Yol. 65.] THE CAULDRON-SUBSIDENCE OP GLEN COE. 



Discussion. 



The President (Prof. Sollas) welcomed this paper as another 

 contribution of the first importance afforded by the prolific region 

 of: Western Scotland. It was an attempt, marked by great 

 originality, to trace the deeper-seated processes connected with 

 cauldron-inbreaks, of which hitherto the superficial manifestations 

 were better known. The flinty crush-breccias were of great interest, 

 but the evidence so far presented did not seem to prove more than 

 crushing in the first place and injection in the second. To account 

 for the injection by fusion due to the thermal transformation of 

 mechanical energy, seemed in the present instance to be accompanied 

 by many difficulties ; and, considering how closely igneous intrusions 

 from below were connected with many of the phenomena under 

 discussion, it might be suggested that an injection of magma might 

 have taken place along crush-planes. It was fortunate that the 

 age of the inbreak relative to the great Caledonian movements 

 could be so definitely determined, and the fact that it followed 

 upon a period of mountain-building seemed to be in harmony with 

 what was known in other cases. 



Dr. Teald said that he had examined a small portion of the area 

 under the guidance of the Authors, and could testify to the care 

 and accuracy with which their observations had been made. The 

 surveying of the region had involved the expenditure of a large 

 amount of physical as well as of mental energy. 



AVith regard to the peculiar flinty crush-rocks which he had 

 examined from other districts, he was not prepared to say that there 

 was no admixture of igneous with crushed material; but, if there 

 were any, the amount must be extremely small. He considered 

 that the main theoretical conclusions at which the Authors had 

 arrived were justified by the facts, but he had not yet fully grasped 

 their explanation of the reasons why the dykes were localized in 

 special localities. He regarded the paper as a very important 

 contribution to geological science. 



Mr. Barrow congratulated the Authors on the originality of their 

 paper, and was pleased to see that they did not consider all the 

 masses of newer granite necessarily laccolites, the feature of which 

 was that they lifted up the roof of overlying rocks. This did occur in 

 Cornwall, but he had rarely seen any evidence of it in the Highlands. 

 He was inclined to believe that, in some cases at least, they pushed 

 the floor down, which seemed the most likely explanation in the case 

 of the Glen Doll complex. The association of faulting with these 

 great intrusions was the rule rather than the exception, and the 

 phenomenon was best shown by the Glen Doll complex, which lay at 

 the head of Glen Clova, above Kirriemuir, in Forfarshire, and was 

 extremely easy of access. This intrusion lay along the line of the 

 greatest known fault within the Highlands ; the fault came up to 

 one edge of the complex, was lost in it, and reappeared on the other 

 side. 



