These cracks or perpendicular caverns in the granite or limestone pass to unknown depths; and it is up these channels that I have endeavoured to shew that the steam rises which becomes afterwards condensed and produces the warm springs of this island, and other parts of the world. (See note on Fucus, Vol. II.) And up these cracks I suppose certain vapours arise, which either alone, or by meeting with something descending into them from above, have produced most of the metals; and several of the materials in which they are bedded. Thus the ponderous earth, Barytes, of Derbyshire, is found in these cracks, and is stratified frequently with lead-ore, and frequently surrounds it. This ponderous earth has been found by Dr. Hoepfner in a granite in Switzerland, and may have thus been sublimed from immense depths by great heat, and have obtained its carbonic or vitriolic acid from above. Annales de Chimie. There is also reason to conclude that something from above is necessary to the formation of many of the metals: at Hawkstone in Shropshire, the seat of Sir Richard Hill, there is an elevated rock of siliceous sand which is coloured green with copper in many places high in the air; and I have in my possession a specimen of lead formed in the cavity of an iron nodule, and another of lead amid spar from a crack of a coal-stratum; all which countenance the modern production of those metals from descending materials. To which should be added, that the highest mountains of granite, which have therefore probably never been covered with marine productions on account of their early elevation, nor with vegetable or animal matters on account of their great coldness, contain no metallic ores, whilst the lower ones contain copper and tin in their cracks or veins, both in Saxony, Silesia, and Cornwall. Kirwan's Mineral. p. 374. The transmutation of one metal into another, though hitherto undiscovered by the alchymists, does not appear impossible; such transmutations have been supposed to exist in nature, thus lapis calaminaris may have been produced from the destruction of lead-ore, as it is generally found on the top of the veins of lead, where it has been calcined or united with air, and because masses of lead-ore are often found intirely inclosed in it. So silver is found mixed in almost all lead-ores, and sometimes in seperate filaments within the cavities of lead-ore, as I am informed by Mr. Michell, and is thence probably a partial transmutation of the lead to silver, the rapid progress of modern chemistry having shewn the analogy between metallic calces and acids, may lead to the power of transmuting their bases: a discovery much to be wished.]