gary, on the contrary, sheltered by the same range from the cold blasts of the north, enjoys a milder climate than any part of Germany.

The inhospitable climate of Siberia arises from its being unprotected on the north from the cold winds of the Arctic, or Frozen Ocean, while on the south a vast chain of mountains intercepts the warm southerly winds whose access would tend to mitigate the rigor of the atmosphere.

The central and southern parts of European Russia are colder than their latitude would lead us to expect, owing to the absence of any chain of mountains to protect them from the influence of cold northerly winds.

4th. THE PROXIMITY OF A COUNTRY TO, OR ITS REMOTENESS FROM, THE SEA.—This is an important element in determining its climate. The waters of the ocean, being of a more uniform temperature than the land, have a tendency to preserve a similar uniformity wherever their influence extends, moderating alike both heat and cold.

A cold wind in passing over the sea becomes warmed, while a hot wind, on the contrary, becomes cooled. Hence, we find that the climate of islands and of countries bordering on the sea, differs from that of countries situated in the interior or remote from the sea; the former being characterized by milder winters and more temperate summers.

5th. THE SLOPE OF THE COUNTRY, OR THE ASPECT IT PRESENTS TO THE SUN'S COURSE.—This has considerable influence upon its climate. The angle at which the sun's rays strike the ground, and, consequently, the power of those rays in heating it, vary with the exposure of the soil relatively to that luminary.

When the sun is elevated on the meridian 45° above the horizon, his rays fall perpendicularly on the side of a hill facing the south at an equal angle, while the plain below receives them at an angle of 45o.

6th. THE GEOLOGICAL CHARACTER OF THE SOIL.-The character of the soil of a country produces marked effects on its climate, which is owing principally to the greater or less power any soil possesses of radiating heat.

Sandy soils become rapidly and intensely heated, and when the sun's rays are withdrawn they readily radiate their heat and thus impart to the atmosphere an increase of temperature.

Clayey soils, on the other hand, become slowly heated, and as slowly part with heat. Marshy ground chills the air, and extensive forest tracts have a similar effect.

7th. THE DEGREE OF CULTIVATION WHICH THE COUNTRY HAS RE

CEIVED. This affects the climate to some extent; for if marshes arc drained, or forests cleared, the temperature will be raised. Such has been the case in some parts of our country, where the clearing of the forests and the progress of cultivation have improved the climate and rendered the winters milder.

"The destruction of forests may, however, be carried to a pernicious extent, either by depriving a country of shelter from particular winds or by lessening too much the quantity of moisture; it being well known that there is a great evaporation from the leaves of vegetables."

8th. THE PREVALENT WINDS OF THE COUNTRY.-The winds of a country produce considerable effect on its climate. The character of a wind, as we have before shown, depends upon the region whence it comes and the nature of the surface over which it passes.

9th. THE ANNUAL QUANTITY OF Rain that FALLS.—The quantity of rain that falls in a country affects the climate by imparting to it a greater or less degree of humidity. In general, more rain falls on islands and on sea-coasts than in inland districts, among mountains than in level regions, and within the tropics than in either of the other zones.

Kinds of Climate.-The climate of a country is said to be excessive or continental when the contrast between the summer and the winter temperature is very great; and insular, when the difference of temperature between these seasons is comparatively small.

For example, the mean summer temperature of Englard is about 63°, and the mean winter about 37°, making a difference of only 26°; whilst, at Pekin, the mean summer temperature is 79°, and the mean winter 23°, making a difference of 56°. The former has an insular, and the latter an excessive, climate.

ISOTHERMAL LINES.

Isothermal Lines (lines of equal heat) are lines drawn upon & map, connecting places on the surface of the globe that have the same mean annual temperature. All places situated on the same isothermal .ine, therefore, have the same mean annual temperature; but this does not necessarily imply that their climates correspond. In some the winters may be mild and the summers only moderately warm, whilst in others the extremes of heat and cold may be experienced.

The Warmth Equator, or line of greatest mean annual heat, extends for the most part north of the equator; which is owing to the position of the great land masses of the earth.

CHAPTER XV.

THE GEOGRAPHICAL DISTRIBUTION OF MINERALS.

It belongs to the science of Mineralogy to treat of the properties of the various mineral substances of the earth: Physical Geography merely takes cognizance of the geographical localities of those minerals which enter largely into the composition of rocks, describing such of their properties as tend to unfold the structure of the earth's

crust.

Minerals. These are natural productions of the earth formed by the action of chemical affinities, and organized, when becoming solid, by the powers of crystallization.

How Deposited.-They are deposited in veins, or fissures of rocks, in masses, in beds, and sometimes in gravel and sand.

How Diffused. They are very widely diffused over the earth; there being but few countries of any extent that do not contain some of them.

METALS.

Metals. They are sometimes found pure, but are generally mixed with other minerals, in a rocky substance which is called ore. The most important metals are gold, platina, silver, iron, copper, zinc, lead, tin, mercury, or quicksilver, cobalt, arsenic, antimony, and bismuth.

Gold. This is the most precious of the metals. It is usually found in grains, or gold-dust in a pure state. Lumps, or "nuggets," are rarely found, and they seldom exceed a few pounds in weight. Its geographical localities are as follows, viz :

IN BRITISH AMERICA.-Small quantities of gold have been found in Canada. IN THE UNITED STATES.-There are two gold regions in the United States, viz:—the Appalachian and the Californian. The Appalachian gold region extends from the Rappahannock River, in Virginia, to the Coosa, in Alabama. The Californian gold region is in the great valley of the Sacramento and the San Joaquin, which extends from north to south about 500 miles, with an average breadth of about 60. The mines of this region are among the richest in the world. They produce annually about 50,000,000 of dollars.

IN MEXICO.--Gold is found in great abundance in various parts of Mexico, and in some districts of Central America.

IN SOUTH AMERICA.—Gold is obtained along the base of the Andes, almost throughout their whole extent. Brazil is also rich in this metal.

IN EUROPE.-Gold is found in most parts of Europe, but nowhere in large quantities. The chief gold mines of this grand division are at Kremnitz, in Austria, which produce more than all the other mines of Europe.

IN ASIA.-Gold is abundant in some parts of Asia, especially in Western Siberia. The deposits at the foot of the Ural Mountains are very rich. Japan is believed to contain considerable quantities of this metal.

IN AFRICA. This country furnishes large quantities of gold, which are washed down from the mountain crevices by the rivers. It is especially abundant in Western Africa, among the Kong Mountains and along the Niger River, also in various parts of the eastern coast.

IN OCEANIA. The gold region of Australia is, next to that of California, the most productive in the world. It occupies the south-eastern part of the Continent. Its annual yield is estimated at nearly 40,000,000 of dollars.

The islands of the Asiatic Archipelago, particularly Borneo, Celebes, and Sumatra produce considerable quantities of gold.

Platina.—This is a grayish metal, more rare, and, on some accounts, more valuable, than gold, and is sometimes found in connection with it. It is obtained in some of the gold washings of South America, and has been discovered in the Ural Mountains in considera: le quantities. Too little, however, has as yet been obtained to render it an important article of commerce.

Silver. This metal is frequently found pure and in large masses; it is also found mixed with gold, copper, arsenic, and sulphur. Its geographical localities are as follows, viz. :

IN THE UNITED STATES.-There are no silver mines worked in this country. All that is produced comes from the gold of California. It has also been discovered in small quantities in lead ore.

IN MEXICO. This country contains the richest silver mines in the world. Their annual yield is estimated at 28,000,000 of dollars.

IN SOUTH AMERICA.-The countries of South America noted for their silver mines, are Peru, Bolivia, and Chili.

The quantity of silver found in other parts of the world is comparatively insignificant. The principal mines in Europe are those of Schemnitz and Kremnitz in Hungary and those of Spain.

Iron. This is the most useful, and the most extensively diffused of all the metals. It is estimated that it forms two per cent of the earth's crust.

The countries where it is found in the greatest abundance are the United States and Europe. In the former, the States most noted for its manufacture are Massachusetts, Connecticut, New York, New Jersey, Pennsylvania, Maryland, Virginia, Ohio, Kentucky, Tennessee, and Missouri. Iron Mountain in the State last named is composed entirely of specular iron ore. It is 1,500 feet in height.

Whitney estimates the entire produce of the iron mines in the United States, in 1854, at 1,000,000 tons; in Great Britain, at 3,000,000; and in Continental Europe, at 1,817,000 tons.

Copper. This metal ranks next to iron in utility, and, though less abund