ways 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 phenomenon, and supposed to be occasioned by the flashing of electric fire from positive toward 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.

OF THE IGNIS FATUUS.

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-alantern.

Q. How is this phenomenon explained?

A. The late discoveries ascribe it to inflamable air, arising from the putrefaction and decomposition of vegetable substances in water, and which

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takes fire by means of the electricity of fogs, and by falling stars which are also of an electric origin. 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.

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 causes of this agitation?

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 upward, 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 also we may account 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?

A. Into for principal 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. 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 cest, 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. Reside 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 in 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 some electrical cause, which occasions a rushing in of the air from all points, an impetuous wind is produced, turning rapidly every way, and threatening ruin. This is called a whirlwind. And,

When these causes are numerous and very violent, accompanied with lightning and thunder, the wind becomes so furious and terrible, that it over throws houses, roots up trees, and destroys every thing in its course. This is denominated a hurricane,

The velocity of wind, in what is termed a gentle breeze, may be from four to six or eight miles an hour; a strong breeze or brisk wind will travel perhaps from ten to fifteen miles an hour; and a hurricane or tempest probably not less than fifty or sixty miles,

The air is often observed, in different regions, to move in contrary currents; and this almost always previous to thunder,

Q. What are clouds ?

A. A quantity of condensed vapours, suspended in the atmosphere,

Q. How are they formed?

A. From a collection of watery particles, rais ed from the earth by solar and subterraneous heat; the particles, at their first rise, are too minute and separate to be perceived; but, meeting, in their ascent, with a greater degree of cold, they are condensed and their parts united, so as to reflect light and become visible,

Q. At what height do you suppose the clouds to Le suspended?

A. From about a quarter of a mile to two alies; according to their specific gravity, and to the elasticity of the atmosphere. They are frequently visible below the tops of very high kills.

Q. Whence are their various forms and colours ?

A. Their figure results from their loose texture, changing into any form according to the different. currents of the air; and their colour is owing to their particular situation with regard to the sun and the different reflections of his light.

It appears from the observable motion of the clouds, that there are different currents in the air at the same time, and in the same quarter, under one another.

OF THE RAINBOW.

Q. What is a rainbow ?

A. A meteor in the form of a party-coloured arch, exhibited in a rainy atmosphere, opposite to the sun.

Q. Of what colours does it consist?

A. They are, beginning from the upper part, red, orange, yellow, green, blue, indigo, violet; and these are called the seven primary colours, for all other colours are composed of some of them.

Every ray of light is a compound body consist