156 ON THE CHARACTERS AND DISPOSITION 



not only an absolute want of observations on this 

 subject, but that the universality of a prejudice in 

 favour of the aqueous origin of granite, renders some 

 observers as unwilling or as unable to discover the 

 truth, to explain appearances in an obvious manner, 

 as others are, from want of experience or other 

 causes, incapable. 



This argument has Jiitherto proceeded on the 

 grounds of analogy and of inference from causes and 

 effects ; but it is time to ask whether the postulate is 

 really true, when it assumes that granite has not 

 overflowed the strata. I have shown in another 

 work, (Western Islands,) that, in Sky, a granite, 

 defining it by its mineralogical characters, is an inte- 

 grant part of a mass of unstratified rocks which lies 

 on a stratified limestone. If I have chosen to consider 

 this rock as a member of the trap family, it is merely 

 because I have thought fit to adopt the difference of 

 age as a criterion between granite and trap, for rea- 

 sons that need not here be stated. The fact, so far 

 as this argument is concerned, remains the same ; but 

 it is plain that it will be necessary to abandon this 

 distinction between trap and granite, whenever it shall 

 be disputed whether the latter has ever overflowed 

 the strata. If, in this particular instance, I had not 

 detected the superposition of the mass, it would of 

 course have been ranked with granite ; and, in confir- 

 mation of this, we have the authority of Von Buch, 

 a testimony never yet questioned, that granite lies 

 above corichiferous limestone in Norway. No evi- 

 dence can be less liable to suspicion than that of a 

 person who denies the truth of the theory of which 

 his own testimony is adduced as a proof. 



We are thus at length brought to consider the fur- 

 ther evidences that may be produced to prove the 



