more rapidly than the water; so, after a while, it becomes actually the colder of the two, and the breeze now sets from the land to the sea. It will be evident, that when the air is sweeping along near the surface of the earth from the ocean to the shore, the space it is leaving must be filled from elsewhere, and what so ready to fill it as the air which has just risen from the heated ground. Accordingly, we always find that when there is a wind of this sort blowing in one direction, there is a contrary current in the upper regions of the atmosphere.

From this we may learn what is constantly taking place on a grand scale over the whole surface of the globe. The great heat near the equator causes a constant upward current, which draws the air from those regions that are colder. Hence there are two gigantic circles of wind, one in each hemisphere:- the air rising, passing through the upper parts of the atmosphere, descending as it nears the poles, and then sweeping again over the surface of the earth towards the equator. But there are several things which interfere with the regularity of this action. In the first place, this globe of ours is always revolving rapidly from west to east; and although this would not affect air when at rest, or blowing around the same latitude, yet it must be remembered that the air starting from the equator has a more considerable impetus than is necessary to accompany the earth in its rotation in higher latitudes; and hence the stream, which blew at first from the south, appears presently to be coming from the south-west; and when it arrives near the pole, it will have become almost a due west wind. The reverse takes place with the stream from the north; for the opposite reason, it is soon found to be blowing from the east of north, and eventually changes in like manner into a regular east wind.

Again, the configuration of the land, the direction of

mountain-chains, local alternations in the temperature of the earth, and a thousand other circumstances, are always interfering, and thus render the problem of the winds an extremely difficult one. The wind, too, meets with resistance in passing near the earth, and thus flows less quickly than it does in the higher regions, just as the water at the bottom and sides of a river never has so great a velocity as that in the middle of the stream.

This great circle above mentioned, between the poles and the equator, is observed in the trade-winds, which blow steadily from the eastward on each side of the "region of calms," that marks the hottest part of the earth's circumference. The returning "trade" in those latitudes is at such a height above the ground that it is only indicated by light films of cloud, which are often seen to move in the opposite direction to the prevailing current below. In our own climate the upper stream frequently descends, and, as a south-west wind, brings to us some of the warmth and moisture of the tropics; though perhaps we more frequently experience the lower current-the north-east wind, which will often blow steadily for weeks together, especially in spring, cold from the pole and the frozen plains of Russia.

When two currents, blowing from opposite directions, meet, they must slide, as it were, past one another; but at their junction a whirlwind will be produced, such as we often see on a small scale in the eddies caused by a house, or some such opposing body. We all know how such little whirlwinds catch up dust or straws into the air, or sometimes play strange pranks with the dress of the unwary traveller; and we can readily understand how, when a larger vortex than these is sweeping, unobstructed, over the sea, the clouds above and the waters below should be caught into it; and meeting in mid-air, should form those waterspouts, which are so dangerous to small vessels. The sailors

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are accustomed to disperse them, as they do human enemies, by firing cannon at them, and so breaking the circle of wind.

The most severe storms are produced, when the great south-west and north-east currents oppose one another. The gigantic whirlwind then formed may be scores of miles in breadth, and will often sweep right across the Atlantic, traverse our own country, and then pass on to Denmark and the Continent of Europe. Through the great attention lately paid to the "circular theory of storms," captains of ships are enabled, by observing the direction of the change of wind, to sail right away from the danger. For instance, if sailing eastward in the Northern hemisphere, he observe the wind veering from south to west, and then to north, the centre of the storm is on his right hand, and he, of course will only have to turn his vessel towards the left, and the tempest may spend its fury harmlessly in the distance. Just in the same way the landsman may judge, by the rapid shifting of the weathercock, what is the course of a hurricane, which may be at that very moment tearing up trees, overthrowing hayricks, and unroofing houses.

Thus, however much we may have been accustomed to view the wind as an emblem of all that is fickle and capricious, we now see that, whether it be a West-Indian tornado, at the speed of seventy miles an hour, devastating whole islands, or a gentle breeze, which scarcely stirs the petals of a flower, it is as subject to fixed and regular laws, and as much a matter of scientific investigation, as the growth of a tree or the course of a planet.

J. H. G.

ON the 12th of March, as I was about to retire to rest, I opened a chink of the window-shutter to let in light in the morning, when I was startled by the magnificent spectacle : such a night of cloudless glory I have seldom seen. The moon was in the midnight splendour of her ripening second quarter; her eastern horn not quite filled, but shining calmly down with a rich golden lustre out of the deep purple sky behind, whose concave was spangled with silvery stars. But what caught my attention was, that close to her, at apparently not more than a yard's distance, was a fiery red and brilliant star, which a glance told me was Mars, evidently in conjunction with the moon. Remembering that there was to be an occultation of that planet by the moon some night this month-for I am not a professed astronomer-I immediately concluded that this was the very night in question.

What a fortunate occurrence! "Forthwith to rub the sleep from my eyes, to reapparel myself," to betake myself to the Nautical Almanac, was the work of a moment. To my great annoyance, however, I found that the occultation would not take place for nearly three hours. It was then about a quarter to twelve: this was a long wait for a tired and sleepy man. There was no alternative. If I went to bed, I should certainly never awake in time, and the whole phenomenon would be a real occultation to me. Then, the opportunity was so tempting, and a planet's occultation such a comparatively rare event, it must not be lost; so I made up my mind at once to fight resolutely with sleep, and see it out. I proceeded, therefore, in the first place, to prepare my great gun, a large refracting telescope 10 feet 6 inches in focus; and having examined the relative position and appearance of the two bodies in question, I commenced my lonely but deeply-fascinating watch.

All was silent in the house; every one sunk in slumber but myself. Alone, in my observatory—which is merely a room, from the south and west windows of which my large telescope is directed-I sat down. No sound broke the perfect stillness that reigned, save the ticking of the clock at hand, or the scraping of some restless mouse in the wainscot, or now and then a gentle sigh of the wind that stole mournfully past the open window, and away round the corners of the house. I took up a volume, and tried to pass some of the interval in reading, but in vain. That view through the open window fascinated me. My attention wandered from my book, and every now and then I was compelled to get up and take a glance through the telescope, or stand gazing away amidst the multitude of the starry host. ever and anon the eye reverted to those two distant shining orbs. There they are, about to overtake and pass each other in the silent sea of space, as ships meet and pass on

And