and suffocating, as to be attended with dreadful effects. These winds, under the name of Solanos, are often felt in the Desert of Arabia and the interior of Africa.

III. OF EARTHQUAKES.

29. For the same reason that we illustrated the various winds, we are now to elucidate earthquakes, which are of two kinds :

1. One kind, caused by the action of subterraneous agents and the explosion of volcanoes, felt only at small distances, and always attended by eruptions, or openings of the earth.

2. Another kind, felt at great distances, shaking extensive tracts of ground without any eruptions taking place, and therefore followed by less dreadful consequences.

Obs. We have only to suppose the access of water to large masses of those peculiar metals which constitute the earthy and alkaline bases, and we are acquainted with all that is necessary to produce the tremendous effects of volcanoes and earthquakes; for what power can resist the expansive force of steam, and the sudden evolution of gaseous fluids, accompanied by torrents of the earth's igneous fusion, to which such a concurrence of circumstances would give rise, and which are the actual concomitants of volcanic eruptions? Of all the phenomena of nature, earthquakes are the most terrific and destructive. They seldom occur in the British islands; but, in 1755, Lisbon was destroyed by one, and they are of nearly annual occurrence in Sicily, and in the West Indian and East Indian islands, and in Mexico and Peru.

IV. OF THE TIDES.

30. Those regular motions of the sea, according to which it ebbs and flows twice in twenty-four hours, are called the TIDEs.

Illus. 1. When the sea, in its flux, has risen for about six hours, it remains, as it were, suspended and in equilibrio for some minutes; and at that time it is called high water.

2. When, in its reflux, the sea has fallen for about six hours,

it remains, in like manner, as it were, suspended and in equilibrio; and at that time it is called low water.

31. The Tides are occasioned by the rotation of the Earth round the common centre of the masses of the Earth and Moon.

Illus. 1. The tides are greatest at the new and full moons, and are called spring-tides: they are least at the first and last quadratures, and are called neap-tides; and the highest tides are near the times of the equinoxes.

2. When the moon is in the northern hemisphere, and in he meridian above the horizon, it produces a greater tide than when it is in the meridian below it; and, when in the southern hemisphere, the reverse is the case.

3. For the same reason, when the moon is in the southern signs, the greatest tides on the other side of the equator will be when it is below our horizon, and when it is above it the tides will be least.

V. SALTNESS OF THE SEA.

32. Sea-water is salt; and, except the Caspian Sea, whose waters are a little brackish, the waters of all lakes and rivers are mild, sweet, and fit for human purposes.

Illus. 1. Salt is one of the original principles in nature, and is mixed, in greater or less quantities, with all other substances. All rivers run into the sea, and therefore carry some salt with them; but no rivers run out of it, nor is any water taken out of it, except by exhalation and evaporation; and no salt ascends in either of these ways; it has consequently been inferred, without supposing great beds of salt originally deposited in the bottom of the sea, that the immense number of rivers which run into it, carry with them a sufficient quantity of salt to give to the whole body of waters of the deep, that saltness, which, with their motions and currents, preserves them from putrefaction.

2. It is obvious that no salt ascends from the sea, because rain water, which falls from the clouds that were originally exhaled from the sea, is the sweetest, purest, and lightest, of all waters, and is made the standard by which philosophers judge of all other waters.

3. Hence many contrivances have been adopted for distil.

ling sea-water at sea for ordinary use on ship-board; and hence the pits or pans for making salt, on many coasts of the sea.

VI. OF THE AURORA BOREALIS.

33. In illustrating the two seasons of the year in the frigid zone (north), we had occasion to mention the benefit derived from the Aurora Borealis : we shall now describe it.

34. That shining light which is often seen by night in the heavens, and which is vulgarly called the northern lights, or streamers, is the Aurora Borealis, which till the month of March, 1716, was not much observed in England.

Obs. This phenomenon is supposed to be the result of electrical fluid passing from one region to another; though some have strangely enough supposed it to be produced by nitrous and sulphureous vapours thinly spread through the atmosphere and above the clouds, where they ferment, and, taking fire, the explosion of one portion kindles the next, and the flashes succeed one another till all the vapour is set on fire. But we know sufficient of the electric fluid's powers and operations not to believe it the cause of those streams of light, which, under the name of the Aurora Borealis, seem to converge towards the zenith of the spectator, or to that point of the heavens which is immediately over his head.

VII. OF THE TEMPERATURE OF THE EARTH.

35. The temperature of the countries which we have studied is not the same in all: some are extremely hot, others are intensely cold.

36. The hottest countries are, in general, those within the tropics; and the coldest are the polar regions.

37. According to its temperature the earth is divided into five zones, of which, two are called the frigid zones, two the temperate zones, and one the torrid zone.

38. The frigid zones are those portions of the globe included within the polar circles; one is the

north, and the other the south, frigid zone. Each zone is 1624 miles broad; and, for the most part, too cold to be inhabited by man.

39. The two temperate zones are the spaces of land and water all round the globe, comprehended between the polar circles and the tropics; each being 2970 miles broad. The north temperate zone lies between the tropic of Cancer and the arctic circle; and the south temperate zone between the tropic of Capricorn and the antarctic circle.

40. The torrid zone is all that portion of the earth and water round the globe, which is included within the tropics, being 3244 miles broad.

41. Heat and cold do not, however, depend solely on a particular situation in the temperate and torrid zones; the higher a country lies above the level of the sea, the colder it is; and, at a certain height, in every zone, it is so cold that snow and ice do not melt.

42. The summits of the highest mountains within the torrid zones are covered with perpetual snows. The Andes of South America have climates of all temperatures, from the torrid to the frigid; and the line above which the snow does not melt is called the snow line. See my "Illustrations of Popular

Geography."

VIII. PRODUCTIONS OF THE EARTH.

43. All natural productions are arranged under three grand classes, called KINGDOMS: 1. The Mineral; 2. The Vegetable; and 3. The Animal kingdom.

44 The Mineral kingdom contains, 1. all earths and stones; 2. mineral combustibles; 3. salts; and, 4. metals.

45. The Vegetable kingdom includes all trees,

shrubs, and plants, whether in the ocean or on the land; hence we speak of marine and terrestrial vegetables..

46. The Animal kingdom contains all living creatures, as, 1. quadrupeds; 2. bipeds; 3. fowls; 4. fishes; 5. reptiles; 6. insects; 7. worms.

47. Man, the chief of the world, is, on earth, the noblest of all God's creatures. The faculties of reason and speech distinguish him as lord of the creation; and his progressive improvement distinguishes his pre-eminence above all other animals.

IX. VARIETIES OF THE HUMAN SPECIES.

48. There are FIVE grand varieties of the human race; but they imperceptibly approach, and are lost in each other.

49. First; the white and brownish nations of Europe, western Asia, and the north coast of Africa ; who, according to our notions of beauty, are the handsomest and best formed of the human race.

Obs. These include the Europeans, Turks, Tartars, Arabians, Persians, and, according to some naturalists, the Hindoos.

50. Second; the yellow or olive-coloured Chinese, Monguls, Calmucks, and other eastern nations of Asia, with whom may be classed also the most northerly aboriginal Americans, having flat foreheads, little eyes, and wide mouths.

51. Third; the copper-coloured American Indians, dispersed over the entire continent; with broad faces, long and bristly hair, and stout masculine limbs.

52. Fourth; the jet black negroes and other Africans of various shades of black, having woolly hair, thick lips, flat noses, prominent chins, and downy skins.

53. Fifth; the dark brown Australians, on the

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