Not only iron but manganese, calamy, and even copper and lead appear in some instances to have been of recent production. Iron and manganese are detected in all vegetable productions, and it is probable other metallic bodies might be found to exist in vegetable or animal matters, if we had tests to detect them in very minute quantities. Manganese and calamy are found in beds like iron near the surface of the earth, and in a calciform state, which countenances their modern production. The recent production of calamy, one of the ores of zinc, appears from its frequently incrusting calcareous spar in its descent from the surface of the earth into the uppermost fissures of the limestone mountains of Derbyshire. That the calamy has been carried by its solution or diffusion in water into these cavities, and not by its ascent from below in form of steam, is evinced from its not only forming a crust over the dogtooth spar, but by its afterwards dissolving or destroying the sparry crystal. I have specimens of calamy in the form of dogtooth spar, two inches high, which are hollow, and stand half an inch above the diminished sparry crystal on which they were formed, like a sheath a great deal too big for it; this seems to shew, that this process was carried on in water, otherwise after the calamy had incrusted its spar, and dissolved its surface, so as to form a hollow cavern over it, it could not act further upon it except by the interposition of some medium. As these spars and calamy are formed in the fissures of mountains they must both have been formed after the elevation of those mountains. In respect to the recent production of copper, it was before observed in note on Canto II. l. 394, that the summit of the grit-stone mountain at Hawkstone in Shropshire, is tinged with copper, which from the appearance of the blue stains seems to have descended to the parts of the rock beneath. I have a calciform ore of copper consisting of the hollow crusts of cubic cells, which has evidently been formed on crystals of fluor, which it has eroded in the same manner as the calamy erodes the calcareous crystals, from whence may be deduced in the same manner, the aqueous solution or diffusion, as well as the recent production of this calciform ore of copper. Lead in small quantities is sometimes found in the fissures of coal- beds, which fissures are previously covered with spar; and sometimes in nodules of iron-ore. Of the former I have a specimen from near Caulk in Derbyshire, and of the latter from Colebrook Dale in Shropshire. Though all these facts shew that some metallic bodies are formed from vegetable or animal recrements, as iron, and perhaps manganese and calamy, all which are found near the surface of the earth; yet as the other metals are found only in fissures of rocks, which penetrate to unknown depths, they may be wholly or in part produced by ascending steams from subterraneous fires, as mentioned in note on Canto II. l. 398.