160 ON THE CHARACTERS AND DISPOSITION 



phenomena have occurred to many observers. The 

 case of Predazzo is one where granites of all charac- 

 ters form a mass with augitic greenstone ; the whole 

 heing later than the red marl and the oolithe lime- 

 stone; and from the observations of Von Buch, 

 Brongniart, Boue, and others, in Norway and else- 

 where, it is evident that what I had so long pointed 

 out, required only to be more generally known to be 

 found a very common occurrence. 



I the mean time I am unable to perceive that any 

 thing is wanting to prove the identity of origin in 

 trap and granite. It is little likely, at least, that 

 geology will often furnish us with evidence of a more 

 decided nature. Nor is it an indispensable requisite 

 to this argument, to produce numerous examples; 

 since there are innumerable cases in science, among 

 which this seems one, where one or two facts are as 

 decisive as a hundred. 



It is unnecessary to add feeble arguments to strong 

 ones; but the prevailing mineral characters through- 

 out the whole range of the unstratified rocks are of 

 a nature to confirm that which is here proved. Yet 

 it will not be superfluous to allude to the probable 

 causes by which the characters of these rocks have 

 been modified; and which have had an effect so 

 generally steady, in distinguishing between those of 

 the families of granite and trap, It is very probable 

 that many of these differences arise from a constitution 

 radically different; from the proportions of the se- 

 veral earths entering into them. In extreme cases, as 

 between claystone and granite, they certainly depend 

 on that cause. To put a hypothetical case: If it be 

 conceived that granite was produced from the fusion 

 of an argillaceous sandstone, and basalt from that of 

 an argillaceous schist, the consequent difference be- 



