An extensive system of currents appears to arise in the Antarctic Ocean. A current of cold water flowing northward joins the equatorial current in the Pacific. Entering the Indian Ocean, it maintains its westerly course until it approaches the shores of Africa; then bending southward it rushes through the Mozambique Channel, and doubling the Cape of Good Hope travels northward until it arrives at the Bight of Benin. This current then joins the equatorial current, and crossing the Atlantic from the coast of Guinea to that of Brazil, it is divided into two branches by the projecting headland of Cape San Roque, one flowing southward and the other northward.
The Gulf Stream. After passing the Island of Trinidad, this great oceanic current enters the Gulf of Mexico, and there acquires a high temperature, and sweeping round that sea it again pours forth into the Atlantic, forming the most powerful of known currents, called the Gulf Stream. Issuing from the Gulf of Mexico, this current of warm water rushes with considerable force through the Bahama Channel; then taking a northerly course it travels along the eastern shores of North America, and at Newfoundland is turned to the eastward by an opposing cold current which sets in from Baffin’s Bay. It now maintains an easterly direction, and crossing the Atlantic arrives at the Azores in about twenty-eight days, and divides its waters on the coast of France and Spain: one portion goes southward and at length joins the grand current which sets from the coast of Guinea; and another portion travels northward and skirts the western coasts of Europe. These currents are seldom more than 500 feet deep.
ATMOSPHERE, CLIMATE AND WEATHER
The atmosphere is the vast ocean of air that envelops the earth and makes life possible on our globe. It absorbs the heat and vapors caused by the action of the sun upon the surface of both land and water, and is the medium through which the ever-changing phenomena of climate and weather are produced. The two great forces of nature acting in connection with it are gravitation and heat, or solar radiation; and the results of their ceaseless action may be summed up as follows: (1) Temperature, or heat, which we soon learn to know by our senses, and to measure by the thermometer. (2) Evaporation, which changes the weight of the air by carrying invisible moisture through it. This change of weight is indicated by the barometer. (3) Condensation, producing fog, dew, rain, hail, and snow; all estimated accurately by the rain gauge or pluviometer. (4) Motions, as in the winds, varying from the gentle breeze to the awful cyclone, the force and velocity of which are indicated by the anemometer. (5) Electricity, producing lightning, thunder, magnetic and chemical changes in the atmosphere. (6) Optical Phenomena, such as rainbows, haloes, coronas, mirage, and the auroras.
THE ATMOSPHERE: ITS EXTENT, CHARACTER, USE AND EFFECT
The Earth is enveloped in its own atmosphere, which like a transparent covering surrounds it, and revolves with it. This atmosphere does not extend to more than forty or fifty miles above the earth’s surface, and is higher at the equator than at the poles.
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