380 spinel and foksterite fkom glenelg. [aug. 1 899, 



Discussion. 



Sir A. Geikie referred to the exceedingly complicated geological 

 -structure of the district described by the Authors of the paper, and 

 to the great interest attaching to the traces of sedimentary materials 

 ;associated with the gneisses and other crystalline rocks. The 

 Lewisian Gneiss of the region consists of enormous len tides, many 

 miles in horizontal extent, which have been torn away from the main 

 mass of the formation and have been pushed westward over younger 

 parts of the pre-Cambrian Series. The sedimentary materials 

 referred to are probably the oldest in the British Isles. No trace 

 of organic remains is to be expected among them ; but possibly 

 such researches as those detailed in the excellent paper to which 

 the Society had listened might lead to the establishment of certain 

 mineral characters by which particular groups of sediments might 

 be identified, and an additional clue might thus be obtained in 

 lunravelling the extremely difficult structure of the ground. 

 Whether this hope were fulfilled or not, it was satisfactory to have 

 the problems attacked in so careful and exhaustive a manner as that 

 followed by the Authors. He congratulated the Society on the 

 addition to its effective strength by the admission of Dr. Pollard as 

 a Fellow that same evening ; and he alluded to a serious accident 

 sustained last spring by Mr. Clough, in consequence of which that 

 active and minutely painstaking geologist had been disabled from 

 field-work during the whole of the rest of last year. 



Mr. J. J. H. Teall also spoke. 



Dr. PoLLAED, in reply to a question, said that he could not state 

 exactly how much of the material occurred ; probably the occurrence 

 not very extensive. 



