In Scotland the most extensive plains are the Moors of Galloway and those of the Highlands.
In Ireland there is a considerable quantity of bogland, all of which is flat and uncultivated.
CHAPTER VI. MINES AND FOSSILS.
MINES.
In many places are found cracks or fissures in the solid rock, which are filled up with some kind of metal, and these are called mineral veins. As these veins are generally sunk deeply in the earth, it is necessary to dig to a great depth to obtain the metal from them, and to erect engines to make passages by which the metal is conveyed to the surface of the earth. This is called sinking and working a mine.
GOLD AND SILVER MINES.
Gold is one of the scarcest of all metals; and though it is found in a great many different places, it is always in very small quantities, and it is either scattered in the sand of rivers in small globules, or compressed into slender veins in rocks of granite or some other very hard kind of stone. Sometimes, however, it exists in a mineralised state, mingled with various kinds of earth or stone. "In this state it would not be recognised to be gold by an inexperienced person; for it is red, white, or black, as it may happen, and shews none of its brilliancy or metallic character." When gold is found in this state, the ore is broken into pieces in a mill, and a quantity of quicksilver is added to the mass, which, having a strong attraction for gold, draws every portion of it from the earthy matters with which it is mixed. The gold is afterwards separated from the quicksilver by the action of fire, by which the quicksilver is driven off, and the gold left pure.
When gold is found mixed with sand, the sand is carried to what in Mexico are called lavaderos, or washing places. Here it is kept continually stirred with iron hooks and rakes, while water rushing in, carries away the earthy matter; and the gold, from its weight, falls to the bottom. If the gold is not entirely freed from the sand by this process, it is put into a shallow dish, deepest in the middle, and filled up with water. With their spread fingers the workmen then whirl the whole round and round; so that the water and sand may pass over the edges of the dish, and the pure grains of gold remain in the central hollow.
Silver veins are more abundant, and as the silver is frequently found in limestone, it is not so difficult to work. There are numerous silver mines in different parts of Europe, particularly in Hungary, Bohemia, Sweden, and Norway. Those in Hungary are celebrated not only for their richness, but for the immense extent to which their operations have been carried on. "There are three principal veins, the course of which is nearly from north to south, and which run parallel to the River Gran, following even the windings of its channel. The dip or inclination of these veins is generally from west to east; and the largest of them is called the Spitaler vein. The second great vein at Schemnitz contains lead ore mixed with the silver. A third great vein is more irregular in its formation than the two others, sometimes rising vertically and sometimes dipping in a contrary direction from east to west." The ores afford occasionally a considerable proportion of gold. These mines appear to have been wrought from a very early period, and the mining operations have been carried to a vast extent. The gallery or level, called the Emperor Francis's gallery, is a channel by which the whole of these mines are drained and cleared of water; it is carried through hard rock, and must have been a work of immense labour and difficulty, being about five English miles in length. This gallery was begun in 1748, and finished in 1765.
The largest silver mines in South America are at Potosi. They are said to have been discovered by an Indian named Hualpa, who, climbing up the side of a mountain in pursuit of a wild animal, caught hold of the stem of a tree to aid him in his ascent. His weight, however, was so great, or rather the tree was so slightly attached to the ground, that it gave way, and he found that he had torn it up by the roots. The animal, of course, escaped; but the hunter was consoled for his disappointment by finding some grains of native silver sticking to the roots of the tree. This led to a further examination, and a rich vein of silver was discovered, which had, in this place, reached nearly to the surface of the ground. The mine is in a mountain by itself, though it is situated high up in the Andes; and the peak enclosing the mine is about eighteen miles in circumference at the base, rising in the shape of a sugar-loaf. The silver lies so near the surface, that it has not been found necessary to sink a mine in the usual manner, as the miners get as much silver as they require by merely scooping out the surface of the hill. In this way they have formed several hundred pits, none of which are above seventy yards in depth.
QUICKSILVER MINES.
The most ancient quicksilver mines in the world are those of Almaden in Spain, which, according to Pliny, were worked 500 years before the commencement of the Christian era. The next most celebrated quicksilver mines are those of Idria in Carniola, about eight leagues from Trieste. The town of Idria, which gives its name to the mountains, stands in a deep valley, surrounded by lofty mountains, which exhibit a mass of dark-coloured slate included between two beds of limestone. The ores, consisting of native mercury and cinnabar, are deposited in this bed of slate, which is sixty feet thick, and of a very considerable extent. The following description of the mines of Idria is extracted from Silliman's Journal, and was communicated to that work by an officer in the American navy, who had made a pedestrian tour through Germany. "These mines have nothing corresponding with the ideas of terror which we are apt to connect with such places, except the atmosphere, which, throughout the mine, is so strongly impregnated with mercurial vapour as frequently to produce salivation in the workmen. On entering, we descended by 727 steps to the depth of 120 fathoms, when we arrived at the region where the cinnabar is chiefly procured. The mining operations are carried on in galleries, the friable nature of the rock not admitting of the formation of large chambers. The cinnabar is in strata of from two to six inches in thickness; sometimes it is of a brilliant scarlet, and in small crystals, but generally it is of a dull red, and in large masses of solid stone, which is, however, so brittle, as to be easily broken by a common pickaxe. The quicksilver is sometimes mixed with the cinnabar, and sometimes occurs imbedded in a friable rock, in particles too minute for the naked eye, but which, when the rock is broken, present themselves in small globules, varying from a size just large enough to be seen, up to that of a common pin's head." The travellers descending still lower, soon came to the richest part of the mine, where the globules of quicksilver are so large, that when the earth is broken they roll out and fall to the bottom of the gallery. The labourers in this place are relieved every four hours, being unable, from the state of the atmosphere, to work longer than this at one time, though in the other parts of the mine they are only relieved every eight hours. The quicksilver which is found in globules, only requires to be washed to separate it from any loose particles of earthy matter which may adhere to it; but the quicksilver that is mixed with rock, requires to be exposed to the action of heat, which forces the quicksilver to rise in the form of vapour, and this, passing into the small chambers adjoining the furnace, is so thoroughly condensed by the cold atmosphere around them, that when the process is over, and the doorways of the chambers are opened, the quicksilver is found adhering in drops to the sides and ceilings. "The cleaning process is very simple, a piece of canvas being merely spread over a funnel, and the quicksilver, being made to pass through it, comes out pure. That intended for home consumption is tied up in sheep's skins, while that for exportation is put into iron bottles, each of which contains sixty eight pounds weight. The furnace is kept in operation only during the winter months, and even then the smoke is a serious annoyance to the town."
There are several other quicksilver mines in different parts of Europe, but those which have been already mentioned are the most important.
COPPER MINES.
Copper mines are found in many countries, and there is a tradition that the copper mines of Spain were worked in the time of the Carthaginians; but "the most extensive and productive copper mine in the world is that of Falun, in the province of Dalecarlia, in Sweden. The mining district occupies a space of nine leagues in length by two and a half in breadth, and is surrounded by a reddish granite, which becomes of a finer grain as it approaches the centre of this space, and is then succeeded by a micaceous rock dividing into rhomboidal fragments. The principal mass, which is of enormous dimensions, consists of iron and copper pyrites lying in a vertical position from north-west to south-east, along the valley in which it is deposited. Here there is an immense opening or gulf 840 feet in length, 720 in breadth, and 240 in depth, which was produced in the year 1687, by the falling in of the superincumbent mass, in consequence of the unskilful manner in which the subterranean operations had been conducted. In this celebrated mine the mass of ore is described as lying in the form of an inverted cone, and the excavation has been carried to a depth of more than 200 fathoms; but it is supposed that this is nearly the utmost extent to which the mass of ore penetrates the earth, as latterly the operations have been conducted upon a more limited scale than in former times. It was in this mine that Gustavus Vasa, when driven from his throne, worked for a time, to procure the means of subsistence." In the mine of Garpenberg, about eighteen leagues from that of Falun, there are fourteen veins in a vertical position, all parallel with each other.
The principal copper mines of Great Britain are in Cornwall; but there are others in Anglesea and Wales, and there was one also in Staffordshire, which was once reckoned one of the most productive in the kingdom. The mines in Cornwall are sometimes wrought to a very great depth; and between Truro and Redruth, there is one the shaft of which is 265 fathoms deep.
IRON MINES.
The iron mines of the Island of Elba are said to be the richest in the world, and their existence appears to have been known from the earliest times. The ore is of the specular kind, and the mass constitutes an entire mountain, surrounded by others consisting of granite, of which the greater part of the island is composed. This mountain, which is called Rio, is about 500 feet in height, and three miles in circumference; and its surface is covered with a reddish kind of earth, full of shining scales of iron. Beneath this slight covering the mountain consists of one mass of metal, or rather, of an immense number of accumulated masses, thrown together without the slightest attempt at stratification. The mines of Elba were wrought in the time of the Romans, and it is supposed that the mass of iron they contain extends from the island under the sea to the adjoining continent.