In other circumstances, probably where less moisture has prevailed, morasses seem to have undergone a fermentation, as other vegetable matter, new hay for instance is liable to do from the great quantity of sugar it contains. From the great heat thus produced in the lower parts of immense beds of morass the phlogistic part, or oil, or asphaltum, becomes distilled, and rising into higher strata becomes again condensed forming coal-beds of greater or less purity according to their greater or less quantity of inflammable matter; at the same time the clay beds become purer or less so, as the phlogistic part is more or less completely exhaled from them. Though coal and clay are frequently produced in this manner, yet I have no doubt, but that they are likewise often produced by elutriation; in situations on declivities the clay is washed away down into the valleys, and the phlogistic part or coal left behind; this circumstance is seen in many valleys near the beds of rivers, which are covered recently by a whitish impure clay, called water-clay. See note XIX. XX. and XXIII. LORD CROMARTIE has furnished another curious observation on morasses in the paper above referred to. In a moss near the town of Eglin in Murray, though there is no river or water which communicates with the moss, yet for three or four feet of depth in the moss there are little shell-fish resembling oysters with living fish in them in great quantities, though no such fish are found in the adjacent rivers, nor even in the water pits in the moss, but only in the solid substance of the moss. This curious fact not only accounts for the shells sometimes found on the surface of coals, and in the clay above them; but also for a thin stratum of shells which sometimes exists over iron-ore. NOTE XVIII.--IRON. _Cold waves, immerged, the glowing mass congeal, And turn to adamant the hissing Steel._ CANTO II. l. 191. As iron is formed near the surface of the earth, it becomes exposed to streams of water and of air more than most other metallic bodies, and thence becomes combined with oxygene, or vital air, and appears very frequently in its calciform state, as in variety of ochres. Manganese, and zinc, and sometimes lead, are also found near the surface of the earth, and on that account become combined with vital air and are exhibited in their calciform state.