To trace the series of these revolutions, to explain their causes, and thus to connect together all the indications of change that are found in the mineral kingdom, is the proper object of a THEORY OF THE EARTH.

[To] explain the phenomena of the mineral kingdom ... systems are usually reduced to two classes, according as they refer to the origin of terrestrial bodies to FIRE or to WATER; and ... their followers have of late been distinguished by the fanciful names of Vulcanists and Neptunists. To the former of these Dr HUTTON belongs much more than to the latter; though, as he employs the agency both of fire and water in his system, he cannot, in strict propriety, be arranged with either.