AQUEOUS AND PLUTONIC FORMATIONS. 17 



23. These different phenomena partly explain to us the manner 

 in which the production of the different formation disseminated 

 on the surface of the globe, must have been effected, formations 

 whose origin date back from an epoch long anterior to that of the 

 creation of man. 



24. In fact, the various formations constituting the common por- 

 tion of the globe differ, as we have already seen, very widely in 

 their nature, in their constitution, and in their mode of arrange- 

 ment. Now, these differences remind us of those which exist in 

 the modern formations above mentioned, and seem to indicate that, 

 in the ancient formations, some were produced in the midst of the 

 waters by the deposit of solid materials held in suspension or in 

 solution by this liquid, and others by the action of heat on earthy 

 materials susceptible of being melted, and of being afterwards 

 hardened by cooling. 



25. Guided by these considerations, geologists have divided the 

 formations into two great classes ; namely, the sedimentary, or 

 stratified formations, and the massif or igneous formations. 

 On account of the presumed method of their production, they are 

 also designated under the names of Aqueous or Neptunian for- 

 mations, and Igneous or Plutonic formations. 



26. The plutonic formations have received this name because 

 they appear to be the product of the action of fire ; they are 

 generally of a dense crystalline structure, and ordinarily form very 

 immense masses; they are not arranged in regularly superposed 

 beds, nor do they contain the remains of organized bodies. Some 

 of them are formed, as we see, by the action of volcanoes, and 

 others are very analogous to the latter ; they contain not only 

 minerals peculiar to volcanic ejections, but sometimes also matters 

 that are produced by the furnaces of our laboratories and work- 

 shops. They seem to have formed the primitive crust of the 

 globe ; for we find them beneath the neptunian formations, but 

 they are also sometimes spread over the surface of the latter, or 

 betwixt the different beds or strata of which they are composed. 



27. The aqueous or neptunian formations appear to have been 

 deposited by the waters ; in general their texture is coarse or com- 

 pact, rarely crystalline, and they are often composed of grains of 

 sand separate or agglutinated, of heterogenous fragments, or ma- 

 terial havinir the aspect of a kind of indurated mud ; they are also 

 frequently called stratified formations, and most of them are also 

 termed SEDIMENTARY FORMATIONS. It is in the midst of these for- 



23. Are the various formations all of the same age ? 



24. In what manner were the various formations produced? 



25. How are the formations divided ? 



26. What is meant by plutonic formations ? How are they produced ? 



27. How were the aqueous formations produced ? Whit are the charao 

 ttrs of aqueous rocks ? 



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