XC1V PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [May I906, 



region, as laccolites, apparently connected with the block-structure 

 which the plateaux themselves exhibit. 



That a large area of Scotland, the North-East of Ireland, and 

 the North of England, formed such plateaux in Tertiary times is 

 suggested by many structural features ; and the idea that laccolitic 

 uplifts occurred is in accordance with our present views concerning 

 the origin of the great intrusive masses of Western Scotland. 



In connexion with this point, I would call attention to the 

 striking similarities between the igneous rocks of the Carrock-Fell 

 complex and those of Tertiary date in Scotland. These rocks and 

 the olivine-bearing rocks of the Skiddaw tract are unlike any other 

 igneous rocks of the district ; and it is interesting to find them in 

 the tract, the drainage of which, as will be presently noted, suggests 

 a subsidiary uplift. 



If the dome was produced by the intrusion of igneous rock, it is 

 a question of interest as to what horizon was occupied by this 

 igneous rock. 



I have elsewhere argued that the lag-faults and tear-faults which 

 affect the Lower Palaeozoic rocks were subsidiary to a great over- 

 thrust beneath the Skiddaw Slates, which caused these slates to be 

 pushed northward over a series of newer rocks. Such a thrust- 

 plane would serve as a plane of weakness, along which igneous 

 matter might be easily injected ; and it is interesting to find that 

 the Carrock intrusion occurs at the junction between the Skiddaw 

 Slates and the newer Drygill Shales, which, as I have suggested, 

 may lie beneath the supposed overthrust. In that case the dome 

 would not possess a horizontal base, but one inclined towards the 

 south. I am not aware of any evidence furnished by the shape of 

 the dome or the nature of the drainage which tells for or against 

 this view, unless it be the fact that the newer rocks on the south 

 rapidly pass below sea-level in Morecambe Bay ; whereas on the 

 north a considerable tract of high ground is occupied by Carboni- 

 ferous rocks, and the New Red Sandstone of the lower parts of the 

 Eden Yalley is still above sea-level. 



Whatever be the date of the uplift, and the exact manner in 

 which it was caused, the geological structure of the district fully 

 proves the existence of one main dome-shaped uplift and of at 

 least one subsidiary uplift, namely, that lying south-east of the 

 main dome. That these uplifts have determined the present main 



