[80] A highly illustrative series of this rock is deposited in the Geological Cabinet at Penzance. [81] Tin appears to have been formerly smelted by the Jews, who in the reign of King John monopolized the tin trade, by merely hollowing out a plot of ground, and fusing the oxide with wood, in an open fire. Many ancient remains of this operation have been discovered in different parts of Cornwall, in which portions of metallic tin embedded in a stratum of charred wood, or charcoal, have been found; and which have given rise to the fallacy respecting the discovery of this metal in a _native state_. In examining a fragment of this kind which was found under the surface of a low and boggy ground in the parish of Kea, the late eminent chemist, _Mr. William Gregor_, observed a _vein of saline matter running through the mass_, which he ascertained to be _muriate of tin_; a full account of this interesting phenomenon is published in the first volume of the Transactions of the Cornish Society. [82] _Culm._ A species of very pure coal containing no sulphur. It is imported from Wales. [83] It is a favourite custom to dress a beef-steak on the pure Tin in the mould, as soon as the surface becomes sufficiently hard to bear it; and it must be admitted to be very far superior to that which is cooked in the ordinary manner. EXCURSION V. TO REDRUTH, AND THE MINING DISTRICTS IN ITS VICINITY. In the present excursion, the traveller in search of the Picturesque will meet with but meagre fare; for many a mile has the face of nature been robbed of all ornament, and the interior of the earth has been scattered over its surface in the anxious pursuit of mineral treasures. The unsightly mounds of rubbish thus produced have been accumulating for centuries, and are so highly impregnated with mineral matter that not a blade of grass will vegetate upon them. The intelligent traveller, however, must not anticipate an excursion as destitute of interest and variety as the surface of the country which he is about to traverse, for like the shabby mien of the miser, its aspect but ill accords with its hoards; and the total absence of cultivation and rural ornament, is soon forgotten amidst the richest field of mineralogical enquiry which any country ever afforded. As our present object is to afford the stranger such directions as may enable him to inspect this mining district with advantage, and to visit whatever is interesting and instructive in connection with it, it may in the first instance be expedient to offer a general outline of the modes in which the Cornish mines are worked, before we enter into the details of topographical description.