1789, 1795, &c. It describes its elliptic orbit about the sun in 6 years, and was seen in 1832 and 1838. The periods of this comet are continually diminishing; in other words, its mean distance from the sun, or the major axis of the ellipse, is dwindling by slow but regular degrees. The probability of a comet coming in collision with the earth, or with any other planet, may be reduced to a very slight amount, if we compare with the small volume of the earth or any other planet, and that of comets, the immensity of the space in which these bodies move. M. Arago observes that the doctrine of chances affords us the means of estimating numerically the probability of such a collision, and shows that there is but one such chance in 281 millions; that is to say, that, on the appearance of a new comet, the odds are 281 millions to one that it will not strike against our globe. 1. Who first proved that comets pass round the sun? 2. What number of comets is supposed to belong to our system? 3. State the periods of return, of the three best known to us. 4. Give particulars of the comet that appeared in 1682. 5. What appearance have these roving stars, when examined through a telescope? 6. What are the tails of comets supposed to be? 7. Who first predicted the reappearance of one of these bodies? 8. What are the chances of a collision between the earth and a comet, as computed by Arago, the great French Astronomer? TRADE WINDS, AND THEIR DISCOVERY. Per'ma-nent, adj. (L. per, maneo), Tran'si-ent, adj. (L. trans, iens, Ex-plore', v. (L. ex, ploro), to der less difficult. which the name of an animal, or other object, has been given, either for distinction's sake, or from some fancied resemblance. Ho-ri'zon, n. (Gr. horos), the line which terminates the view, where the earth or sea and sky seem to meet; an imaginary line equally distant from the zenith and the nadir, dividing the globe into hemispheres. Phos-pho-res cent, adj. (Gr. phōs, phero), shining with a faint light, and without being sensibly hot. Qua'drant, n (L.quatuor), the fourth part of a circle; an instrument for taking the altitudes of the sun or stars, of great use in astronomy and navigation. THE trade winds are permanent, following the same direction throughout the year. They are met with between the tropics, and a few degrees to the north and south of those limits. The well-known name applied to them is a phrase of doubtful origin, but probably derived from the facilities afforded to trade and commerce, by their constant prevalence and generally uniform course, though Hakluyt speaks of the "wind blowing trade," meaning a regular tread or track. The parallels of 28° north and south latitude mark the medium external limits of the trade winds, between which, with some variations, their direction is from the north-east,' north of the equator, and from the south-east, on the other side of the line, hence called the north-east and south-east trades. They are separated from each other by the region of calms, in which a thick foggy air prevails, with frequent sudden and transient rains attended by thunder and lightning. 2 We owe the discovery of the trade winds to Columbus, and this would have been prominently connected with his name, had it not been supplanted by the glory of a greater achievement, the revelation of a new world to the knowledge of mankind. The ancients were entirely unacquainted with these permanent breezes, and though maritime adventure had been largely prosecuted by the Portuguese at the instigation of Prince Henry, they had not penetrated into the region of the trades. Proceeding cautiously along the shores of Barbary, they had explored the coasts of Africa to Cape de Verde, rescued the Azore Islands from the "oblivious empire of the ocean," and afterwards under Vasco di Gama3 doubled the Cape of Good Hope; but these voyages carried them clear of the district of the north and south-east trade winds. But soon after leaving the Canaries in the Santo Maria, Columbus fell in with the former, which in the summer extend to the latitude of those islands, and, for the first time, a sail from the Old World swelled before the steady breath of the northern tropic. This circumstance, favourable to the success of his expedition, speedily excited the apprehensions of his crew, who found themselves 1 In speaking of the direction of currents of air and water, the indicating terms are used in an inverse sense, an easterly wind signifying a breeze coming from that quarter, an easterly stream, a flow of water towards it. 2 Christopher Columbus, the discoverer of the New World, a native of Genoa, born 1435, and, to the everlasting disgrace of Spain, died poor and broken-hearted at Valladolid, 1506. He discovered San Salvador, October 11th, 1492. 3 Vasco di Gama, a native of Portugal, doubled the Cape of Good Hope 1497,-5 years after the discovery of America by Columbus. borne, day after day, by a permanent breeze, farther from their native shores, and inferred the impossibility of returning, as they observed no change in its direction. Fortunately for his fame, and for the world, the great navigator firmly held on his course, reached the bounds of the before supposed illimitable ocean, and re-crossed it in the region of the variables, to the north of the northern trade wind. Now, in passing from the Canaries to Cumana, on the north coast of South America, it is scarcely ever necessary to touch the sails of a ship; and with equal facility the passage is made across the Pacific, from Acapulco, on the west coast of Mexico, to the Philippine Islands. If a channel were cut through the Isthmus of Panama, the voyage to China would be remarkably facilitated by the trade winds of the Atlantic and Pacific Oceans, be more speedy, agreeable, and safe, than the usual route by the Cape, the chief interruption to its uniformity occuring in the Carribean Sea and the Gulf of Mexico, where the trade wind blows impetuously, the sea is stormy, and the sky grey and cloudy. All mariners and passengers have spoken with delight of the region of the trade winds, not only on account of the favouring gale, but its genial influence, the transparent atmosphere, the splendid sunsets, and the brilliancy of the unclouded heavens, day and night. Columbus, in recording his first voyage into their territory, compares the air, soft and refreshing without being cool, to that of the pure and balmy April mornings he had experienced in Andalusia, wanting but the song of the nightingale and the sight of the groves to complete the fancy that he was sailing along the Guadalquivir. Humboldt lingers with pleasure, upon his first acquaintance with the tropical regions at sea, upon the mildness of the climate and the beauty of the southern sky, gradually opening new constellations to the view, stars contemplated from infancy progressively sinking and finally disappearing below the horizon, an unknown firmament unfolding its aspect, and scattered nebulæ rivalling in splendour the milky way. "A traveller," he states, "has no need of being a botanist, to recognise the torrid zone, on the mere aspect of its vegetation; and without having acquired any notions of astronomy, without any acquaintance with the celestial charts of Flamstead and De la Caille, he feels he is not in Europe, when he sees the immense constellation of the Ship, or the phosphorescent clouds of Magellan, arise on the horizon. We pass those latitudes as if we were descending a river, and we might deem it no hazardous undertaking if we made the voyage in an open boat." Mr. Bailey, in his "Four Years in the West Indies," relates an adventure nearly answering to that here referred to. The master of one of the small fishing smacks that ply along the coasts of Scotland, who had no other knowledge of navigation than that which enabled him to keep his dead reckoning, and to take the sun with his quadrant at noon-day, having heard that sugar was a very profitable cargo, determined, by way of speculation, upon a trip to St. Vincent, to bring a few hogsheads of the commodity on his own account into the Scottish market. Accordingly, he freighted his vessel; made sail; crossed the Bay of Biscay in a gale; got into the trade winds, and scudded before them at the rate of seven knots an hour, trusting to his dead reckoning all the way. He spoke no vessel during the whole voyage; and never once saw land until on the morning of the thirty-fifth day, when he descried St. Vincents right ahead, and running down, under a light breeze, along the windward coast of the island, came to anchor. The private signal of the little vessel was unknown to any of the merchants, and it immediately attracted notice. The natives were perfectly astonished-they had never heard of such a feat before; and deemed it quite impossible that a mere fishing smack, worked only by four men, and commanded by an ignorant master, should plough the billows of the Atlantic, and reach the West Indies in safety-yet so it was. This relation justifies the title given by the Spaniards to the zone where the trade winds are constant, el Golpo de las Damas, the Sea of the Ladies, on account of the ease with which it may be navigated, the uniform temperature prevalent night and day, and its pacific aspect. 1. Whence has the name Trade Winds most likely been derived? 2. State the limits between which they prevail. 3. In what direction do they blow north of the Equator, and in what south? 4. What separates the N. E. from the S. E. Trades? 5. To whom do we owe the discovery of the "Trades?" 6. Why is this rarely mentioned with the name of Columbus? 7. When did Columbus discover San Salvador, one of the Bahamas? 8. Who discovered the route to India by the Cape of Good Hope, and when? 9. How did the crew of Columbus feel in the N. E. trade wind? 10. What voyages are most easily made by these favouring gales? 11. In what terms does Humboldt speak of the tropical regions at sea? 12. What was the amount of knowledge possessed by the master of the fishing smack spoken of? 13. On the morning of what day from his starting did he descry St. Vincents? 14. What name do the Spaniards give the zone of the Trades? 15. To whom should we ever look in prosecuting the voyage of life? THE VOLCANO AND THE EARTHQUAKE. Vin-dic'tive, adj. (L. vindex), re- mark; trace. E-rup'tion, n. (see p. 45). Lu'mi-nous, adj. (L. lumen), full of Fu'sion, n. (L. fusus, see fundo), THE first impression made on the mind by the history of volcanic action is, that its effects are examples rather of vindictive justice than of benevolence. And such is the light in which they are regarded by Mr. Gisborne, an able English divine, in his "Testimony of Natural to Revealed Religion." He looks, indeed, upon all the disturbances that have taken place in the earth's crust as evidence of a fallen condition of the world, as mementos of a former penal infliction upon a guilty race. And aside from the light which geology casts upon the subject, this would be a not improbable conclusion. Take for an example the case of volcanoes and earthquakes. A volcano is an opening made in the earth's crust by internal heat, which has forced melted or heated matter through the vent. An earthquake is the effect of the confined gases and vapours, produced by the heat upon the crust. When the volcano, therefore, gets vent, the earthquake always ceases. But the latter has generally been more destructive of life and property than the former. Where one city has been destroyed by lava, like Herculaneum,' Pompeii, and Stabiæ, twenty have been shaken down by the rocking and heaving of earthquakes. The records of ancient as well as modern times abound with examples of these tremendous catastrophes. Pre-eminent on the list is the city of Antioch. Imagine the inhabitants of that great city, crowded with strangers on a festival occasion, suddenly 1 Herculaneum, Pompeii, and Stabiæ, were overwhelmed by an eruption of Mount Vesuvius, in the reign of the Roman Emperor Titus, A D. 79. They have been re-discovered, and in them found statues, paintings, bronzes, vases, and domestic implements of all varieties of forms and uses. The Elder Pliny, the celebrated Roman Historian, in going too near to examine the phenomena of the eruption, and also to afford relief to the sufferers, unfortunately perished. |