The higher and lower parts of morasses were necessarily produced at different periods of time, see Note XVII. and would thus originally be formed in strata of different ages. For when an old wood perished, and produced a morass, many centuries would elapse before another wood could grow and perish again upon the same ground, which would thus produce a new stratum of morass over the other, differing indeed principally in its age, and perhaps, as the timber might be different, in the proportions of its component parts. Now if we suppose the lowermost stratum of a morass become ignited, like fermenting hay, (after whatever could be carried away by solution in water was gone,) what would happen? Certainly the inflammable part, the oil, sulphur, or bitumen, would burn away, and be evaporated in air; and the fixed parts would be left, as clay, lime, and iron; while some of the calcareous earth would join with the siliceous acid, and produce sand, or with the argillaceous earth, and produce marl. Thence after many centuries another bed would take fire, but with less degree of ignition, and with a greater body of morass over it, what then would happen? The bitumen and sulphur would rise and might become condensed under an impervious stratum, which might not be ignited, and there form coal of different purities according to its degree of fluidity, which would permit some of the clay to subside through it into the place from which it was sublimed. Some centuries afterwards another similar process might take place, and either thicken the coal-bed, or produce a new clay-bed, or marl, or sand, or deposit iron upon it, according to the concomitant circumstances above mentioned. I do not mean to contend that a few masses of some materials may not have been rolled together by currents, when the mountains were much more elevated than at present, and in consequence the rivers broader and more rapid, and the storms of rain and wind greater both in quantity and force. Some gravel-beds may have been thus washed from the mountains; and some white clay washed from morasses into valleys beneath them; and some ochres of iron dissolved and again deposited by water; and some calcareous depositions from water, (as the bank for instance on which stand the houses at Matlock-bath;) but these are of small extent or consequence compared to the primitive rocks of granite or porpyhry which form the nucleus of the earth, or to the immense strata of limestone which crust over the greatest part of this granite or porphyry; or lastly to the very extensive beds of clay, marl, sandstone, coal, and iron, which were probably for many millions of years the only parts of our continents and islands, which were then elevated above the level of the sea, and which on that account became covered with vegetation, and thence acquired their later or superincumbent strata, which constitute, what some have termed, the new world.