CHAEACTEES OF A SEEIES OF SCOTCH EOCKS. 167 



Discxrssiow. 



The Peesidext remarked upon the importance of the question 

 discussed in the paper. 



l[r. Hudlestox agreed with the author in regarding the Glen- 

 Docherty beds as presenting important points of difference from 

 those lying to the eastward. He believed that in Assynt the ap- 

 pearance of the dolomitic limestone passing under the peculiar 

 gneissic rock which the older geologists had described as igneous, 

 was due to the folding over of a really lower gneiss. On the other 

 hand, as tending to remove the a priori objections to the possibility 

 of the "upper gneiss " being of Silurian age, he referred to the 

 important discoveries made by the Norwegian geologists as to 

 the metamorphism of fossiliferous rocks — a view also supported by 

 31. Renard. 



Prof. Bosket described the three types which he had recognized 

 in the specimens sent to him by Dr. Hicks and by other observers, 

 and pointed out the probable cause of the occasional difficulty in 

 distinguishing them. As regards the Norwegian instances of 

 metamorphism mentioned by Mr. Hudleston, he thought that, 

 remembering how faults, overturns, and simulation of older rocks in 

 new rocks made of their materials, had in the past misled geologists, 

 we should be wise to be sceptical as to the more startling conclusions 

 of the workers whom he had named. As regards Prof. Renard, he 

 thought there was some misconception — the Franco-Belgian rocks 

 on which he had written were but slightly metamorphosed compared 

 with most of the Highland schists. 



Dr. G. J. Hixe-e stated that the Highland rocks exhibited by the 

 author greatly resembled the Laurentian of Canada. 



Prof. Seelet asked as to the evidence on which the faults had 

 been inserted on the map. 



Mr. Topley asked whether the author regarded the pebbles in the 

 conglomerates as derived from the eastern or the western area. 



The Author, in reply, said that he regarded some of the eastern 

 and western series as the same. The faults were indicated by a 

 total and sudden change in the characters of the rocks, as proved 

 by microscopic examination and also by stratigraphical evidence. 

 He remarked on the complete absence of fossils in the supposed 

 altered Silurian rocks of the Highlands. He believed that the 

 Norwegian geologists had fallen into error in the interpretation of 

 their sections, some of which they confessed were equally to be 

 explained by inversion of the strata. The few cases cited by them 

 could, however, have very little bearing on the large question touched 

 upon in the present paper. The pebbles in the conglomerates varied 

 usually in accordance with the rocks upon which they reposed. 

 Some .showed clearly that rocks of the eastern types had yielded the 

 materials. 



