A. In the present advanced state of electricity, lightning is universally allowed to be an electrical phenomenon: for, as before observed, it has been proved by a variety of experiments, that the lightning of electricity, and the lightning which glares in the clouds, are precisely the same; both in kind and operation.

Q. What is the cause of lightning?

A. The air, when in one place, electrified positively, and in another, negatively, (according to the theory of Franklin,) causes particular clouds, and different parts of the earth, to possess opposite electricities; so that, on their approach within a certain distance, a discharge will be made from the one into the other; and, in the discharge, a flash of lightning will be observed.

Q. How is thunder produced?

A. By a concussion in the air, from an electrical explosion; the rattling noise being probably caused by the sound excited among clouds hanging one over another, and the agitated air passing irregularly between them.

Q. What is the reason that thunder is not heard till some time after the lightning is seen?

A. Because sound is much longer in arriving at our ears, than light is at our eyes: for, light moves almost instantaneously; but sound moves only at the rate of 1142 feet in a second.

Q. I have heard of thunderbolts, and of their strange effects: pray, what are they?

A. What is vulgarly called a thunderbolt, is only lightning when it acts with extraordinary violence, and breaks or shatters any thing. When the explosion is high in the air, it will do no mischief; but, when near the earth, it may kill animals, destroy trees, burn houses, &c.

Q. How can we ascertain its distance?

A. It may be estimated by the interval of time between the flash and the noise. The ordinary difference between the two, is about seven seconds, which, at the rate of 1142 feet in a second, gives the distance of about a mile and a half: but sometimes it comes in a second or two; which shows that the explosion is very near us, or even among

us.

OF THE AURORA BOREALIS.

Q. What is the aurora borealis?

A. An extraordinary luminous meteor, showing itself in the night after a dry season, chiefly in the northern parts of the atmosphere; and, hence, the vulgar give it the name of northern lights or streamers.

Q. Pray, describe this meteor.

A. It appears most commonly in the form of an arch; partly bright, and partly dark: but always transparent, and usually of a red colour, inclining to yellow. It sends out frequent coruscations of pale light, which seems to rise from the horizon in a pyramidial undulating form, and shoot with great velocity, toward the zenith, or that point which is immediately over the head of the spectator.

Q. How is it accounted for?

A. It is deemed an electrical plenomenon, and supposed to be occasioned by the flashing of electric fire, from positive towards negative parts of the atmosphere, at a great distance, and in the upper region where the resistance is least; and that it appears chiefly in the northern parts, because the alteration in the heat of the air is there the greatest.

Q. What is the ignis fatuus?

A. A common ignited meteor; chiefly seen at night, in meadows, marshes, and other moist places. It is known among the vulgar by the appellations, Will-with-a-wisp, and Jack-with-a-lantern.

Q. How is this phenomenon explained?

A. The late discoveries ascribe it to inflamma. ble air; arising from the putrefaction and decomposition of vegetable substances in water, and taking fire by means of the electrical matter contained

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in fogs. In short, positive and negative electricity in the air, with a proper quantity of moisture to serve as a conductor, will readily account for these, and other, fiery phenomena.

OF WIND.

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Q. What is wind!

A. A sensible agitation of the air, by which a large quantity flows in a current, out of one region into another.

Q. What are the principal causes of this agita. tion:

A. Local alterations in the state of the air, by means of heat. For, when the air is heated over one part of the earth more than over another, the warmer air, being rarefied, becomes specifically lighter than the rest: it is therefore overpoised by it, and raised upwards; the higher parts of it diffusing themselves every way over the top of the atmosphere; while the neighbouring air below rushes in on all sides, till the equilibrium is restored. Hence, we may account also for the ascending of smoke in a chimney; and for the rushing of the air through the keyhole of a door, or any small chink, into a room where there is a fire.

Q. How are the winds divided?

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A. Into four principle ones; the north, south, east, and west; which take their names from the four cardinal points of the world.

Q. What is the nature of each?

A., In the northern hemisphere, the north wind is cold; because it comes from the frigid zone, or countries remote from the influence of the sun: the east, is damp: because it comes from the bosom of the Atlantic, where it imbibes large quantities of vapour: the west, coming from temperate regions across the American continent, is pleasant, pure, and exhilarating: the south, coming from the torrid zone, is

warm.

Q. Are the winds deemed beneficial?

A/ Besides their use in moving various machines, and their utility in navigation, they serve to purify and refresh the air, to convey the heat or cold of one region to another, and to produce a circulation of vapours from the ocean to inland countries. But, though their effects, on the whole, may be of great benefit, their violence is sometimes very detrimental. For,

When a violent and very sudden alteration happens in any particular part of the atmosphere, by means of a cloud, or of some electrical cause, which occasions a rushing in of the air from all points, an impetuous wind is produced, turning rapidly every way, and threatning ruin. This is called a whirlwind. And,

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