The mines are sunk to the depth of one hundred and thirty fathoms, and are extended under the sea to places where there is, above them, sufficient depth of water for ships of large burden. These are the deepest coal mines which have hitherto been wrought; and perhaps the miners have not, in any other part of the globe, penetrated to so great a depth beneath the surface of the sea, the very deep mines in Hungary, Peru and elsewhere, being situated in mountainous countries, where the surface of the earth is elevated to a great hight above the level of the ocean. In these mines there are three strata of coal, which lie at a considerable distance one above the other, and are made to communicate by pits; but the vein is not always continued in the same regularly inclined plane, the miners frequently meeting with hard rock, by which their further progress is interrupted. At such places there seem to have been breaks in the earth, from the surface downward, one portion appearing to have sunk down, while the adjoining part has preserved its ancient situation. In some of these places the earth has sunk ten, twenty fathoms, and even more; while in others the depression has been less than one fathom. These breaks the miners call _dikes_, and when they reach one of them, their first care is to discover whether the strata in the adjoining part are higher or lower than in the part where they have been working; or, according to their own phrase, whether the coal be _cast down_ or _cast up_. In the former case they sink a pit; but if it be cast up to any considerable hight, they are frequently obliged, with great labor and expense, to carry forward a level, or long gallery, through the rock, until they again reach the stratum of coal. Coal, the chief mineral of Scotland, has been there worked for a succession of ages. Pope Pius II., in his description of Europe, written about 1450, mentions that he beheld with wonder black stones given as alms to the poor of Scotland. This mineral may, however, be traced to the twelfth century; and a very early account of the Scottish coal mines, explains with great precision, the manner of working the coal, not neglecting to mention the subterraneous walls of _whin_ which intersect the strata, particularly a remarkable one, visible from the river Tyne, where it forms a cataract, and passes by Prestonpans, to the shore of Fife. The Lothians and Fifeshire, particularly abound with this useful mineral, which also extends into Ayrshire; and near Irwin is found a curious variety, named ribbon-coal. A singular coal, in veins of mineral, has been found at Castle Leod, in the east of Ross-shire; and it is conjectured that the largest untouched field of coal in Europe, exists in a barren tract of country in Lanarkshire.