whole region lying within the arctic circle, causing there uninterrupted day. In the position W, the northern half of the earth's axis being turned away from the sun, this region will be immersed in unbroken night. As regards the intermediate positions, the days will gradually lengthen, and the nights will equally shorten, (since day and night together make up 24 hours,) from the vernal equinox to the summer solstice, when we have the longest day; from this to the autumnal equinox, the days will shorten and the nights lengthen, until they are once more equal; from the autumnal equinox to the winter solstice, the days will shorten; and from this to the vernal equinox, they will lengthen. In the southern hemisphere the succession of the seasons is reversed; the spring of this corresponding to the autumn of the northern, the summer to the winter, and so on.

17. The inclination of the earth's axis to the plane of her orbit leads to the division of the earth's surface into zones, which differ greatly in their temperature. These zones are five in number. That which lies between the north pole and the arctic circle is called the north frigid zone; that between the south pole and the antarctic circle the south frigid zone. The extreme cold of these zones is occasioned by the total disappearance of the sun during their winter, and the great obliquity of his rays during their summer. Those two portions of the earth's surface, which lie between the polar circles and the tropics, are called the north and south temperate zones. That portion which lies between the two tropics, 2310 on each side of the equator, is called the torrid zone. The sun is always vertical over some part of it, and hence its extreme heat.

18. Latitude and Longitude.-The position of any place on the earth's surface is expressed by its distance from the equator, and from an arbitrary great circle called the first meridian. To ascertain these distances, draw a meridian through the given place the length of the arc of this meridian between the given place and the equator, expressed in degrees, minutes, and seconds, will be its distance from the equator; and is called its latitude. It is either north or south, according as the place is north or south of the equator. A place situated upon the equator will of course have no latitude; whilst the greatest possible latitudes will be those of the N. and S. poles, viz. 90° N. and 90° S. Since every meridian is a great circle, all degrees of latitude will be of nearly the same length.

19. Next, draw a circle through the given place parallel to the equator: the length of the arc of this parallel (as it is called) between the given place and the point where it intersects the first meridian, expressed in degrees, minutes, and seconds, will be its distance from the first meridian, and is called its longitude. It is usually reckoned as east or west, increasing from 0°, which is the longitude of all places upon the first meridian, to 180°, which is both E. and W. Some geographers are now beginning to adopt the preferable reckoning of eastward only; so that all longitudes are E. and increase up to 360°. The English take as their first meridian that which passes through the Observatory at Greenwich; the French that which passes through the Observatory at Paris; other first meridians are taken by other nations. Since every parallel is a small circle, the degrees of longitude will be of different lengths, de

creasing from 69 English miles, their length at the equator, to nothing, their length at the N. or S. poles.

20. Since the meridians on which latitude is measured, mark longitude on the equator, they are called meridians of longitude. Since the parallels on which longitude is measured, mark latitude on the first meridian, they are called parallels of latitude.

21. Time and Longitude.-Since the sun appears to move from east to west, noon will occur earlier in the east than in the west. Since 15° is the twenty-fourth part of 360°, a place 15° east of London will have noon an hour earlier; a place 30° west of London will have noon two hours later; and so in proportion for all other places.

22. Points of the Compass.-The following are the 32 points of the compass.

23. Terrestrial Magnetism.-The magnetic needle, the essential part of the mariner's compass, was introduced into Europe about A.D.1180: it had been long known to the Chinese. It was first used in navigation by Marco Paolo. Its peculiar property is to turn towards the north and south; but it is sometimes on the east, sometimes on the west, of the geographical meridian: this difference is termed the magnetic variation. Neither does the magnetic needle remain horizontal, when freely suspended: but it undergoes a dip; which, however, nearly disappears at the equator. The whole rationale of terrestrial magnetism is at present most obscure and difficult.

SECTION II.

GENERAL DISTRIBUTION OF LAND AND WATER.

24. The land occupies from one-fourth to onethird of the whole surface of the earth, and may be divided into three great portions called worlds, which are completely separated from each other by the ocean; viz. the Old World, subdivided into Europe, Asia, and Africa; the New World, subdivided into North and South America; and the Maritime World, or Oceanica, subdivided into Malaysia, Australia, and Polynesia.

25. Europe, Asia, Africa, and America are often called continents, because they contain several countries. A portion of land entirely surrounded by water is called an island. A portion of land almost surrounded by water is called a peninsula. A narrow

neck of land connecting two larger portions is called an isthmus. A portion of land projecting into the sea is called a cape; if high or mountainous, a promontory.

26. The water occupies from two-thirds to threefourths of the whole surface of the earth, and constitutes, strictly, one immense ocean; which, however, is usually thus divided and subdivided. 1. The Western Ocean, which includes (1) the Northern, (2) the Atlantic, (3) the Ethiopic Oceans; all three being often called the Atlantic. 2. The Eastern Ocean, which includes (1) the Indian, (2) the Pacific, (3) the Southern Oceans.

27. A sea is a smaller portion of water than an ocean, and is somewhat bounded by land. A gulph is a portion of water almost surrounded by land. A bay is a portion of water running into the land, with a wider opening than a gulph. A lake is a portion of water entirely surrounded by land. The application of these terms, however, is somewhat capricious. A strait is a narrow passage of water, connecting two seas; when so shallow that it may be fathomed, it is called a sound. A channel is a passage longer and broader than a strait. A harbour is a small gulph or bay. The terms road, port, or creek, are also applied to small portions of the sea. A river is a current of fresh water, rising in the land, and flowing into the sea. The mouth of a river widening into the sea is called an estuary or frith. The right and left banks of a river are those on our right or left hands as we go down the stream; that is, from the head to the mouth.

28. We have observed the great inequality of land and water in respect of their extent on the earth's surface; the inequality of distribution in respect of