The unfitness of water to hold the sub stances forming the primitive rocks in solution has been considered as a power ful objection : but it is to be considered, that the menstruum cannot be supposed to have been simple water, but, as Mr. Kirwan observes, this primitive fluid must have contained all the various sim ple saline substances, and indeed every simple substance, variously distributed, " forming, upon the whole, a more com plex menstruum than any that has since existed, and consequently endued with properties very different from any with which we have been since acquainted." Geological Essays, P. II.
Considerable difficulty must, however, continue, in adapting any system which confines the production the various geological phenomena, which present themselves to our observation, to too few and to too limited causes ; since, however necessary it may be to refer the general phenomena 'to the operation of one par ticularly powerful agent, it still must be necessary to take into the reckoning the sinking and the raising of particular spots from subterraneous submarine fires ; as well as the changes produced by the sub version of lofty mountains, rapid and vio lent currents of water, and various other powerful causes.
By the preceding sketch of the nume rous systems which have been advanced, and by these cursory remarks on some of the objections which have been made against those which appear to possess the greatest share of probability, the mind becomes better prepared to attend to the system of the celebrated Werner, to whom, in the opinion of his learned and zealous annotator, we owe almost every thing that is truly valuable in this import ant branch of knowledge. For the pur pose of conveying some notion of this in genious system, the following sketch is taken from the view of it, given in the " Elements of Geognosy," by Professor Jameson.
Agreeable to this system, the earth is supposed to have existed originally in a state of aqueous fluidity, which is infer red from its spheroidal form, and from the highest mountains being composed of rocks, possessing a structure exactly re sembling that of those fossils, which have as it were, under the eye, been formed by water. From this circumstance it also follows, that the ocean must have former ly stood very high over these mountains ; and as these appear to have been firmed during the same period of time, it follows, that the ocean must have formerly cover ed the whole earth at the same time.— Contemplating the formations of the mountains themselves, Werner discover ed the strongest proofs of the diminution of the original waters of the globe. lit
ascertained, 1st, that the outgoings (the upper extremities as they appear at the surface of the earth) of the newer strata are generally lower than the outgoings of the older, from granite downwards to the alluvial depositions, and this, not in particular spots, but around the whole globe. 2d. That the primitive part of the earth is entirely composed of chemical precipitations, and that mechanical de positions only appear in those of a later period, that is, in the transition class, and thence they continue increasing, through all the succeeding classes of rocks. This evidence of the vast diminution of the volume of water which stood so high over the whole earth is assumed to be perfectly satisfactory, although we can form no correct idea of what has become of it.
By the earliest separations from the chaotic mass, which are discoverable in the crust of the globe, was formed a class of rocks, which are therefore termed primitive rocks, being chiefly composed of silex, alumina, and magnesia, constitut ing, by their various intermixtures, 1, granite ; 2, gneiss ; 3, mica-slate ; 4, clay slate ; 5, primitive limestone; 6, primi tive-trap ; 7, serpentine ; 8, porphyry ; 9, sienite ; 10, topaz rock ; 11, quartz rock ; 12, primitive flinty slate ; 13, pri mitive gypsum; 14, white stone. The circumstances which chiefly mark the high antiquity of these rocks are, that they form the fundamental rock of the other classes ; and that the outgoings of their strata are generally higher than those of the other classes. Having been formed in the uninhabitable state of the glove, they contain no petrifactions; and, excepting the small portions which sometimes accompany those which will be next mentioned, they contain no me chanical deposits, but are throughout pure chemical productions. Small por tions of carbonaceous matter occur only in the newer members of the class.
Before the summits of the mountains appeared above the level of the ocean, and before the creation of vegetables and animals, a rising of the waters is supposed to have taken place, during which that class of rocks which are said to be of the second porphyry and sienite formation was deposited. The rocks of this forma tion are of clay-porphyry, pearl-stone porphyry, obsidian porphyry, sienite, and pitch.stone. They contain very little mechanical depositions, are of complete chemical formation, and contain little or no carbonaceous matter, and never any petrifactions.