Theory of the Earth

the crystalline salt is suddenly exposed to a sufficient degree of heat, that is, somewhat more than boiling water, it enters into the state of aqueous fusion, and it boils, in emitting the water by means of which it had been crystallized in the cold, and rendered fluid in that heated state. It is not possible to crystallize this alkaline salt from a dissolved state, without the combination of that quantity of water, nor to separate that water without destroying its crystalline state.

BUT in this mineral specimen, we have a solid crystalline salt, with a structure which, upon fracture, appears to be sparry and radiated, something resembling that of zeolite. It contains no water in its crystallization, but melts in a sufficient heat, without any aqueous fusion. Therefore, this salt must have been in a fluid state of fusion, immediately before its congelation and crystallization.

IT would be endless to give examples of particular facts, so many are the different natural appearances that occur, attended with a variety of different circumstances.

THERE is one, however, which is peculiarly distinct, admits of sufficiently accurate description, and contains circumstances from which conclusions may be drawn with clearness. This is the iron-stone, which is commonly found among the argillaceous strata, attendant upon fossil coal, both in Scotland and in England.

THIS stone is generally found among the bituminous schistus, or black argillaceous strata, either in separate masses of various shapes and sizes, or forming of itself strata with are more or less continuous in their direction among the schistus or argillaceous beds.

THIS mineral contains in general from 40 to 50 per cent. of iron, and it loses near one third of its weight in calcination. Before calcination it is of a gray colour, is not penetrable by water, and takes a polish. In this state, therefore, it is perfectly solid; but being calcined, it becomes red, porous, and tender.

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