AUGITIC ROCKS. 45 



localities ignigenous masses, traversed by veins of the same 

 nature, it may be at once affirmed that two eruptions of 

 trap are indicated ; but this seems to be the full extent of 

 our knowledge. If our opinion in regard to the elevation 

 of the greywacke systems of the Lammermuir and Moor- 

 foot hills be correct, it is rendered highly probable that the 

 unstratified rocks associated with these transition forma- 

 tions have been erupted before the deposition of the carbo- 

 niferous group, or the protrusion of the Plutonic rocks as- 

 sociated with them ; and that their upburst, perhaps, in some 

 respects, may have been the cause of the upraisure of the 

 previously undisturbed greywacke and transition slates. 

 Though this may have been the case, however, it does not 

 follow that the actions of the igneous rocks associated with 

 the secondary strata, were confined to them : on the con- 

 trary, they may have sent erupted masses into the older 

 rocks ; so that, though amongst the one series of strata, 

 rocks of a formation posterior to them, perhaps, only occur ; 

 in the transition series two classes of Plutonic rocks, each 

 of different relative ages, may be found. 



We have now arrived at a part of the subject which is re- 

 plete with interest. We are to describe those changes which 

 igneous matters, erupted in former ages of the world, have 

 effected on the rocks through which they issued, and be- 

 tween and over which they have flowed. When we consi- 

 der that we now live in a land where the shock of the earth- 

 quake, and the impetuosity and desolation attending a lava 

 stream, are neither felt nor dreaded, it is highly interesting 

 to find, by geological examination, that the country in which 

 we dwell with such repose was, at one time, ravaged by sub- 

 terraneous action, — that its strata have been traversed by 

 streams of liquid mineral matters, — that it has had its 

 " phasis" of disturbance. 



