Sea more or less regularly from June till November, recurring with tremendous violence once in three years.

Cy'clones, or hurricanes which whirl in circles at the same time as they advance, are frequent in the Indian Ocean between September and May, and in the West India seas between June and October. All whirlwinds are caused by the contact of two currents of air blowing in opposite directions. On land, they are often so powerful as to carry hay-stacks into the air, to tear off branches of trees, and to unroof houses. At sea, and in the clouds, they often produce Water-spouts.

The Pamperos are south-west winds which blow from the pampas of South America across the La Plata estuary.

Ete'sian Winds are the north-east winds which, in July and August, blow across the Mediterranean towards the heated surface of Africa.

QUESTIONS.-What does Physical Geog-| raphy describe?

the word physical.

becomes of the soil which a river sweeps Give the etymology of away from its banks? What sometimes takes place when it is deposited at the

1. What surrounds the globe? At what mouth of a river? Which are the most redistance above the earth does the atmos-markable deltas? phere disappear? Of what is atmospheric air composed? What element in it supports animal life? What supports vegetable life? What is conveyed through the air as a medium? What is one of its most important functions?

2. Whence does the vapour of water come? Where is evaporation greatest? Why? How much moisture does the ocean impart to the air per day? What causes condensation? What is cloud?

3. What is rain? What is hail? What is snow? What is dew? What is mist? Wherein does it differ from dew?

4. What becomes of the moisture which the earth receives from the air? How does it pass into brooks and rivers? Where do brooks and rivers carry it? What is the difference between a river and a pond? What is the bed of a river? What are the sides of the channel called? Which is the right bank? What is the junction of two rivers called? What is a tributary? What does a precipice in the bed of a river cause? What are the different sources of rivers?

5. What is a river-system? How do you mark off a river-basin? What is the high land between two adjoining riverbasins called? What is the effect of a mountain-system being far from the sea? Name the chief river-basins in Scotland, and the water-sheds between them.

6. In what respects are rivers important to a country? Mention rivers which are great highways of traffic. What is said of the greatest sea-ports in the world? What

7. How are mountains believed to have been formed? In what form does ice do this work? What does the glacier carry forward with it? Where does it deposit these? How are fragments of rocks detached in the region of glaciers? What is an iceberg? What does it carry on its surface? Where does it deposit these? What are proofs that glaciers once existed where there are none now? What has been the origin of many lakes? What is peculiar in Lake Titicaca? Mention lakes that have no outlet. Which is the largest fresh-water lake in the world?

8. What is a current of air called? What are the chief causes of wind? Explain this? What other causes are there? What is a hurricane? What two forces combine to produce the Trade Winds? Why are they so called? In what directions do they blow? Where are they most regular? What is peculiar in the Pacific trades? and in those of the Indian Ocean? Where is the region of the trade winds? What lies between the northern and southern? What lies outside of them? What are Monsoons? To what are they owing? When does the south-west monsoon blow? By what is it caused? When does the northeast monsoon blow? What change takes place on it in its passage from Asia to Africa? By what is the change of the monsoons accompanied? Where else do partial monsoons occur? What is the Simoom? the Harmattan? the Sirocco ? What are Typhoons? Cyclones? Pamperos? Etesian Winds?

II.-LAND AND WATER.

The surface of the globe consists of Land and Water; but the water-area greatly exceeds the extent of the land. Little more than one-fourth of the Earth is land; nearly three-fourths are water. Most of the land lies to the north of the Equator; most of the water to the south. If we could be ele

vated over London sufficiently high to be able to see one-half of the globe (that is, a hemisphere), our view would include nearly all the land surfaceall except a small portion of South America, a smaller portion of Africa, some of the East India Islands, and Australia. London is nearly the centre, or pole, of the hemisphere of greatest land.

1. THE CONTINENTS.

The land of the Earth is arranged in two great masses, lying nearly opposite each other on the globe. The larger mass lies in the Eastern Hemisphere, and is called the Old World, because it has been longer the home of civilization and science. The other, lying in the Western Hemisphere, is called the New World, because it is but a few hundred years since it became known to civilized man.

It should be noted that eastern and western, as applied to the hemispheres, are purely relative terms. Asia is west of America, as America is west of Europe. But as America was discovered by Europeans, who sailed westward, the New World was naturally called by Europeans the Western Hemisphere.

Both worlds are very broad in the north, so much so as nearly to touch each other; but they gradually separate, and extend southward in three different masses, terminating in three points very distant from each other.

Each of these masses of land is broken midway by the sea, which nearly or quite divides it, thus forming six distinct masses of land called Continentsthree on the north and three on the south. The northern continents are Asia, Europe, and North America; the southern are Australia, Africa, and South America.

In the Old World, Europe and Asia form really one great continent.

Australia and Africa are smaller portions connected with it, the former by a chain of islands, the latter by an isthmus. Thus the direction of the great mass of the Old World is east and west.

In the New World, both the continents are triangular in form, with their narrowest points turned southward. Thus the New World has its greatest extent from north to south.

The Old World is nearly double the size of the New, and forms-Australia apart-a much more compact mass.

The continents are very unequal in size: Asia is the largest, and Australia the smallest. Australia is three-fourths of the size of Europe; South America would make two continents like Europe; North America, a little more than two; Africa, a little more than three; and Asia, four and a half.

LOW-LANDS AND HIGH-LANDS.-Those lands which are nearly at the level of the sea—and that level is everywhere the same-are called Lowlands; those which are much above it, High-lands.

Low-lands are either valleys or plains. A Valley is a narrow belt of lowland between higher lands. A Plain is a wide extent of low-land. The most remarkable plains in the world are the Great European Plain, extending from the North Sea to the Ural Mountains; the Australian Plains; the Prairies and Savannas of North America; the Silvas, Llanos, and Pampas of South America; and the Steppes of Russia and Siberia.

High-lands are either plateaux or mountains. A Plateau, or table-land, is a high plain. It is called a table-land because, when compared with a lowland plain, it is like the top of a table compared with the floor. The most noted plateaux in the world are the Great Table-land of Central Asia; the Plateau of Iran, or Persia; the south of Siberia; the Table-land of Castile in Spain; the Plateau of Abyssinia in Africa; and the Table-land of Mexico in North America. A Mountain range is a ridge of high land extending through a country. Such are the Ural Mountains and Caucasus in the Eastern Hemisphere, and the Appalachians in the Western.

We generally find a number of mountain ranges connected with one another. They then form a Mountain System. Such are the Alps, Apennines, and Carpathians in Central Europe; the Himalaya, Thian-Shan, Kuenlun and Khin-gan Mountains in Central Asia; and the double and triple ranges of western heights in North America.

Upon the elevation and direction of the mountain system of a country depend its drainage, its slope, and its exposure; and hence, to a certain extent, its climate and productiveness.

Volcanoes are mountains which throw out from their interior dark clouds of vapour, ashes, red-hot lava, and sometimes hot water. Volcanoes are usually of a conical form, with a bowl-shaped mouth, called the crater, in place of a peak. Many rise from the midst of a surrounding plain, like Vesuvius in Italy; others from the top of a mountain range, like those of the Sierra Nevada in North America. They are most numerous within the Tropics, and occur either in groups or in chains. There are more than 270 active volcanoes on the globe. Some of these are of moderate size; but others, as Cotopaxi (18,875 feet) in Ecuador, and Popocatepetl (17,783 feet) in Mexico, are among the highest mountains on the Earth. The higher the

crater is, the less frequent are the eruptions. This is believed to be due to the fact that volcanoes are in direct connection with the fire which is raging in the interior of the globe. In fact, volcanoes may be regarded as safety-valves by which the excess of internal agitation finds vent, and but for which earthquakes would be more frequent than they are. In proof of this it has been observed, that in the neighbourhood of volcanoes earthquakes seldom occur, and are slight when they do occur. In volcanic regions, slight earthquakes are often the forerunners of eruptions, showing that both are due to the same cause. Thus, for several days before the great eruption of Mount Vesuvius in 79 A.D., which destroyed Pompeii* and Herculaneum, shocks of earthquake were felt in all the neighbouring towns and villages. The wide range of the influence of earthquakes shows that they proceed from a remote centre. Thus the great earthquake by which Lisbon was destroyed in 1755, and in which 50,000 inhabitants perished, was felt in Scandinavia, in Scotland, and even at Lake Ontario in North America.

Akin to volcanoes and earthquakes in their origin are hot-water springs, the most remarkable of which are the Geysers (that is, Ragers) of Iceland. Within the space of a few acres more than fifty of these geysers may be The greatest of them explodes once in forty hours or more, and then it sends into the air a column of hot water to the height of seventy feet.

seen.

THE CRUST OF THE EARTH (the study of which is called Geology) is composed of a great variety of mineral substances, metallic and non-metallic. The depth to which the Earth's crust has been examined is very small in comparison with its radius. The distance from the Earth's surface to its centre is nearly 4000 miles. The deepest mine has not been sunk more than one-third of a mile in perpendicular depth! The comparison of the shell of an egg with its yolk would give quite an exaggerated view of the fraction of the Earth's crust that has been examined.

An examination of this portion, however, shows that the same rocks occur in all parts of the Earth; and that the order of the strata, or layers of rock, is always the same. These rocks are of two great classes: 1st, Igneous, or Eruptive Rocks, which have been produced by fire; as basalt and granite. In connection with these the metals occur. 2nd, Aqueous, or Sedimentary Rocks, which have been deposited by water; as limestone and sandstone. In connection with these coal occurs.

From these, two classes of mixed rocks have been produced;-Conglomerates, such as the Essex pudding-stone, formed of pebbles and fragments of stone of different kinds cemented into masses; and Metamorphic, or crystalline rocks, such as gneiss, quartz-rock, and clay-slate, formed out of sedimentary rocks by the action of fire,

2. THE OCEANS.

The three great masses of land which stretch southward from broad bases near the Arctic Circle, are separated from one another by three great oceans -the Atlantic, the Pacific, and the Indian. The Atlantic separates Europe and Africa from America; the Pacific separates America from Asia and

* See lesson on The Destruction of Pompeii, p. 286.

Australia; the Indian separates Australia from Africa. These great oceans are the highways of communication between the continents.

Two smaller oceans surround the North and the South Pole respectively, and are called the Arctic, or North Polar, and the Antarctic, or South Polar Oceans.* These are of no importance as commercial highways, but they are resorted to, especially the former, for their valuable whale fisheries.

The greatest depth of the ocean that has been measured is probably southeast of Newfoundland, where it is about 30,000 feet. The average depth of the ocean seems to be greater than the mean height of the land.

The disturbances to which the waters of the ocean are subject are waves, tides, and currents.

1. WAVES.-Waves are occasional agitations of the surface of the sea, caused by the violence of the wind. The influence of waves extends comparatively a little way below the surface. Even in the most violent storm, the sea at the depth of 50 fathoms (300 feet) is perfectly quiet. The action

of the waves of the sea upon the coast is constantly wearing away both rock and soil. Where a coast is steep and rocky, the constant dash of the waves cuts and wears away the base of the cliff, sometimes leaving the top, which is beyond their reach, jutting over, as in the illustration. This is especially the case where the under part is a softer stratum than the upper. This * For a particular description of The Five Oceans, see ROYAL READER No. V.; and Nelsons' Geography and Atlas.