On the Transition Rods of the Qatar aqui. 445 



ated,or that the limestone would not entirely lose its usual dark ap- 

 pearance, and become white, more crystalline, or incinerated.* It 

 is certainly dangerous ground, at present, to attempt to combat the 

 numerous hosts of ignipotent knights, who have appeared in the lists 

 of modern geology ; but still theirs is yet only the armor of theory, 

 and may not prove impervious to the keen-edged weapons of fact. 



That all the singular appearances in the granitic aggregates should 

 be easily accounted for, by the rocks containing them, and chiefly 

 the amphibolic ones, having undergone their changes of character 

 and situation from protrusion and the other supposed effects of vol- 

 canic agency, is a matter I must confess not all so easily settled to 

 my own conviction, and although I have lately and carefully peru- 

 sed the arguments adduced in Professor Hitchcock's Report to the 

 state legislature of Massachusetts, which, with its numerous dia- 

 grams, embraces more details of the igneous theory of the early 

 rocks than I have elsewhere observed, I am not convinced that the 

 numerous instances there adduced of the appearances of granite, 

 gneiss, and mica slate, being pierced by small or large dykes and 

 veins of granite, may not just as easily be accounted for by the one 

 theory as the other, and may in fact all have arisen from the mere 

 modification of the different elements of which rocks so intimately 

 connected in their relations are composed, either from unequal 

 pressure, a greater proportion of the particles in one situation than 

 another, chemical action in the act of crystallization, and other well 

 known causes. 



Why in fact, should not granite, gneiss, quartz rock and mica slate, 



be all classed under one head, instead of being divided as they now 

 are, for they are all mere modifications of the constituent parts of 

 the old rocks, and may as well be reckoned as one family, as the 

 numerous and almost endless varieties of limestone from chalk to the 



oldest transition limes are. 



It appears to me that, although there are still great difficulties in 

 the classification of the early rocks, there is not any absolute dis- 

 proof, that they may extend far into the Hemilysian period, and that 

 their appearance there, may be as satisfactorily explained, as the ap- 

 pearance of the transition lime containing few or no fossils, which 



S" 



* The fact of lava containing shells, where it was in contact with the ocean, 

 does not militate against this, as the gradual cooling would be sufficient to allow 

 shells to sink into it. without much alteration. 



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