MINES.

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soil. A great many descend beneath the level of the ocean; and a few even extendUnder its billows, and are separated from them by a thio partition of rock, which allowstheir noise, and the rolling of the pebbles, to be heard.

In 1792, there was opened, at Valenciana, in Mexico, an octagonal pit , fully 7|- yardswide, destined to have a depth of 560 vards, to occupy 23 years in digging, and to cost240,0001.

The great drainage gallery of the mines of Olausthal, in the Hartz, is 11,377 yards, orsix and a half miles long, and passes upward of 300 yards, below the church of Clausthal .Its excavation lasted from the year 1777 till 1800, and cost about 66,0001. Severalother galleries of efflux might also be adduced, as remarkable for their great length andexpense of formation.

The coal and iron mines subservient to the iron works of Mr. Crawsliay, at Merthyr-Tydvil, in Wales , have given birth to the establishment, interiorly and above ground,of iron railways, whose total length, many years ago, was upward of 100 English Bales.

The carriage of the coal extracted from the mines in the neighborhood of Newcastleto their points of embarkation, is executed almost entirely, both under ground and onthe surface, on iron railways, possessing an extent of upward of 500 miles.

There is no species of labor which calls for so great a development of power as thatof mines; and accordingly, it may be doubted if man has ever constructed machines sopowerful as those which are now employed for the working of some mineral excavations.The waters of several mines of Cornwall are pumped out by means of steam-engines,Whose force is equivalent in some instances to the simultaneous action of many hundredhorses.

Mines, General Summary or.

Mines maybe divided into three great classes : 1. Mines in the gealogical formationsUtiterior to the coal strata; 2. Mines in the secondary formations ; 3. Mines in alluvialdistricts.

The first are opened, for the most part, upon veins, masses, and metalliferous beds.

The second, on strata of combustibles, as coal; and metalliferous or saliferous beds.

The last, on deposites of metallic ores, disseminated in clays, sands, and other alluvial■natters, usually superior to the chalk; and even of far more recent formation.

The mines of these three classes, placed, for the most part in very different physicallocalities, differ no less relatively to the mode of working them, and their mechanical■■eatment, than in a gealogical point of view.

MINES OF FORMATIONS ANTERIOR TO THE COAL.

These mines are situated in a few mountainous regions, and their whole amount formsBut a small portion of the surface of the earth. The most remarkable of these are—■he Cordilleras of South America; the mountains of Hungary ; the Altayan mountains;■he Ural mountains; the Vosges and the Black Forest ; the Hartz, and the east ofRomany ; the centre of France; the north of Portugal , and the adjacent portions of®Pain; Britanny ; the corresponding coasts of Great Britain and Ireland ; the north ofh-Urope ; the Allegany chain; the south of Spain ;, the Pyrenees ; the Alps; the schistosedistricts on the banks of the Rhine and the Ardennes; the calcareous mountains of^ugland and of Daouria.

MINES OF THE CORDILLERAS OF SOUTH AMERICA .

T ew regions are so celebrated for their mineral wealth as the great chain which, under

name of the Cordillera of the Andes, skirts the shores of the Pacific ocean , from the* a nd of the Patagonians to near the northwest point of the American continent. Who^ as not heard of the mines of Mexico and Potosi ? The mineral wealth of Peru hasPassed into a proverb.

The most important mines of the Cordilleras are those of silver; but several of gold,^rcury, copper, and lead, have likewise been opened. These mountains are not equally*i et alliferous in their whole extent. The workings occur associated in a small number1 districts far distant from each other.

the Andes of Chili, particularly in the province of Coquimbo, some silver mines• re explored, which afl'ord chiefly ores of an earthy or ferruginous nature, mingled with^Perceptible portions of ores with a silver base, known thereunder the name of Pacos.

^ same province also presents copper mines of considerable im portance, from which' r< ^ extracted native copper, orange oxide of copper, carbonate of copper (malachite),a j}d copper pyrites, associated with some muriate of copper. In a few mines, masses

Native copper of extraordinary magnitude have been found.

The second metalliferous region of the Andes occurs between the 21st aud lothAgrees of south latitude. It includes the celebrated mountain of Potosi : situated in