270 ON THE PARTICULAR ORDER OF 



lowest tracts of Scotland and the Baltic. But the 

 history of the successions of rocks, as they actually 

 exist, require some further detail. 



It was once universally believed that no stratified 

 rock existed below granite ; but if this substance is to 

 be defined by its mineral composition, that opinion 

 is unfounded, since I have already remarked that such 

 a compound lies above conchiferous limestone. Never- 

 theless, in the arrangement of rocks which I have 

 adopted, founded chiefly on geological position, the 

 original opinion is retained; an arrangement that 

 will not be objectionable to those who maintain the 

 doctrine of fixed successions and the universal in- 

 feriority of granite. 



Of the general Successions of Rocks. 



It is unnecessary to commence these remarks by 

 detailing the imaginary order of succession formerly 

 received. Were it necessary to multiply examples 

 of irregularity, it would be easy to refer to the writings 

 of numerous geologists. They who are inclined, may 

 consult the remarks of Ebel, of Breislak, and others. I 

 shall here limit myself, chiefly for the convenience of 

 British readers, to illustrations drawn from our own 

 country, and, for the accuracy of which, myself and 

 other British geologists must of course be responsible. 



Granite is succeeded by gneiss very generally in 

 Aberdeenshire, as it has been supposed necessarily to 

 be everywhere. In the same country, it is followed 

 by micaceous schist, as it is in Arran, in Upper Lorn, 

 and in many other places. It is perhaps of little 

 moment to say that it is often succeeded by horn- 

 blende schist, as this rock is noted for its versatility 

 of place; but in various parts of Perthshire, and of 



