25 . II. RELICS, into Min. Kingd. 



are peculiar to^ the ocean ending with the time, 

 at which the ocean, after a gradual subsidence 



21. Alluvial and Volcanic tracts have been formed at various 

 periods ; but, in general, since the sea retired within its present 

 limits. 



(Obs. Alluvial beds have been deposited by rivers, lakes, and 

 inundations of fresh-water. The modern are found in vales, on 

 the banks of rivers, and other low situations. They principally con- 

 sist of gravel, sand, clay, &c, the debris of more ancient strata. 

 The ancient alluvial are, perhaps, some sand-stone, shales, and 

 coal-strata.} 



22. Veins have also been formed at various periods, during the 

 consolidation of the strata they traverse; but generally before the 

 sea had quitted the mountainous parts of our continent. 



23. Veins were originally empty rents or fissures, open at the 

 surface of the rock or stratum, through which they run. 



24. These fissures were gradually filled, with the mineral sub- 

 stances they contain, through their openings, from above. 



(Obs. According to Werner's theory of Veins. Mr. Kirwan is of 

 opinion, however, that, though some veins have undoubtedly been 

 thus filled, the materials in most have been deposited by successive 

 percolations.) 



" Such are the leading principles of the Neptunian Theory, now 

 generally adopted by the Wemerian school. The geological facts, 

 on which these principles are founded, are very numerous; those 

 which appertain to extraneous fossils we have stated ; for the rest, 

 we must refer our reader to the works of Werner, De Luc, 

 Saussure, Pallas, Charpentier, Kirwan, Jameson, Williams, &c. 

 Those who wish to examine the objections to which the Neptu- 

 nian system is liable, may consult, with great advantage, Pro- 

 fessor Playfair's excellent " Illustrations of the Huttonian Theory 

 of the Earth/' and an answer to the same, of considerable merit, 

 intitled " a comparative view of the Huttonian and Neptunian 

 Systems of Geology." 



E 



