observed that the parts of a bell-wire which fell on the floor being broken and partly melted by lightning, did actually burn into the boards; and Mr. Kinnersley has found that a fine iron wire, melted by electricity, has had the same effect.

On the Primary and Secondary Electro-Chemical Phenomena. By M. BECQUEREL.*

By the aid of electric forces of a single pair of metals long continued, chemical effects, more or less considerable are obtained, whether the affinity of the liquid for one of the polar metals be in accordance with those forces, or operates in the contrary direction.

We every day observe that nature, having at her disposal unlimited periods of time for her operations, produces immense effects with very slender means. These means, however, frequently escape our senses, and have not been studied with care, in consequence of our attention not being directed towards them in the usual routine of our researches. It is by working on a small scale only, and close observation in every stage of the process, that chance is afforded to discover any part of the resources which nature brings into play in the production of phenomena due to molecular attraction. We will now proceed to shew some decompositions obtained by apparently feeble electric forces.

It is an established fact that voltaic action may produce chemical effects; but we are ignorant to what extent that action when very feeble, influences affinities; and whether there may not be produced at the moment these become manifest, particular phenomena, which disappear in the general effects when a pile of certain energy is employed.

We know, for example, that when we immerse in a metallic solution two wires of any metal whatever, which communicate with the poles of a voltaic pile, sufficiently energetic, we always obtain at the negative wire either hydrogen, liberated metal, or an oxide; but when the tension is extremely feeble do the phenomena appear in the same manner? Do all the metals possess this property in the same degree? To be enabled to resolve these questions it is necessary to diminish successively the intensity of the electricity, and at the same time to observe what passes in the decompositions. This is what we are about to do.

Place in a cylindrical glass vessel a metallic solution, a solution of copper for example, and afterwards, with great care, pour on the top of it distilled or acidulated water, so that the two liquids may not mix, but remain separate: the water being above the metallic solution. If now we immerse a plate of copper into these unmixed liquors, and permit it to remain a few hours, we find that it has become covered with precipitated copper in a metallic state. Different metallic solutions gave similar results. Hence we understand that metals may form, with their own solutions and pure water, or with water acidulated, circles of electric action sufficient to precipitate the metals.

In this case there are two electrical effects: the one resulting from the reaction of the two liquids on each other; the second from the

Becquerel's "Traité de l' Electricité et du Magnetisme," vol. iii, p. 287.

reaction of the acidulated water on the metallic plate. It is, therefore, a compound phenomenon; for the actions conspire or antagonize accordingly as their directions are in the same, or in opposite directions. In the present case the two actions conspire.

Certain thermo-electrical phenomena and simple chemical actions, ordinarily disengage a sufficiency of electricity to produce decompositions resembling those we have already described. We will first direct our attention to those decompositions which are accomplished by thermo-electric currents.

Several philosophers have endeavoured, but in vain, to decompose water by the thermo-electric currents. To succeed, however, they ought to have experimented on such solutions as are easily decomposable by very feeble currents, such as the nitrate of silver and the oxide of potassium, and arranged the apparatus so as to be enabled to determine the production of the new compound.

Let us employ two wires, one of platinum the other of copper, each a few inches in length, and about a fifteenth of an inch diameter. At the end of each wire we form a small loop, by means of which they are to be linked together. The platina loop is much smaller than the copper one, which is about an eighth of an inch diameter. If we solder the two loops, the current invariably proceeds in one and the same direction, from the platinum to the copper, whether the heat be applied on the right or on the left of the point of junction. Now solder a second wire of copper to the free end of the platinum wire, after which burn a small bit of sulphur on the loop of the copper wire; this done, apply the flame of a spirit lamp to the platinum wire so as to raise it to a red heat, at the same time keeping the copper loop as cool as possible, which is best done by keeping the platinum wire in the extremity of the white part of the flame, so that it may be but at a short distance from the copper loop. If now we join the free ends of the copper wires to the ends of the wire of a galvanometer coil, we discover a current of considerable energy flowing from the platinum to the copper.

We make the copper loop much larger than the other for the purpose of keeping it less heated when the temperature of the platinum is raised to redness. If, on the other hand, we apply the focus of the heat on the side of the copper wire, the electrical effects become inverted and if for the platinum wire we substitute one of copper, the electrical effects will still be the same. By exposing the two loops to the same degree of temperature, no electrical effects are produced.

:

The case of sulphur with which we cover the loop of the copper wire, enhances the electric action very sensibly.

Hence, therefore, two distinct electric effects are obtained in a closed circuit composed of two wires of different kinds of metal, accordingly as they are soldered together, or in mere contact with one another. In the first case, the current invariably proceeds in the same direction, whether we apply the heat to the right or to the left of the point of junction: in the second case it is not in the same