this mine, in which 3,500 officers, artificers, and labourers are usually employed. The rich ore in this mine is found only in dispersed strata and interrupted veins. Pure silver is dug out of it; and in the year 1647 gold was also discovered. The veins of silver extend in various directions, and there were several fresh mines opened during the last century; but that which has been most productive is named Old God's Blessing, and this has yielded in one week several hundred pounds weight of rich ore. This mine fills the beholder with astonishment from its immense depth, which is no less than 180 perpendicular fathoms, terminated by an extensive plain. Here the sight of thirty or forty piles burning on all sides in this gloomy cavern, and continually fed, in order to mollify the stone in the prosecution of the mines, seems to present an apt image of Pluto's dreary regions; and the swarms of miners covered with soot, and bustling about in habits appropriated to their several employments, present a strange and extraordinary picture. When an explosion is about to take place they all exclaim with a loud voice, Berg livet! Berg livet! which means, “ take care of your lives."

"The method of blasting rock by gun-powder, is now so very familiar to miners, that little attention is paid to it; but the use of gunpowder may be considered as constituting an important era in mining. The daring ingenuity of man has, however, led him to still more enterprising and more efficacious methods. In Prussia, the mineralogists have lately availed themselves of lightning to accomplish the same end as that of blasting by gun-powder. For this purpose, an iron rod, similar to a conductor is fixed in the rock that is intended to be blasted; when the occurrence of the first thunder-storm generally conveys the electric fluid down the rod in such quantity as to split the rock into several pieces without displacing it.

"The hammer and metallic wedges were probably the first instruments made use of for splitting rocks. The application of wooden, wedges, seems a later invention: it is the property of dry wood to expand itself when wetted with water; the miners therefore availed themselves of this property, and driving dried wedges of wood into the natural or artificial crevices of the rocks, they then profusely watered them. The wood greedily imbibing the moisture, it suddenly expanded to so great a degree, that large pieces of the

rock were detached by the force with which it endeavoured to free itself from its confinement.

"Of the force of moisture I shall mention one more instance in overcoming the greatest resistances, as being curious and simple, and interesting. When a mass of millstone has been found sufficiently large, it is cut into the form of a cylinder, several feet in height, and the question then is, how to cut it it into horizontal pieces with the least labour and trouble, so as to make many millstones. For this purpose, circular and horizontal indentures are cut out quite round it, and at proper distances, according to the thickness to be given to the millstones. Wedges of willow dried in an oven, are then driven into these indentations by means of a mallet. When the wedges have sunk to a proper depth they are moistened, or exposed to the humidity of the night air; and next morning the different pieces are found separated from each other. Such is the process according to M. de Mairan, in different places for making millstones.

"It appears almost incredible, Sir," said Edward, "that moisture should have so extraordinary a power."

DR. WALKER.-"It appears to me to be the effect of attraction, by which the water is made to rise in the exceedingly narrow capillary vessels with which the wood is filled. Let us suppose the diameter of one of these tubes to be only the hundredth part of a line: let us suppose also, that the inclination of the sides is one second, and that the force with which the water tends to introduce itself into the tube, is the fourth part of a grain; this force, so very small, will tend to separate the flexible sides to the tube with a force of about 50,000 grains; which make about 84 pounds. In the length of one inch let there be only fifty of these tubes, which gives 2,500 in a square inch, and the result will be an effort of 21,875 pounds! As the head of a wedge, of the kind I have just mentioned, may contain four or five square inches, the force it exerts will be equal to about 90 or 100 pounds; and if we suppose ten of these wedges in the whole circumference of the cylinder, intended to form millstones, they will exercise together an effort of 900,000, or 1,000,000 pounds. It needs then excite no surprise that they should separate those blocks into the intervals between which they are introduced.

"Before the discovery of blasting rocks by gunpowder,

it was the custom of our English miners, as well as those of Germany, to split them by wood fires. It is a very ancient mode of mining, and Diodorus Siculus gives an account of it, in which he paints the sufferings of the poor slaves employed by the Egyptians, in such glowing colours, as makes the blood run cold. You know, Edward, Hannibal is said to have opened himself a passage through the Alps, by applying fire and vinegar to the rocks, which opposed his route. Hannibal might have seen this method practised in the silver mines of Spain. This account of Hannibal's splitting the rocks by vinegar, is generally deemed fabulous, from an idea that a sufficient quantity of vinegar could not be procured to effect his purpose; but the rocks were not to be dissolved by vinegar; they were, perhaps, split to that degree only, so as to facilitate the use of the crow and pick-axe, or whatever tools the ancients were in the habit of using."

An explosion by gunpowder took place in the mine while our travellers were within it. The tremendous noise of the concussion, the shouts of the men, and the uncommon singularity of the whole scene, made a deep impression upon the mind of Edward, and he felt quite rejoiced when he again saw the cheerful light of the sun.

"Silver," said Dr. Walker, as they directed their steps homeward," is not only found native, but likewise in various states of combination; it therefore furnishes a more numerons series of ores than gold.

"Native silver occurs crystallized and in a variety of other forms, it is malleable, and enjoys most of the characters of the pure metal; it usually contains traces of antimony, copper, or arsenic, and, like gold, its principal veins are in primitive mountains,

"Schlangenberg in Siberia, Andreasberg in the Hartz, are mines whence large quantities of native silver have been drawn; it has been found in Cornwall and in Scotland. In 1666 a mass was found in Norway weighing 560 lbs. And in 1478, Duke Albert of Saxony descended into one of the Schneeberg mines, and used as a dining table a block of silver weighing nearly twenty tons. But the quantity of silver found in various parts of America far exceeds that of the old world; and the earlier visitors of Mexico and Peru saw in the possession of the natives such abundance of this metal, obtained by little industry and less skill, as induced

them to hope for inexhaustible stores, as the recompense of more intelligent and persevering efforts. In 1545 the rich silver mines of Potosi were, according to Fernandez, accidentally discovered by an Indian clambering up a mountain in search of a lama that had strayed from his flock, and shortly after, the equally valuable mines of Sacotecas in New Spain were opened. Since that period the working of silver mines is greatly increased, and the evidence of modern travellers concerning the profusion of their produce is such as to astonish an inhabitant of the ancient hemisphere. It is difficult to form an estimate of the exact produce in silver of the mines of the New World, but we know that it has been greatly on the increase, and that the precious metals have altogether become more common in Europe. It has been supposed that such are the treasures of those mines, that if properly worked such quantities of silver would be obtained as to shake our commercial system by its abundance.

"Besides native silver and its alloy with gold we have several other important ores, of which antimonial, arsenical, and sulphuretted silver are the principal.

"Antimonial silver is a soft sectile and white ore, and when crystallized is in four and six-sided prisms. It consists of 78 parts silver, and 22 antimony. Before the blow-pipe it exhales oxyde of antimony and leaves pure silver.

"Arsenical silver is more grey than the former; harder, and rather brittle. It is crystallized in small four-sided prisms. It exhales a garlic smell before the blow-pipe, and leaves impure silver. A specimen from Andreasberg analysed by Klaproth, gave

"Arsenic
Iron

Silver

Antimony

35

"Another yielded

"Arsenic

Iron

Silver

Antimony

"The native compounds of sulphur and silver are numerous and important. The brittle sulphuret contains about 72 per cent. of sulphuret of silver, 10 antimony, and 10 iron, copper, and arsenic. One of the most beautiful ores

of silver is the red or ruby silver, crystallized in six-sided prisms and their modifications. It is a compound of silver, antimony, and sulphur, and is well marked by decrepitating before the blow-pipe, exhaling antimony and sulphur, and leaving a globule of pure silver; its component parts are

Silver
Antimony
Sulphur

"The mines we have just visited, of Schemnitz, and the Hartz, have furnished exquisite specimens of this ore; it ́also constitutes a great part of the riches of the Mexican mines.

"These are the principal ores of silver which we recognize in the cabinet of the mineralogist, and they are the prolific though by no means the only sources of the metal, for large quantities of silver are likewise procured from other ores, in which it constitutes a very small relative proportion, consequently they remain for after consideration."

"In extracting the silver from the ores that contain it native, they are either fused with lead, and cupelled, which is the modern method, or they are triturated with quicksilver, which forms an amalgam. This is a very ancient process, and was first employed in the Mexican and Peruvian mines, by Pedro Velasco in 1566. The less pure ores may be roasted with common salt, and put into tubs with mercury, iron plates, and water.

“Nitric acid is the readiest solvent of silver, and when the solution is evaporated it gives crystals, which fused and run into moulds produce lunar caustic.

"This salt is possessed of some curious properties; it is decomposed by the action of light and by phosphorus, hydrogen, charcoal, sulphur, and several of the metals. The silver is precipitated in a beautiful arborescent form by quicksilver, forming the arbor Dianæ, or silver tree. At some future time, I will explain how you may make iron and lead

trees.

"When a solution of 40 grs. of silver in 2 oz. of nitric acid diluted with 2 oz. of water, is heated with 2 oz. of alcohol, or pure spirit, a white powder precipitates, which is fulminating silver. It detonates when gently heated or rubbed. Its composition is not exactly known.

"The quantity of the precious metals annually raised from the mines amounts to about 10 millions sterling, of which 2 millions are in gold, and eight in silver.