shower. The pieces were flat, rugged, and of all sorts of outline, some of them three inches broad, and very many as like as possible to bits of broken ice-plate from the surface of a lake.

Hail showers are commonly formed in very disturbed states of the atmosphere, or at the crises of great and violent changes in its electric conditions. Most are confined within very small limits; and those which traverse any considerable distance have a surprisingly narrow breadth. They are most frequent and devastating in the south of Europe; but they sometimes fall with disastrous effects both in the colder temperate regions and within the tropics. Many beat down crops, strip trees, and desolate gardens; and some strew a land with havoc, and kill birds and beasts anď men. A recent hail storm in India fell almost like a discharge of musketry; and many hail-storms figure in both ancient and modern records in as terrible power and with as dismal effects as famine and pestilence. Very many hail storms, or all, might serve to inflict divine chastisement on nations just as readily now as in the times of the ancient Egyptians and of the Canaanites; and since the vast majority fall lightly and do no harm, but on the contrary serve well to purify the atmosphere and to fertilise the soil, they ought to be regarded as sublime evidences of the long-suffering and mercy of the All-Benevolent Deity.

Winds may seem to careless observers very uninteresting or even unmeaning and annoying things, yet they really rank high among the wonders of the world. If the atmosphere had been incapable of them—if it stood stagnant in perpetual calm—all its many mighty

properties would be useless to both plants and animals. Winds maintain an equable diffusion of the atmosphere's foreign admixtures. They promptly restore disturbed balances among its proper ingredients. They disperse into speedy dilution the noxious exhalations from swamps and towns. They carry clouds and vapours from the regions of the ocean and of wet lands to the dry and parched countries which lie sick and faint for want of moisture. They invigorate splashy regions by assisting to dry them, and refresh hot and arid ones by fanning and cooling them. They agitate seas and lakes, and prevent their waters from becoming putrid. They scatter seeds and give exercise to plants. They ventilate the dens of wild beasts, and the habitations of the domesticated animals and of man. They drive machinery and impel ships. They give circulation and activity to all moveable immaterial things, and impel the energies and promote the health of all air-absorbing and air-breathing creatures. Without them, the whole atmosphere would speedily become a stagnant pool, and the whole surface of land and sea an expanse of vileness. Even a brief cessation of them on the ocean, a very few days' continuance of a calm at sea, where their action is incomparably less needed for any uses of organic existence than on land, is one of the most dismal themes of human thought. Whoever has witnessed one in the tropics will give a ready response to the well-known lines of Coleridge,

«All in a hot and copper sky,

The bloody sun at noon,

Right up above the mast did standj
No bigger than the moon.

Day after day, day after day,

We stuck, nor breath nor motion,
As idle as a painted ship

Upon a painted ocean.

Water, water everywhere,

And all the boards did shrink;

Water, water everywhere,

Nor any drop to drink.

The very deep did rot;-how strange,

That ever this should be!

Yea, slimy things did crawl with legs
Upon the slimy sea."

A

Winds are produced by the beautifully simple means of the action of heat upon the elasticity of the air. Whenever heat, either direct from the sun's rays, or reflected from the surface of land or sea, or put into play in any other manner, is greater than the surrounding or adjacent temperature, it expands the air, drives it upward or outward, and occasions an influx of denser and cooler air to supply its place. disturbance by expansion over but a small extent, through but a brief period, occasions a long and farspread wind. When the water of a pond is suddenly lowered at only one small point by the opening of a sluice, it becomes affected far and wide by a current; and, on a similar principle, when the air of but a small region of the atmosphere is suddenly expanded and pushed aloft by a rise of temperature, it draws on a rush or commotion from a great distance. Where the play of superior heat is constant, as happens along the equatorial zone, it produces the constant currents called the trade-winds. When it is seasonal, or acts during one season of months and does not act during

another, as happens over all the Indian Ocean, it produces the seasonal currents called monsoons. Where it is diurnally alternating, or acts at one time of the day along one course of surface and at another time of the day along another, as happens along multitudes of the sea coasts of the world, and very specially along those of the torrid zone, it produces the alternating currents of day and night, which are called land and sea breezes. And wherever it acts fitfully, whether from the peculiar relations of a country to the earth's rotation, or from the peculiar configuration of its surface, or from the disturbing influence of its sands or marshes or forests, or from changes in the state of the evaporation and the clouds, or from evolutions and outbursts of the electric fluid, or from any other of the causes or combinations of causes which control the temperature and variegate the seasons, it produces some one or other of the many kinds of currents which are called variable winds. All these are interesting; but only two classes, the noxious and the tempestuous, require any remark.

Noxious winds are an exception to the beneficial effects of currents in the air, yet perhaps more an apparent than a real one; for as they derive their noxiousness from the exhalations or influences of the regions whence they blow, they probably prevent awful catastrophes by sweeping away accumulations of aeriform poison. The worst arise only in the deserts and arid plains of Africa and South-western Asia, and bear the names of harmattan, sirocco, simoom, and samiel.

The harmattan blows periodically from Central Africa to the Atlantic. It is accompanied by thick dry fogs, and by quantities of very fine sand. It contains not

a trace of humidity, and does not permit the deposit of a drop of dew. And it dries furniture to splinters, withers growing grass into hay, and produces painfully parching effects on flocks and men.

The sirocco blows from the Sahara across the Mediterranean to Italy and Greece and the Levant. It seldom lasts longer than about a day and a half, yet commonly works much disaster. It operates in the manner of intolerable heat and of a deficiency of oxygen. It has a medium temperature of about 112 deg., and produces the same kind of sensation on the face as scalding steam from an oven. Fires burn languishingly in it, and animals have difficulty of breathing. It kills plants, produces extreme langour in brutes, sinks strong native men into profound depression, and is dangerous or deadly both to sick natives and to healthy foreigners. Persons who are best acquainted with it, and have the best known appliances for resisting it, simply shut themselves up in their houses, cut off every possible communication with the open air, and keep down the temperature by sprinklings of

water.

The simoom occurs in the deserts of Egypt, Syria, and Arabia, and in the adjacent countries. It may at first be only light and rapid, but it soon becomes burning and portentous. It careers on with a heat of at least 128 deg., and with obscuring loads of minute dust. The sun becomes lurid or blood-like; the air exhibits various tints of yellow and blue and red, and seems all on fire; and living creatures are hurled into a struggle with suffocation or death. The wind happily moves a little above the ground, and is of brief continuance, else it might destroy the life of all breath