DESCRIPTION OF RAVENSHEUGH. 407 



saltic rock, is nearly the reverse of what it ap- 

 pears to be on the south side. The explanation of 

 this curious and interesting appearance, is easy 

 and natural, if we consider the trap of Raven* 

 sheugh as a rock subordinate to the sandstone, and 

 belonging to the same period of formation ; but 

 the peculiarity which has been described, seems 

 to be altogether irreconcilable with the prin- 

 ciples of the igneous theory. To perceive this^ 

 let us attend a little to what is meant by cotem- 

 poraneous formation. 



It cannot be meant, that a w^hole mass of stra- 

 tified or amorphous matter is instantaneously de- 

 posited ; this appears inconceivable. But there is 

 no difficulty in supposing, that layers or substances 

 on the great scale, are formed by continuous suc-^ 

 cessive accretion of matter deposited from a sol- 

 vent, as we see in the instances of crystallization 

 or deposition, w^hich fall under our observation, 

 either in nature, or in the laboratory of the che- 

 mist. Let us, therefore, now conceive, that, after 

 the sandstone was deposited, but before its com* 

 plete consolidation had taken place, a mass of 

 trap followed next in the order of successive de- 

 position. What would be the consequence ? Would 

 not the superincumbent mass sink by its gravity 

 to a certain depth among the softer strata under- 

 neath, presenting the very appearance observed 

 at Ravensheugh,— mdre especially, if deposited, 



Dd2 



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