vol. 52.] granophyres of strath (skye). 329 



Discussion. 



Sir Archibald Geikie referred to the fact that Mr. Harker had 

 been appointed to the Geological Survey only last spring, and that 

 the present paper was the result of his tir.st season's work. The 

 region described by the Author was exceedingly familiar to the 

 speaker, and he rejoiced to welcome this application of modern 

 petrographical methods to its investigation. The paper had a double 

 value. In the first place, it was important in regard to the local 

 geology of the Western Isles, for it demonstrated by new evidence 

 the posteriority of the granophyres to the gabbros ; and in tue second 

 place, it had a suggestive bearing upon questions of theoretical 

 interest regarding the possible modification of eruptive rocks by the 

 incorporation of foreign material into their substance. He felt sure 

 that further and even more extensive evidence of the same kind 

 would be encountered in other parts of the same region of Skye. 

 The inspection of Mr. Harker's specimens reminded the speaker of 

 some puzzling rocks on the flanks of Glamich and other hills, which 

 many years ago he saw to be too acid for the gabbros and too basic 

 for the granophyres. He looked forward to having these and many 

 other problems solved by the continuation of the same paiient and 

 skilled observation as had been shown in the investigations described 

 in the present paper. 



Lieut.-Geu. M c Mahon said that he had listened to Mr. Harker 

 with great interest, and looked forward with pleasure to studying 

 the details of the paper. He was quite prepared to accept the 

 Author's conclusions, because he had found augite in the granite of 

 the Chor Mountain, North-western Himalayas, and attributed its 

 presence to the digestion of fragments of basic rocks caught up by 

 the granite. Mr. R. D. Oldham, Superintendent or the Gjological 

 Survey of India, had also found hornblende lociily abundant in the 

 granite of one part of the Chor, and attributed it to the granite 

 having ' dissolved and absorbed the rocks whose position it occupies.' 

 The presence of magnetite, however, stood on a different footing. 

 It was rather abundant throughout the granite of the .forth- western 

 Himalayas ; but if the Author could show that its presence in the 

 granophyre of Skye was due to the assimilation of gabbro, the fact 

 would be very interesting. 



Prof. Miers called attention to a large mass of coarsely-granular 

 basic rock which exists in the granophyre on the western flank of 

 Marsco, and may be distinguished from the summit of Scuir-na- 

 Gillean as a dark band about 20 feet in breadth, traversing the face 

 of the hill in a vertical direction. 



Mr. W. W. Watts pointed out that Prof. Sollas's researches at 

 Barnavave had prepared the Society for this paper. He a.luded to 

 the association of gabbro and granophyre at so many places, including 

 Radnor and Carrock Fell, and pointed out that the Whin Sill at 

 Caldron Snout passed into a rock which was practically a gabbro 

 embedded in granophyre. 



Dr. Du Riche Prellek said that already on a former occasion 



